Patent Publication Number: US-6988238-B1

Title: Method and system for handling errors and a system for receiving packet stream data

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to detecting and handling errors in the packetized data, and more specifically to detection and handling of MPEG-2 transport stream errors. 
     BACKGROUND OF THE INVENTION 
     The international organization for standards (ISO) moving pictures experts group (MPEG group), approved an audio video digital compression standard known as MPEG-2 in an effort to provide a versatile compression standard capable of being utilized for a wide variety of data. The MPEG-2 standard provides explanations needed to implement an MPEG-2 decoder through the use of syntax and semantics of a coded bit stream. MPEG-2 is an open standard which continues to evolve and be applied to a variety of applications ranging from video conferencing to high definition television. As a generic standard, MPEG-2 is intended to be used for variety of audio and video coding applications. Part one of the MPEG-2 standard (ISO 13818-1), was designated to improve error resilience and carry multiple programs simultaneously without a common time base between programs. 
     The transport stream (TS) specified by the MPEG-2 standard, offers a high degree of robustness for noisy channels, and can be used to carry multiple programs, such as multiple TV services. The transport stream is based on a 188 byte long packet suited for hardware error correction and processing schemes. The use of a robust protocol, such as the transport stream, allows for reception over noisy environments such as terrestrial and satellite transmissions. Even in these environments it is possible to obtain fast program access, channel hopping, and synchronization between multiple elementary streams carried within the packetized elementary streams which are subdivided into transport packets. 
     Prior art  FIG. 1  illustrates a Transport Packet Stream defined by the MPEG-2 standard. The transport stream, based on a 188 byte long packet, is well suited for hardware error correction and processing schemes. Such a configuration can carry multiple programs within the same multiplex, even when the transmission environment is noisy. For example, MPEG-2 data can be transferred successfully over coaxial cable networks and satellite transponders with asynchronous multiplexing of constant or variable bit-rate programs to allow fast program access, channel hoping and synchronization between services. 
     As illustrated further in  FIG. 1 , MPEG-2 transport stream consists of fixed length Transport Stream Packets (TSP or packets) based on 4 bytes of header followed by 184 bytes of TSP payload. TSP payload carries Packetized Elementary Stream (PES) data obtained by chopping up an Elementary Stream (ES), which consists of data of a common type and program. For example, audio for a specific program would form one elementary stream, while video for the same program would form a second elementary stream. 
     The TS header consists of a synchronization byte (SyncByte), flags, information indicators for error detection and timing, an adaptation field indicator, and a Packet_ID (PID) field used to identify Elementary Streams carried in the payload. The adaptation field, when present, contains flags, and timing information. 
     The PID Field is used not only to distinguish separate Elementary Streams, but also separate Program Specific Information (PSI) tables. Prior art  FIG. 2  illustrates two types of PSI tables—a Program Association Table  210  (PAT), and a Program Map Table  220  (PMT). The PAT table lists unique program numbers as identifiers for each program, or elementary stream, in a multiplex, and the PID number associated with each program number. A fixed PID number of 0x0000 is assigned to the PAT table, making it possible for the system to download the PAT table on startup by retrieving PID 0x0000 packets. 
     Each program identified the PAT table has a related Program Map Table (PMT) having its own PID identifier. Each PMT table lists the PIDs for all Elementary Streams (components) making a given program associated with the PMT. A specific PMT table maybe constructed for each program separately, or may be common for a group of programs. In the first case, there are many PMT tables with just one section, and each PMT table has a different PID value. In the second case one PMT table may have many sections, each relevant to one program. 
     In order to provide multiple services over the same multiplex, data associated with different multimedia services are transmitted, with packet multiplexing, such that data packets from several Elementary Streams of audio, video, data, and others are interleaved on a packet by packet basis into a single MPEG-2 transport stream. Synchronization between Elementary Streams forming a common program is achieved using presentation time stamps and program clock references which can be transmitted as part of the adaptation field specified in the header. 
     Prior art  FIG. 3  illustrates the fields associated with a PES stream. Each PES stream contains a header portion and a data portion. In addition, an optional header portion may exist. The header portion includes a Packet Start Prefix, a stream ID, and a packet length indicator. 
     Transport stream information can be provided either through a direct broadcast, or through a service provider broadcast. Direct broadcast generally refers to signals which are received directly by an end user. Examples of direct broadcasts include satellite broadcasts received by satellite dishes and provided to a decoder at the end user&#39;s location, which receives and decodes the transport stream data. Another type of direct broadcast is the traditional composite television/radio broadcast. In their most elementary forms, these broadcasts are not digital broadcasts. However, the transmission of digital broadcast in MPEG-2 format is being explored and occurring as an alternative. In this manner, the user would have a tuner capable of receiving the direct terrestrial link information containing the television or radio signals. Once demodulated, the transport stream information could be provided to a desktop unit, or decoder, owned by the end user. 
     Service provider broadcast would include broadcast to the home provided by cable television providers, telephone company providers, or other independent providers. In this configuration, the service provider first receives the number of signals which can be ultimately provided to the end user. Examples of such received signals include satellite feeds, terrestrial feeds, switched video sources, local video sources such as tapes, or laser disk DVD&#39;s, as well as traditional table feeds. Based upon the end users demands, the received information can be selectively provided to the end user. 
     In one manner, the selected feed by the service provider can be provided directly to an end user through a twisted pair connection, which may include a high speed digital subscriber link (DSL) capable of providing data at higher rates than traditionally associated with plain old telephone system (POTS) connections. 
     In another implementation, the service provider would provide information from a central office or a head-end to a fiber node. A specific fiber node is generally used to support more than one end user. Examples of the use of such fiber nodes includes a fiber coaxial bus (FCB) whereby a fiber link provides the signal containing a large amount of data to a fiber node which in turn drives coaxial cable having a taps. A decoding device attached to taps at user side can receive the appropriate broadcasting signal. 
     Another example of a fiber node is bi-directional fiber coaxial bus. While similar to the FCB bus, the bidirectional FCB bus is also capable of transmitting data back to the central office or the head-end as well as receiving it. Yet another fiber node example is a hybrid fiber coax, which uses coaxial cable and branch topology toward network interface units. Yet another example associated with service providers is known as fiber to the curb, whereby digital signaling is carried from the central office to the optical network unit which serves only a few dozen homes. Locally, a hybrid twisted pair coaxial pairs will connect to the optical network unit with the consumer&#39;s decoder. Twist repair cable carries digital video in the 5 to 40 megahertz range to no more than 500 feet from the fiber connection. Therefore, the number of homes capable of being served by a single optical network unit is limited. Analog television signals are carried in a coaxial cable from the fiber node. 
     One problem associated with the flexibility of the MPEG-2 standard is that once the transport stream is received, demodulated, and decrypted, the resulting data stream can still have a variety of variations which need be known before the data stream can be properly utilized. For example, the MPEG-2 specification does not indicate a specific set of control signals to be provided with the transport stream, how received data and control signals are qualified, nor the precise format of the actual data transmitted. As a result, implementations of set top boxes require specific service provider information. Specific service provider information results in an incompatibility among transport streams schemes provided by different service providers or cable operators. As a result, chip sets are designed and dedicated to support specific service provider&#39;set top boxes. 
     Prior art  FIG. 4  illustrates a prior art system for parsing a transport stream. The transport parser of the prior art would receive individual packets from the framer. Based upon the PID value, the transport parser would store the TSP data to be used by the system or the graphics engine in a local buffer. 
     When the transport parser&#39;s local buffer was filled, the transport parser would cause a bus request to the appropriate controller (system or video) to initialize a transfer of at least some of the buffered data. 
     However, when the prior art host video or graphics system needed more data from the transport parser prior to the transport parser initializing the transfer, the system would initialize the transfer by generating a request to access data in the transport parser buffer. Since the bus used internally by the transport parser buffer may have other clients, the host system may have to wait to access the bus. The overall performance of the host system is reduced as a result of the system waiting on data. 
     Therefore, a system and method of receiving transport stream information that allows for more flexibility and improved performance in terms of data handling, data parsing, design implementation, data stream acquisition would be advantageous. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates, in block form, prior art fields associated with a transport stream packet; 
         FIG. 2  illustrates, in tabular form, a prior art Program Specific Information tables; 
         FIG. 3  illustrates, in block form, prior art fields associated with Packetized Elementary Stream; 
         FIG. 4  illustrates, a prior art representation of a parser system; 
         FIG. 5  illustrates, in block diagram form, a transport stream core in accordance with the present invention; 
         FIG. 6  illustrates a tabular representation of a register set; 
         FIG. 7  illustrates, in block diagram form, another embodiment of a transport stream core in accordance with the present invention; 
         FIG. 8  illustrates, in block diagram form, a framer receiving a transport stream signal; 
         FIG. 9  illustrates, in timing diagram form, the relationship among individual data signals comprising a transport stream; 
         FIG. 10  illustrates, in flow form, a state diagram for implementing a function associated with the framer of  FIG. 3 ; 
         FIG. 11  illustrates an algorithmic state machine associated with the framer of  FIG. 3 ; 
         FIG. 12  illustrates, in tabular form, global status registers associated with a portion of  FIG. 6 ; 
         FIG. 13  illustrates, in tabular form, interrupt registers associated with a portion of  FIG. 6 ; 
         FIG. 14  illustrates, in tabular form, global control registers associated with a portion of  FIG. 6 ; 
         FIG. 15  illustrates, in block and logic form, a portion of a framer in accordance with the present invention; 
         FIG. 16  illustrates, in block and logic form, a transport packet parser in greater detail; 
         FIG. 17  illustrates, in block and tabular form, a data output controller in greater detail; 
         FIG. 18  illustrates, in tabular form, video control registers associated with a portion of  FIG. 6 ; 
         FIG. 19  illustrates, in tabular form, auxiliary PID control registers associated with a portion of  FIG. 6 ; 
         FIG. 20  illustrates, in flow diagram form, a method in accordance with the present inventions; 
         FIG. 21  illustrates, in block and logic form, a video packetized elementary stream parser in greater detail; 
         FIG. 22  illustrates, in flow diagram form, a method in accordance with the present inventions; 
         FIG. 23  illustrates, in block diagram form a video packetized elementary stream parser; 
         FIG. 24  illustrates, in tabular form, global status registers associated with a portion of FIG.  6  and fully associated with  FIGS. 21 and 23 ; 
         FIG. 25  illustrates, in tabular form, interrupt registers associated with a portion of FIG.  6  and fully associated with  FIGS. 21 and 23 ; 
         FIG. 26  illustrates, in block form, an output controller and memory in accordance with the present invention; 
         FIG. 27  illustrates, in flow diagram form, a method in accordance with the present invention; 
         FIG. 28  illustrates, in block diagram form, a detailed view of an adaptation field parser; 
         FIG. 29  illustrates, in tabular form, global status registers associated with a portion of FIG.  6  and fully associated with  FIG. 28 ; 
         FIG. 30  illustrates, in tabular form, interrupt registers associated with a portion of FIG.  6  and fully associated with FIG.  28 . 
         FIG. 31  illustrates, in tabular form, global status registers associated with a portion of FIG.  6  and fully associated with  FIG. 28 ; 
         FIG. 32  illustrates, in block diagram form, an alternate embodiment of a transport packet demultiplexor; 
         FIG. 33  illustrates, in block diagram form, a detailed view of a private packet packetizer of  FIG. 32 ; 
         FIG. 34  illustrates, in block form, representations of private packets from the packetizer of  FIG. 33 ; 
         FIGS. 35-38  illustrate, in flow diagram form, a method of splicing video in accordance with the present invention; 
         FIGS. 39-42  illustrate, in flow diagram form, a method of performing blind acquisition of an MPEG-2 data stream; and 
         FIG. 43  illustrates, in block form, a general purpose computer system in accordance with the present inventions. 
         FIG. 48  illustrates, in block diagram form, an alternate embodiment of a portion of the system of  FIG. 7 ; 
         FIG. 49  illustrates, in block diagram form, an alternate embodiment of a portion of the transport packet parser of  FIG. 16 ; 
         FIG. 50  illustrates, in block diagram form, an alternative embodiment of a portion of the PESP of  FIG. 23 ; 
         FIG. 51  illustrates, in flow diagram form, a method in accordance with a specific embodiment of the present invention; 
         FIGS. 52 and 53  illustrate, in tabular form, portions of the register set accordance with the system of FIG.  7 . 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     In accordance with a specific embodiment of the present invention, detection and/or handling of error condition is enabled for an error being in the transport packet stream. A determination is made whether received data contains detectable error. If so, an error recovery operation is performed that includes the following: notification of the host CPU, MPEG video decoder, a display processor, and/or disregarding the data. The present invention is better understood by example with reference to the Figures herein, and in particular with reference to  FIGS. 48-53 . 
     In operation, the TS core  400  receives transport stream packets. Each packet is synchronized to the TS core  400 , and demultiplexed. Each packet is demultiplexed based upon its Packet IDentifier (PID), which identifies the type of data carried in the packet. The TS core  400  is bufferless in that no packet data is stored within the TS core  400  for access by video or system processing. Instead, the demultiplexed data is stored in one or more locations within each of the Video memory  471 , and the system memory  472 . 
     Transport Stream Core  400  includes a Framer  410 , Transport Packet Parser  420  (TPP), a PES Parser (PESP)  430 , Adaptation Field Parser (AFP)  450 , Buffer Controller  460 , and register set  480 . 
     The register set  480  is further illustrated in FIG.  6 . Generally, the register set  480  includes interrupt mask registers, control registers, status registers, and system interface registers. Interrupt mask registers are used to enable or disable specific interrupts. Control registers specify how various aspects of the TS core  400  are to operate. Further examples of types of control registers include Global Control Registers; Video Control Registers, which control how video packets are handled by the TS core; and Non-Video Control Registers, which control how non-video packets are handled by the TS core. 
     In operation, the framer  410  receives a raw transport stream which is analyzed to isolate and provide individual transport stream packets (TSP) to the bus  405 . In one embodiment, the bus  405  receives byte wide data (the data bus width could also be 16 or 32 bits) and a control signal to indicate when the current byte of data is valid. In addition, the Framer  410  generates a signal labeled PACKET START to indicate the first byte of a packet, and a signal labeled IN SYNC to indicate when the data on the bus  405  is synchronized, or locked onto by the Framer  410 . 
     The TPP  420  is connected to the bus  405 , and receives the IN SYNC and PACKET START signals. Parsing of a TSP (packet) by the TPP  420  is enabled when the IN SYNC signal and the PACKET START signals are asserted indicating the beginning of a new packet. During parsing of the header portion of a packet the PID number is obtained. Based upon the value of the PID number, registers are updated, and a determination is made whether the TSP is to be saved, further processed, or discarded. 
     When it is determined to save the packet, the TPP  420  asserts the signal labeled TPP DEN which is received by the Buffer Controller  460 . Based upon this enable signal, the Buffer controller  460  retrieves the packet data and stores it in a predefined memory location. 
     When it is determined to discard the packet, no further action by the TPP  420  is needed, resulting in the remainder of the TSP being ignored. 
     When it is determined to further process the packet by one of the other parsers  450  or  430 , the TPP  420  asserts one of their respective enable signals. For example, if it is determined that the packet contains video data, the TPP  420  will assert the signal labeled EN PESP, likewise, if it is determined that the packet contains adaptation field data, the TPP  420  will assert the signal labeled AFP EN. Based upon these signal being active, the respective parser will further process the packed data. 
     In response to being enabled by the TPP, the Video PES Parser  430  further processes the packet by parsing the header of the video PES. Based upon information carried in the header of the video PES, registers are updated, and the video payload may be stored or discarded. 
     When it is determined to save the video payload, the PESP  430  asserts the signal labeled PESP DEN which is received by the Buffer Controller  460 . Based upon this enable signal, the Buffer controller  460  retrieves the packet data and stores it in a predefined location of video memory. 
     The Buffer controller  460  receives and stores the data payload based upon control signals received from the parsers. Because the packet data is stored directly in the system memory  472 , associated with a main system (not shown), or the video memory  471 , associated with a video adapter (not shown), the packet data is not stored in TS core  400 . Therefore, the core  400  and each of its parsers are described as bufferless. By storing data directly in the system memory  472  and the video memory  471 , the system does not have to access memory space within the TS core  400 . This eliminates delays associated with the prior art which occurred when the system had to wait on TS core bus accesses to be completed before the needed data could be retrieved. 
     The bus connections between the buffer controller  460  and the system memory  472  can vary depending upon the implementation chosen. For example, both the video memory  471  and system memory  472  can be connected to the buffer controller  460  through a PCI (Peripheral Components Interconnect) bus, or the system memory  472  can be connected to the buffer control  460  through a PCI bus, while the video memory  471  is connected to the buffer controller  460  through an AGP (Accelerated Graphics Port). 
       FIG. 7  illustrates another embodiment of a TS core in accordance with the present invention. The TS core of  FIG. 7  includes framer  710 , TPP  720 , AFP  750 , PESP  730 , buffer controller  760 , and registers  780 . 
     The registers  780  are analogous to registers described with reference to FIG.  5 . 
     The framer  710  provides transport stream data labeled FRAMER DATA on an eight-bit bus, (or 16 or 32) and provides a signal labeled FRAMER DEN. The FRAMER DATA an eight-bit wide data byte, or word, which has been received from the transport stream. The FRAMER DATA is qualified by the signal FRAMER DEN, which is an enable signal. The signal FRAMER DEN is asserted during each valid FRAMER DATA. 
     The FRAMER DATA and FRAMER DEN signals are provided to each of the parsers of  FIG. 7 , and the Buffer controller  760 . The TPP parser  720  receives the header information of new packets when the framer  710  asserts an IN SYNC signal and a PACKET START signal. The combination of these signals, when asserted, indicate that the present FRAMER DATA is part of the packet header. As a result, the TPP  720  receives the FRAMER DATA from the data bus for parsing. 
     In a specific embodiment, the IN SYNC signal provided by the framer  710  will be active whenever the framer  710  is locked onto, or synchronized with, the transport stream. If the IN SYNC signal is deasserted, the TPP will not receive the data. Furthermore, the PACKET START signal can be a single pulse asserted during the first byte of a new packet, or it can be a signal that is asserted during the first byte of the packet and not deasserted until the last byte of the packet. The first byte of the packet can be defined in different manners. For example, the first byte can be defined to be the sync byte of a packet, or the first byte after the sync byte. 
     Based upon the PACKET START signal, the TPP  720  can maintain a byte count indicating the location of a current byte within the packet being received. Based upon this count, the TPP  720  will parse the header of the packet which is the first four bytes. 
     During parsing of the packet header, the TPP receives the PID of the current packet. Based upon the PID value, the TPP can enable other parsers to perform additional parsing operations. For example, when the PESP  730  of  FIG. 7  is a dedicated video PES parser, and the PID associated with a packet received by the TPP is the video PID, the TPP will enable the PESP  730  by asserting the signal labeled VIDEO. Additionally, TPP asserts the signal labeled VSTART when the current frame is the first frame of a PES stream. This indicates to the PESP that the elementary stream header is at least partially within the current frame. The VSTART signal allows the PESP to locate and parse the header of the video PES, while the VIDEO signal allows subsequent video payload to be retrieved. Likewise, when the adaptation field control of a packet header indicates that adaptation field data is to follow, the TPP will provide a signal labeled AFSTART to indicate the beginning of the adaptation field. In response, the AFP  750  will parse the adaptation field of the current packet. 
     When a current packet, that is not a video packet, is to be received by the TS Core of  FIG. 7 , the TPP will receive the packet from FRAMER DATA and provide the entire packet one byte at a time as TPP DATA to the Buffer controller  760 . Similarly, when the packet is a video packet, the PESP  730  will receive video data payload from the FRAMER DATA and provide it to the Buffer controller  760 , which is subsequently framing data bytes into double words as PESP DATA. Any data associated with the adaptation field of the packet will be provided to the buffer controller  760  from the AFP parser  750  as AFP data. 
     In response to the various data and control signals received from the parsers, the buffer controller stores the data. In a specific mode, where all packets are to be stored, the FRAMER DATA and control signal FRAMER DEN can be received directly at the buffer controller  750  for storage. 
     In accordance with the present invention, each of the parser modules  720 ,  730 , and  750 , and the framer  710 , as well as any other module which may be included, are implemented to have modular layouts. For example, the layout of the TPP  720  is modular when its layout is performed independent of the layout of any of the other module. As a result, the TPP  720  will have a localized layout independent of the other modules. Independent development and reuse of modules is readily accomplished using modular layouts for modules having independent functions. This is an advantage over the prior art, which did not differentiate the parsing functions using modular layouts, in that it provides greater flexibility and reuse in the design and implementation of transport stream parsers. 
     The framer is best understood with further reference to the  FIGS. 5 , and  8  through  15 .  FIG. 8  illustrates a block diagram representation of the transport stream signal received at framer  710 . In the embodiment illustrated, the transport stream includes five signals. A clocking signal labeled TCLOCK, a data signal labeled TDATA, a data valid signal labeled TVALID, a packet start signal labeled TSTART, and an error signal labeled TERROR. The TDATA signal can be either a single or multiple bit wide data stream. Each of the control signals of  FIG. 8  are single bit signals received by the framer  710 . 
     The transport stream data and control signals can be received either from a direct broadcast or through a specific service provider. The signals actually received by the framer  710  can vary depending on the specific network interface module (NIM) provider of direct broadcast implementation. At a minimum, TCLOCK, and TDATA are needed. The TCLOCK and TDATA signals contain the basic information necessary to retrieve this information. While  FIG. 8  illustrates seperate TDATA and TCLOCK signal, it is possible to provide the data and clock as an integrated signal, whereby the clock signal would be extracted from the received data. 
     Where only TCLOCK and TDATA are provided, the TCLOCK signal active, I.E. toggled, only when data is transmitted. When a valid signal, TVALID, is also provided TCLOCK can be a constantly running synchronous clock. In that case the data is qualified with the TVALID signal. 
     The TSTART signal, when provided, is used to indicate when transmission of a new transport stream packet occurs. When TSTART is available, the synchronization process is trivial because the provider of the transport stream NIM is required to specify the start of each new packet. 
     The TERROR signal, when present, indicates that the data being received may be corrupted due to a potential error in the data path. TERROR the decoder that the information at this point is at best suspect, if not incorrect. 
     As previously indicated, various combinations of signals comprising the transport stream can occur. In addition, the format of individual signals can vary. For example, TCLOCK can qualify the TDATA signal on either a rising edge or a falling edge. In accordance with a specific embodiment of the present invention, the TCLOCK edge that qualifies TDATA can be defined in the framer  710 . 
     Another transport stream variation is how the TDATA is transmitted to the framer  710 . TDATA can be transmitted in one of either MSB first or a LSB mode. When transmitted in MSB first mode the most significant bit of each data byte is received first, and in LSB first mode the least significant bit of each data byte is received first. In accordance with a specific embodiment of the present invention, whether data is transmitted LSB first or MSB first can be defined in the framer  710  to properly receive bytes of TDATA. 
     Another transport stream variation is the polarity of an active control signal. For example, the control signal can be active at either a logic level 1 or a logic level 0, depending upon the system implementation. In accordance with a specific embodiment of the present invention, the polarity of control signals can be defined in the framer  710  to properly identify the correct asserted logic level. 
     TDATA can be received bit-by-bit, byte-by-byte, or by other various word size. Within the received stream, the individual units of data are referred to having a location. For example, the first byte associated with the data stream is referred to being at a first location, while the 188 th  byte would be referred to as the 188 th  location. The use of the term “location” also implies a point in time, whereby a first byte would occur at a first time, or period, and the 188 th  byte would occur at a 188 th  time period as references to the TCLOCK. 
       FIG. 9  illustrates the relationship between the various control and data signals of the transport stream. Specifically,  FIG. 9  illustrates a TCLOCK signal having a rising edge for qualifying each data byte of the TDATA signal. Likewise, in the illustration of  FIG. 9 , the TVALID signal is always asserted during the first byte indicating that the data is valid. The TSTART signal is synchronized to the first byte of the TDATA signal, which is a synchronization byte. In a specific implementation, the synchronization byte of the TDATA signal will always have the Hexadecimal value 47h. The TERROR signal is not illustrated, however it would be asserted to indicate when an error has occurred. 
     While the timing diagram of  FIG. 9  does not explicitly show bits of TDATA being received serially, it should be understood that for each byte representation of TDATA in  FIG. 9 , 8 individual data bits can be received, qualified by eight TCLOCK pulses, to form the byte illustrated. When TDATA is received in a bit-by-bit manner, without a TSTART signal, there is no knowledge as to which of the bits being received represents the first bit of a byte, where by “first bit” it is meant the first bit received when the device is turned on and started latching the data. Likewise, the same is true for the first byte, let alone which byte represents the first byte of the frame. The state diagram of  FIG. 10  is a state diagram describing synchronizing the decoder of  FIG. 7  to the transport stream being received. 
       FIG. 10  illustrates a state diagram for the framer  710 . The state diagram of  FIG. 10  includes four states. State A is the synchronization lost state. State B is a synchronization search state. State C is a synchronization verify state. State D is a synchronization lock state. Upon a hardware or software reset the system in accordance with the present invention enters State A through transition  504 . When in State A, synchronization to the data packets has been lost. When synchronization to the transport stream has been lost, it is not known where a new packet begins or an old packet ends. As a result, it is not possible to receive data. Note that when a TSTART signal is provided as part of the transport stream synchronization is known and guaranteed, therefore State C, synchronization verify, is will not be entered if TSTART is active. For illustration purposes, this diagram assumes that the incoming stream is already byte aligned and that there is no need to look for byte boundaries. 
     The first byte is a sync byte for the transport stream, and has a predetermined value. In MPEG-2 implementation, the synchronization byte has the hexadecimal value 47h. Transition path  511  loops into State A whenever a byte received is not equal to the synchronization value 47h. During the transition  511 , a synchronization lock counter (SyncLockCnt) is set to a stored value. This value of the synchronization lock counter indicates the number of consecutive successful synchronization bytes that must be detected prior to determining the system is synchronized. In the specific implementation, each byte is received by the framer is compared to the value 47h. In one embodiment where a serial bit-stream is received, and the byte boundary within the bit stream is not known, the bit-stream is monitored on a shifted 8-bit basis in order to monitor every possible combination of the bits in the stream to detect the synchronization value. The transition path  513  is taken once the synchronization value is detected. 
     During transition  513 , the synchronization lock counter is decremented to indicate a successful detection of the synchronization value. By identifying a first synchronization byte, the synchronization lock count is decremented the first time. Note that if the synchronization byte value is equal to 47h and the synchronization lock count is equal to zero the transition  512  is taken to State D to indicate successful synchronization. 
