Abstract:
An apparatus for processing a source of compressed digital video and control data occuring in transport packets. The apparatus comprises a deriving means responsive to the source for deriving copy control data from the transport packets. A generating means responsive to the copy control data for generating a copy control word. A forming means for forming a superpacket including the copy control word and the transport packets.

Description:
This invention relates to a bus interface system/apparatus for coupling digital audio, video and data processing systems, and in particular to coupling signals for control of recording apparatus. 
     BACKGROUND OF THE INVENTION 
     The advent of digitally compressed audio and video transmission systems, such as the Grand Alliance HDTV system for terrestrial high definition television broadcasting, or the DirecTV™ direct broadcast satellite TV system currently employing the NTSC system, demonstrate that virtually studio quality audio and video signals can be delivered to a viewing audience. However, such exemplary quality signals are instantly degraded when time shifted for later viewing by means of currently available consumer analog recording formats, for example, VHS, S-VHS, 8 mm and Hi 8. 
     The introduction of consumer quality digital video recording cameras, for example DVC, demonstrates that consumer quality digital recording may yield sound and picture quality virtually indistinguishable from the original material. Other consumer products are emerging, for example, D-VHS, video disc, DVD, digital cameras, scanners and computers with digital processing capabilities which permit multiple generation digital signal dubbing, copying, replicating or editing, with sound and picture quality remaining essentially equal to that of the original recorded source. The high levels of technical quality and performance delivered by such consumer digital equipment raises concern with respect to copyright infringement by unauthorized copying. Proposed legislation in the form of the “VIDEO HOME RECORDING ACT of 1996” requires that digital audio/video signals include copy protection information to allow the copyright owner to determine and control the audience size viewing the copyrighted material. Implementation of copy protection requires that copy control information be included with or within the copyrighted material and be maintained throughout subsequent processing procedures. In addition such copy control information may be amended as a result of subsequent processing to retain control the copyright owner&#39;s intellectual property. A digital recording device is disclosed in EP A 0 498 617 which extracts copy control data from an input data stream to control recording and to amend copy contol data subsequent to recording. A further digital recording device is disclosed in EP A 0 717 564 which accepts an MPEG bit stream containing a PES header which includes copyright and copy control data. The recording device decodes and decrypts copy prevention information and in response thereto encrypts the bit stream for recording. A second embodiment disclosed in EP 0 574 892 is directed to copy control by means of information superimposed in one horizontal period of the vertical blanking interval of an analog video signal. 
     SUMMARY OF THE INVENTION 
     In an inventive arrangement, an apparatus processes a source of compressed digital audio, video and control data occurring in transport packets. The apparatus comprises a deriving means responsive to the source for deriving copy control data from the transport packets. A generating means responsive to the copy control data for generating a copy control word. A forming means for forming a superpacket including the copy control word and the transport packets. In a further inventive arrangement copy control information is derived from a packetized source and processed for coupling via a control data bus. In another inventive arrangement a replicating device receives the formatted transport packet with copy control header and responsive to the copy control information initiates replication and amends the copy control header to preclude any further copying of the formatted transport packet and copy control header. In yet another inventive arrangement a replicating device receives the formatted transport packet and copy control header and the copy control information from a control data bus. The replicating device implements commands contained in the copy control information only if the copy control information from the two sources correspond. In yet a further inventive arrangement a replicating device periodically receives copy control information from a control data bus and absent said periodic reception assumes a copy prohibited status. Another inventive arrangement controls a replicating device responsive to copy control information such that a copy is made but simultaneous transport packet decoding for viewing is precluded. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 illustrates an exemplary digital receiver and digital replicator employing various inventive arrangements. 
     FIGS. 2A and 2B illustrate inventive arrangements for bus communication employing a superpacket. 
     FIGS. 3A and 3B illustrate exemplary bus connected digital sources and replication systems including inventive arrangements. 
     FIG. 4 illustrates an exemplary digital signal source and analog replication device including inventive arrangements. 
    
