Source: https://patents.google.com/patent/US20040047417A1/en
Timestamp: 2019-04-25 02:09:31+00:00

Document:
A method and apparatus for compressing a plurality of video sequences, where each sequence has information that is common with other video sequences. The invention ensemble encodes the video sequences into an MPEG compliant transport stream using less predicted frame information than separately encoding each video sequence. One illustrative application of the invention is efficiently encoding and transmitting a user interface such as a program guide, interactive program guide, electronic program guide, navigator and the like. The user interface is illustratively embodied in an interactive program guide (IPG).
U.S. patent application Ser. No. 09/384,394 is also a continuation-in-part of U.S. patent application Ser. No. 09/293,535 filed Apr. 15, 1999, which is hereby incorporated herein by reference in its entirety.
The method of invention works with MPEG-1, MPEG-2, and any future derivatives of MPEG that are compliant with these first two versions. It is also important to note that the invention is equally applicable to any encoding system, including systems that does not utilize MPEG video and transport stream formats.
FIG. 12 depicts a matrix representation of program guide data with the data groupings shown for efficient encoding in accordance with the present invention.
FIG. 1 depicts a high-level block diagram of an information distribution system  100, e.g., a video-on-demand system or digital cable system, that incorporates the present invention. The system 100 contains service provider equipment (SPE) 102 (e.g., a head end), a distribution network 104 (e.g., hybrid fiber-coax network) and subscriber equipment (SE) 106. This form of information distribution system is disclosed in commonly assigned U.S. patent application Ser. No. 08/984,710 filed Dec. 3, 1997. The system is known as DIVA provided by DIVA Systems Corporation.
In general, the SPE  102 produces a plurality of digital streams that contain encoded information in MPEG compressed format. These streams are modulated using a modulation format that is compatible with the distribution network 104. The subscriber equipment 106, at each subscriber location 106 1, 106 2, . . . , 106 n, comprises a receiver 124 and a display 126. Upon receiving a stream, the subscriber equipment receiver 124 extracts the information from the received signal and decodes the stream to produce the information on the display, i.e., produce a television program, program guide page, or other multimedia program.
To assist a subscriber (or other viewer) in selecting programming, the SPE  102 produces an interactive program guide that is compressed for transmission in accordance with the present invention. The IPG contains program information, e.g., title, time, channel, program duration and the like, as well at least one region displaying full motion video, i.e., a television advertisement or promotion. Such informational video is provided in various locations within the program guide screen.
The invention produces the IPG using a compositing technique that is described in commonly assigned U.S. Pat. No. 6,415,437, issued Jul. 2, 2002, and U.S. patent application Ser. No. 09/359,561, filed Jul. 23, 1999 (attny dockets 168 and 168 CIP1), which are hereby incorporated by reference herein. The compositing technique, which will not be discussed further herein, enables full motion video to be positioned within an IPG and have the video seamlessly transition from one IPG page to another. The composited IPG pages (i.e., a plurality of video frame sequences) are coupled from a video source  114 to an encoding and multiplexing unit 116 of the present invention. Audio signals associated with the video sequences are supplied by an audio source 112 to the encoding and multiplexing unit 116.
The encoding and multiplexing unit  116 compresses the frame sequences into a plurality of elementary streams. The elementary streams are further processed to remove redundant predicted frames. A multiplexer within unit 116 then assembles the elementary streams into a transport stream.
The transport stream is then modulated by the digital video modulator  122 using a modulation format that is compatible with the distribution network 104. For example, in the DIVA™ system the modulation is quadrature amplitude modulation (QAM); however, other modulation formats could be used.
The subscriber equipment  106 contains a receiver 124 and a display 126 (e.g., a television). The receiver 124 demodulates the signals carried by the distribution network 104 and decodes the demodulated signals to extract the IPG pages from the stream. The details of the receiver 124 are described below with respect to FIG. 5.