     From State B, transition path  522  is taken for each received byte until the expected location of the next synchronization byte is reached. Because MPEG-2 transport stream packet is 188 bytes long, there will be additional 187 bytes before the next synchronization byte is expected. This is necessary because the value 47h might occur elsewhere in the stream (i.e. this value is not a reserved value). Therefore, on the 187 byte of the packet transition path  521  is taken to return to State A so that the next byte can be evaluated. If at State A it is determined that the 188 th  byte is has a valid synchronization value of 47h the state machine will transition either on transition path  512 , or transition path  513  depending on how many valid synchronization bytes have been identified. In the event that the 188 th  byte doesn&#39;t have synchronization value, transition  511  is taken, the synchronization lock count is set to the synchronization lock register value, and the system returns to State A. 
     By transitioning in the manner described between State A and State B, the framer  710  is able to monitor a data stream and determine a valid synchronization location using only the TCLOCK and TDATA signals. Once the valid synchronization location has been identified, by receiving a predefined number of correct sync values, the transition path  512  is taken to State D. 
     State D indicates that the framer  710  has currently obtained a synchronization lock state. However, in order to assure that the data stream continues to be a valid data stream, the transition  542  is used to determine when the next expected sync byte location is to occur. Transition  541  places the system in state C at reception of the transport stream sync byte to verify synchronization. If synchronization is verified, the system transits to state D along transition path  533 . As a result of transitioning along path  533 , a drop count is reset to a stored value, which indicates how many sync bytes must be missed before synchronization is lost. This way the incoming stream is continuously monitored for any errors. 
     By allowing for a predefined number of missed synchronization bytes, intermittent glitches can be ignored. This is useful depending upon the desired data integrity. For example, a drop count value of three would indicate that more than three lost synchronization values in a row will result in the state machine entering State A the synchronization lost state. 
     When the synchronization value is not found, transition path  533  is taken back to state D. As a result, the synchronization drop count (SyncDropCnt) is decremented to indicate the sync value was not valid, but SyncDropCnt is not yet zero. When the synchronization value is not found, transition path  531  is taken to State A when the synchronization drop count is equal to zero indicating synchronization has been lost. 
     In the manner indicated, the state machine of  FIG. 10  allows synchronization to be detected by framer  710  based upon a predetermined number of recognized synchronization values. The predetermined number specifies how many valid packets need to be detected sequentially before it is determined that a valid synchronization lock state has occurred. Likewise, once a valid synchronization lock state has been encountered, the number of missed transport stream packets that must occur can be user defined. 
       FIG. 11  illustrates an Algorithmic State Machine (ASM) diagram in accordance with the framer. Upon reset the flow proceeds to step  602 . 
     At step  602  a variable labeled ByteCnt is set equal to zero indicating the current byte is believed to be the transport stream sync byte, while the variable InSync is also set equal to zero indicating the system is not yet synchronized. At step  602 , the framer  710  is in a state labeled frame 13  byte indicating that the current byte is expected to be a transport stream sync byte, and therefore is to be evaluated. 
     At step  603 , a determination is made whether or not a current byte being evaluated is equal to the hexadecimal value of 47h. When not equal to this value, the flow proceeds to step  621 . At step  621 , a variable synchronization lock count (SyncLockCnt) is set equal to a register value that specifies the number of valid synchronization bytes needed before synchronization is declared. From step  621  flow proceeds back to step  602 . 
     If at step  603  the synchronization byte value is detected, the flow continues to step  604 . At step  604  a variable byte boundary (Byte_Boundary) is set equal to a value bit count (BitCnt), which is zero at step  604 . 
     At step  605  the synchronization lock count variable is decremented to indicate a successful transport stream sync frame detection. 
     At step  606  a next byte is received. At step  606 , the framer  710  is in a state labeled sync_search to indicate the next expected sync byte is being identified. 
     At step  607 , a determination is made whether or not the next byte is the byte to be evaluated for synchronization. If the byte is not to be evaluated the flow proceeds to steps  622  and  606  where the byte count is incremented and a new byte received. In this manner the loop comprising step  606 ,  607  and  622  is expected until the next byte is the expected sync byte to be evaluated is received, and the flow proceeds to step  608 . 
     At step  608  the variable ByteCnt is set equal to zero, allowing for the next transport packet to be identified. Also, the InSync flag is set equal to zero. At step  608 , the framer  710  is in a state labeled sync_lost. 
     At step  609  a determination is made whether or not the current byte has a value equal to the synchronization value. When the value is not equal to the synchronization value a further determination is made at step  623  whether or not the TSTART signal is active. If the TSTART signal is active, indicating that the start of the transport stream is occurring, the flow will proceed to step  608  for further synchronization. However, if the TSTART signal is not active, or not currently used, the flow will proceed to step  602  for further synchronization. If at step  609  a determination is made that the synchronization value matches the current byte, the flow will proceed to step  610 . 
     At step  610 , the variable SyncLockCnt is decremented to indicate successful detection of the transport stream sync value. 
     At step  611  a determination is made whether or not the synchronization lock count value has been met indicating the framer has locked onto the transport stream. In the specific example, since the synchronization lock count is decremented, when the SyncLockCnt value is equal to zero the condition has been met. If the desired number of consecutive synchronization bytes have not been received, the flow proceeds to step  608 . However, if the desired number of consecutive synchronization has been made the flow proceeds to step  612 . 
     At step  612 , the synchronization drop count is set equal to the register value indicating how many sync frames must be missed before synchronization is declared lost, and an interrupt is issued to indicate synchronization lock (SyncLock) has been obtained. 
     At step  635 , a variable InSync is set equal to one to indicate the system is synchronized to the transport stream. Therefore, at step  602 , the framer is in a state labeled sync_lock. 
     At step  636 , a determination is made as to whether or the current byte is the expected sync byte value. If not, the flow proceeds to steps  644  and  635  receiving the next byte and incrementing the byte count value. If so, the flow proceeds to step  632 . At step  632  the InSync variable is maintained equal to one, and the byte count variable is set to zero. At step  632 , the framer is in a state labeled sync_verify. 
     At step  633  a comparison is made of the value of the received byte in order to determine if it is equal to the synchronization value. In the event the byte does match the synchronization value flow proceeds to step  634 , where the sync drop count register is set equal to a predefined register value. By setting the sync drop counter value equal to the register value, it is indicated that a predefined number of synchronization values must be missed before synchronization is deemed to be lost. 
     If at step  633  the synchronization value is not encountered, the flow continues at step  641 . At step  641 , the SyncDropCnt is decremented to monitor how many synchronization bytes missed. 
     At step  642 , a determination is made whether synchronization has been lost. Specifically, synchronization has been lost if SyncDropCnt is equal to zero. If so the flow will continue at step  643 . If not, the flow continues at step  635  previously discussed. 
     At step  643  the SyncLockCnt is set to the number of a valid synchronization values which must be recognized before synchronization lock is achieved, and an interrupt is generated indicating that synchronization has been lost (SyncLost). The flow proceeds from step  643  to step  624 . 
     At step  624 , a determination is made whether or not the signal TSTART is active. In the event TSTART is not active the flow will proceed to step  602  in the manner previously discussed. In the event that the TSTART is active the flow will proceed to step  608  where the proper synchronization signal will be monitored. 
     One skilled in the art will recognize that the state diagram of FIG.  10  and the ASM diagram of  FIG. 11  implement similar methodologies in order to accomplish synchronization to a transport stream using the framer  710 . 
       FIGS. 12-14  illustrates specific registers capable of being utilized to implement specific framer features. For example, various variables described herein are described in the registers of  FIGS. 12-14   
       FIG. 12  illustrates the status and state registers of the framer  710 . A field labeled FramerSyncLock is used to indicate that frame synchronization has been acquired, this is analogous to State D of  FIG. 10 , and/or having arrived at sync_lock, step  635 , of FIG.  11 . 
     A field labeled FramerSyncDrop is utilized to indicate when synchronization has been lost. This is analogous to State A of  FIG. 10 , and/or having arrived at SyncLost, step  608 , of FIG.  11 . This is analogous to the FramerSyncLock variable. 
     The register Field labeled CurrentFramerState indicates one of five states. In a first state, the framer is in the process of capturing a new byte. In a second state the framer is out of transport packet frame synchronization. In the third state, the framer is searching for synchronization. In a fourth state of the framer is checking for synchronization. Finally, in the third state, the framer is in transport packet frame synchronization. Depending upon the location within the state machine of  FIG. 10 , or the diagram of  FIG. 12 , the values of  FIG. 12  will be updated. 
       FIG. 13  illustrates a list of the interrupt registers. A field labeled enable global demultiplexer interrupt (EnableGlobalDemuxInterrupt) is utilized to enable all core interrupts. When negated all the core interrupts would be disabled. 
     An event interrupt mask field (EventInterruptMask) is utilized to mask specific interrupt sources including the FrameSyncLock interrupt, and the FrameSyncDrop interrupt. The framer synchronization drop bit is used to disable an interrupt that would occur when drop synchronization drop has occurred. 
       FIG. 14  illustrates a portion of a configuration register illustrating various field options associated with the framer. A framer sync lock length field (FramerSyncLockLength) comprises 5 bit field used to select the number of consecutive transport packets, with valid sync bytes, that need to occur sequentially to determine synchronization lock has occurred. The field FramerSyncLockLenth is analogous to the variable SyncLockReg of  FIG. 5 , and the register value indicated at steps  621  and  643  of FIG.  11 . 
     A framer sync drop length field (FramerSyncDropLength) comprises a 3 bit field to select a number of consecutive transport packets that must be consecutively missed before the synchronization is declared lost. The field FramerSyncDropLength is analogous to the variable SyncDropReg of  FIG. 10 , and the register value indicated at steps  612  and  634  of FIG.  11 . 
     A framer bit polarity field (FramerBitPolarity) is a single bit used to indicate whether the transport stream data is being received MSB first or LSB first. 
     A framer clock polarity field (FramerClockPolarity) is a single bit that when asserted indicates transport stream data that is latched on a rising clock edge. Conversely, when negated, data is latched on a falling clock edge. 
     A framer mode field (FramerMode) comprises two bits for defining a combination of external transport stream control signals to be used to determine synchronization. In a first mode, only the TSTART value is used to determine when the latched data is valid. In a second mode, the TVALID signal is used determine when synchronization is valid. In the third mode, the framer will use both TSTART and TVALID to determine when synchronization is valid. In the fourth mode, the framer will use TCLOCK and TDATA to latch the bit stream in. 
     Each of the control signals TVALID, TSTART, and TERROR have an respective register fields TVALID Polarity, TSTART Polarity, and TERROR Polarity to indicate whether the signals are active high signals, or active low signals. 
     By providing the control information described in the configuration registers of  FIG. 14 , it is possible to program a decoder core  700  in order to interface to a large number of transport stream protocols. 
       FIG. 15  illustrates a specific implementation of a portion of the framer  710  using the control register information. The implementation utilizes various configuration registers to select modes of operation. In the specific embodiment illustrated, the transport stream data (t_data) is received serially and loaded into four registers  1010  through  1013 . The serially loaded data is provided at a parallel output associated with each of the registers. The parallel outputs of registers  1010  and  1011  are received at inputs of multiplexer  1020 . Parallel outputs of registers  1012  and  1013  are provided to the inputs of a multiplexer  1021 . The parallel outputs from the multiplexers  1020  and  1021  are provided to inputs associated with the multiplexer  1022 . The output of multiplexer  1022  is provided to two bit shifters  1030  and  1031 . Parallel outputs of the bit shifters  1030  and  1031  are provided to a comparator  1040 . 
     In operation, registers  1010  and  1011  receive the serial bits of data on rising clock edge, while registers  1012  and  1013  receive the serial bits of data on falling clock edge. This assures proper storage of data without knowledge of TDATA&#39;s relationship to TCLOCK. Clock triggers registers  1010  and  1011  store the data either from left-to-right, or from right-to-left. By loading data from opposite directions it is assured that whether data is received MSB first or LSB first that the data is stored in a manner consistent with the architecture. For example, a hexadecimal value 11h stored in register  1010  will be stored as a hexadecimal value of 88h in register  1011 . 
     Register field FramerBitPolarity is to select either the MSB first registers  1011  and  1013 , or LSB first registers  1010  and  1012 , while the register field FramerClockPolarity will select the register having the appropriate clock qualification. 
     The data provided to the bit shift registers  1030  and  1031  is shifted bit-by-bit, to provide all possible byte combinations to the sync byte comparator  1040 , which determines when the synchronization value has been encountered, and asserts the control bit in response to a successful compare. When a successful compare occurs, it is assumed that the byte and Packet boundaries have been located. 
     The synchronization hardware illustrated below multiplexer  1022  of  FIG. 15  is isolated from the external clock. This is advantageous over the prior art, in that a loss of the TCLOCK signal does not shut down the control logic associated with synchronization of the transport stream. 
     In accordance with the present invention, it is possible to provide a flexible framer capable receiving a variety of physical transport stream formats and determining synchronization when only clock and data are present, and to provide appropriate synchronization control signal. 
     One skilled in the art will recognize that many specific implementations of the framer can be incorporated. For example, the framer may have a first in first out (FIFO), or other type buffer associated with it. In addition, instead of selecting specific configuration parameters using registers, other configuration specification means could be used, such as making them pin selectable, or any other of various types methods capable of describing selectable features. 
       FIG. 16  illustrates a more detailed view of the TPP  720 . TPP  720  further includes storage locations  721 , a counter controller  722 , register controller  723 , video PID location  724 , and adaptation field start detect circuit  725 . 
     In the implementation shown, each of the various header fields of a transport stream packet have a storage location within the storage locations  721 . Because the transport stream data is received on a byte-by-byte basis, and because the header field locations are fixed, the data for the individual fields is readily obtained. In the embodiment of  FIG. 16 , each storage location for a specific data field is connected to the appropriate bits of the data bus, and the counter controller  722  provides enable signals to each field location to load values at the correct time. 
     Once a specific field has been parsed, register fields dependent upon the specific field can be updated. The register set  780  is accessed and updated by the register controller  723  of  FIG. 16 , which is connected to storage locations  721 . In addition, the register controller  723  can retrieve register data as needed. For example, the value stored in the video PID storage location  724  is retrieved from register set  780  by the register controller  723 . 
     The TPP  720  generates the VIDEO signal, which indicates the current packet is a video packet, by comparing the value stored in the video PID location  724  to the PID value stored in storage locations  721 . When a match is detected, a video packet has been received. When the VIDEO signal is asserted and the Payload start indicator is also asserted, the packet is the first packet of a new video PES, and the VSTART signal is asserted. 
     The TPP  720  generates the AFSTART signal using the start detect module  725 , which monitors the value of the adaptation control field, which in turn specifies the start of a new adaptation packet 
     The TPP  720  generates the PCR signal, which indicates the current packet is responsible for providing program count reference (PCR) values to the video decoder associated with the video memory of the system of  FIG. 7  or FIG.  4 . When a match is detected, the PCR related fields of the packet need to be parsed to determine if PCR data has been provided. When both the VIDEO and PCR signals are asserted the PCR data is retrieved from the video packet. 
       FIG. 17  illustrates another portion of the TPP  720  that determines if a specific packet is to be saved.  FIG. 17  includes an allocation table  727 , an output data controller  726 , and a portion of the storage locations  721 . 
     In operation, the Output data controller  726  provides data packets to the Buffer controller  760  of  FIG. 7 , when the PID value associated with the data packet is included in the allocation table  727 . Therefore, each valid entry of the allocation table  727  is compared to the current PID value stored in storage location  721 . If any of the valid entries match, the Output data controller  726  will provide the entire packet to controller  760  for storage. Because the current PID value is not available until after the fourth byte of the header is received, the output data controller  726  saves the first three byte in case they need to be stored. 
     The allocation table  727  illustrated lists 32 PID indexes (PID_ 0 -PID_ 31  ) which have PID values associated with them. The allocation table  727  can actually be an abstraction of register locations from the register set  780 .  FIG. 18  illustrates video control registers, which are a portion of the register set  780 . The PID value associated with the PID_ 0  entry of the allocation table  727  is defined to be the active video PID value, which is received from the VideoPID field of the Video Control Registers of FIG.  18 . Likewise,  FIG. 19  illustrates Demultiplexer Control Registers, which are a portion of the register set  780  used to identify packets, other than current video packets, which are to be saved. The PID values associated with the PID_ 1  through PID_ 31  entries of the allocation table  727  are received from their respective register locations within the Demultiplexer Control Registers of FIG.  19 . For an entry to be valid, the EnableParsing field of the PID register needs to be enabled. 
     If a received packet&#39;s PID number is not listed in the PID Allocation Table, the packet is not processed further, i.e. discarded, and the next received TSP is analyzed. However, if the PID of the current packet is listed in the PID allocation table, and it is not the video PID, the packet is saved to memory. 
       FIG. 20  illustrates a method associated with the TPP parser. At step  211 , the TSP is received by the framer as discussed with reference to  FIGS. 10 and 11  herein. 
     At step  212 , the packet is received at the TPP. In the manner discussed herein, the packet is made available to the TPP one byte at a time. The framer provides an indicator where the first byte of the packet is located. 
     In response to receiving the first byte of the packet, the TPP will parse the packet header at step  213 . From the parsing of the header, the TPP will retrieve the PID value of the packet. 
     At step  214 , a determination is made whether the packet is identified as a valid packet. As previously described, one way to be identified as a valid packet is be specified in an allocation table, which can be derived from specific register information. When a PID value is listed in the allocation table, the packet is to be further processed. 
     At step  215 , a determination is made whether the packet is a packet that is to be additionally parsed. For example, step  215  specifically indicates that a determination is being made whether the PID value indicates the packet is a video packet. If so, flow proceeds to step  226  for video parsing as indicated in FIG.  22 . If the PID does not indicate a packet for special processing, i.e. not a video packet, the flow proceeds to step  227  where the data is send the buffer controller for storage, as indicated with reference to FIG.  22 . 
     When the PID allocation table, or other means, indicates the packet is a video packet the Packetized Elementary Stream Parser (PESP) is enabled to allow further processing. In the specific embodiment of the PID allocation table listed above, the video PID is stored as PID_ 0 . However, other methods of identifying the video PID, such as the use of a flag or other indicator are also possible. The operation of the PESP is controlled by the PESP Control Registers, as illustrated in FIG.  18 . 
       FIG. 21  illustrates the PESP  730  in greater detail. PESP, of  FIG. 21 , includes a counter controller  752 , storage location  751 , register controller  753 , data output controller  756 , video data control module  755 , and portions of register set  780 . 
     In the implementation of  FIG. 21 , a storage location within the storage locations  751  is reserved for the STREAM ID header field of a transport stream packet. In the embodiment shown at  FIG. 21 , inputs of the storage location for STREAM ID are connected to the appropriate bits of the data bus and the counter controller  752 , to receive stream ID data from the FRAMER DATA representation of the transport stream at the correct time. The counter controller  752  receives the VSTART signal indicating the start of a new video PES and generates enable signals to capture the stream ID, and other information, from the video PES header. The counter controller is controlled by the signals VIDEO, FRAMER DEN, and VSTART. The VIDEO signal indicates the current packet is a video packet. The FRAMER DEN signal indicates when the current FRAME DATA byte is valid, and VSTART indicates when the current packet is the first packet for the video PES, in other words, VSTART indicates when the video packet contains video PES header data to be parsed. Based upon the VSTART signal, and the FRAMER DEN signal, the counter controller  752  can determine which byte of the header is currently being received. 
     In another implementation, control module  755  is controlled by the EnableParsing field (not shown in  FIG. 21 ) of the video control registers of FIG.  18 . The EnableParsing field is a one bit field, which when deasserted, prevents further parsing of the video packet by the video PESP. Therefore, when the EnableParsing field is negated, the header of the video packet would not be parsed, and therefore, the packet would be discarded. The counter controller can be controlled directly from the EnableParsing bit of the video control registers, or indirectly where the VIDEO signal is disabled by the TPP  720  in response to the EnableParsing bit being deasserted. 
     Once the video PES header field has been parsed, register fields dependent upon the specific fields of the video PES header can be updated. The register set  780  is accessed and updated by the register controller  753  of  FIG. 21 , which is connected to storage locations  751  of the PESP. In addition, the register controller  753  can retrieve or access register data as needed. For example, the values EnableParser, ProcessStreamID, and StreamID are register values from register set  780 . 
     The video data control module  755  contains logic that enables the video data payload of the present packet to be stored. Operation of the control module  755  is determined in the content of various video control registers, as illustrated in FIG.  18 . The EnableParsing field is a one bit field, which when negated prevents any data from the current video packet from being saved. The ProcessStreamID field is 1 bit-field. When asserted, it enables further parsing based upon a specific stream ID value of the video PES header, such that if the video control register field StreamID of  FIG. 18 , does not match the parsed steam ID from the current packet, the data of the packet will not be saved. This is an advantage over the prior art, where filtering on the stream ID field of the video PES was done in software, generally by the system. 
     In the specific implementation illustrated, only the data payload of the video PES is stored. Since the parsing is done in hardware, there is no need for the header information to be stored. 
     In another embodiment, the field labeled StartFromPUSICommand is used to indicate whether video PES parsing is to start immediately with the next packet or wait until a new PES stream is received as indicated by the VSTART signal, where the acronym PUSI stands for Payload Unit Start Indicator and is a part of MPEG-2 syntax. Once the new video PES stream is identified, the StartFromPUSICommand field is negated, and all subsequent video packets are further processed by the PESP. 
     The video PESP parser is bufferless in that no local buffers are used to store the payload data for access by other parts of the system. The prior art parsers stored the parsed data in large buffers locally, which were then capable of being accessed by system components by requesting access to the local bus. The bufferless parsers of the present invention do not store data locally for access by the system. Instead, parsed data to be buffered is transmitted to the buffer controller  460 , which buffers data in system or video memory. 
       FIG. 22  illustrates a method associated with a video PESP parser. At step  216 , the PESP has received an indication that video packet is ready to be parsed. The notification can be directly from the TPP, a polling mechanism, or other type interrupt. Step  216  determines whether parsing of video stream is enabled. This can be determined based upon the field labeled EnableParsing of the video control registers of FIG.  18 . When parsing of the video packet is not enabled, a specific action will occur. One action would be to perform no further processing of packet, as illustrated. In another implementation, the packet would be automatically stored without further parsing, perhaps with the packet header field. When parsing of the video packet is enabled, the flow proceeds to step  217 . 
     At step  217 , a determination is made whether the packet is to be parsed immediately, or whether parsing of video packets is to wait until a new video PES is detected. If the packet is to be parsed immediately, the flow proceeds to step  223 . If the packet is not to be parsed immediately, flow proceeds to step  218  to determine when the proper criteria for parsing is met. Field StartFromPUSICommand indicates whether parsing is to be immediate. 
     At step  218 , a determination is made whether the present packet is the first packet of the video PES. If the packet is a new video PES packet, the field StartFromPUSICommand is disabled, and flow proceeds to step  219 . If the new packet is not the first packet of a video PES, the flow will terminate as indicated with no further processing. 
     At step  219 , a determination is made whether the current video packet is to be parsed based upon the packet stream ID. If so, flow proceeds to step  220 , if not, flow proceeds directly to step  223 . 
     At step  220 , the PESP parses the stream ID from the PES header as discussed with reference to FIG.  21 . In addition,  FIG. 23  illustrates addition hardware parsing which can be performed by the PESP. 
     At step  222 , a determination is made whether the parsed steam ID from the PES header is equal to the value stored at register field StreamID of the video control registers of FIG.  18 . If so, the field StartFromPUSICommand is disabled to allow subsequent packets associated with the video PES to be stored, and flow proceeds to step  223 . If no match occurs, the flow terminates as indicated, and no further processing occurs. 
     At step  223 , the packet data is sent to the buffer controller for storage, as discussed with reference to FIG.  24 . 
     Note that additional parsing steps can occur between steps  217  and  223 , such that from step  217  additional parsing would occur. The parsing steps illustrated in  FIG. 22  are all by-passed if the current transport stream packet is to be immediately routed to a system memory and parsed by the host processor. 
       FIG. 23  illustrates additional parsing features of the PESP  730 .  FIG. 23 , includes a counter controller  752 , storage location  751 , register controller  753 , and data output controller  756 . 
     In the implementation of  FIG. 23 , a storage locations within the storage locations  751  are reserved for the specific PES header field of the Packetized Elementary Stream. In the embodiment of  FIG. 21 , inputs to the storage locations  751  for specific PES header fields are connected to the appropriate bits of the data bus, while the counter controller  752 , which receives the VSTART signal indicating the start of a new video PES, receives PES header data from the FRAMER DATA representation of the transport stream at the correct time. 
     The counter controller  752  will generate enable signals to capture the various PES header fields based upon the values stored in locations  736 , and a counter value generated by counter  737 . The counter controller is controlled by the signals VIDEO, FRAMER DEN, and VSTART. The VIDEO signal indicates the current packet is a video packet. The FRAMER DEN signal indicates when the current FRAME DATA byte is valid, and VSTART indicates when the current packet is the first packet for the video PES, in other words, VSTART indicates when the video packet contains video PES header data to be parsed. Based upon the VSTART signal, and the FRAMER DEN signal, the counter controller  752  can determine which byte of the header is currently being received. As indicated with reference to the StartFromPUSICommand register of  FIG. 18 , the counter controller can either allow for immediate PES parsing upon receiving a video packet, or it can wait to parse the PES data until a packet containing PES header information is received. Where PES parsing is immediate, the video data is provided to the output buffer. 
     In operation, a compare operation determines if the present counter  737  values is equal to any of the values stored in location  736 . If so, it indicates that the current clock cycle is providing data to be stored in one of the fields of storage locations  751 . As a result, the controller  752  will generate an enable to the appropriate one or more fields represented in the current clock cycle, and the field data will be latched. 
     The compare function  738  can be implemented in many different ways. For example, a state machine or logic can be used to indicated which of the storage locations  751  are to be stored at a specific time. In addition, feedback is provided to the controller  752  from various storage locations  751  to assure proper operation. For example, all PES header will have the field portions  766  of storage location  751 . However, depending upon various values of these, and other fields, the field portions  767 - 769  may or may not be present in a particular PES header. 
     For example, whether the fields portions  767  exist in a current header is determined by whether the binary framing indicator “10” immediately follows the PES packet length field as in  FIG. 3 , and as stored in the OptionalHeader indicator field. This OptionalHeader indicator field is compared to the expected value and the results are provided to the controller  752  to indicate additional parsing is to be done. As a result, the parser  752  continues to generate control signals to store the fields associated in the field portions  767 . 
     In a similar manner, the Flags field of storage portion  767  indicates which of the storage portions  768  are present, and the ExtentionFlags of storage portion  768  indicate which of the storage portions  769  are present. In this manner, the controller  752  determines which header fields are present and need to be stored in storage locations  751 . 