    
     DETAILED DESCRIPTION 
     The Grand Alliance HDTV terrestrial system and the DirecTV™ system utilize an MPEG standard and an MPEG like standard respectively to transmit program material in transport packets. The transport packets may contain multiple programs which are multiplexed together and processed for transmission. At the receiver error correction is performed and a user determined program packet stream is separated and assembled from the multiplexed mixture of programs. The burgeoning array of consumer digital audio and video products, computers, imaging apparatus etc. necessitated a simple, low cost means for interconnection. For example, a serial data bus has been standardized by the IEEE and is known as 1394. The 1394 standard multiplexes a variety of compressed digital audio, video, MIDI and device control commands onto two twisted pair conductors. A third conductor pair provides one conductor for power supply ground with the second conductor providing an optional coupling for power insertion or extraction. Devices may be interconnected in a daisy chain manner by a small, thin, flexible cable terminated with standardized connectors. An example of a simplified bus is depicted in the block diagram of FIG.  1 . The simplified bus provides coupling of serial digital audio, video and control transport packet streams and is described in U.S. application Ser. No. 08/292,908 and PCT Applications Ser. Nos. PCT/US96/07581, and PCT/US96/07391. 
     However, a simplified description of the system depicted in FIG. 1 is as follows. An integrated receiver decoder or IRD  100 , receives a radio frequency signal from, for example, antenna  10  or a cable source, not shown. The radio frequency signal is tuned by tuner  11  to receive a user selected program. The tuner output signal is coupled to packet source block  101 , which demodulates and error corrects the modulated transmission signal. An output from packet source  101  is coupled to block  102  which demultipexes or separates the user&#39;s selected program transport stream TP from other program streams present in the received packet stream. The user selected transport stream TP may be coupled for MPEG decoding by decoder  109  which generates audio and video signals for display  99 . 
     The demultiplexed user selected program transport stream TP may be formatted at block  108 , for example as a superpacket, as illustrated in FIG. 2B. A superpacket comprises the user selected transport stream packets TP and a control data header. FIG. 2B shows an exemplary control data header of 32 bits which includes a time stamp TS, copy control data bits, bits which may determine recorder play back rate, and two bits reserved for future usage. The superpacket SP is coupled via an audio, video and data bus  500  to a recording or replicating device  200 . Data bus  500  is received by interface port  102  and coupled to demux  30  which reads the exemplary control data. The copy control data bits may assert a number of possible control conditions, for example, unlimited copying, single copy replication or copying prohibited. Thus to achieve the required control conditions, the copy control data bits are coupled to controller  208  which is controllably coupled to various replicator sub-systems. A detailed description of the various control aspects resulting from the copy control conditions is provided later. 
     Superpackets SP or SPa are coupled for recording, replication or copying processing at block  206 A. The superpackets may be processed for error detection and correction and may also be transformed to modify their spectral energy content. An output signal stream from block  206 A is coupled to form copy  210  on medium  299 , for example a magnetizable surface. When recorder  200  is operated in a reproduction mode, copy  210  is transduced from medium  299  and coupled to playback processor  206 B. Playback processor  206 B essentially reverses any record signal encoding and may detect and correct errors in copy  210  resulting from the recording medium  299 . The error corrected signal PBSP is coupled to demultiplexor  31  and superpacket restorer  32 . The control data header of the play back superpacket PBSP is read by demultiplexor  31  and coupled to various locations. The time stamp PBTS from the header is coupled to clock controller  39  where the time stamp value is employed to determine the output packet timing or initiation of an output superpacket RSP from block  32 . The replayed, restored superpacket RSP is coupled to interface  102  for transmission to integrated receiver decoder IRD  100  via AVD bus  500 . 
     It is assumed that the signal to be communicated is provided in the form of transport packets such as defined in the system layer of the MPEG2 video standard, or the transport layer of the Grand Alliance signal format. In both the MPEG2 video standard and the transport layer of the Grand Alliance signal format, transport packets are associated with timestamps or PCRs which allow re-synchronization of local system clocks to the original encoder clock frequency. Hence, having synchronized the local system clock generator, the transport packets may be processed to remove jitter or timing perturbations which may accumulate, for example, during transmission by switched bus structures and processing etc. In FIG. 1 the program clock reference PCR, is read by demultiplexor  102  and coupled to synchronize clock oscillator  17 , which has a nominal frequency of 27 MHz. The MPEG standard allows for an intermittent occurrence of the program clock reference PCR within transport stream. The resultant intermittent oscillator synchronization is fully adequate to permit MPEG decoding. However, the transport packet stream may be subject to timebase modulation, for example resulting from mobile transmission, causing signal flutter and mutlipath transmission reflections. Timebase modulation may also result from recording and replay buffering and mechanically instabilities. Such timebase variations or errors may exceed the oscillator synchronization range or rate of change, hence each transport packet is repackaged to form a superpacket containing a timestamp specific to the occurrence of the transport packet it contains. The provision of a timestamp for each transport packet permits the correction of unwanted timebase modulation and facilitates the delivery of each transport packet to the decoder at substantially the same time as the transport packet would have been decoded had it not been recorded and or perturbed. 
     FIG. 2B illustrates a superpacket which comprises a control data header of 32 bits and a transport packet of either 188 bytes or 140 bytes representing respectively the GA or DirecTV™ systems signals. The control data header includes a 20 bit time stamp, 6 bits of copy control data, a 4 bit playback rate code and 2 bits of reserved data. The timestamp is a sample of an oscillator count taken at a specific instant, for example, at the occurrence of a frame clock pulse FC, and as described, may be utilized for the correction of timing jitter and perturbations impressed on each superpacket. The playback rate code may be used by a recording device to determine the rate at which a particular signal is to be recorded or played back. The playback rate is coded relative to the recording rate and is read and utilized by any recording devices connected to the AVD bus. The purpose of the playback rate code is to allow recording at a relatively high bit rate and playback at a normal bit rate. Copy control data comprises three 2 bit words which provide control of, digital copy control or CGMS-D, analog copy control or CGMS-A and control information for an analog APS system developed by MACROVISION™. Table 1 shows the allocation and function of 6 copy control data bits. 
     