FIG. 2 depicts a block diagram of the encoding and multiplexing unit  116 of FIG. 1 which produces a transport stream comprising a plurality of encoded video, audio, and data elementary streams. The invented system is designed specifically to work in an ensemble encoding environment, where a plurality of video streams are generated to compress video information that carries common and non-common content. Ideally, the common content is encoded into a single elementary stream and the non-common content are encoded into separate elementary streams. However, in a practical MPEG encoding process, some common information will appear in the stream intended to carry non-common information and some non-common information will appear in the stream intended to carry common information. In this way, the common content is not duplicated in every stream, yielding significant bandwidth savings. Although the following description of the invention is presented within the context of IPG, it is important to note that the method and apparatus of the invention is equally applicable to a broad range of applications, such as broadcast video on demand delivery, e-commerce, internet video education services, and the like, where delivery of video sequences with command content is required.
Specifically, the encoding and multiplexing unit  116 receives a plurality of video sequences V1-V10 and, optionally, one or both of a audio signal SA and a data signal SD.
The video sequences V 1-V10 includes imagery common to each other, e.g., common IPG background information and common video portion information. On the other hand, the programming information (program grid graphic) is different in every sequence V1-V10.
The audio source SA comprises, illustratively, audio information that is associated with a video portion in the video sequences such as an audio track associated with still or moving images. For example, in the case of video sequence V 1 representing a movie trailer, the audio stream SA is derived from the source audio (e.g., music and voice-over) associated with the music trailer.
The encoding and multiplexing unit  116 comprises a plurality of real time MPEG-2 encoders 220-1 through 220-10 (collectively encoders 220), an encoding profile and clock generator 202, a plurality of picture isolators 230-1 through 230-10 (collectively picture isolators 230), a plurality of packetizers 240-1 through 240-13 (collectively packetizers 240), a plurality of buffers 250-1 through 250-13 (collectively buffers 250), a transport multiplexer 260, an audio delay element 270 and an optional data processor 280.
The video sequences V 1-V10 are coupled to respective real time encoders 220. Each encoder 220 encodes, illustratively, a composited IPG screen sequence to form a corresponding compressed video bit stream, e.g., an MPEG-2 compliant bit stream having associated with it a predefined group of pictures (GOP) structure. A common clock and encoding profile generator 202 provides a clock and profile to each encoder 220 to ensure that the encoding timing and encoding process occur similarly for each video sequence V1-V10. As such, the encoding is performed in a synchronous manner.
For purposes of this discussion, it is assumed that the GOP structure consists of an I-picture followed by ten B-pictures, where a P-picture separates each group of two B-pictures (i.e., “I-B-B-P-B-B-P-B-B-P-B-B-P-B-B”), however, any GOP structure and size may be used in different configurations and applications. It is preferable that the same encoding profile, including the GOP structure, is used by each of the real time encoders  220 to have uniform encoding across multiple streams and to produce approximately the same size encoded I- and Predicted-Pictures. Moreover, by utilizing the same profile and predefined GOP structure, multiple instances of the same encoder are used to realize the encoding and multiplexing unit 116, thereby driving down costs. Note also that the encoding process can be performed by one encoder or a plurality of encoders depending on implementation choice.
Each of the real time encoders  220 produces an encoded MPEG-2 bit stream (E1-E10) that is coupled to a respective picture isolator 230. Each of the picture isolators 230 examines the encoded video stream to isolate I-pictures within the MPEG-2 compliant streams E1-E10, by analyzing the stream access units associated with I-, P- and B-pictures.
The first picture isolator  230-1 receives the MPEG-2 compliant stream E1 from the first real time encoder 220-1 and responsively produces two output bit streams PRED and I1. The remaining picture isolators 230-2 to 230-10 produces only I frame streams. Note that the PRED stream can be generated by any one of the picture isolators.