     Once the video PES header field has been parsed, register fields dependent upon the specific fields of the video PES header can be updated. The register set  780  is accessed and updated by the register controller  753 , which is connected to storage locations  751  of the PESP. In addition, the register controller  753  can retrieve or access register data as needed.  FIG. 24  illustrates a subset of the Status Register Fields associated with on implementation the PESP, while  FIG. 25  illustrates interrupt mask registers having corresponding bits. 
     Once the header has been completely parsed, the data associated with the payload portion of the current PES packet can be provided to the data output controller  756  as discussed with reference to FIG.  21 . In an alternate embodiment, the 16 bytes of optional PESPrivate data associated with the PES header and stored in storage locations  769  are provided external the PESP to a private data packetizer as will be discussed in greater detail herein. 
       FIG. 26  includes a detailed view of buffer controller  460  of  FIG. 5 , video bus/memory controller  488 , system bus/memory controller  468 , video memory  471 , and system memory  472 . In the specific embodiment illustrated in  FIG. 26 , the buffer controller  460  includes a data path for handling video PES data to be stored in the video buffer  500  of video memory  471 , and a data path for handling other PES data that is to be stored in system memory buffers  501 - 503  of the system memory  472 . The data path for handling other PES data includes the System FIFO (First In First Out) controller  466 , FIFO  462 , and System HBI (Host Bus Interface) Controller  463 . The data path for handling video PES data includes a Video FIFO controller  486 , FIFO  461 , Video HBI Controller  483 . Each of the System and Video data paths accesses transport demultiplexer register  465 . 
     In operation, the System FIFO controller  466  provides an interface between the Parsers of  FIGS. 5 and 7  and the FIFO  462 . The controller  460  allows filtered packet data to be received and stored in FIFO  462 . Once stored in the FIFO  462 , the System HBI controller  463  requests access to the system memory  472  through the controller  468 . The controller  468  may include a system bus controller, a memory controller, or a combination of a memory/system bus controller. Generally, the controller  468  will control access to other system resources as well. 
     In accordance with the invention, the System Memory  472  has been partitioned by the system host to include one or more system circular buffers  501 - 503 . The system buffers  501 - 503  are implemented as circular buffers and are filled by operation of the controller  483 . The controller  483  handles the buffer “write” pointer. The “read” pointer for the buffers is managed by the software on the system host side (not shown) which retrieves data from the buffers  501 - 503 . There can also be a “high water” mark register associated with each buffer (not shown). The purpose of a “high water” mark register is to provide an interrupt when the write pointer crosses the value in this register. However, because there is generally only one interrupt for each of the plurality of buffers, software polling can be used to determine the cause of the interrupt. 
     In a specific implementation, the number of system buffers is limited to 15 buffers. The transport core may use fewer than 15 buffers. More than one PID per buffer is allowed. However they have to be different, i.e. the same PIDs can not be allocated to more than one buffer (i.e. one TSP packets can be routed into only one destination ring buffer). The Transport Demultiplexer registers of  FIG. 19  are used to specify where data associated with a specific PID is to be stored. For each PID to be saved, a buffer index is used to specify one of the 15 buffer locations in system memory. Multiple PID types can be stored at a common buffer by specifying the same buffer in the BufferIndex field. In an alternate embodiment, data associated with all system PIDs can be stored to a single buffer, which may be specified or defined by default. Note with reference to  FIG. 7 , the buffer index, or location, can be determined by one of the parsers, and provided to the Buffer controller  760 . 
     The video data path of  FIG. 26  is handled in a manner analogous to the system path described above. However, in the specific embodiment, only one buffer, in video memory, is associated with the video path. 
     The physical memory location and the size of the ring memory buffers  500 - 503  is specified by the system host using buffer configuration and management registers (not shown). The host processor has to initially specify buffer start address and length of the buffer. Other buffer data can also be used, for example, a threshold register can be implemented. 
     The size of the video buffer depends on horizontal and vertical pixel resolution, frame rate, profile and level, maximum bit rate and video buffering verifier (VBV). ATSC requires a buffer of minimally 0.95 MB (VBV=488); while for MPEG-2 Main Level at High Profile, the size is 1.17 MB (VBV=597). The buffer controller  460  will manage a write pointer for the video stream. The read pointer is managed by the control  488  associated with the video adapter. Hardware or software can generate an interrupt if the write pointer is equal to the read pointer−1 (overflow condition). 
     Regarding the audio buffer requirements, the worst case is for a when the nominal audio bit rate 640 kbps with sampling frequency of 32 kHz. The actual size of the compressed bit stream audio buffer depends on a priority and the rate of occurrence of the audio decoder thread, when audio is decoded in software. 
     On a channel change, software will flush the buffers by setting the read pointers to be equal to the write pointers after the transport stream parser has been turned off. 
       FIG. 27  illustrates a method in accordance with the present invention describing the operation of the system HBI controller  463  of FIG.  26 . The flow is also applicable to the video HBI controller  483 . At step  801 , a determination is made whether there is data stored in the FIFO  462 . If not, flow remains at step  801  until data is present, otherwise, the flow proceeds to step  810 . At step  810 , the buffer to which the data is to be stored is identified. The destination buffer is identified when matching and crossing the PID number, or identifier, to the buffer number in the transport demultiplexer register  465 . The buffer can be identified by accessing the allocation table, or by receiving a buffer index from the transport parser or other portion of the transport core. 
     At step  802 , a determination is made whether the identified buffer is full, or otherwise not capable of receiving additional data. If the buffer is not capable of receiving additional data, the flow loops back to step  802  through step  811 , which implements a delay. Note the delay of step  811  may be a fixed delay, as result of polling to determine if the buffer is full, or the delay of step  811  may be variable, such as where the delay is based an interrupt which indicates when the buffer is available. Once the desired buffer is no longer full, flow proceeds to step  803 . 
     At step  803 , a bus request is made to allow access to one of the buffers  501 - 503 . Once the bus connected to the buffer has been acquired, the next block of data is written to the appropriate buffer at step  804 . A block of data can be a word, double word, or any other size of data specified by the system. In a specific embodiment, the parsers of  FIG. 5  assure data is provided to the FIFO only in whole blocks by always writing entire blocks of data to the FIFOs. 
     At step  805 , a determination is made whether the identified buffer  501 - 503  is now full. If so, the flow proceeds to step  807  where the bus is released, if not full, the flow proceeds to step  806 , where it is determined if more data is to be written. 
     At step  806 , a determination is made whether more data resides in the FIFO  462 . If so, flow proceeds to step  804 , otherwise, the flow proceeds to step  807  where the bus accessing the Buffer is released and flow returns to step  801 . In another embodiment, the bus would be released after each block is transferred, instead of determining if more data is to be written. By implementing the flow of  FIG. 26 , the data stored in the FIFO  462  is transferred to the buffers. 
     The buffer implementation described provides an advantage over the prior art in that moving the buffers in to system and video memory associated with an external system, such as a general purpose computer, allows for bufferless parsers. As a result, the system and video resources do not have to wait to access buffers local to the parsers. The performance improvements using bufferless parsers has been observed by the present inventors to be up to 40% over the prior art. In addition, by allowing for parsing of the PES data, it is possible to limit the amount of bandwidth used to store unused data. One skilled in the art will recognize the present invention has been described with reference to a specific embodiment, and that other implementations and variations of the present invention would be anticipated. For example, when a TSP is “sent” from the TP to the PESP or the buffer controller, it is to be understood that not necessarily all of the header information need be sent. In fact, in would generally be necessary for only the PID associated with the packet be forwarded. In addition, the location and implementation of the register sets and functionality described herein can be partitioned in ways other than the specific implementations described. 
     The AFP parser  750 , illustrated in  FIGS. 5 and 7 , parses data associated with the adaptation field of a transport packet. The Transport Packet Parser  720  enables operation of the Adaptation Field Parser  750  when the adaptation field of the header indicates the presence of an adaptation field.  FIG. 28  illustrates, in block diagram form, a detailed view of the Adaptation Field Parser  750 . 
     The AFP  750  illustrated in  FIG. 28  includes adaptation control counter  782 , latch  785 , register logic  786 , and storage and register locations  781 ,  783 , and  784 . In operation, the adaptation control counter  782  receives signals on connections labeled AF START, FRAMER DEN, and FRAME DATA. The connection labeled AF START receives signals from the Transport Packet Parser  720 , and indicates the beginning of the transport packet&#39;s adaptation field. The connection labeled FRAMER DEN receives signals from the Framer  710 , and indicates when each new byte of data is available on the FRAMER DATA bus. Based upon the received signals, the adaption control counter  782  provides the control signals necessary to parse specific field information data received on the FRAME DATA bus. 
     In operation, the Transport Packet Parser  720  will assert a signal on to the connection AF START in response to the adaptation field control portion of the transport packet header indicating the presence of an adaptation field. The signal on the AF START connection will be asserted in relation to the assertion of the first byte of adaptation field data onto the FRAMER DATA bus. 
     The first byte of the adaptation field indicates the length adaptation field. Therefore, the adaptation control counter  782  will latch the first byte of the frame data into a storage location labeled AF LENGTH to determine the length of the adaptation field. Accordingly, the adaptation field has a variable length between 1 and 183 bytes long. By decrementing the adaptation field length by one as each new byte of data is received on the FRAME DATA bus, the adaptation control counter  782  can monitor which fields, or field portions, of the adaptation field are present on the FRAME DATA bus at a specific time. Accordingly, the adaptation control counter  782  provides operational control signals to each of the storage locations of storage portion  781  to correspond to the presence gets data on the FRAME DATA bus. 
     Generally, the storage locations  781  correspond to specific registers of the register set  780  of FIG.  7 . For example, the discontinuity indicator field is known to be the first bit, of the second byte, of the adaptation field. Therefore, the storage location labeled Discontinuity Indicator of storage area  781  will be connected to only the first bit of the FRAME DATA bus. Furthermore, logic associated with the Adaptation Control Counter  782  will provide a latch control signal to the Discontinuity Indicator of storage location  781  only when the counter associated with the Adaptation Control Counter  782  indicates the second byte of data is present on the FRAME DATA bus. In a similar fashion, the other specific adaptation bit-fields associated with locations  781  will be parsed. Note that the individual locations of storage locations  781 , may be the actual register locations of register set  780 , or may be storage locations local to the adaptation field parser  750 . Where the storage locations are local to the parser  750 , a register control portion (not shown) can be used to update values within the register set  780 . 
     The Optional Flags field of storage locations  781  is connected back to the adaptation control counter  782  in order to provide feedback. The need for this feedback is best understood with reference to prior art FIG.  1 . Prior art  FIG. 1  illustrates that the adaptation field can include five optional fields. The presence of each of these five optional fields is indicated by flag bit. The field labeled Optional Flags represents the five flags of the adaptation field to indicate the presence of the optional fields. Therefore, by providing feedback from the optional field location, the adaptation control counter  782  can correctly determine which optional field data is present, and when to receive optional field data. 
     Storage locations  784  generally represent register locations whose values are determined based upon the parsed information of storage locations  781 . Specifically, the register logic  786  monitors the operation of the adaptation control counter  782  and/or the contents of the locations  781  to determine when the PCR value has been received. In addition, the displaced countdown value received at the adaptation field parser is monitored determine when the actual video splicing point occurs. 
     When the optional flags indicate that the optional fields includes transport private data, the adaptation control counter  782  will provide the private data from the FRAME DATA bus to a PESP PRIVATE DATA bus through either directly, or through a latch  785 . In addition, the adaptation control counter  782  will provide a signal to a node labeled PRIVATE DATA ENABLE to indicate when the PESP PRIVATE DATA bus has valid data. In one embodiment, the PRIVATE DATA ENABLE node is clocked for each valid byte of data written to the PESP PRIVATE DATA bus. In another embodiment, the PRIVATE DATA ENABLE node would include multiple nodes, whereby one node pulsed to indicate each valid byte of data written to the PESP PRIVATE DATA bus, while the other node indicated the valid PESP private data cycle. The valid PESP private data node would be asserted for the entire assertion of PESP private data from a common transport packet. 
     Operation of the adaptation field parser  750  is better understood with reference to  FIGS. 29 through 31  which illustrates portions of the register set  780  associated with the adaptation field parser  750 . Specifically,  FIG. 29  illustrates status registers,  FIG. 30  illustrates interrupt mask registers, and  FIG. 31  illustrates control registers. 
       FIG. 29  illustrates a number of status register fields associated with the register set  780  of  FIG. 7 , which are associated with the operation of the adaptation field parser  750 . Video AFPcrReceived is a single read bit, which is set to 1 after arrival and extraction of the PCR sample in the adaptation field. The assertion of this bit will cause an interrupt be generated if the VideoAFPPcrReceived bit of the event interrupt mask is enabled. Subsequent read access of this field will cause it to be cleared. 
     Register field VideoAFPcrDiscontinuity is a single bit of R/W field data that is set to 1 when a discontinuity indicator in the adaptation field is asserted. The assertion of this bit will cause an interrupt to be generated if the VideoAFPCRDiscontinuity bit of the event interrupt mask of  FIG. 30  is enabled. Subsequent access of this field by software will cause the field to be cleared. 
     Register field VideoAFDiscontinuityFlag is a single bit R/W field that is set to 1 after a discontinuity indicator flag has been asserted in the adaptation field of the video transport packet. Assertion of the discontinuity indicator flag indicates discontinuity on the continuity counter. The assertion of this bit will cause an interrupt to be generated if the VideoAFDiscontinuityFlag of the event interrupt mask register of  FIG. 30  is asserted. The subsequent access of this field by software will cause this field to be cleared. 
     Register field VideoAFRandomAccess is a single bit R/W field that is set to 1 when the video packet has a random access flag asserted in the adaptation field. This indicates the start of the new elementary stream. The assertion of this bit will cause an interrupt be generated if the VideoAFRandomAccess bit of the event interrupt mask register of  FIG. 30  is asserted. The subsequent access of this field by software will cause the field be cleared. 
     Register field VideoAFSplicingFlag is a single bit R/W field that is set to 1 when the video packet has the splicing point flag asserted in the adaptation field. This flag indicates that a splicing point is approaching. The assertion of this bit will cause an interrupt to be generated if the VideoAFSplicingFlag bit of the event interrupt mask register of  FIG. 30  is asserted. The subsequent access of this field by software will cause the field to be cleared. 
     Register field VideoAFSplicingPoint is a single bit R/W field that is set to 1 when the video packet has the VideoAFSplicingFlag asserted and the AF Splice Countdown register has a value of 0. The setting of this bit is controlled by the register logic  786  of FIG.  28 . The assertion of this bit will cause an interrupt to be generated if the VideoAFSplicingPoint bit of the event interrupt mask register of  FIG. 30  is asserted. The subsequent access of this field by software will cause the field to be cleared. 
     Register field VideoAFPrivateData is a single bit R/W field, which when set to 1 indicates the video packet has adaptation field private data. The assertion of this bit will cause an interrupt be generated if the Video AF Private Data bit of the event interrupt mask register of  FIG. 30  is asserted. The subsequent access of this field by software will cause the field to be cleared. 
     Register field AFSpliceCountdown is a byte wide R/W field that contains the current splice countdown value from the current adaptation field. 
       FIG. 31  illustrates control registers associated with register set  780  that control operations associated with the Adaptation Field Parser  750 . 
     Register field EnabledAFPrivateData is a single bit R/W field that when asserted enables parser of the adaptation field private data. 
     Register field AFPrivateDataBufferIndex is a four bits field which specifies 1 of up to 15 destination buffers in the system memory where the private data is to be stored. 
     Register field PCRIndex is a five bits field which specifies one of 32 PID values from which the PCR data is to be extracted. 
     Register field Enabled Auto Splicing is a single bit R/W field that enables automatic splicing of the video elementary stream. 
       FIG. 32  illustrates an alternate embodiment of a portion of the transport demultiplexer illustrated in FIG.  7 . Specifically,  FIG. 32  illustrates a Private Data Packetizer  740  connected to the Adaptation Field Parser  750  and the Video PESP  730 . The Adaptation Field Parser  750  is connected to the Private Data Packetizer  740  through the AFP PRIVATE DATA bus and node PRIVATE DATA ENABLE. The Video PESP  730  is connected to the Private Data Packetizer  740  through the bus labeled VIDEO PRIVATE DATA and node labeled VIDEO PRIVATE DATA ENABLE. The Private Data Packetizer  740  receives private data from the AFP  750 , and video PESP  730  and associated control signals. In turn, private data packetizer  740  provides the private data packet on a bus labeled PRIVATE DATA to buffer controller  760 , and a control signal on the node labeled PRIVATE DATA ENABLE to the buffer controller  760 . 
     In operation, private data associated with the video PESP  730  has a fixed length of 16 bytes. However, the private data associated with the transport packet, which is parsed by the AFP  750 , has a variable length from 1 to 181 bytes. Because the FIFOs  761  and  762  of the buffer controller  760  store double words, it is possible, and in fact likely, that the private data associated with the adaptation field of transport packet will not provide to the FIFOs private data that ends on a double words boundary. The significance of this is best understood with a discussion of the operation of one embodiment of the buffer controller  760 . 
     During normal operation of the buffer controller  760 , bytes of data associated with transport packets from the Transport Packet Parser  720  and video data from the Video PESP  730  are provided to the buffer controller  760 . Each parser has a corresponding double word buffer in the buffer controller  760 , which receives and stores the individual bytes of data until an entire double word has been received. For example, the first byte of data provided by the Transport Packet Parser  720 , is stored in the first byte location of a double word buffer  763 , while the second, third, and fourth data bytes will be stored in second, third, and fourth byte locations of the double word buffer  763  respectively. When the double word buffer  763  has received the fourth byte, the double word is written from the double word buffer  763  to the FIFOs  761 , thereby freeing up the double word buffer  763  for subsequent bytes. 
     When a specific data packet of a packetized elementary stream does not end on a double word boundary, the double word buffer  763  will be partially filled and therefore not send the end of the reception of the specific data packet. However, this is not a problem if specific data packet is repeatable over many packetized elementary streams, because the subsequent data packet associated with the same packetized elementary stream can be expected to be received within a relatively short amount of time to complete filling the double word buffer. Once the double word buffer is filled using data bytes from the subsequent data packet, the field double word buffer  763  will be sent to the FIFOs  761 . 
     While it is not problematic for a specific packet of a packetized elementary stream to not completely fill the double word buffers associated with the buffer controller  760 , the same is not true of private data associated with specific transport stream or packetized elementary stream. This is because the private data associated with packetized elementary stream has a fixed length and is not streaming data of the type associated with the transport packet parser  720  or the video of the video PESP  730 . Because the private data from be transport packet has a variable length, there is no guarantee that the private data will end on a double word boundary. If the private data does not end on a double word boundary, the partial double word portion of private data at the end will not be sent to the FIFO until additional private data from unrelated source is received. Therefore, the system software that interprets private data, would have incomplete data. The private data packetizer  740 , illustrated in  FIG. 32 , addresses this problem. 
     In operation, the private data packetizer  740 , can receive private data from each of the Adaptation Field Parser  750 , and the Video PESP Parser  730 , and forms a private data packet to be sent to the buffer controller  760 , which is guaranteed to have a length that ends on a double word boundary. Note that both the packetized elementary stream data from the Transport Packet Parser  720 , and the private data generated by the private data packetizer  740  are sent to the system FIFOs  761 . An index indicator, which specifies which circular buffer in system memory the private data is to be stored, is provided to the FIFOs  761 . The index indicator is specified in the register field labeled AFPrivateDataBufferIndex, which was discussed with reference  FIG. 31  herein. Therefore, all private data, whether from the Adaptation Field Parser  750  or from the Video PESP  730 , is been provided to the same buffer in system memory.  FIG. 33  illustrates the private data packetizer  740  in greater detail. 
     The private data packetizer  740  of  FIG. 33  includes counter controller  741 , the AF Data Type Code storage location  742 , PES Data Type Code storage location  743 , Stuffing Code storage location  744 , AFP Data Latch  745  PESP Data Latch  746 , and fixed length Indicator Code  747 . 
     The Af Data Type Code storage location  742  stores the specific eight-bit type indicator associated with adaptation field private data. The PES Data Type Code storage location  743  stores the specific the eight-bit type indicator associated with the PESP private data. The Stuffing Code storage location  744  stores the specific eight-bit stuffing code which is used to pad private data packet to insure the private data packet always ends on a double word boundary. The AFP Data Latch  745  is used to store the actual private data from the adaptation field parser to be provided to the buffer controller  760 . Similarly, the PESP Data Latch is used to store the actual private data from the PESP parser is to be provided to the buffer controller  760 . The fixed length indicator code  747  stores the fixed length value associated with the PESP parser private data. In the specific example, the PESP parser private data will always be 16 bytes of data, or 0x10 hexadecimal. 
     In operation, the counter controller  741  can be enabled either by be AFP Data Enable signal, or by the PESP Data Enable signal. When the counter controller  741  is enabled by the PESP Data Enable signal, the number of bytes of private data is fixed at 16 bytes, therefore, the value of 16 will be used by be AFP counter controller  741  to generate the appropriate signal for the PRIVATE DATA bus. Unlike PESP private data, AFP private data has a variable length. The actual number of bytes of AFP private data, not including the length byte, is transmitted in the first byte of the AFP private data field of the data packet. Therefore, the counter controller receives the number of bytes of transport packet private data by latching the first byte of the private data field of the data packet. The first byte of the private data field is received on the APP DATA bus on or after the PES Data Enable signal has been received. Based upon the source of the private data and the length of private data, the private data packetizer  740  will construct the private data packet. 
       FIG. 34  illustrates a specific embodiment of a private data packet generated by the private data packetizer  740 . Data block  771  illustrates the format of the private data packet having specific fields: type, length, data, and stuffing. 
     The type field of the private data packet indicates the source of the private data, either transport packet private data, or video PES data. In a specific embodiment, the hexadecimal value of 0x55 is used to indicate private data associated with the transport packet received from the AFP  750 , and a hexadecimal value of 0xAA is used to indicate private data from the video PES received from the video PESP. Note that in other embodiments of the present invention, additional data types can be received from other sources. 
     The length field of the private data packet specifies the length of private data that is to follow the private data packet. Note that in the specific embodiment illustrated, be value of the length field does not include a count for the length field byte. 
     The stuffing field of the private data packet is used to assure the private data packet ends on a double word boundary. As indicated, the stuffing field can include zero to three bytes of data. 
     Data block  772  of  FIG. 34  illustrates a private data packet associated with the video PES stream. Specifically, private data packet  772  has a type value of hexadecimal value 0xAA indicating the private data packet is associated with a video PES. The length field of packet  772  has a hexadecimal value of 0x10, which indicates that 16 bytes are contained within the subsequent data field. Accordingly, the subsequent data field of the private data packet includes 16 bytes, 0 through F. Because the length of the fields type, length, and data is no one, the number of stuffing bytes needed to insure the private data packet ends on a double word boundary is readily determined. Therefore, two stuffing bytes of 0xFF are represented in the stuffing field of private data packet  772 . 
     By adding to stuffing bytes in the stuffing field of the private data packet, the length of the private data packet ends on a double word boundary. Therefore, when the data bytes of the private data packet  772  of  FIG. 34  are provided to the buffer controller  760 , and more specifically to the double word buffer  764  of the buffer controller  760 , it is assured that the entire private data packet will be provided to the FIFOs  761  without delay. Once the data is provided to the FIFO  761 , the double word of data will be provided to the appropriate buffer in system memory. System software will, therefore, be able to access the private data stored in system memory without delay, and determine the type of data based upon type field, and length of the data based upon length field. Private data packet  773  of  FIG. 34  illustrates another specific private data packet. Specifically, packet  773  has a type value of hexadecimal value 0x55, which represents an adaptation field data packet. The length field of the packet  773  has a hexadecimal value of 0x0F, which indicates 15 bytes of data are associated with the adaptation field private data. As a result, 15 bytes of data 0 through E are represented in the data field, and a total of three stuffing bytes are needed in order to assure that private data packet ends on a double word boundary. 
     Data blocks  774  and  775  indicate other specific private data packets associated with the transport packet provided by the adaptation field parser  750 . Specifically, the length of the private data has been varied in packet  774  and  775  to illustrate packets having a single stuffing byte, and no stuffing bytes respectively. 
     Referring to  FIG. 33 , the counter controller  741  provides the appropriate data type code to the buffer controller  760  by selecting storage location  742  or  743  respectively depending upon whether adaptation field private data or video PES private data is being received. As a result, the appropriate data type will be provided onto the bus labeled PRIVATE DATA. Note the bus labeled PRIVATE DATA is illustrated to be a wired-OR bus, however any type of multiplexing would be the appropriate. 
     The length field of the private data packet is provided to the PRIVATE DATA box differently depending upon whether adaptation field private data or video PES private data is being provided. The length of video PES private data, which is always 16 bytes, is provided to the PRIVATE DATA bus by selecting the storage location  747 , which contains the hexadecimal value 0x10. Enabling the storage location  747  allows the hexadecimal value 0x10 be provided to be PRIVATE DATA bus. The length of adaptation field private data is provided to the PRIVATE DATA bus by latching the first byte of the adaptation field private data into be AFP data latch  745 . Because the first byte of the adaptation field private data specifies the number of private data bytes that follow, the appropriate length value for the length field is provided to the PRIVATE DATA bus. 
     Once the type and length field data have been provided to the PRIVATE DATA bus, the actual data is provided to the PRIVATE DATA bus. This is accomplished in a similar manner for both the adaptation field private data and a video PES private data. Specifically, the counter controller  741  latches the data into one of the appropriate data latches AFP data latch  745 , or PESP data latch  746 . In response, be associated private data is provided to the PRIVATE DATA bus. Note the private data could be provided to the PRIVATE DATA bus directly to transmission gates, or any other appropriate logical interface. 
     The generation of stuffing codes, from the stuffing code register  744 , is controlled by the control counter  741 . Because the control counter  741  knows the length of the private data provided, it can readily determined the number of bytes needed, if any, to assure the private data packet ends on a double word boundary is readily calculated. Therefore, after the last byte of the private data, from either the AFP or PESP, the appropriate number of stuffing codes are been provided to the PRIVATE DATA bus by selecting the storage location the  744  determined number of times this assures the buffer controller  760  will receive a number of bytes that and on a double word boundary. As a result, the private data can be provided to the system buffer controller  760  without delay. 
       FIG. 35 through 38  illustrate a method of performing automatic splicing using the data parsed herein provided to their respective registers. The term splicing refers to the process of switching between two video streams. For example, splicing can be used to switch between the video of the main program and a video of a commercial, between video to a commercial, and from a commercial video back to the main program video. The method of  FIGS. 35 through 38  is contingent upon being enabled by the compound to field of the control register. Splice points can be sorted as Out Points or In Points. 
     An Out Point is a location in the stream where the underlying elementary stream is well constrained for a clean exit (usually after I or P frame). An Out Point/Packet is the packet of the PID stream preceding an Out Point. MPEG-2 syntax defines Out Points at transport layer as:
     splicing_point_flag=1, splice_countdown=0, seamless_splice_flag=1;   