       
         
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
             
             
               
                   
                   
                 CGMS-D DIGITAL COPY CONTROL 
               
               
                 Bit 6 
                 Bit 7 
                 INFORMATION 
               
               
                   
               
               
                 0 
                 0 
                 Unlimited copying permitted 
               
               
                 1 
                 0 
                 Only one copy permitted 
               
               
                 1 
                 1 
                 Copying prohibited 
               
               
                   
               
               
                 Bit 8 
                 Bit 9 
                 APS ANALOG CONTROL INFORMATION 
               
               
                   
               
               
                 0 
                 0 
                 Dynamic control of MACROVISION parameters 
               
               
                 0 
                 1 
                 Dynamic control of MACROVISION parameters 
               
               
                 1 
                 0 
                 Dynamic control of MACROVISION parameters 
               
               
                 1 
                 1 
                 Dynamic control of MACROVISION parameters 
               
               
                   
               
               
                   
                   
                 CGMS-A ANALOG COPY CONTROL 
               
               
                 Bit 10  
                 Bit 11  
                 INFORMATION 
               
               
                   
               
               
                 0 
                 0 
                 Unlimited copying permitted 
               
               
                 1 
                 0 
                 Only one copy permitted 
               
               
                 1 
                 1 
                 Copying prohibited 
               
               
                   
               
             
          
         
       
     