The picture isolators  230 process the received streams E1-E10 according to the type of picture (I-, P- or B-picture) associated with a particular access unit and also the relative position of the pictures within the sequence and group of pictures. As noted in the MPEG-1 and MPEG-2 specifications, an access unit comprises a coded representation of a presentation unit. In the case of audio, an access unit is the coded representation of an audio frame. In the case of video, an access unit includes all the coded data for a picture and any stuffing bits that follows it, up to but not including the start of the next access unit. If a picture is not preceded by a group start code or a sequence header code, then the corresponding access unit begins with the picture start code. If the picture is preceded by a group start code and/or a sequence header code (e.g., an I-picture), then the corresponding access unit begins with the first byte of the first start code in the sequence or a GOP. If the picture is the last picture preceding a sequence end code in the stream, then all bytes between the last byte of the coded picture and the sequence end code (including the sequence end code) belong to the access unit. Each of the remaining B- and P-picture access units in a GOP includes a picture start code. The last access unit of the GOP (e.g., a terminating B-picture) includes, in addition, a sequence end code indicating the termination of the GOP.
The I 1 stream, as the first picture of the sequence, consists of a sequence header, a sequence extension, GOP header, picture header, picture extension, and I-picture data until the next picture start code. By contrast, the PRED stream comprises only P- and B-picture access units, starting from the second picture start code (illustratively a B-picture) and all data until the next group start code, thereby including all access units of the GOP except those representing the I-picture.
Each of the second  230-2 through tenth 230-10 picture isolators receive, respectively, the MPEG-2 compliant streams E2 through E10 from the corresponding real time encoders 220-2 through 220-10, each producing one respective output stream I1-I10 comprising only the sequence header and all data until the respective second picture start codes (i.e., the access unit data associated with an I-picture at the beginning of the respective GOP).
FIG. 3 illustrates a high-level flow sequence in isolating pictures suitable for use in the picture isolators unit  230 of FIG. 2.
The picture isolator method  300 is entered at step 305 and proceeds to step 310, where it waits for a sequence header or a group start code, upon detection of which it proceeds to step 315.
At step  315, the sequence header and all data until the second picture start code is accepted. The method 300 then proceeds to step 320.
At step  320, the accepted data is coupled to the I-picture output of the picture isolator. In the case of picture isolators 230-2 through 230-10, since there is no PB output shown, the accepted data (i.e., the sequence header, I-picture start code and I-picture) is coupled to a sole output. The method 400 then proceeds to step 325.
At step  325, a query is made as to whether non-I-picture data is to be processed. That is, a query is made as to whether non-I-picture data is to be discarded or coupled to a packetizer. If the query at step 325 is answered negatively (non-I-picture data is discarded) then the method 300 proceeds to step 310 to wait for the next sequence header. If the query at step 325 is answered affirmatively, then the method 300 proceeds to step 330.
At step  330, the second picture start code and all data in a GOP until the next group start code is accepted. The method 400 then proceeds to step 335.
At step  335, the accepted data is coupled to the non-I-picture output of the frame isolator 230 to form the PRED stream.
In summary, the picture isolator method  300 examines the compressed video stream produced by the real time encoder 220 to identify the start of a GOP, the start of an I-picture (first picture start code after the group start code) and the start of predicted-pictures (second picture start code after the group start code) forming the remainder of a GOP. The picture isolator method couples the I-pictures and predicted-pictures to packetizers for further processing in conformance with the invention.
The first packetizer  240-1 packetizes the PRED stream into a plurality of fixed length transport packets according to, e.g., the MPEG-2 standard. Additionally, the first packetizer 240-1 assigns a packet identification (PID) of, illustratively, one (1) to each of the packets representing information from the PRED stream, thereby producing a packetized stream PID-1. The second packetizer 240-2 packetizes the I stream to produce a corresponding packetized stream PID-2.
The I 2 through I10 output streams of the second 230-2 through tenth 230-10 picture isolators are coupled to, respectively, third 240-3 through eleventh 240-11 transport packetizers, which produce respective packetized streams PID-3-PID-11.
In addition to the video information forming the ten IPG screens, audio information associated with IPG screens is encoded and supplied to the transport multiplexer  260. Specifically, the source audio signal is subjected to an audio delay 270 and then encoded by a real time audio encoder 220-A, illustratively a Dolby AC-3 real time encoder, to produce an encoded audio stream EA. The encoded stream EA is packetized by a 12th transport packetizer 240-12 to produce a transport stream having a PID of 12 (PID-12). The PID-12 transport stream is coupled to a 12th buffer 250-12.