     An In Point is a location where the stream is well constrained for a clean entry (usually just before a sequence_header and I frame at the closed GOP. MPEG-2 syntax defines In Points at transport and PES layers as:
     splicing_point_flag=1, splice_countdown=−1, seamless_splice_flag=1;   payload_unit_start_indicator=1 random_access_indicator=1, data_alignment_indicator=1;   

     At step  301 , of  FIGS. 35 , the interrupt mask register is written to, in order to enable reception of interrupts based upon the video splicing flag and the video splicing point. The video splicing flag and the video splicing point values are determined by parsing performed by the Adaptation Field Parser  750 . The video splicing flag indicator is one of the optional flags of storage location  781  of  FIG. 28 , and is represented by register field VideoAFPSplicingFlag in the global status register of FIG.  29 . The video splicing point is determined by register logic  786  of  FIG. 28 , and results in the register field labeled VideoAFSplicingPoint being set when the video splicing flag is set and the splicing countdown register, labeled AFSpliceCountdown, is equal to 0. 
     At step  302 , the method of  FIG. 35  waits for an interrupt to occur. 
     At step  303 , an interrupt has been received, and a determination is made as to the interrupt type. If the interrupt type is a splice point, the flow proceeds to connector A, which is continued at FIG.  38 . If the interrupt type is a splice flag, the flow proceeds to step  304 . If the interrupt type is a different type of interrupt, the flow returns back to step  302 . 
     At step  304 , a determination is made as to the type of splice represented by the splice flag interrupt. This can be determined by analyzing the splice countdown value received by the adaptation field parser  750  of FIG.  28 . Specifically, if the splice countdown value is a positive value it is an indication that the splice flag has identified an out-splice point. An out-splice point indicates that the current video elementary stream being received is about to end, and the flow proceeds to connector B, which continues at FIG.  36 . 
     If at step  304  the splice countdown value is equal to zero, it is an indication the splice flag has identified a splice point. The splice point is as identified as that point in time were video is to be switched from a current video stream to a next video stream. A splice point flag is set and the adaptation field parser  750  of  FIG. 28 , when the splice flag is asserted, and the splice countdown register is equal to 0. (Note that under normal operation, the splice point path from step  304  will not be taken because the splice point should have been detected at step  303 , thereby bypassing step  304 ). 
     If at step  304 , it is determined that the splice countdown value is negative, it is an indication that an in-splice point has been identified. And in-splice point indicates that the current video elementary stream being played is just began, and the flow proceeds to connector C that continues in FIG.  37 . 
     One skilled in the art will recognize that specific register values identifying splice-in points and splice-out points could be provided in the same manner the separate register location was provided for the splicing point. Likewise, many other variations of the specific flow herein can be made without departing from the inventive intent. 
     When out point has been detected at step  304 , the flow proceeds to FIG.  36 . At step  310 , of  FIG. 36 , the splice flag interrupt is disabled. The splice flag interrupt is disabled because specific method illustrated in  FIGS. 35 through 38  only needs to execute and out point routine one time. Since the splice countdown value for an out point includes the values from 7 to 1 the out point routine disables the splice flag interrupt at step  310  in order to avoid having to unnecessarily process interrupts caused by the subsequent out point values. 
     At step  311 , splice point interrupts are enabled. Note that splice point interrupts should already be enabled from step  301  of FIG.  35 . Therefore, the step  311 , under ideal operating conditions, will be redundant and not strictly necessary. 
     At step  312 , acquisition of the PAT table is requested. The PAT table is discussed with reference to prior art FIG.  2 . 
     At step  313 , a determination is made whether or not the PAT table version number has changed. If the PAT table version number was not changed, the flow proceeds to step  314 . However, if the PAT table version number was changed, the flow proceeds to step  317 . 
     At step  317 , if the PAT table version number has changed, a new PMT table, see  FIG. 2 , is fetched and the flow proceeds to step  314 . 
     At step  314 , a determination is made whether or not the current splice is valid. A valid splice point is recognized by asserted (set to 1) splicing_point_flag and seamless_splice_flag. Flags are stored in the global status register. If it is determined that the current splice point is not valid, the flow proceeds to step  302  of FIG.  35 . However, if it is determined that the current splice point is valid, the flow proceeds to step  315 . 
     At step  315 , a request is made to receive the break duration time as an optional bit-field available in the splice_info_section that indicates an approximate time when the break will be over and when the network In Point will occur. At step  316 , the new PID number, received from the new PMT table, is written to a register that shadows the VideoPid register of FIG.  18 . Referring to  FIG. 16 , the VIDEO PID storage location  424  provides the PID value which identifies the current video stream, while the shadow register associated with location  424  (not illustrated) stores the PID value of the next video stream to be accessed at the splice point. Subsequent to step  316 , flow proceeds back to step  302 . 
     When it is has been determined at either step  303  or step  304  that the splice point has occurred, the flow proceeds to FIG.  38 . At step  331  of  FIG. 38 , the PID value stored in the shadow register is transferred into the active PID register. As result, the value stored in the VIDEO PID location  424  of  FIG. 16  is updated to the new PID value, resulting in the new video PID packets been identified, and selected, as the current video stream. In effect, the newly selected video image will be displayed. 
     At step  332 , a request is made to update the STC counter. The STC counter is updated in order to synchronize the system counter with the new program counter, i.e. a new time base. 
     At step  333 , the splice flag interrupt is enabled. The Splice Flag Interrupt Enable Bit is asserted in order to allow for the recognition of the splice in point. From step  333 , the flow proceeds to step  302  of FIG.  35 . Note that in another embodiment of the present invention, a determination step could be made at the beginning of the flow of  FIG. 38  as to whether the new PID is associated with a desirable program. If not, an alternate flow ignoring the PID, or using a dummy or alternate PID, could be used. For example, this feature could be used eliminate viewing commercials or other program types. 
     If at step  304 ,  FIG. 35 , it is determined that an in-splice point is occurring, the flow proceeds to FIG.  37 . At step  336 , of  FIG. 37 , a determination is made whether or not this is the first in-splice point interrupt service request. The first in-splice point interrupt service request, is generally associated with the value minus 1 of the splice countdown register. However, in order to accommodate for possible lost packets, the determination of step  320  may be used along with an indicator as to whether or not to the previous in-splice point interrupt service request has occurred. If this is not the first in-splice point, the flow proceeds to step  302  of FIG.  35 . If this is the first in-splice point, the flow proceeds step  337 . 
     At step  337 , a determination is made whether or not the in-splice point indicator is valid. The in-splice point indicator is validated by determining whether or not random access flag register is set along with discontinuity flag register. The random access flag register, and discontinuity flag register, should both be set because the first packet of a new data stream will indicate the current pack is capable of being randomly accessed by the system, and since no previous packets are associated with the PES stream the discontinuity flag should be set. 
     At step  338 , a request for PMT table acquisition is made. This is done to verify that current PID assignment for a present program is as before the brake (or before added commercial). At step  339 , a determination is made whether the PCR and video PID values are valid. PIDs are verified by analyzing a content of received PMT table for known MPEG-2 program_number. Change formidable if the PCR and PIDs are okay, flow proceeds to step  302  of FIG.  35 . Otherwise, flow proceeds to step  340 . 
     At step  340 , the new PID values are updated. 
     The method described  32  through  35  provides advantages over the prior art by allowing for the automated handling of in-splice point. Utilizing register values updated by the hardware parsers described herein, automatic splicing is enabled. The amount of saved system software bandwidth provides an advantage over the prior art. 
     Therefore, one skilled in the art will recognize that providing for hardware parsing of adaptation fields, and the generation of the private data packet regardless of the source of private data, provides advantages over the prior art. In addition, the splicing method described herein, provides for automatic hardware splicing control, which provides advantages over prior art methods of software control splicing. 
     In another embodiment of the disclosure, a transport stream demultiplexer core register set is initialized to indicate a possible set of transport stream characteristics. An acquisition routine is executed. If acquisition of the transport stream signal does not occur during a predetermined amount of time, the acquisition is not successful. When not successful, the register set is initialized to indicate a different possible set of transport stream characteristics, and the acquisition routine is once executed. This process continues, until the transport stream core acquires the transport stream signal. 
       FIGS. 39-42  illustrate a specific implementation of a method for blind synchronization to a transport stream. Blind synchronization allows the framer to acquire the transport stream, i.e. lock onto the transport stream, without any prior knowledge of the transport stream characteristics. 
     As discussed with reference to  FIGS. 8 and 9 , the transport stream can include a variety of signals. At a minimum, the transport stream will include a data signal (TDATA) and a clock signal (TCLOCK). Additional signals that may exist include TSTART, TVALID, and TERROR. Based upon these signals, the transport stream has a number of characteristics, such as individual signal polarities, and data ordering. 
     One transport stream characteristic is the polarity of the control signals, which can vary based upon the service provider implementation. In other words, each of the control signals TVALID, TSTART, and TERROR can be either active high or active low signal. As illustrated in  FIG. 14 , each of the control registers has respective register field (T_ValidPolarity, T_StartPolarity, and T_ErrorPolarity) to specify the active edge of each control signal. 
     An additional characteristic is the data ordering, or the bit polarity. Because the data is received bit at a time, or by bytes, whether the LSB is first or the MSB is first can vary. A field labeled FramerBitPolarity is used to select between a LSB and MSB bit polarity of TDATA. 
     Another transport stream characteristic is whether the TCLOCK signal latches data on a rising edge or on a falling edge. A field labeled FramerClockPolarity is used to select between these two characteristics. 
     At step  911  of  FIG. 39 , these variables are initialized to represent a specific set of transport stream characteristics. As further illustrated in step  921  of  FIG. 40 , the registers T_ErrorPolarity, T_StartPolarity, and T_ValidPolarity are set equal to zero. For purposes of discussion, a value of zero will represent an active low polarity, while a value of one will represent an active high polarity. 
     A variable BIT_ORDER, which corresponds to field FramerBitPolarity, is set to LSB to indicate the LSB of TDATA is to be received first, or right justified bytes of data are received. The variable BIT_ORDER can also be set equal to LSB to indicate the MSB of TDATA is to be received first, or will be right justified where bytes of data are received. 
     A variable labeled CLOCK_POLARITY, which corresponds to the field labeled FramerClockPolarity in  FIG. 14 , is set to zero, where zero indicates that TDATA is latched on a falling edge. 
     At step  922  of  FIG. 40 , other initialization overhead functions are performed. For example,  FIG. 14  illustrates a field labeled FramerMode that specifies the signals associated with the transport stream. Step  912  can include initialization of this field as well. 
     As step  912  of  FIG. 39 , a verification routine is executed. The verification routine is illustrated in greater detail with respect to FIG.  41 . At step  931  of  FIG. 41 , reception of the transport stream is enabled. In effect, it implements settings of the current transport stream characteristic. Upon enabling reception of the transport stream, the framer portion of transport stream demultiplexer core begins operation as described previously in an attempt to achieve synchronization. 
     At step  932  a predetermined amount of delay time occurs to allow the framer to detect a synchronization byte. When the data stream being received is an MPEG-2 data stream the synchronization byte is a hexadecimal 47 (47 h). The predetermined delay is used to detect one 188 byte long MPEG-2 packet, and depends on a stream bit-rate and is typically under 100 microseconds. 
     At step  933 , a determination is made whether the synchronization byte was detected. If not, the flow proceeds to step  935 , if so, the flow proceeds to step  934 . 
     At step  934 , a determination is made whether or not additional synchronization bytes need to be detected before synchronization is declared. In  FIG. 14 , the variable labeled FramerSyncLockLenghth indicates how many consecutive transport packet synchronization frames need to be detected before synchronization is declared, Based upon this value, the flow will return to step  932  until the specified number of synchronization values has been detected. When the specified number of synchronization frames has been detected, the flow returns to FIG.  39  and indicates a successful verification. 
     At step  935 , it has been determined that the transport stream reception has not been successful. As a result, no further attempt is made to acquire the transport stream with the present settings of the transport stream physical characteristic. Therefore, step  935  performs any overhead functions needed, for example, reception of the transport stream can be disabled. Note in other embodiments, reception of the transport stream with improper characteristic settings continues. 
     From step  935 , the verification flow of  FIG. 41  returns to FIG.  39  and indicates that the verification was not successful. 
     At step  913  of  FIG. 39 , a determination is made whether the verification routine was successful. If so, the flow proceeds to step  914 , if not, the flow proceeds to step  915 . 
     At step  914 , the proper set of transport stream characteristics has been found and any necessary cleanup occurs. Examples of necessary cleanup items would include notifying the use of successful synchronization, storing of the synchronization characteristics. 
     At step  915  the transport stream characteristics are incremented.  FIG. 42  illustrates one method of incrementing the characteristics specified with respect to step  911 . 
       FIG. 42  illustrates a flow diagram that increments the transport stream characteristic in such a manner that all possible combinations are covered. By executing this routine, a successful increment will be indicated for all values, except for when BIT_ORDER variable is equal to MSB, and all other characteristics are equal to one. This state indicates that all possibilities have been tested, and an unsuccessful return occurs. 
     At step  916  of  FIG. 39 , a determination is made whether the increment of the transport stream characteristic variables was successful. If so, the flow returns to step  912  where the verification routine is executed again. If the increment of the transport stream characteristic was not successful, indicating that no lock was obtained, the flow proceeds to step  914  for appropriate cleanup. 
     The present method provides a fast method for acquiring a transport stream having unknown characteristics. Variations of the method described herein would include varying the number of consecutive synchronization byte required for acquisition to be successful, varying the order in which the variables are varied. Varying the framer mode to indicate the possible combinations of transport stream signals, i.e. clock and data only. 
     It should be understood that the specific steps indicated in the methods herein may be implemented in hardware and/or software associated with the specific parsers or controller described. For example, a specific step may be performed using software and/or firmware executed on one or more a processing modules. In general, a system for handling transport stream data may include a more generic processing module and memory performing the functionality described herein. Such a processing module can be a single processing device or a plurality of processing devices. Such a processing device may be a microprocessor, microcontroller, digital processor, micro computer, a portion of the central processing unit, a state machine, logic circuitry, and/or any device that manipulates the transport stream. The manipulation of the transport stream is generally based upon operational instructions. The memory may be a single memory device or a plurality of memory devices. Such a memory device may be a read only memory a random access memory a floppy disk memory, magnetic tape memory, erasable memory, a portion of a system memory, and/or any device that stores operational instructions in a digital format. Note that when the processing module implements one or more of its functions to be a state machine or logic circuitry, the memory storing in the corresponding operational instructions is embedded within the circuitry comprising the state machine and/or other logic circuitry. 
       FIG. 43  illustrates, in block diagram form, a processing device in the form of a personal computer system  1000 . The computer system  1000  is illustrated to include a central processing unit  1010 , which may be a conventional proprietary data processor, memory including random access memory  1012 , read only memory  1014 , input output adapter  1022 , a user interface adapter  1020 , a communications interface adapter  1024 , and a multimedia controller  1026 . Note the central processing unit  1010 , the communications interface adapter  1024 , and video/graphics controller can individually be considered processing devices. 
     The input output (I/O) adapter  1022  is further connected to, and controls, disk drives  1047 , printer  1045 , removable storage devices  1046 , as well as other standard and proprietary I/O devices. 
     The user interface adapter  1020  can be considered to be a specialized I/O adapter. The adapter  1020  is illustrated as connected to a mouse  1040 , and a keyboard  1041 . In addition, the user interface adapter  1020  may be connected to other devices capable of providing various types of user control, such as touch screen devices. 
     The communications interface adapter  1024  is connected to a bridge  1050  such as is associated with a local or a wide area network, and a modem  1051 . By connecting the system bus  1002  to various communication devices, external access to information can be obtained. 
     The multimedia controller  1026  will generally include a video graphics controller capable of displaying images upon the monitor  1060 , as well as providing audio to external components (not illustrated). 
     In accordance with the present invention, the transport core can be implemented at various portions of the system  1000 . For example, the transport core can be part of the Communication Interface Adapter  1024 , as part of the Multi-Media Controller  1026 , or as a separate component of the system connected directly to the bus  1002 . In a specific embodiment, the video memory of  FIG. 5  resides within the Multi-Media Controller  1026 , while the system buffers  501  to  503  would generally reside in RAM  1012 . In other implementations, a unified memory can be used. 
     Verification of a system implementing various hardware and methods described herein can be accomplished by implementing an MPEG-2 transport demultiplexer in C language in order to verify the parsing transport files to the level of elementary streams. The produced elementary streams have been compared against streams generated by reference transport stream generation equipment, which in this case, has been used as a reference transport/PES stream decoder. 
     A Behavioral C model operates on the MPEG-2 transport stream on MPEG-2 transport stream files and has capabilities to perform functions described herein, including:
     Analyzing a stream and provide a list of PID numbers of the component streams.   Demultiplexing (to files) specified component streams in a sense that video stream is parsed to the level of the elementary stream, while all other streams are just demultiplexed on a simple PID filter. Up to 16 output files can be created. Output files contain entire transport packets. Depending on a setup of the auxiliary PID control registers, output files contain packets identified by a single or a multiple PID values. For example, all 31 non-video transport packets can be routed in a single file. This closely models interface between output FIFO of the demultiplexer hardware and the host bus interface unit (HBIU).   Modeling the operation of all registers and output stream pointers, according to the naming convention in the functional specifications of the demultiplexer hardware. This can then be used to develop actual VHDL or Verilog Hardware Description Language code for MPEG-2 demultiplexer system-on-a-chip.   Modeling the operation of the framer, transport layer parser, PES layer parser, and a full-duplex interface between demultiplexer and MPEG2 video decoder (one path transfers PTS, PTS byte count, latched STC and current STC to the video decoder, other path receives various private data from the video decoder at the sequence GOP or picture level).   