The IPG grid foreground and overlay graphics data is coupled to the transport multiplexer  260 as a data stream having a PID of thirteen (PID-13). The data stream is produced by processing the data signal SD as related for the application using the data processor 280 and packetizing the processed data stream SD′ using the thirteenth packetizer 240-13 to produce the PID-13 signal, which is coupled to the thirteenth buffer 250-13.
Each of the transport packetized streams PID- 1-PID-11 is coupled to a respective buffer 250-1 through 250-11, which is in turn coupled to a respective input of the multiplexer 260, illustratively an MPEG-2 transport multiplexer. While any type of multiplexer will suffice to practice the invention, the operation of the invention is described within the context of an MPEG-2 transport multiplexing system.
Multiplexer  260 processes the packetized data stored in each of the 13 buffers 250-1 through 250-13 in a round robin basis, beginning with the 13th buffer 250-13 and concluding with the first buffer 250-1. That is, the transport multiplexer 260 retrieves or “drains” the PID 13 information stored within the 13th buffer 250-13 and couples that information to the output stream TOUT. Next, the 12th buffer 250-12 is emptied of packetized data which is then coupled to the output stream TOUT. Next, the 11th buffer 250-11 is emptied of packetized data which is then coupled to the output stream TOUT and so on until the 1st buffer 250-1 is emptied of packetized data which is then coupled to the output stream TOUT. It is important to note that the processing flow is synchronized such that each output buffer includes all the access units associated with an I-picture (250-2 through 250-11) suitable for referencing a GOP, a particular group of P- and B-pictures (250-1) suitable for filling out the rest of the GOP, a particular one or more audio access units (250-12) and an related amount of data (250-13). The round robin draining process is repeated for each buffer, which has been filled in the interim by new transport packetized streams PID-13 to PID-1.
FIG. 4 depicts a data structure  400 for a transport stream produced by the encoding and multiplexing unit as a result of processing in a round robin basis. The figure shows one GOP portion of a transport stream, which is indicated by “START” and “END” phrases. The data structure starts with data transport packet 401 having PID-13, then it proceeds with an audio packet 402 having PID-12, which are followed by I-picture packets 403-412 assigned as PID-11 to PID-2. The remaining packets 413 to 425 carry the PRED stream with PID-1. The packets 423 to 425 in the figure show the terminating access units of the previous GOP.
In the preferred embodiment, the exemplary data structure (and related other varied embodiments that still incorporate the above teachings) is encapsulated in one multi-program transport stream. Each program in the program map table (PMT) of MPEG-2 transport stream includes an I-PID (one of the illustrative ten I-PID's  403 to 412), the PRED stream PID-1, data PID-13 401, and audio PID-12 402. Although the multiplexer 260 of FIG.-2 couples a PRED stream access units 413-425 to the multiplexer output TOUT only once per GOP, the PMT for each program references PRED stream PID-1. For the illustrative organization of video input sources in FIG. 2, there would be ten programs, each consisting of one of ten I-PID's 403 to 413, PRED PID-1, audio PID-12, and data PID-13.
In an alternative embodiment, the information packets are formed into a single program and carried with a single program transport stream. In this embodiment, the complete set of PID's  401 to 425 are coupled into a single program.
FIG. 5 depicts a block diagram of the receiver  124 (also known as a set top terminal (STT) or user terminal) suitable for use in producing a display of a user interface in accordance with the present invention. The STT 124 comprises a tuner 510, a demodulator 520, a transport demultiplexer 530, an audio decoder 540, a video decoder 550, an on-screen display processor (OSD) 560, a frame store memory 562, a video compositor 590 and a controller 570. User interaction is provided via a remote control unit 580. Tuner 510 receives, e.g., a radio frequency (RF) signal comprising, for example, a plurality of quadrature amplitude modulated (QAM) information signals from a downstream (forward) channel. Tuner 510, in response to a control signal TUNE, tunes a particular one of the QAM information signals to produce an intermediate frequency (IF) information signal. Demodulator 520 receives and demodulates the intermediate frequency QAM information signal to produce an information stream, illustratively an MPEG transport stream. The MPEG transport stream is coupled to a transport stream demultiplexer 530.
Transport stream demultiplexer  530, in response to a control signal TD produced by controller 570, demultiplexes (i.e., extracts) an audio information stream A and a video information stream V. The audio information stream A is coupled to audio decoder 540, which decodes the audio information stream and presents the decoded audio information stream to an audio processor (not shown) for subsequent presentation. The video stream V is coupled to the video decoder 550, which decodes the compressed video stream V to produce an uncompressed video stream VD that is coupled to the video compositor 590. OSD 560, in response to a control signal OSD produced by controller 570, produces a graphical overlay signal VOSD that is coupled to the video compositor 590. During transitions between streams representing the user interfaces, buffers in the decoder are not reset. As such, the user interfaces seamlessly transition from one screen to another.
The video compositor  590 merges the graphical overlay signal VOSD and the uncompressed video stream VD to produce a modified video stream (i.e., the underlying video images with the graphical overlay) that is coupled to the frame store unit 562. The frame store unit 562 stores the modified video stream on a frame-by-frame basis according to the frame rate of the video stream. Frame store unit 562 provides the stored video frames to a video processor (not shown) for subsequent processing and presentation on a display device.
Controller  570 comprises a microprocessor 572, an input/output module 574, a memory 576, an infrared (IR) receiver 575 and support circuitry 578. The microprocessor 572 cooperates with conventional support circuitry 578 such as power supplies, clock circuits, cache memory and the like as well as circuits that assist in executing the software routines that are stored in memory 576. The controller 570 also contains input/output circuitry 574 that forms an interface between the controller 570 and the tuner 510, the transport demultiplexer 530, the onscreen display unit 560, the back channel modulator 595, and the remote control unit 580. Although the controller 570 is depicted as a general purpose computer that is programmed to perform specific interactive program guide control function in accordance with the present invention, the invention can be implemented in hardware as an application specific integrated circuit (ASIC). As such, the process steps described herein are intended to be broadly interpreted as being equivalently performed by software, hardware, or a combination thereof.
In the exemplary embodiment of FIG. 5, the remote control unit  580 comprises an 8-position joy stick, a numeric pad, a “select” key, a “freeze” key and a “return” key. User manipulations of the joy stick or keys of the remote control device are transmitted to a controller via an infra red (IR) link. The controller 570 is responsive to such user manipulations and executes related user interaction routines 500, uses particular overlays that are available in an overlay storage 376.
Once received, the video streams are recombined via stream processing routine  502 to form the video sequences that were originally compressed. The following describes three illustrative methods for recombining the streams.
In this method, an I-Picture stream and the PRED stream to be recombined keep their separate PID's until the point where they must be depacketized. The recombination process is conducted within the demultiplexer  530 of the subscriber equipment 106. For illustrative purposes, assuming the preferred embodiment of the transport stream discussed above (multi-program transport stream with each program consisting of an I-PID, PRED-PID, audio-PID, and data-PID), any packet with a PID that matches any of the PID's within the desired program are depacketized and the payload is sent to the elementary stream video decoder. Payloads are sent to the decoder in exactly in the order in which the packets arrive at the demultiplexer.
FIG. 6 illustrates the details of this method, in which, it starts at step  605 and proceeds to step 610 to wait for (user) selection of an I-PID to be received. The I-PID, as the first picture of a stream's GOP, represents the stream to be received. Upon detecting a transport packet having the selected I-PID, the method 600 proceeds to step 615.
At step  615, the I-PID packets are extracted from the transport stream, including the header information and data, until the next picture start code. The header information within the first-received I-PID access unit includes sequence header, sequence extension, group start code, GOP header, picture header, and picture extension, which are known to a reader that is skilled in MPEG-1 and MPEG-2 compression standards. The header information in the next I-PID access units that belongs to the second and later GOP's includes group start code, picture start code, picture header, and extension. The method 600 then proceeds to step 620 where the payloads of the packets that includes header information related to video stream and I-picture data are coupled to the video decoder 550 as video information stream V. The method 600 then proceeds to step 625.