     The video elementary stream output file can be compared bit by bit with the output of the reference test and measurement device (transport stream analyzer—TSA). TSA has ability to work in real time on a byte parallel transport stream or on a file. If operated on a file, it will generate video elementary stream stored in a file. This file will be used to compare against the elementary stream (ES) video output file of our C model. This way, about 90% of the C model can be verified (a framer, transport and PES parser and video FIFO). Up to 31 non-video PID filters and the transport packet router can be verified with the transport packet header syntax analyzer software. This completes the verification of a C model. 
     A transport stream generator, or composer is described below for generating test streams, and for testing hardware and software models of transport stream demultiplexers. These streams are generated through a C program and text file containing script command language. It consists of one through several hundred MPEG-2 transport stream packets that would contain different PID&#39;s, PES data, etc. Each test stream can scope a specific function of the parser. These test streams are files that can be fed to a behavioral model that reads this file and feed it as a serial bit-stream to the VHDL. These tests can be run to result in bit-maps residing in either the frame buffer memory, or in the system memory. 
     A data record, in accordance with a specific embodiment of the present invention, is described below capable of implementing the tests used for verifying a C model, or a hardware device or a system. The data record illustrated below allows simple ASCI, or other text based, description of TP or PES syntax.
         ; This is a comment line   FILE “YourFilename.ES”; Name of the file containing MPEG-2 elementary stream to be packetized into PES and TP formats.   ; The following portion is the PES, also referred to as a data stream, description, and is relevant to PES layer syntax.       

     
       
         
           
               
               
               
               
             
               
                   
               
             
            
               
                 [REPEAT_PES 
                 M1] 
                   
                   
               
            
           
           
               
               
               
               
               
            
               
                   
                 [PES_SCP 
                 N0] 
                   
                   
               
               
                   
                 [PES_SID 
                 N1] 
               
               
                   
                 [PES_SC 
                 N2] 
               
               
                   
                 [PES_DAI] 
               
               
                   
                 [PES_C] 
               
               
                   
                 [PES_OOC] 
               
               
                   
                 [PES_PTS_FLAG 
                 N3  
                 N4] 
               
            
           
           
               
               
               
               
            
               
                   
                 [PES_ESCR_FLAG 
                 N5] 
                   
               
               
                   
                 [PES_ESRATE_FLAG 
                 N6] 
               
               
                   
                 [PES_DSM_FLAG 
                 N7] 
               
               
                   
                 [PES_ACI_FLAG 
                 N8] 
               
               
                   
                 [PES_CRC_FLAG 
                 N9] 
               
               
                   
                 [PES_HEADER_DATA_LENGTH 
                 N10] 
               
            
           
           
               
               
               
               
               
            
               
                   
                 [PES_PD_FLAG 
                 [N11] 
                 [RANDOM] 
                 [“TextString1”]] 
               
               
                   
                 [PES_PH_FLAG 
                 N12] 
               
               
                   
                 [PES_PPSC_FLAG] 
               
               
                   
                 [PES_PSTD_FLAG 
                 N13] 
               
               
                   
                 [PES_EXT2_FLAG 
                 N14] 
               
               
                   
                 [PES_STUFFING 
                 N15] 
               
               
                   
                 [PES_PAYLOAD_LENGTH 
                 N16  
                 [N17] [RANDOM] 
                 [“TextString2”]] 
               
               
                   
                 [END] 
               
            
           
           
               
            
               
                 ; The following portion is the transport packet description 
               
               
                 [REPEAT_TP    M2] 
               
            
           
           
               
               
               
            
               
                   
                 [[TP_SYNC N18 N19    [[RANDOM] 
                 [BITSHIFT]]] 
               
            
           
           
               
               
            
               
                   
                  [TP_TEI N20] [TP_TEI_CONSECUTIVE N21 N22] [TP_RANDOM_TEI] 
               
            
           
           
               
               
               
               
               
            
               
                   
                   TP_PID 
                 N23 
                   
                   
               
               
                   
                  [TP_TSC 
                 N24 
                  N25] 
                 [TP_TSC_CONSECUTIVE N26 N27 N28] 
               
            
           
           
               
               
            
               
                   
                 [TP_RANDOM_TSC N29] 
               
            
           
           
               
               
               
               
               
            
               
                   
                 [TP_CC 
                 N30 
                  N31 
                 [DISCONTINUITY]  [TP_CC_RANDOM] 
               
            
           
           
               
               
               
               
            
               
                   
                 [TP_PAYLOAD 
                 [N32] 
                 [RANDOM] [BITSHIFT] [“TextString3”]] 
               
            
           
           
               
               
               
            
               
                  [[[TP_DUPLICATE N33] 
                 [TP_DUPLICATE_RANDOM]] 
                 [DOUBLE]] 
               
               
                 [END]  
               
            
           
           
               
            
               
                 ; The following portion is an adaptation field description 
               
            
           
           
               
               
               
               
               
            
               
                 [AF_LENGTH 
                   
                 N34] 
                   
                   
               
               
                 [AF_DI 
                   
                 N35] 
               
               
                 [AF_RAI 
                   
                 N36] 
               
               
                 [AF_PCR_FLAG 
                 N37 
                 N38] 
               
               
                 [AF_OPCR_FLAG 
                   
                 N39] 
               
               
                 [AF_SP_FLAG 
                 N40 
                 N41] 
               
               
                 [AF_TPD_FLAG 
                 N42 
                 [N43] 
                 [RANDOM] 
                 [“TextString4]] 
               
               
                 [AF_EXT_FLAG 
                 N44 
               
               
                   
               
            
           
         
       
     
     All optional fields are given in [] braces; a syntax is relevant to a single PID transport stream. In the specific implementation, multiple PID transport stream files are created by muxing single PID files with simple utility program. All numbers (N1. . . N43) are given as decimal numbers. Additional syntax relevant to the PES data record listed above is as follows:
     M 1  (DWORD) specifies a number of PES packets under REPEAT—END structure.   PES_SCP is the packet_start_code_prefix of PES packet set to numeric value N0 (DWORD). If [PES_SCP N0] is not given, packet start code should be set to default 0x000001. Purpose of [PES_SCP N0] is to define error on PES packet start code. N0 is 24 bit. If more than one PES packet exist, this error is injected on the first PES packet only, all other PES packet start codes are 0x000001.   PES_SID is PES stream_id field set to numeric value N1 (BYTE). If command [PES_SID N1] is not given, stream_id is encoded as 0xE0. Purpose of [PES_SID N1] is to define error on stream_id field, which occurs on every PES packet.   PES_SC is the PES_scrambling_control bit-field set to a numeric value N2 (BYTE). If [PES_SC N2] command is not specified, PES_scrambling_control should be encoded as 0, indicating non-scrambled (clear) PES payload. Purpose of [PES SC —N 2] is to define error or legal case of scrambled PES payload, which ASIC should skip. N2 ε {0,1,2,3} and is applied to first PES packet only, all others are generated as clear packets with PES_scrambling_control=0.   PES_DAI (BOOL) is data_alignment_indicator. If this line is specified in the script file, the data_alignment_indicator of the PES header has to be set to 1 to first PES packet only. If PES packets are creating from ES video, this flag is set when video sequence header is found.   PES_C (BOOL) is copyright bit. If this command is specified, copyright bit of the PES header has to be set to 1, otherwise it is 0. This applies to every PES packet.   PES_OOC (BOOL) is original_or_copy bit. If this line is specified in the script file, original_or_copy bit of the PES header has to be set to 1, otherwise is 0. This applies to every PES packet.   PES_PTS_FLAG is the PTS_DTS_flags bit-field specifying existence of the PTS or PTS &amp; DTS values in the PES header. N3 (BYTE) gives encoding type (N3 ε {0,1,2,3}), and N4 (ULONGLONG) gives exact value of the PTS (only 33 LS bits are meaningful, others has to be set to 0). This line of the script file allows verification of the PTS extraction circuit of transport demux ASIC. We don&#39;t process DTS value, so if N3 is set to 3, DTS can be encoded as 0 or 0x1FFFFFFFF or the same as PTS. If PES packets are creating from ES video, this flag is set when video sequence header is found, otherwise PTS is applied to the first PES packet only.   PES_ESCR_FLAG (BOOL) is ESCR_flag. N5 ULONGLONG) encodes ESCR_value. Applies to the first PES packet only.   PES_ESRATE_FLAG (BOOL) is ES_rate_flag. N6 (DWORD) encodes ES_rate value. Applies to the first PES packet only.   PES_DSM_FLAG (BOOL) is DSM_trick_mode_flag. N7 (BYTE) encodes a full DSM byte field of the first PES packet only.   PES_ACI_FLAG (BOOL) is additional_copy_info_flag. N8 (BYTE) encodes additional_copy_info of every PES packet.   PES_CRC_FLAG (BOOL) is PES_CRC_flag. N9 (WORD) encodes 16 bit CRC sum. This allows verification of the ASIC&#39;s CRC hardware engine. Specified value is injected to second PES packet only, CRC on all others is calculated. First PES packet has no CRC field.   PES_HEADER_DATA_LENGTH is the PES_header_data_length syntax element. N10 (BYTE) gives actual length, which is adjusted with stuffing.   PES_PD_FLAG (BOOL) indicates that 16 private data bytes exist in the header. If N11 (BYTE) is given, private data bytes are set as numeric string which starts from N11 and increases for 1. If RANDOM is defined, private data bytes are set as random bytes. If text string is given, private data bytes are set to ASCII string with 0xFF padding if the string length is less than 16, for example “PES private data”. This applies to every PES packet.   PES_PH_FLAG (BOOL) is pack_header_field_flag. N12 (BYTE) gives the length of the pack header. If N12 is set to 13, than a regular 12 byte MPEG-1 pack_header is inserted, otherwise it is encoded with stuffing bytes (0xFF). N12 should be some small number (N12&lt;20). This applies to the first PES packet only.   PES_PPSC_FLAG (BOOL) is the program_packet_sequence_counter_flag, indicating that every PES packet has PES sequence counter.   PES_PSTD_FLAG (BOOL) is the P-STD_buffer_flag. N13 (WORD) encodes P-STD_buffer_size (13 LS bits). For parsed video stream, P-STD_buffer_scale is always 1, indicating units of 1 KB. This applies to every PES packet.   PES_EXT 2 _FLAG (BOOL) is the PES_extension_flag_ 2  indicating second extension field whose length is specified with N14 (BYTE). ASIC skips over 2 nd  extension field and stuffing area. The second extension is added to the first PES packet only. N14 should be some small number (N14&lt;20).   PES_STUFFING N15 (BYTE) indicates the number of stuffing bytes added to every PES packet header. N15&lt;32.   PES_PAYLOAD N16 (WORD) indicates length of the PES payload, whose content can be specified as numerical string starting from value N17 (BYTE) with roll over to 0 after 255, random numerical string or ASCII text string. Only one of the 3 options is valid at the time, for example text string “This is a PES payload” where PES_PAYLOAD_LENGTH is set to 21. This applies to every PES packet.
 