At step  625, the predicted picture packets PRED-PID, illustratively the PID-1 packets of fourteen predicted pictures 413 to 425 in FIG. 4 in a GOP of size fifteen, are extracted from the transport stream. At step 630, the payloads of the packets that includes header information related to video stream and predicted-picture data are coupled to the video decoder 550 as video information stream V. At the end of step 630, a complete GOP, including the I-picture and the predicted-pictures, are available to the video decoder 550. As the payloads are sent to the decoder in exactly in the order in which the packets arrive at the demultiplexer, the video decoder decodes the recombined stream with no additional recombination process. The method 600 then proceeds to step 635.
At step  635 a query is made as to whether a different I-PID is requested. If the query at step 635 is answered negatively, then the method 600 proceeds to step 610 where the transport demultiplexer 530 waits for the next packets having the PID of the desired I-picture. If the query at step 635 is answered affirmatively, then the PID of the new desired I-picture is identified at step 640 and the method 600 returns to step 610.
The method  600 of FIG. 6 is used to produce a conformant MPEG video stream V by concatenating a desired I-picture and a plurality of P- and/or B-pictures forming a pre-defined GOP structure.
The second method of recombining the video stream involves the modification of the transport stream using a PID filter. A PID filter  504 can be implemented as part of the demodulator 520 of FIG. 5.
FIG. 7 illustrates the details of this method, in which, it starts at step  705 and proceeds to step 710 to wait for (user) selection of an I-PID to be received. The I-PID, as the first picture of a stream's GOP, represents the stream to be received. Upon detecting a transport packet having the selected I-PID, the method 700 proceeds to step 715.
At step  715, the PID number of I-stream is re-mapped to a predetermined number, PID*. At this step, the PID filter modifies all the PID's of the desired I-stream packets to PID*. The method then proceeds to step 720, wherein the PID number of the predicted picture stream, PRED-PID, is re-mapped to PID*. At this step, the PID filter modifies all the PID's of the PRED-PID packets to PID*. The method 700 then proceeds to step 725.
At step  725, the packets of the PID* stream is extracted from the transport stream by the demultiplexer. The method 700 then proceeds to step 730, where the payloads of the packets that includes video stream header information and I-picture and predicted picture data are coupled to the video decoder 550 as video information stream V. The method 700 then proceeds to 735.
At step  735, a query is made as to whether a different I-PID is requested. If the query at step 735 is answered negatively, then the method 700 proceeds to step 710 where the transport demultiplexer 530 waits for the next packets having the PID of the desired I-picture. If the query at step 735 is answered affirmatively, then the PID of the new desired I-picture is identified at step 740 and the method 700 returns to step 710.
The method  700 of FIG. 7 is used to produce a conformant MPEG video stream V by merging the reference stream information and predicted stream information before the demultiplexing process.C3.
FIG. 8 illustrates the details of this method, in which, it starts at step  805 and proceeds to step 810 to wait for (user) selection of an I-PID to be received. The I-PID, as the first picture of a stream's GOP, represents the stream to be received. Upon detecting a transport packet having the selected I-PID, the method 800 proceeds to step 815.
At step  815, the I-PID packets are extracted from the transport stream until, and including, the I-PID packet with slice countdown value of zero. The method 800 then proceeds to step 820 where the payloads of the packets that includes header information related to video stream and I-picture data are coupled to the video decoder 550 as video information stream V. The method 800 then proceeds to step 825.
At step  825, the PID filter is re-programmed to receive the predicted picture packets PRED-PID. The method 800 then proceeds to 830. At step 830, the predicted stream packets, illustratively the PID-1 packets of fourteen predicted pictures 413 to 425 in FIG. 4 in a GOP of size fifteen, are extracted from the transport stream. At step 835, the payloads of the packets that includes header information related to video stream and predicted-picture data are coupled to the video decoder 550 as video information stream V. At the end of step 835, a complete GOP, including the I-picture and the predicted-pictures, are available to the video decoder 550. As the payloads are sent to the decoder in exactly in the order in which the packets arrive at the demultiplexer, the video decoder decodes the recombined stream with no additional recombination process. The method 800 then proceeds to step 840.