Additional syntax relevant to the transport packet record listed in the table above is as follows:
   M 2  (DWORD) specifies a total number of transport packets defined in the REPEAT —END structure. It is relevant only if there is no underneath PES stream (no previous PES syntax).   Line TP_SYNC N18 N19 [RANDOM] [BITSHIFT] is used to specify errors on the sync_byte. Sync_byte, generated as random unsigned 8 bit integer [RANDOM] or bit-shifted variant of initial sync value 0x47 [BITSHIFT] is set from transport packet N18 (DWORD) in all next N19 (DWORD) transport packets, and after that is set to 0x47. If this line is omitted, sync_byte shall be set to error free value (0x47) in all transport packets.   TP_TEI (BOOL) is transport_error_indicator. It can exist with the specified rate (TP_TEI with rate specified as DWORD N20), it can be generated from packet N21 (DWORD) in all N22 (DWORD) consecutive packets; or it can be randomly generated [TP_RANDOM_TEI]. In the first case, repetition rate is N19, i.e. if N20 is set to 0, TEI occurs only once, at the first packet, if N20 is 1, every packet has TEI error flag, if N20 is 2 every second packet has TEI error and so on. If neither of three specifiers is given, all packets have no TEI flag set.   Line TP_PID N23 specifies the PID of the current transport stream encoded as WORD with 13 LS bits as actual PID value.   transport_scrambling_control can be set as:
       repetitive with command TP_TSC and TSC value in BYTE N24 and repetition ratio in DWORD N25. If N25 is zero, transport_scrambling_control is set to value N24 on first packet only, if N25 is 1 every packet has transport_scrambling_control field set to N24, if N25 is 2 every second packet has transport_scrambling_control field set to N24, and so on. N24 ε {0,1,2,3};   constant with command TP_TEI_CONSECUTIVE and set to value BYTE N26 ε {0,1,2,3} from transport packet N27 (DWORD) in all N28 (DWORD) next transport packets, and after that set to 0, indicating no scrambling.   constant with command TP_RANDOM_TSC and set to value N29 (BYTE), but on randomly selected packets.
 
If this line is not specified, transport scrambling control is set to 0 (not scrambled) in all transport packets.
   
       continuity_counter can be set as to BYTE value N30 ε {0,1,2, . . . 15} starting from packet N31 (DWORD). Optional DISCONTINUITY specifier, if exists defines a‘legal’ discontinuity on the continuity counter field, set in the adaptation field. This line may exist as TP_CC_RANDOM where random transport packets are chosen to add random 4-bit value for continuity counter. If this line is not specified, continuity_counter field should start from 0 with first transport packet, and doesn&#39;t have any discontinuity in all transport packets.   Payload of the transport packet can be set to a numeric string starting from BYTE value N32 with roll over to 0 after 255, or it can be filled with random bytes (RANDOM), bit shifted start codes (BITSHIFT, i.e. 0x47 bit shifted) or set to ASCII text string for example “Transport packet payload” as a good, known payload. If FILE directive is specified, a payload is built from underneath PES packets of ES stream and command TP_PAYLOAD is illegal in that case.   Optional line TP_DUPLICATE N33 or TP_DUPLICATE_RANDOM defines duplicate transport packet as the image of the latest transport packet with duplicate rate in DWORD N33 or randomly generated rate of duplication. Optional DOUBLE specifier means that a duplicate packet is duplicated creating three consecutive packets with the same content. If N33 is set to 0, only first transport packet is duplicated, otherwise every N33 th  transport packets is duplicated.
 
Additional syntax relevant to the adaptation fields portion listed in the table above is as follows:
   Line AF_LENGTH N34 specifies designed length of the adaptation field, including stuffing bytes. BYTE N34 encodes length. The actual length depends on specified flags and fields, and possible stuffing and is determined on packet by packet base. N34 allow us to define length in such a way that influence of errors on the adaptation — field_length can be tested. If specified length N34 is in conflict with the actual, computed adaptation_field_length, then adaptation field should contain all specified fields and flags with no stuffing and adaptation_field_length set to N34. If specified N34 complies with the possible computed length(s), then N34 should be used with actual length adjusted with stuffing.   BOOL AF_DI N35 is used for discontinuity_indicator. DWORD N35 is the repetition rate of the discontinuity_indicator. If N35 is set to 0, the discontinuity_indicator should exist only once, in the first transport packet, otherwise it repeats on every N35 transport packets (if N35 is 1, discontinuity_indicator is repeated in every TP).   BOOL AF_RAI N36 is used for random_access_indicator. DWORD N36 is the repetition rate of the random_access_indicator. If N36 is set to 0, random_access_indicator should exist only once, in the first transport packet, otherwise it repeats on every N36 transport packets (if N36 is 1, random_access_indicator is repeated in every TP).   BOOL AF_PCR_FLAG N37 N38 stands for PCR_flag with initial value encoded in the LONGLONG N38 and the repetition rate defined by DWORD N37. If N37 is set to 0, PCR exists only once, in the first transport packet, otherwise it repeats every N37 transport packets. N38 should increase by step 100000/N35;   BOOL AF_OPCR_FLAG N39 stands for OPCR_flag with the repetition rate defined by DWORD N39. If N39 is 0, OPCR exists only once, in the first transport packet, otherwise it repeats every N39 transport packets. Because our ASIC doesn&#39;t extract OPCR value, OPCR can be set to the latest PCR value.   BOOL AF_SP_FLAG N40 N41 stands for the splicing_joint_flag. BYTE N40 indicates initial splice_countdown value and DWORD N41 is its repetition rate. If N41 is set to zero, splicing_pont_flag exists only once, in the transport packet with splice_countdown set to 0 (splicing point), otherwise it repeats on every N41 st  transport packets. Term: N41&gt;N40;   BOOL AF_TPD_FLAG N42 [N43] [RANDOM] [“TextString 4 ”] stands for the transport_private_data_flag; transport_private_data_length is defined by BYTE N42. Data content can be set to increasing numeric value defined by BYTE N43 (step is+1), or to the random byte numeric string, or to the ASCII text string with 0xFF padding to the length N42. Private data of the adaptation field are inserted only once, in the first transport packet. All other TP packets have no AF private data.   Last line BOOL AF_EXT_FLAG N44 stands for adaptation_field_extension_flag with adaptation_field_extension_length defined by BYTE N44. Although our ASIC doesn&#39;t process extension field (just skips over), ltw_flag, piecewise rate_flag and seamless_splice_flag should be set to 0 creating extension field with reserved content only. Extension of adaptation field are inserted only once, in the first transport packet. All other TP packets have no extension of AF field.   

     In operation, if FILE specifies a filename of a file containing MPEG-2 video elementary stream that is packetized into PES (first step) and then into TP (second step) formats. Proposed extensions of the created streams are .PES and .TP; If FILE is not specified, PES payload shall obey directive:
     [PES_PAYLOAD_LENGTH N15 [N16] [RANDOM] [“TextString 2 ” ]],
 
where the payload is filled with random content (if RANDOM is given), known ASCII string (if given as “some text . . . ”) or as padding with 0xFF;
   

     When building PES packets from specified ES stream fields, the composer determines the values of PES_DAI, PES_PTS_FLAG, PES_ESCR_FLAG, PES_ESRATE_FLAG, and PES_PAYLOAD_LENGTH, which depends on the content of video ES stream, and are provided by the transport stream generating software, (i.e. composer @4520 of FIG.  45 ). For example, presentation time stamping must exist at every 0.7 sec or more frequently. The packetizer needs to know the bit rate of the video ES stream in order to generate PTS, ESCR, and ESRATE fields. In one mode of operation, the bit rate is obtained from the elementary stream file. PES_PPSC is generated in every PES packet if PES_PPSC request is found in the script file. PES_PSTD is generated only once, in the first PES packet. 
     At the transport layer, the length of the adaptation field is determined by existence of optional flags. PCR samples have to exist at least 10 times per second and be inserted in correlation with targeted bit-rate of transport packets (higher than video bit-rate); random_access_indicator shall be inserted at the start of every GOP, sequence or I frame. Continuity_counter is regular with random errors if TP_CC_RANDOM is selected. Payloads of generated transport packets are determined by existence of adaptation field. 
     In the case of video stream, the composer operates to set the following fields as indicated:
         PES_DAI is set on PES packet containing start of video sequence, group of pictures or I frame.   PES_PTS is set on every I frame and PTS value is calculated from initial given value and bit-rate of the stream.   PES_ESCR is set on every 25 th  packet based on 90 KHz timer.   PES_ESRATE is set on PES packet containing start of video sequence.       

     The first sequence of test streams verifies basic operations of the transport stream in ideal, error free stream environment. At the transport level this means:
         correct value of sync byte (0x47) on every packet   no TEI error signaling   payload_unit_start_indicator signaled in one and the first transport packet   transport scrambling_control set to ‘00’ indicating no scrambling at the transport layer level   no discontinuities on continuity counter   accurate adaptation_field_length (adaptation field)   exact splice_countdown value (adaptation field)   incremental, linearly increasing PCR value in sub-sequent packets with PCR rate of 10 per second, at least (adaptation field)   script file based, user defined ASCII private data string with exact transport_private_data_length   content of extension area in the adaptation field is not relevant, stuffing area is also not relevant, because AFP parser is not processing more than private data record of adaptation field (ignores adaptation_field_extension_flag and stuffing_bytes)
 
At the underneath PES level no-error requirements are:
   correct packet_start_code_prefix (0x000001)   stream_id as 0xE0 . . . 0xEF   exact PES_packet_length   PES_scrambling_control set to ‘00’ indicating no scrambling   exact PES_header_data_length   incremental, linearly increasing PTS value in sub-sequent PES packets in PTS or PTS_DTS field   exact previous_PES packet_CRC value   script file based, user defined ASCII private data string   no pack header   optional extension field with exact PES_extension_field_length   exact stuffing record   exact length of the payload record with incremental byte values from 0x00 towards 0xFF       

     For transport layer test, header of the PES packet should contain only first 9 bytes (no flags set to 1) with PES payload starting from 0x00 towards 0xFF and rolling over. For PES layer tests, transport packets should not contain any indicators or flags of second byte of adaptation field set to 1. Only exception is when testing combined private data at the transport and PES layer. Length of adaptation fields should be adjusted by stuffing. Verification methods are:
     FCV—file comparison verification; IRV—interrupt response verification; GKV—good, known value based verification;
 
The following tables list specific error free test streams:
   

     
       
         
           
               
               
               
             
               
                   
               
             
            
               
                   
                   
                 Comments: Transport Layer Test 
               
               
                 Test Name 
                 Goal &amp; Verification 
                 (AF = 0, M1 = 1, PES_PAYLOAD_LENGTH = 175) 
               
               
                   
               
               
                 BasicFrame 
                 Parser &amp; Video 
                 Simple test with one transport packet, transferred to frame memory. 
               
               
                   
                 FIFO test; 
                 To test immediate parsing with a short PES packet with 9byte header 
               
               
                   
                 FCV method 
                 encaps ulated in one transport packet 
               
               
                 BasicMain 
                 Router and 
                 Simple test with one transport packet, transferred to system memory. 
               
               
                   
                 FIFO test; 
                 To test routing of single transport packet with payload set to FF 
               
               
                   
                 FCV method; 
                 (PES irrelevant) to the system memory. 
               
               
                   
               
               
                   
                   
                 Comments: Transport Layer Test 
               
               
                 Test Name 
                 Goal &amp; Verification 
                 (AF = 0, M1 = 1, PES_PAYLOAD_LENGTH = 5775) 
               
               
                   
               
               
                 SyncLock 
                 Framer and synchro 
                 A stream 33 transport packets long all containing single PID. The 
               
               
                   
                 locking logic; FCV; 
                 purpose of this test is to insure that framer synchronization is achieved 
               
               
                   
                 IRV (SyncLock). 
                 immediately or after 1 to 31 packets or immediately, on a first packet 
               
               
                   
                   
                 based on a SyncLock register set-up. 
               
               
                   
               
               
                   
                   
                 Comments: Transport Layer Test 
               
               
                 Test Name 
                 Goal &amp; Verification 
                 (AF = 0, M1 = 1, PES_PAYLOAD_LENGTH = 5775) 
               
               
                   
               
               
                 PIDFilter 
                 PID comparator and 
                 MPEG-2 transport stream of 1,056 transport packets long to test all 32 
               
               
                   
                 PID syntax element; 
                 PIDs and acquisition of up to 32 packets per PID, after programmable 
               
               
                   
                 FCV; 
                 framer lock (up to 32 packets) is established. Must contain 32 different PIDs. 
               
               
                   
               
               
                   
                   
                 Comments: Transport Layer Test 
               
               
                 Test Name 
                 Goal &amp; Verification 
                 (AF = 0, M1 = 1, PES_PAYLOAD_LENGTH = 17500) 
               
               
                   
               
               
                 VideoPayload 
                 Transport packet 
                 A transport stream of 100 single video PID transport packets with no 
               
               
                   
                 payload extraction; 
                 adaptation fields. To test processing of payloads only 
               
               
                   
                 FCV; 
                 (adaptation_field_control = ‘01’). 
               
               
                   
               
               
                   
                   
                 Comments: Transport Layer Test 
               
               
                 Test Name 
                 Goal &amp; Verification 
                 (AF ≠ 0, M1 = 0, no PES stream) 
               
               
                   
               
               
                 VideoAF 
                 Adaptation field 
                 A transport stream of 100 single video PID transport packets with 
               
               
                   
                 extraction; FCV; 
                 adaptation fields only. To test processing of adaptation fields only 
               
               
                   
                 PCR based GKV; 
                 (adaptation_field_control = ‘10’). 
               
               
                   
                   
                 AF should contain PCR_flag, OPCR_flag and PCR + OPCR_flag, 
               
               
                   
                   
                 alternating sequentially. PCR field should be encoded to some known 
               
               
                   
                   
                 value to compare against. 
               
               
                   
               
               
                   
                   
                 Comments: Transport LayerTest 
               
               
                 Test Name 
                 Goal &amp; Verification 
                 (AF ≠ 0, M1 = 1, PES_PAYLOAD_LENGTH = 15500) 
               
               
                   
               
               
                 VideoAF_and 
                 AF and payload 
                 A transport stream of 100 single video PID transport packets with 
               
               
                 Payload 
                 extraction; FCV; 
                 adaptation fields and payloads. 
               
               
                   
                 PCR based GKV; 
                 AF should contain PCR_flag, OPCR_flag and PCR + 
               
               
                   
                   
                 OPCR_flag, alternating sequentially. Payload should contain some 
               
               
                   
                   
                 known value. 
               
               
                   
               
               
                   
                   
                 Comments: Transport Layer Test 
               
               
                 Test Name 
                 Goal &amp; Verification 
                 (AF ≠ 0, M1 = 0, no PES stream) 
               
               
                   
               
               
                 VideoSplice 
                 splicing_point_flag, 
                 A transport stream of 1,000 single video PID transport packets with 
               
               
                   
                 splice_countdown; 
                 splicing_flag, splicing_point and video PID change after splicing point. 
               
               
                   
                 FCV; IRV; splice 
                 No packet errors. AF should contain splicing_point_flag only. To test 
               
               
                   
                 countdown based GKV 
                 ‘auto splicing’ feature on video PID. 
               
               
                   
               
               
                   
                   
                 Comments: Transport Layer Test 
               
               
                 Test Name 
                 Goal &amp; Verification 
                 (AF ≠ 0, M1 = 0, no PES stream) 
               
               
                   
               
               
                 VideoAF 
                 transport_private —   
                 A transport stream of 1,000 single video PID transport packets with 
               
               
                 PrivateData 
                 data_flag; 
                 private data in the AF. To test extraction and transfer of private data 
               
               
                   
                 transport_private —   
                 to a system memory. AF only has transport_private_data_flag. 
               
               
                   
                 data_length; FCV, IRV; 
               
               
                   
               
               
                   
                   
                 Comments: Transport Layer Test 
               
               
                 Test Name 
                 Goal &amp; Verification 
                 (AF ≠ 0, M1 = 0, no PES stream) 
               
               
                   
               
               
                 STCProcess 
                 IRV on PCR_flag; 
                 To test extraction of the PCR fields and STC allignment with 27MHz 
               
               
                   
                 program_clock —   
                 generation over the M/N divider. A single video PID stream of at least 
               
               
                   
                 reference_base; 
                 10,000 transport packets is required. AF only has PCR_flag. 
               
               
                   
                 program_clock —   
               
               
                   
                 reference_extension; 
               
               
                   
               
               
                   
                   
                 Comments: Transport Layer Test 
               
               
                 Test Name 
                 Goal &amp; Verification 
                 (AF ≠ 0, M1 = 0, no PES stream) 
               
               
                   
               
               
                 PCR 
                 IRV on discontinuity —   
                 A single video PID stream of at least 10,000 transport packets is 
               
               
                 Discontinuity 
                 indicator; PCR based 
                 required. AF only has PCR_flag. A regular PCR discontinuity 
               
               
                   
                 GKV; 
                 (discontinuity_indicator set to 1) should occur with no CC errors and a 
               
               
                   
                   
                 new PCR value should start from 0 (much different than the value of the 
               
               
                   
                   
                 latest sample). To test extraction of a new timebase. 
               
               
                   
               
               
                   
                   
                 Comments: Transport Layer Test 
               
               
                 Test Name 
                 Goal &amp; Verification 
                 (AF ≠ 0, M1 = 0, no PES stream) 
               
               
                   
               
               
                 Legal CC 
                 IRV on discontinuity —   
                 A single video PID stream of at least 100 transport packets is required. 
               
               
                 Discontinuity 
                 indicator; mismatch 
                 AF only has PCR_flag. In adaptation field a discontinuity_indicator has 
               
               
                   
                 on continuity_counter 
                 to be set to 1 with CC errors but no PCR sample in the same packet. 
               
               
                   
                   
                 ASIC should not generate CC error interrupt. 
               
               
                   
               
               
                   
                   
                 Comments: Transport Layer Test 
               
               
                 Test Name 
                 Goal &amp; Verification 
                 (AF ≠ 0, M1 = 1, PES_PAYLOAD_LENGTH = 0) 
               
               
                   
               
               
                 VideoAFPES 
                 TP: adaptation_field —   
                 A transport stream of 100 single video PID transport packets with one 
               
               
                 StuffingData 
                 control == ‘10’; 
                 PES packet. No flags of a PES header should be set to 1. Stuffiing only 
               
               
                   
                 AF: stuffing_byte; 
                 in AF &amp; PES, no payload. 
               
               
                   
                 PES: stuffing_byte; 
                 No extension field in the AF (adaptation_field_extension_flag = 0); 
               
               
                   
                   
                 stream_id should be set to 0xE0. No interrupt should occur; All transport 
               
               
                   
                   
                 packets and full PES skipped. 
               
               
                   
               
               
                   
                   
                 Comments: Transport &amp; PES Layer Test 
               
               
                 Test Name 
                 Goal &amp; Verification 
                 (AF ≠ 0, M1 = 1, PES_PAYLOAD_LENGTH = 17500) 
               
               
                   
               
               
                 VideoAFPES 
                 TP: data_byte; 
                 A transport stream of 100 single video PID transport packets with one 
               
               
                 PayloadData 
                 PES_packet_data_byte; 
                 PES packet. No flags of a PES header should be set to 1. No stuffiing in 
               
               
                   
                   
                 AF or PES header, payload only in all transport packets and in one full 
               
               
                   
                   
                 PES packet. 
               
               
                   
               
               
                   
                   
                 Comments: PES Layer Test 
               
               
                 Test Name 
                 Goal &amp; Verification 
                 (AF ≠ 0, M1 = 1, PES_PAYLOAD_LENGTH = 17400) 
               
               
                   
               
               
                 VideoAFPES 
                 Single IRV on ‘new 
                 A transport stream of 100 single video PID transport packets with one 
               
               
                 StuffPayload 
                 PES header available’ 
                 PES packet. No flags in AF or PES header should be set; 100 PES 
               
               
                   
                   
                 stuffing bytes and payload after. 
               
               
                   
               
               
                   
                   
                 Comments: PES Layer Test 
               
               
                 Test Name 
                 Goal &amp; Verification 
                 (AF ≠ 0, M1 = 1, PES_PAYLOAD_LENGTH = 1000) 
               
               
                   
               
               
                 PES Header 
                 IRV on extraction of 
                 Single PID transport streams with individual PES header data 
               
               
                   
                 PES header fields; 
                 (data_alignment_flag, copyright, original_or_copy, 
               
               
                   
                   
                 additional_copy_info, ESCR, ES_rate DSM_trick_mode, 
               
               
                   
                   
                 previous_PES_packet_CRC, P-STD_buffer_size). To test parsing of 
               
               
                   
                   
                 various PES header elements in the same PES header. 
               