At step  840, a query is made as to whether a different I-PID is requested. If the query at step 840 is answered negatively, then the method 800 proceeds to step 850 where the PID filter is re-programmed to receive the previous desired I-PID. If answered affirmatively, then the PID of the new desired I-picture is identified at step 845 and the method proceeds to step 850, where the PID filter is re-programmed to receive the new desired I-PID. The method then proceeds to step 845, where the transport demultiplexer 530 waits for the next packets having the PID of the desired I-picture.
The method  800 of FIG. 8 is used to produce a conformant MPEG video stream V, where the PID to PID switch is performed based on a slice countdown concept.
To illustrate the applicability of the invention to encoding IPG sequences, FIGS. 9 and 10 depict a frame from two different sequences of IPG pages  900 and 1000. The common information is everything except the programming grid 902 and 1002. The non-common information is the programming grid 902 and 1002. The programming grid 902 and 1002 changes from sequence 900 to sequence 1000. This grid changes for each channel group and each time interval. The IPG display 900 of FIG. 9 comprises a first 905A, second 905B and third 905C time slot objects, a plurality of channel content objects 910-1 through 910-8, a pair of channel indicator icons 941A, 941B, a video barker 920 (and associated audio barker), a cable system or provider logo 915, a program description region 950, a day of the week identification object 931, a time of day object 939, a next time slot icon 934, a temporal increment/decrement object 932, a “favorites” filter object 935, a “movies” filter object 936, a “kids” (i.e., juvenile) programming filter icon 937, a “sports” programming filter object 938 and a VOD programming icon 933. It should be noted that the day of the week object 931 and next time slot icon 934 may comprise independent objects (as depicted in FIG. 9) or may be considered together as parts of a combined object. Details regarding the operation of the IPG pages, their interaction with one another and with a user are described in commonly assigned U.S. patent application Ser. No. 09/359,560, filed Jul. 22, 1999 (attorney docket no. 070 CIP2) which is hereby incorporated herein by reference.
The video streams representing the IPG are carried in a single transport stream or multiple transport streams, within the form of a single or multi-programs as discussed previously in this invention. A user desiring to view the next 1.5 hour time interval (e.g., 9:30-11:00) may activate a “scroll right” object (or move the joystick to the right when a program within program grid  902 occupies the final displayed time interval). Such activation results in the controller of the STT noting that a new time interval is desired. The video stream corresponding to the new time interval is then decoded and displayed. If the corresponding video stream is within the same transport stream (i.e., a new PID), then the stream is immediately decoded and presented. If the corresponding video stream is within a different transport stream, then the related transport stream is extracted from the broadcast stream and the related video stream is decoded and presented. If the corresponding transport stream is within a different broadcast stream, then the related broadcast stream is tuned, the corresponding transport stream is extracted, and the desired video stream is decoded and presented.
FIG. 11 illustrates the ten IPG user interface page streams in a matrix representation  1100. The horizontal axis, h, in the figure represents the PID dimension consisting of 10 PID's, which corresponds to E1-E10 outputs of the real time encoders RTE1 to RTE10 of FIG. 2.
The matrix entries  1102 to 1130 in column-1 describes fifteen pictures of the first IPG page, PID-1. The guide portion, marked as g1, at each time unit, t1 to t15, does not change within a GOP of PID1. The same principle applies to PID-2 to PID-10 streams in columns-2 to 10, where guide portions, g2 to g10, at each time unit t1 to t15, does not change. On the other hand, each stream in column-1 to column-10 shares the same motion video portion, marked as v1 to v15.
Conversely, the guide region g changes from g 1 to g10 in horizontal dimension. For example, in row-1, the pictures 1102 to 1148 contains different guide portions g1 to g10, although each has the same motion video picture v1, as the matrix is traversed in horizontal dimension. The same principle applies to row-2 to row-15, where guide portion g changes from g2 to g10, each stream in column-1 to column-10 sharing the same motion video picture, v2 to v15.
FIG. 12 graphically illustrates an efficient compression algorithm  1200 that substantially minimizes the number of pictures that represents the information in FIG. 11. The same matrix representation as FIG. 11 is used, where the horizontal axis, h, represents the PID dimension consisting of 10 PID's, and the vertical axis, v, represents the time domain.
The element groupings, which are marked with dash-lines,  1202 to 1222 shows the data that can efficiently represent the complete matrix entries. In other words, using only the elements 1202 to 1222, it is possible to reconstruct all other elements in each row and column of the matrix.
A first element grouping  1202 includes all of the elements of the first column (PID-1) excluding the element in first row, 1204. The next group of elements in row-1, 1204 to 1222, illustrates the next group of elements required to represent the complete program guide elements of FIG. 11. Thus, rather than storing or transmitting 150 elements (i.e., all the elements of each row and column), the invention reconstructs the same amount of information using only 24 elements.
Specifically, the group of fourteen elements  1202 corresponds to the predicted picture stream that represents the common information. Each of the elements 1204 to 1222 is an intra-coded I-picture that represents the non-common information among 10 PID's. While each sequence, PID-1 to PID-10, is encoded in vertical dimension, e.g., for PID-1 producing I1 B1 B1 P1 . . . B1 B1, it can be observed that the prediction error images at each time unit, t2 to t15, does not change from PID to PID in horizontal dimension. Therefore, the grouping 1202 of PID-1 also includes the same information as the corresponding pictures of PID-2 to PID-10 at the same time units t2 to t15.
Alternatively, if the recombination method is employed, a GOP (consisting of fifteen pictures) which requires 2 Mbps is transmitted only once and the remaining 24 Mbps is allocated to 60 I-pictures, assuming that an I-picture occupies approximately 20 percent bitrate of a sequence (yielding 400 Kbps I-pictures in a 2 Mbps video sequence). Therefore, the present invention supports carrying  61 video streams each having a different IPG program page, within a 27 Mbps transport stream, versus 13 video streams in a regular encoding implementation not benefiting from the invention.
a second portion comprising predicted pictures from one of said video streams.
2. The bitstream of claim 1 wherein each of said first portions is identified by a distinct packet identifier and said second portion is identified by a packet identifier.
3. The bitstream of claim 1 wherein said first portion represents a program guide graphic of each of a plurality of interactive program guide pages.
4. The bitstream of claim 1 wherein said second portion represent non-changing imagery amongst a plurality of interactive program guide pages.
5. The bitstream of claim 1 wherein said first portion comprises reference pictures of an MPEG elementary stream and said second portion comprises predicted pictures of an MPEG elementary stream.
6. The bitstream of claim 1 further comprising an audio portion.
7. The bitstream of claim 1 further comprising a data portion.
a decoder for decoding the extracted packets to form an uncompressed video sequence.
9. A stream recombination apparatus of claim 8, wherein said packet identifier filter is part of a demodulator.
conducting a query if said reference picture is desired and identifying a new packet identifier if a new reference picture is desired.
11. The method of claim 10 wherein said concatenating step comprises coupling said reference pictures and said predicted pictures to the decoder in exactly the order in which said packets arrive at a demultiplexer.
12. The method of claim 10 being conducted within a demultiplexer.
13. The method of claim 10 wherein said payloads of said first plurality of packets contain imagery information that changes across a plurality of interactive program guides and said payloads of said second plurality of packets contain common imagery information of a plurality of interactive program guide pages.
conducting a query if a reference picture is desired and identifying a new packet identifier if a new reference picture is desired.
15. The method of claim 14 wherein said payloads of said first plurality of packets contain imagery information that changes across a plurality of interactive program guides and said payloads of said second plurality of packets contain common imagery information of a plurality of interactive program guide pages.
17. The method of claim 16 wherein said payloads from said reference stream contain imagery information that changes across a plurality of interactive program guides and said payloads from said predicted picture stream contain common imagery information of a plurality of interactive program guide pages.
18. The method of claim 16 wherein said coupling step further comprises the step of reprogramming a packet identifier filter to receive said packets having said new packet identifier.
19. The method of claim 16 wherein said coupling step comprises the step of coupling said payloads from said reference stream and said payloads from said predicted stream to the decoder in exactly the order in which said packets arrive at a demultiplexer.

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