               
                   
               
               
                   
                   
                 Comments: PES Layer Test 
               
               
                 Test Name 
                 Goal &amp; Verification 
                 (AF ≠ 0, M1 = 1, PES_PAYLOAD_LENGTH = 15500) 
               
               
                   
               
               
                 VideoPTS1 
                 PTS_DTS_flags = ‘10’ 
                 To test extraction of the PTS/DTS field and interrupt signaling on 
               
               
                 VideoPTS2 
                 PTS_DTS_flags = ‘11’ 
                 video PID with a single PID transport stream with 100 transport 
               
               
                   
                   
                 packets and one PES packet; 
               
               
                   
               
               
                   
                   
                 Comments: PES Layer Test 
               
               
                 Test Name 
                 Goal &amp; Verification 
                 (AF ≠ 0, M1 = 2, PES_PAYLOAD_LENGTH = 7750) 
               
               
                   
               
               
                 Video 
                 PES_CRC_flag; 
                 A transport stream of up to 200 transport packets carrying two PES 
               
               
                 PESCRC 
                 previous_PES_packetCRC 
                 packets with no CRC16 code on first and exact CRC on second (to test 
               
               
                   
                   
                 PES CRC calculation); 
               
               
                   
               
               
                   
                   
                 Comments: PES Layer Test 
               
               
                 Test Name 
                 Goal &amp; Verification 
                 (AF ≠ 0, M1 = 1, PES_PAYLOAD_LENGTH = 15800) 
               
               
                   
               
               
                 VideoPES 
                 IRV and GKV on 
                 A transport stream of 100 single video PID transport packets with 
               
               
                 PrivateData 
                 known PES header 
                 private data in the PES header in only one PES packet. PES header 
               
               
                   
                 private data string. 
                 contains only PES_extension_flag and PES_private_data_flag. To test 
               
               
                   
                   
                 extraction and transfer of private data to a system memory. No private 
               
               
                   
                   
                 data in the adaptation field. 
               
               
                   
               
               
                   
                   
                 Comments: PES Layer Test 
               
               
                 Test Name 
                 Goal &amp; Verification 
                 (AF ≠ 0, M1 = 2, PES_PAYLOAD_LENGTH = 14800) 
               
               
                   
               
               
                 VideoAFPES 
                 IRV and GKV on 
                 A transport stream of 100 single video PID transport packets with 
               
               
                 PrivateData 
                 known AF and PES 
                 private data in the adaptation field and PES header. Only one PES 
               
               
                   
                 header private data 
                 packet. PES header contains only PES_extension_flag and 
               
               
                   
                 strings. 
                 PES_private_data_flag. Adaptation field contains 
               
               
                   
                   
                 transport_private_data_flag. PES header must span to at least two transport 
               
               
                   
                   
                 packets. To test extraction and transfer of private data to a system memory. 
               
               
                   
               
            
           
         
       
     
     While originating errors on transport layer, PES layer should be error-free and vice-versa. For transport layer test, header of the PES packet should contain only first 9 bytes (no flags set to 1) with PES payload starting from 0x00 towards 0xFF and rolling over. For PES layer tests, transport packets should not contain any indicators or flags of second byte of adaptation field set to 1. Length of adaptation fields should be adjusted by stuffing. 
     The following tables indicate specific test streams &amp; methods with introduced errors: 
     
       
         
           
               
               
               
             
               
                   
               
             
            
               
                   
                   
                 Comments: Transport Layer Test 
               
               
                 Test Name 
                 Goal &amp; Verification 
                 (AF = 0, M1 = 0, no PES stream) 
               
               
                   
               
               
                 SyncErrors1 
                 IRV on SyncLock- 
                 A stream 100 transport packets long with one PID only. These 
               
               
                   
                 SyncDrop sequence; 
                 packets are full of random number of “sync” bytes, and bit-shifted 
               
               
                   
                   
                 versions of the sync byte after 4 byte transport packet header. The 
               
               
                   
                   
                 purpose of this test is to insure framer does not sync on wrong transport 
               
               
                   
                   
                 packet start code sequence. First 32 packets should have correct start 
               
               
                   
                   
                 code (0x47), all others should be wrong, generated as random bytes. 
               
               
                   
                   
                 No PES packet should exist (payload_unit_start_indicator = 0); 
               
               
                   
               
               
                   
                   
                 Comments: Transport Layer Test 
               
               
                 Test Name 
                 Goal &amp; Verification 
                 (AF = 0, M1 = 0, no PES stream) 
               
               
                   
               
               
                 SyncErrors2 
                 IRV on SyncLock- 
                 MPEG-2 transport stream 100 transport packets with one PID only. 
               
               
                   
                 SyncDrop-SyncLock 
                 These packets are full of random number of “sync” bytes, and bit-shifted 
               
               
                   
                 sequence; 
                 versions of the sync byte in the payload of the transport packet. 
               
               
                   
                   
                 The purpose of this test is to insure framer locks, drops  and locks again 
               
               
                   
                   
                 on the start of MPEG-2 transport packet. First 32 packets have correct 
               
               
                   
                   
                 start codes, then next 32 packets has errors on start codes, all other 
               
               
                   
                   
                 packets are error-free and have correct start code (0x47). No PES 
               
               
                   
                   
                 packet should exist (payload_unit_start_indicator = 0); 
               
               
                   
               
               
                   
                   
                 Comments: Transport Layer Test 
               
               
                 Test Name 
                 Goal &amp; Verification 
                 (AF ≠ 0, M1 = 1, PES_PAYLOAD_LENGTH = 16000) 
               
               
                   
               
               
                 VideoTE1 
                 IRV on transport —   
                 A transport stream of 100 single video PID transport packets with 
               
               
                   
                 error_indicator; 
                 random TEI insertion. To test acceptance or rejection of TEI packets 
               
               
                   
                 Routing or rejection 
                 and insertion of video sequence_error_code in the video FIFO. All 
               
               
                   
                 of transport packet. 
                 syntax elements are correct. No AF and PES packet flags. 
               
               
                   
                   
                 One PES packet within 100 transport packets with known payload. 
               
               
                 OthersTE1 
                 Relevant for SW parser 
                 A transport stream of 3200 transport packets (32 PIDs) with random 
               
               
                   
                   
                 TEI insertion. 
               
               
                   
               
               
                   
                   
                 Comments: Transport LayerTest 
               
               
                 Test Name 
                 Goal &amp; Verification 
                 (AF ≠ 0, M1 = 1, PES_PAYLOAD_LENGTH = 175000) 
               
               
                   
               
               
                 Duplicate 
                 continuity_counter; 
                 A transport stream of 1000 single video PID transport packets with 
               
               
                 Packets 
                 dropping of duplicate 
                 random duplicate packets signaled at the continuity counter. 
               
               
                   
                 vid. transport packets 
                 No discontinuities on CC counter. 
               
               
                   
                   
                 To test dropping of second, third, etc. duplicate packets. 
               
               
                   
                   
                 Regular PES packet underneath. 
               
               
                   
               
               
                   
                   
                 Comments: Transport Layer Test 
               
               
                 Test Name 
                 Goal &amp; Verification 
                 (AF ≠ 0, M1 = 1, PES_PAYLOAD_LENGTH = 175000) 
               
               
                   
               
               
                 CCErrors 
                 random discontinuities: 
                 A transport stream of 1000 single video PID transport packets with 
               
               
                   
                 continuity_counter of 
                 random CC errors. To test CC error detection and insertion of video 
               
               
                   
                 vid. transport packets 
                 sequence_error code. No duplicate transport packets. CC error with 
               
               
                   
                   
                 payload_unit_start_indicator == 1; One PES packet. 
               
               
                   
               
               
                   
                   
                 Comments: Transport Layer Test 
               
               
                 Test Name 
                 Goal &amp; Verification 
                 (AF ≠ 0, M1 = 1, PES_PAYLOAD_LENGTH = 175000) 
               
               
                   
               
               
                 CCDuplicate 
                 continuity_counter; 
                 A transport stream of 1000 single video PID transport packets with 
               
               
                   
                 dropping of duplicate 
                 random CC errors and random duplicate packets. To test dropping of 
               
               
                   
                 vid. transport packets 
                 duplicate packets and CC error detection and insertion of video 
               
               
                   
                 IRV on CC errors 
                 sequence_error code in video FIFO buffer. CC error with 
               
               
                   
                   
                 payload_unit_start_indicator == 1; One PES packet with no flags in 
               
               
                   
                   
                 PES header. 
               
               
                   
               
               
                   
                   
                 Comments: Transport Layer Test 
               
               
                 Test Name 
                 Goal &amp; Verification 
                 (AF ≠ 0, M1 = 1, PES_PAYLOAD_LENGTH = 175000) 
               
               
                   
               
               
                 Scrambled 
                 transport_scrambling —   
                 A transport stream of 100 single video PID transport packets with 
               
               
                 Transport 
                 control; rejection of 
                 random number of ‘scrambled’ packets (transport_scrambling_control |= 
               
               
                 Packet 
                 scrambled transport 
                 ‘00’ but not with payload_unit_start_indicator ==1). To test dropping 
               
               
                   
                 packets; IRV and GKV 
                 of scrambled transport packets. One PES packet with no flags in PES 
               
               
                   
                 on known PESpayload 
                 header and predefined (known) PES payload. 
               
               
                   
               
               
                   
                   
                 Comments: Transport Layer Test 
               
               
                 Test Name 
                 Goal &amp; Verification 
                 (AF ≠ 0, M1 = 1, PES_PAYLOAD_LENGTH = 175000) 
               
               
                   
               
               
                 WrongAFLenX 
                 error on adaptation —   
                 A transport stream of 100 single video PID transport packets with 
               
               
                 X ε {0, 1, 2}; 
                 field_length; 
                 adaptation_field_length: larger than 183 or equal to zero or larger than 
               
               
                   
                 to test search for PES 
                 actual (real) length for 10 bytes. 
               
               
                   
                 packet_start_code_prefix 
                 One full PES packet with no flags and known payload underneath. 
               
               
                   
                   
                 Three indipendent test streams. 
               
               
                   
                   
                 ASIC should skip 0 length adaptation field. 
               
               
                   
               
               
                   
                   
                 Comments: Transport Layer Test 
               
               
                 Test Name 
                 Goal &amp; Verification 
                 (AF ≠ 0, M1 = 1, PES_PAYLOAD_LENGTH = 155000) 
               
               
                   
               
               
                 WrongAFPDL 
                 transport_private —   
                 A transport stream of 100 single video PID transport packets with 
               
               
                   
                 data_flag; 
                 transport_private_data_length shorter or longer for 10 bytes than 
               
               
                   
                 private_data_byte; 
                 actual (real) length. 
               
               
                   
                 To test transport layer 
                 Exact adaptation_field_length is required. 
               
               
                   
                 parser; IRV and GKV 
                 If transport_private_data_length is shorter than actual private 
               
               
                   
                 on known AF private 
                 data byte field, transport layer parser should process AF with no syntax 
               
               
                   
                 data content; 
                 parsing problems, only partial private data loss will occur. If the 
               
               
                   
                   
                 transport_private_data_length extends AF over the length specified 
               
               
                   
                   
                 by adaptationfield_length, transport layer parser should cut AF private 
               
               
                   
                   
                 data processing at the exact end of the adaptation field. If increase in 
               
               
                   
                   
                 transport_private_data_length goes into stuffing, some private data 
               
               
                   
                   
                 corruption will occure but with no failure of the transport layer parser. 
               
               
                   
               
               
                   
                   
                 Comments: PES Layer Test 
               
               
                 Test Name 
                 Goal &amp; Verification 
                 (AF ≠ 0, M1 = 2, PES_PAYLOAD_LENGTH = 8750) 
               
               
                   
               
               
                 PacketStart 
                 Error on packet —   
                 Single PID transport stream of 100 transport packets carrying two full 
               
               
                 CodeError1 
                 start_code_prefix; 
                 PES packets. Second packet should have wrong 
               
               
                   
                 packet rejection. 
                 packet_start_code_prefix. No legal (0x000001) start code should exist 
               
               
                   
                   
                 in the header or payload of both PES packets. No flags in PES packets. 
               
               
                   
                   
                 PES parser should reject full second packet. 
               
               
                   
               
               
                   
                   
                 Comments: PES Layer Test 
               
               
                 Test Name 
                 Goal &amp; Verification 
                 (AF ≠ 0, M1 = 2, PES_PAYLOAD_LENGTH = 8750) 
               
               
                   
               
               
                 PacketStart 
                 Error on packet —   
                 Single PID transport stream of 100 transport packets carrying two full 
               
               
                 CodeError2 
                 start_code_prefix; 
                 PES packets. Second packet should have wrong 
               
               
                   
                 Test of the false lock. 
                 packet_start_code_prefix. No legal (0x000001) start code should exist 
               
               
                   
                   
                 in the header or payload of first PES packets. No flags in PES packets. 
               
               
                   
                   
                 Payload of the second packet should have continuous sequence of start codes. 
               
               
                   
                   
                 False lock on correct start code should occure even if 
               
               
                   
                   
                 payload_unit_start_indicator is 0. 
               
               
                   
               
               
                   
                   
                 Comments: PES Layer Test 
               
               
                 Test Name 
                 Goal &amp; Verification 
                 (AF ≠ 0, M1 = 2, PES_PAYLOAD_LENGTH = 8750) 
               
               
                   
               
               
                 StreamID 
                 wrong stream_id 
                 Single PID transport stream of 100 transport packets carrying two full 
               
               
                 Error 
                 packet rejection on 
                 PES packets with stream_id on first set to 0xE0 and known payload, 
               
               
                   
                 Stream_id mismatch. 
                 and stream_id of the second packet set to 0xF0 and known (different payload). 
               
               
                   
                   
                 Second packet should be rejected. 
               
               
                   
               
               
                   
                   
                 Comments: PES Layer Test 
               
               
                 Test Name 
                 Goal &amp; Verification 
                 (AF ≠ 0, M1 = 2, PES_PAYLOAD_LENGTH = 8750) 
               
               
                   
               
               
                 Scrambled 
                 PES_scrambling —   
                 Single PID transport stream of 100 transport packets carrying two full 
               
               
                 PESPacket 
                 control.; FCV &amp; GKV 
                 PES packets with PES_scrambling_control on first set to ‘00’ and 
               
               
                   
                 on known PES payload 
                 known payload, and PES_scrambling_control of the second packet set 
               
               
                   
                   
                 to ‘01’ and known (different payload). 
               
               
                   
                   
                 Second packet should be rejected. 
               
               
                   
               
               
                   
                   
                 Comments: PES Layer Test 
               
               
                 Test Name 
                 Goal &amp; Verification 
                 (AF ≠ 0, M1 = 2, PES_PAYLOAD_LENGTH = 8750) 
               
               
                   
               
               
                 PESHeaderData 
                 PES_header_data_len 
                 Single PID transport stream of 100 transport packets carrying two full 
               
               
                 LengthErrorX 
                 IRV and GKV on 
                 PES packets with error on PES_header_data_length on the second 
               
               
                 X ε {0, 1, 2}; 
                 known PES payload. 
                 packet and known PES payload. 
               
               
                   
                   
                 Length should be set to 0 (legal value) or value larger or smaller for 10 
               
               
                   
                   
                 than exact value. Only additional_copy_info_flag should exist in PES 
               
               
                   
                   
                 header. 
               
               
                   
               
               
                   
                   
                 Comments: PES Layer Test 
               
               
                 Test Name 
                 Goal &amp; Verification 
                 (AF ≠ 0, M1 = 2, PES_PAYLOAD_LENGTH = 8750) 
               
               
                   
               
               
                 CRC16Error 
                 PES_CRC_flag; 
                 Single PID transport stream of 100 transport packets carrying two full 
               
               
                   
                 IRV and GKV on 
                 PES packets with errors in the previous_PES_packet_CRC and known 
               
               
                   
                 known PES payload. 
                 PES payload. To test PES CRC calculation engine. Some default and 
               
               
                   
                   
                 known wrong CRC value should be given. 
               
               
                   
               
            
           
         
       
     
     Examples of specific script files are indicated below. In one embodiment, each script file contains one data record, and multiple script files can be combined using a basic piping function. In another embodiment, a script file can have a multiple records delineated by a record identifier. 
     
       
         
           
               
             
               
                   
               
               
                 Examples of script files 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
            
               
                 ; Test name: BasicMain ---------------------------------------------------------- 
               
               
                 PES_C 
               
               
                 PES_OOC 
               
            
           
           
               
               
            
               
                 PES_PAYLOAD_LENGTH 175 
                 “BasicMain test - ASCII text string 
               
               
                   
                 in the PES payload” 
               
               
                 TP_PID     1023 
               
            
           
           
               
            
               
                 ; Test name: SyncLock ----------------------------------------------------------- 
               
               
                 PES_PAYLOAD_LENGTH 5775 0 
               
               
                 TP_PID 1023 
               
               
                 ; Test Name: VideoAFPrivateData ---------------------------------------------- 
               
               
                 REPEAT 1000 
               
            
           
           
               
               
            
               
                   
                 TP_PID 1023 
               
               
                   
                 TP_PAYLOAD “VideoAFPrivateData test” 
               
            
           
           
               
            
               
                 END 
               
            
           
           
               
               
            
               
                 AF_TPD_FLAG 
                 26 “Video AF private data” 
               
            
           
           
               
            
               
                 ; Test name: CRC16Error -------------------------------------------------- 
               
               
                 REPEAT 2 
               
            
           
           
               
               
            
               
                   
                 PES_CRC_FLAG    A55AH 
               
               
                   
                 PES_PAYLOAD_LENGTH    8750    0 
               
            
           
           
               
            
               
                 END 
               
               
                 TP_PID 1023 
               
            
           
           
               
               
               
            
               
                 TP_PAYLOAD 
                 15 
                 “TP payload data” 
               
               
                 AF_PCR_FLAG 
                 1000 
                 10 
               
               
                 AF_OPCR_FLAG 
                   
                 11 
               
               
                 AF_TPD_FLAG 
                 15 
                 “AF private data” 
               
            
           
           
               
            
               
                 ; Test name: SyncErrors2 -------------------------------------------------- 
               
               
                 REPEAT 100 
               
            
           
           
               
               
               
            
               
                   
                 TP_SYNC 32 32 
                 BITSHIFT 
               
               
                   
                 TP_PID 1023 
               
               
                   
                 TP_PAYLOAD 
                 BITSHIFT 
               
            
           
           
               
            
               
                 END 
               
               
                   
               
            
           
         
       
     
       FIG. 44  illustrates a system  4100 , which includes a system  4110 , which may be of the type illustrated in  FIG. 43 , and a system, or device under test  4120 . Note that the system under test may actually be a software module being simulated in the system  4110 . In operation, the system  4110  generates, and outputs the transport packet stream to the device under test  4120 , which in turn performs the demultiplexing function described herein. As a result, the data from various transport packets are provided to the memory  4124 . More specifically, in accordance with the invention, the video packets are routed to the video buffer  4241 , and other data packets are routed to one of a plurality of auxiliary buffers  4242 - 4243  based upon their respective PID. 
       FIG. 45  illustrates a memory portion of the system  4110  of  FIG. 44. A  memory portion  4510  stores the various data records associated with a test suite of transport data. This test suite is read by the composer software, which is stored in the memory portion  4520 . The composer can store the generated transport streams in files (not illustrated) and can output the desired transport streams directly to an external device under test, or an internal simulator, which simulates a system under test. The simulator is stored in memory portion  4530 , and outputs results to one of the buffers  4541 - 4543 . 
     In an alternate embodiment, the device under test  4120  of  FIG. 44 , can provide the buffered data back to the system  4110  to be stored in the memory portions  4551 - 4553  and be compared to the data stored in the buffers  4241 - 4243  for verification of the external device under test to the simulated device under test. 
     Another tool for use with verification of the systems described herein is a simulator. The following describes such implementation of a simulator. 
     The purpose of this section is to provide some guidelines for a specific implementation as how to implement MPEG-2 transport demultiplexer in C language in order to verify the parsing of transport files to the level of elementary stream. Produced elementary stream has been compared against stream generated by reference transport stream generation equipment, which, in this case, has been used as a reference transport/PES stream decoder. 
     Developed C model operates on MPEG-2 transport stream files and has capabilities to parse the video PID and route up to 31 other (auxiliary) full transport packets to the maximum 15 other files. This way, the capabilities of the output interface are modeled. 
     The transport parser routes video elementary stream of PID_ 0  to buffer 0 allocated in the frame memory. Buffers  1  to  14  are used to route single PIDs. If more than 12 PIDs exist, PIDs above 12 are routed into buffer  15 . 
     The same behavior is followed on output files. If&lt;filename&gt;.TSP is input file name (filename of MPEG-2 multiplexed transport stream) then:
     filename_PID0.ES contains elementary stream of video, PID0 has been set to 4 hex digits of the video PID;   filename_PID1.TS . . . filename_PID14 contains full packets of PIDs 1 to 14;   filename_PID15.TS contains all other transport packets acquired on a PID match from PID numbers 13 to 31.   

     Again, PIDx has a 4 hex digits which represents actual PID value. Video PID is identified by processing PAT/PMT PSI tables (if exist in the transport files). 
     To speed up and simplify a C model development, all file I/O and user interface was implemented as the multithreaded C console application. Beside a main loop function, a monitor thread has been created to gather statistics about processor utilization Also, a serial bit-stream framing process and a serial CRC16 process were simulated. This is under conditional compilation because it slows down a processing speed of the model. Model simulates operation of the framer synchronization logic, transport packet processor (TPP) and PES header processor (PESP). Under Visual C/C++ environment, a console application is defined with debug multithread option and libcmt.lib library. With option to ignore all default libraries. 
     Transport packet based parsed data are saved in the memory buffer. The content of the buffer is routed to one of the output files at the end of the current transport packet (end of TPP) or at the time of the private data extraction (end of AFP or inside PESP). The output FIFO of developed ASIC works the same way. If its length is less than one packet, it will request a read-out after a threshold is reached. 
     The following naming convention applies to all interface signals, interface buses, internal variables, registers and counters of TPF, TPP or PESP units. 
     
       
         
           
               
               
               
             
               
                   
               
             
            
               
                 BOOL 
                 oBitXXXX_SignalName; 
                   
               
            
           
           
               
            
               
                 This is used for any digital output signals, XXXX = 
               
               
                 {TPF, TPP, AFP, PESP}; 
               
               
                 For example: oBitTPF_InSyncSignal, oBitTPP_Pusi, etc. 
               
               
                 unsigned char oBusXXXX_BusName; 
               
               
                 This is used for any digital output bus signals, XXXX = 
               
               
                 {TPF, TPP, AFP, PESP}; 
               
               
                 For example: oBusTPF_Data, oBusTPP_PidIndex, etc. 
               
            
           
           
               
               
               
            
               
                 BOOL 
                 iSignalXXXX_Name; 
                   
               
            
           
           
               
            
               
                 Internal synchronization signal (internal to XXXX unit). 
               
               
                 For example: iSignalTPP_VideoCC, iSignalTPP_PcrCC, 
               
               
                 iSignalTPP_Header; 
               
            
           
           
               
               
               
            
               
                 unsigned char 
                 iRegXXXX_RegName; 
                   
               
            
           
           
               
            
               
                 Internal register (internal to XXXX unit and usually not visible to 
               
               
                 programmer). 
               
            
           
           
               
               
               
            
               
                 unsigned char 
                 iCntXXXX_CntName; 
                   
               
            
           
           
               
            
               
                 Internal counter (internal to XXXX unit and usually not visible to 
               
               
                 programmer). 
               
               
                   
               
            
           
         
       
     
     MPEG relevant data extracted from transport or PES headers (usually flags) were named according to their original ISO138181-1 names to allow easier understanding of the parsing logic and operations. For example: discontinuity_indicator, random_access_indicator, etc. All parsing engines were designed as byte oriented state machines. The objective is to minimize the number of interface signals and buses between them and provide independent, self-contained behavior and achieve:
     Autonomous VHDL design and simple verification.   Independent, concurrent work on TPF, TPP &amp; PESP parsing units by simultaneous allocation of four design engineers.
 
The transport packet framer portion of the simulator includes following variables:
   

     
       
         
           
               
             
               
                   
               
             
            
               
                 /* Interface signals of the transport packet framer (TPF) ------------------ */ 
               
            
           
           
               
               
            
               
                 BOOL 
                 oBitTPF_PacketStartSignal, oBitTPF_InSyncSignal, 
               
               
                   
                 oBitTPF_Irq; 
               
            
           
           
               
            
               
                 /* Four possible states of a Transport Packet Framer (TPF)--------------- */ 
               
            
           
           
               
               
               
            
               
                 #define 
                 FRAMER_STATE_SYNC_LOST 
                 0 
               
               
                 #define 
                 FRAMER_STATE_SYNC_SEARCH 
                 1 
               
               
                 #define 
                 FRAMER_STATE_SYNC_VERIFY 
                 2 
               
               
                 #define 
                 FRAMER_STATE_SYNC_LOCK 
                 3 
               
            
           
           
               
            
               
                 /* Transport Packet Framer *********************************** * 
               
               
                  * Next group of variables should be used for TPF only, not visible to 
               
               
                 other blocks ----- */ 
               
            
           
           
               
               
            
               
                   
                 unsigned char iRegTPF_FramerState; 
               
               
                   
                 unsigned char iCntTPF_ByteCnt, iCntTPF_SyncLock, 
               
               
                   
                 iCntTPF_SyncDrop; 
               
            
           
           
               
            
               
                 iRegTPF_FramerState records one of the four states of the framer. 
               
               
                 iCntTPF_ByteCnt is modulo 188 local packet byte counter. 
               
               
                 iCntTPF_SyncLock is lock counter. 
               
               
                 iCntTPF_SyncDrop is drop counter. 
               
               
                   
               
            
           
         
       
     
     Signal oBitTPF_PacketStartSignal is active for a full byte time of the first byte (0x47) of the transport packet and is used to synchronize a transport packet parser (whose internal byte counter is set to 0). 
     Signal oBitTPF_InSyncSignal is activated at the start of the transport packet when transport frame synchronization is achieved. It is deactivated after the loss of synchronization. These events also generate interrupt request (IRQ) on a separate line oBitTPF_Irq. This signal enables further processing of the transport packet parser. When oBitTPF_InSyncSignal is at its inactive level all further processing is disabled. 
     The transport packet parser portion of the simulator includes following variables: 
     
       
         
           
               
             
               
                   
               
             
            
               
                 /* Interface signals of the Transport Packet Parser (TPP) ----------------- */ 
               
            
           
           
               
               
            
               
                 unsigned char 
                 oBusTPP_PidIndex; 
               
               
                 unsigned char 
                 oRegTPP_Header1, oRegTPP_Header2, 
               
               
                   
                 oRegTPP_Header3; 
               
               
                 BOOL 
                 oBitTPP_Irq, oBitTPP_VideoCC, oBitTPP_PcrCC; 
               
               
                 BOOL 
                 oBitTPP_AFStartSignal, oBitTPP_PusiSignal; 
               
            
           
           
               
            
               
                 /* Seven possible states of a transport packet parser (TPP) with fix 
               
               
                 assignments */ 
               
            
           
           
               
               
               
            
               
                 #define 
                 TP_PARSER_STATE_OFF 
                 0 
               
               
                 #define 
                 TP_PARSER_STATE_READY 
                 1 
               
               
                 #define 
                 TP_PARSER_STATE_VIDEO_AF 
                 4 
               
               
                 #define 
                 TP_PARSER_STATE_VIDEO_PES 
                 2 
               
               
                 #define 
                 TP_PARSER_STATE_OTHERS_FULLPACKET 
                 3 
               
               
                 #define 
                 TP_PARSER_STATE_OTHERS_AF_PCR_ONLY 
                 5 
               
               
                 #define 
                 TP_PARSER_STATE_OTHERS_AF_PCR_ROUTE 
                 6 
               
            
           
           
               
            
               
                 /* Transport Packet Parser ************************************* * 
               
               
                  * Next group of variables should be used for TPP only, not visible to 
               
               
                  other blocks --- */ 
               
               
                  unsigned char iRegTPP_ParserState, iCntTPP_AFLength, 
               
               
                  iCntTPP_ByteCnt; 
               
               
                  unsigned char iCntTPP_VideoCC, iCntTPP_PcrCC, 
               
               
                  iCntTPP_DeltaCC; 
               
            
           
           
               
               
            
               
                  BOOL 
                 iSignalTPP_VideoCC, iSignalTPP_PcrCC, 
               
               
                   
                 iSignalTPP_Header; 
               
            
           
           
               
            
               
                  unsigned short int PID; 
               
               
                  unsigned char adaptation_field_control, continuity_counter; 
               
            
           
           
               
               
            
               
                  BOOL 
                 transport_error_indicator, payload_unit_start_indicator; 
               
               
                   
               
            
           
         
       
     
     Bus signal oBusTPP_PidIndex (5 bits) is used to indicate which of 32 PIDs are currently active (PID_ 0  is reserved for video). This signal is used to access appropriate PID control register and determine 1 of 16 output paths for routing of parsed data or full transport packets. 
     Eight bit internal registers oRegTPP_Header 1 , oRegTPP_Header 2 , oRegTPP_Header 3  are used as a scratch pad registers to hold bytes  2 ,  3 ,  4  of the transport packet header until the determination of a PID. If any of PIDs 1 . . . 31 is selected, or if there are any private data in the adaptation field or a PES packet header within a current transport packet, content of those 3 internal registers is used to reassemble a packet. 
     Digital output oBitTPP_AFStartSignal synchronizes byte counter of AFP parser. 
     Digital output oBitTPP_PusiSignal synchronizes byte counter of PES parser. 
     Internal register iRegTPP_ParserState works as a state register. 
     Internal counter iCntTPP_ByteCnt is transport packet byte counter which determines a parsing logic on transport packet header and fifth byte (length of the adaptation field, if one exists). 
     Transport Packet Parser (TPP) can be in one of 7 states. State assignment is done at the end of reception and processing of the 4 th  byte of the transport packet header or at the end of adaptation field. State assignment should not be changed due to simple verification of states 4,5,6 (all of them has to process adaptation field due to video parsing, or PCR extraction on PCR PID on transport packet selected for PCR process only or for PCR process and routing to the system memory.  FIG. 46  shows a state diagram of the TPP parser. Next states exist: 
     TP_PARSER_STATE_OFF (0) when it is completely disabled and the current packet is ignored. This occurs in the case of wrong packet start code, PID mismatch, scrambling at the transport packet level or illegal adaptation field indicator value (‘00’). All further parsing logic is disabled until the start of next transport packet. 
     TP_PARSER_STATE_READY (1) is a state after a start code verification (0x47). From this state, parsing logic can step back to TP_PARSER_STATE_OFF (in the case of PID mismatch, scrambling at the transport packet level or illegal adaptation field indicator value (‘00’) or it can advance into one of five next processing state: 
     TP_PARSER_STATE_VIDEO_PES (2) is a state of parsing useful payload of the transport packet carrying a video stream. 
     TP_PARSER_STATE_OTHERS_FULLPACKET (3) is a state where a fill transport packet is routed to a system memory after a PID match. 
     A continuity counter check exists for a video PID. CC check has to detect CC samples on duplicate transport packets, 15 to 0 rollover, signaled discontinuities on CC counter and real discontinuities when a few transport packets are missing due to uncorrectable errors in the communication channel. Suggested algorithm calculates a first difference between a stream CC value and a current value of the CC counter BEFORE it is being incremented. This yields to a less complex algorithm and less expensive HW implementation than a method based on the first increment of the local CC counter and comparison later. If delta is 0 it means that we have a duplicate transport packet, which should be ignored by setting a parsing engine from READY to OFF state. If delta is 1 it means a regular condition, and we should increment a local CC counter. If delta is 15 it means a rollover and we assign a counter value to a stream value (0). Any other value means CC error and local counter HAS to be initiated from a stream CC value, so this event is only once signaled. This behavior is illustrated on a next set of continuity counter values: 
     The PES parser includes the following variables: 
     
       
         
           
               
             
               
                   
               
             
            
               
                 /* Interface signals of the PES Parser (PESP) ------------------------------- */ 
               
            
           
           
               
               
            
               
                 BOOL 
                 oBitPESP_PrivateDataFlag, oBitPESP_Irq; 
               
            
           
           
               
            
               
                 /* Four possible states of a PES packet parser ------------------------------- */ 
               
            
           
           
               
               
               
            
               
                 #define 
                 PES_PARSER_STATE_READY 
                 0 
               
               
                 #define 
                 PES_PARSER_STATE_HEADER 
                 1 
               
               
                 #define 
                 PES_PARSER_STATE_STUFFING 
                 2 
               
               
                 #define 
                 PES_PARSER_STATE_PAYLOAD 
                 3 
               
            
           
           
               
            
               
                 /* PES Packet Parser ***************************************** * 
               
               
                  * Next group of variables should be used for PESP only, not visible to 
               
               
                  other blocks -- */ 
               
            
           
           
               
               
            
               
                  unsigned char 
                 iRegPESP_ParserState, iCntPESP_Headelength; 
               
               
                  unsigned short int 
                 iCntPESP_ByteCnt, iCntPESP_LocalByteCnt, 
               
               
                   
                 iCntPESP_LocalPTSByteCnt; 
               
               
                  BOOL 
                 PTS_DTS_flag, PTS_flag; 
               
               
                  BOOL 
                 ESCR_flag ES_rate_flag, 
               
               
                   
                 DSM_trick_mode_flag; 
               
               
                  BOOL 
                 additional_copy_info_flag, 
               
               
                   
                 PES_CRC_flag, PES_extension_flag; 
               
            
           
           
               
            
               
                  /* In the extension field of the PES header -------------------------------- */ 
               
            
           
           
               
               
            
               
                  BOOL 
                 PES_private_data_flag, pack_header_field_flag; 
               
               
                  BOOL 
                 program_packet_sequence_counter_flag; 
               
               
                  BOOL 
                 P_STD_buffer_flag, PES_extension_flag2; 
               
               
                   
               
            
           
         
       
     
     PES Parser (PESP) is organized as a state machine with only 4 states, defined by the state register iRegPESP_ParserState: 
     PES_PARSER_STATE_READY (0) that is intermediate state after reset or errors in header detected by parsing engine. This essentially allows self-synchronization after errors and search (hunting) for PES packet start code (0x000001). Depending on the current byte value, local byte counter is set to 0 or 1 (if pattern 0x00 is being detected). Stream conditions that turn PESP engine to PES_PARSER_STATE_READY are:
     wrong packet start code.   wrong stream_id (different than 0xBD as private_stream_ 1 , 0xEX where X ε {0,1, . . . 15} as MPEG video stream number, 0xF 2  or DSM CC stream, 0xF 2 −0xF 9  but not 0xF 8 );   stream_id mismatch (if instructed to process stream_id in the video PID control register).   syntax error on 2 ms bit positions of byte  6  of PES header.   scrambled payload of the PES packet (as indicated by PES_scrambling_control of byte  6 ).   

     PES_packet_length field (4 th  and 5 th  bytes of PES header) is not acquired and the actual length of the PES packet is not verified because in a transport stream environment this field usually has a legal value of zero (unbounded). Processing of this field would require 16 bit counter and check logic if stream value is different from 0. 
     PES_PARSER_STATE_HEADER (1) is the parsing state where the PES packet start code detection is taking place. First 9 bytes of the PES header are always parsed. All flags within 8 th  byte are saved and a PES_header_data_length from 9 th  byte is saved in the local byte counter iCntPESP_HeaderLength and is used to identify end of optional stuffing field and start of the PES payload that contains elementary video stream. For byte counting, which identifies bytes within PES header, local counter iCntPESP_ByteCnt is used. PTS values from the PTS or PTS_DTS field are extracted and saved. PTS byte count, managed with the iCntPESP_LocalPTSByteCnt is saved and transferred to the video decoder&#39;s compressed video bit-stream buffer. This counter is incremented only when processing a PES payload. After saving all 8 flags from 8 th  byte and PES_header_data_length field, parser is processing optional fields (PTS, ESCR, ES_rate, DSM, additional_copy_info and CRC) by using iCntPESP_LocalByteCnt as local byte counter which keeps tracking the byte position inside optional field of the byte aligned PESP. Reserved data from the extension field are ignored. P-STD_buffer_size is the very last parsed field within extension area of PES header. 
     PES_PARSER_STATE_STUFFING (2) is the parsing state where optional, variable length, stuffing field at the end of PES header is processed (skipped entirely). If 9 th  byte of PES header (PES_header data_length) is zero or if, after parsing a PES header, local counter iCntPESP_HeaderLength has a value of 0 indicating that there is no stuffing, parser advances to the 4 th  and last state: 
     PES_PARSER_STATE_PAYLOAD (3) is a parsing state where a payload of a PES stream carrying ES video is being routed byte by byte to the video FIFO and then to the frame memory. In this process only a PTS byte count is refreshed and a CRC engine is turned on. At the present moment, payload is not verified against PES_packet_length field.  FIG. 47  shows the state machine of the PES parser. 
       FIGS. 48  to  53  illustrate a specific embodiment of the present invention for error detection and handling.  FIG. 48  illustrates an alternative embodiment of a portion of the transport packet demultiplexer illustrated in FIG.  7 . Specifically, the embodiment of  FIG. 48  includes an additional signal labeled V_ERROR being provided to the PESP  730  from the transport packet parser  720 , along with the VSTART and VIDEO signals. 
     Operation of the system portion illustrated in  FIG. 48  is better understood with reference to the method of  FIG. 51 , and specific system implementations of  FIGS. 49  and  50 . At step  4701  of  FIG. 51 , an error recognition feature is enabled. In a specific embodiment, this includes enabling the detection of a specific type of error by asserting an interrupt field of a register location. Specific types of errors capable of being detected include errors associated with transport packet streams and errors associated with packetized elementary streams. 
     In accordance with the present invention, specific errors are indicated in various registers illustrated in  FIGS. 52 and 53 . Furthermore, specific embodiments can use status codes indicating specific error types. Status codes indicating errors associated with a transport packet stream include:
         000—to indicate no error has occurred;   001—to indicate a video PID is received, and the transport packet is scrambled;   002—to indicate and illegal adaptation field control bit field occurs, such as ‘00’   003—to indicate a duplicate video transport packet has been received;   004—to indicate an illegal length of the adaptation field;   005—to indicate an illegal length of adaptation field private data.
 
Status codes indicating errors associated with a video PES include:
       000—to indicate no error has occurred;   001—to indicate a received video stream ID does not match a video stream ID specified in a system register;   002—to indicate the PES header includes a non-video stream ID (i.e. not in the range from 0xE0 to 0xEF);   003—to indicate a syntax error, such as a value other than binary value 10 on the first two bits of the sixth byte of the PES header;   004—to indicate the PES payload is scrambled, as indicated in the PES scrambling control field.   

     The errors listed in the status codes above are based upon specific information associated with the headers of the specific packets. For example, in the transport packet header, the value of the transport scrambling control bits can be used to indicate an error when the transport packet payload is scrambled and decoding device expects a clear, non-encrypted stream. 
     In addition to the specific errors indicated by the status codes, a transport packet having its transport error indicator bit asserted can be identified as an error, and in a specific embodiment can have it own error code. 
     Another condition that can be enabled and recognized by the system as an error is the presence of TError signal of the physical stream interface illustrated in FIG.  8 . In a specific embodiment different errors associated with the TError signal can be recognized depending upon whether the TError signal is asserted before or after reception of the transport packet&#39;s PID. 
     Other error types include CRC errors for transport or PES packets, and continuity counter errors.  FIG. 49  illustrates a system portion for detecting when a continuity discrepancy such as a continuity counter error occurs. For example, when the current transport packet continuity counter value is hexadecimal value 0x7, and the previous transport packet continuity counter value was hexadecimal value 0x5, the continuity counter check portion  4501 , of  FIG. 49 , will detect that the video transport packet having the hexadecimal value 6 was not received. This is known as a continuity counter error. Likewise, the continuity counter check portion can detect when a duplicate packet is received. 
     Yet another error type includes an error based upon an error rate of one or more of the above identified errors. For example, a transport error rate and/or a continuity counter error rate can be maintained. One method of determining an error rate is to subtract a count indicating the total number of packets having a specific error type from the total number of transport packets received during the same period, and dividing the result by total number of packets. This provides a calculated rate, which can be compared to desired error rate to identify an error condition. The calculation of such an error rate can be controlled, or requested, by an external system. For example, the external host processor can request error rates be calculated based upon a request from the transmitting office or head-end device. 
     At step  4702  of  FIG. 51 , a packet is received. A received packet can include a transport packet, a PES, or a different packet type. At step  4703 , the packet is parsed, or otherwise analyzed to determine if an error, such as one of the types described previously is associated with the packet. 
     Detected errors can be handled by one or more methods. When an error occurs in a transport packet, a signal labeled V_ERROR is generated by the TPP  720 , see  FIG. 48 , and provided to the PESP  730 .  FIG. 49  illustrates a specific implementation for performing the function of generating the V_ERROR signal. In the example, illustrated, the generation of the V_ERROR signal is gated to the VIDEO signal such that it is only provided when the current transport packet is a video packet. In addition, the generation of the V_ERROR signal is gated to the detection of one or more errors. Specifically illustrated are errors for the transport error indicator being asserted or a continuity counter error occurring. The occurrence of one of these errors or any other transport stream error can result in V_ERROR being asserted. In a similar manner, a PES header error signal can be generated by the PESP  730 . 
     At step  4704 , an error recovery operation occurs. An error recovery operation includes disregarding the packet data, as well as providing notification to one or more processors, which in turn may take specific actions. In one example, upon receiving the V_ERROR signal from the transport packet parser  720 , the sequence error code enabled portion  4601  of the PESP  730 , illustrated in  FIG. 50 , provides a selected signal to the multiplexor  4603  so that the sequence error start code  4602  is provided to the data output controller  756 . In the specific embodiment illustrated, the sequence error start code  4602  storage location is set to hexadecimal value 0x000001B4. 
     In one embodiment the sequence error start code value is provided to the data out controller  756  instead of compressed video data when the error occurs. In other embodiments, the sequence error start code value can precede or overwrite a portion of the compressed payload data associated with the packet. As illustrated in  FIG. 50 , this error code is provided to the data output controller  756 , which in turn provides the compressed video stream, which now includes the sequence error start code, to a video decode processor. In a specific implementation, a sequence error start code is transmitted under the following circumstances: when a TError signal is detected after the PID is received; when a continuity counter error is detected and the transport packet discontinuity bit is not set; when a transmit error indicate bit is asserted; if any transport packet header error is detected. 
     Another method for handling errors is to disregard the data packet. This can be the sole data handling remedy, or can be combined with other data handling remedies. Disregarding the payload data can include not further parsing the header, and/or disregarding the payload of the packet. In specific implementation, a transport packet is dropped or ignored under the following error conditions: when it is determined that a transport packet has a duplicate continuity counter value as the previous transport packet of the same PID; when the transport error indicator is set; when TError signal is asserted before the PID is received; 
     Another method for handling errors is to send an interrupt to a system, or host processor. In a specific implementation, a generic interrupt is provided, whereby the system can query registers associated with the present invention to determine the error. For example, the system can read a register having the status codes describe above. In another embodiment, individual interrupts, or interrupts with vectors can be applied. In a specific implementation, an interrupt is generated for the following error conditions: when a continuity counter error is detected and the transport packet discontinuity bit is set; when a CRC error occurs; when a predefined error rate condition is met (i.e. specific error rate, or rates, is above a predefined value). 
     It should now be apparent, that the present invention allows for flexible detection, recovery, and handling of errors can be obtained. For example, the sequence error code can be inserted directly into the compressed video stream in order to notify video processor and error condition has occurred. Likewise, system level interrupts can be provided to a host system whereby the host system connections error codes and other register values in order to determine the status of errors and act according.