     Various equipment system combinations may be envisioned comprising, for example, analog or digital recorder players, such equipment may present differing connection and control capabilities, and in addition operation in recording and or replay modes must be considered. These various combinations may be broadly separated into several exemplary systems. 
     FIG. 1 depicts a first exemplary system where a digital receiver and display are coupled to a digital recorder by a simple data bus configuration. However, regardless of the data bus configuration, copy control or CGMS data must be recovered or demultiplexed from the selected packet stream and formatted for coupling to the recording or replicating device. The recorder or replicator must demultiplex or recover the formatted copy control bits and implement the control function specified therein. In FIG. 1 copy control data is demultiplexed from the selected transport packet stream at block  104  and coupled to a copy control word generator at block  105 . Superpackets are formatted at block  108  which combines the selected transport packet stream with the copy control word from block  105 , a timestamp from block  107  and a playback rate code from block  106 . 
     As already described the 6 bit copy control word provides for control of both digital and analog systems. Hence in the first exemplary system of FIG. 1, demultiplexor block  30  of digital recorder  200 , extracts the digital copy control or CGMS-D commands present as bits  6  and  7  of the superpacket header. Bits  6  and  7  define three states, namely, unlimited copying, no copying or only one copy permitted. Separated bits  6  and  7  are coupled to control block  208  which is controllably coupled to various subsystems of recorder  200 . Clearly, if CGMS-D bits  6  and  7  indicate a first state which permits unlimited copying, no control action is required by controller  208  and copy  210  may be formed on medium  299 . 
     When CGMS-D bits  6  and  7  indicate a second state which prohibits copying, controller  208  may disable record processor  206 A by means of control line INH. In addition an electronic signal path, or EE mode, through the recorder may be inhibited responsive to copy prohibition by bits  6  and  7 . Controller  208  may also cause the generation of an on-screen display message indicating the prohibited recording status of the user selected program. The on-screen display message may generated within recorder  200  or be caused to be generated within IRD  100 . 
     Advantageously, integrated receiver decoder  100  may demultiplex and interpret CGMS-D bits  6  and  7 . Thus when a prohibited recording status is required, coupling of transport packets or superpackets to the serial data bus may be inhibited within IRD  100 . In addition the interpreted status of the 6 copy control bits may be presented for user information as an on-screen display. 
     The third state defined by bits  6  and  7 , namely one copy permitted, requires that the copy control bits be amended prior to or concurrent with replication by recorder  200 . Thus CGMS-D command bit  7  of the superpacket header is changed, as indicated in table 1, from logical 0 to logical 1. In FIG. 1 superpacket SP from demux is coupled to block RESET CC  204  which amends the logical state of bit  7  responsive to control signal RS generated by controller  208 . Hence a single copy  210  of the exemplary superpacket SP is replicated which contains a CGMS-D command prohibiting any further copying. 
     In a further advantageous control situation the copyright owner may establish a differential pricing structure where an exemplary live event may be priced higher for live viewing than for a time shifted, or non-real time viewing resulting from a recording of the live event. Thus CGMS-D bits  6  and  7  may indicate the third state permitting a single copy, with decoder inhibition signalled by, for example, at least one bit within the playback rate area or the reserved data bits. However, other copying or copyright control data resident in the users selected program stream may be demultiplexed at, for example block  104 . Such filtered or demuxed control data from block  104  may be coupled to controller  111  to inhibit decryption by block  103 , and or decoding at  109 , of the received signal for immediate, real time viewing at display  99 . In addition controller  111  may communicate this viewing inhibit command via the control conductor CRL of data bus  500  to recorder  200 RP. Control commands from data bus  500  are coupled to controller  208  which inhibits, via signal INHPB, electronic or EE coupling of the input packet signal to the recorder output. Reproduction and output data generation of the recorded copy is facilitated, even though the copy comprises transport packets containing the embedded viewing inhibit command, because exemplary bit  7  of the copy control word was amended when recorded to prohibit further copying. Thus IRD  100  may logically compare the status of exemplary bits  6  and  7  with the embedded viewing inhibit command and deduce that the replay only copy may be decoded for non-real time viewing at display  99 . 
     FIG. 3A depicts as functional blocks a second exemplary system where a digital recorder player  200 P is coupled to a digital receiver  100  and display  99  via a simple data bus configuration. Functional blocks of FIG. 3A which provide the same function as those depicted in FIG. 1 are similarly numbered. FIG. 3A depicts the reproduction of copy  210 , from an unshown medium, where copy  210  includes digital copy control or CGMS-D commands present in both the exemplary superpacket header and the transport packet. 
     The copy control bits define the three states described above. Clearly, if the copy control bits permit unlimited copying, no control response is required or initiated by reproducer  200 P. The second and third copy control states preclude copying or permit only a single copy. However, since FIG. 3A depicts digital reproduction of copy  210  from player  200 P to digital receiver  100 , and to display  99 , once again no control response is required or initiated by reproducer  200 P since receiver  100  is assumed incapable of replication. 
     However, FIG. 3B depicts an interconnection between digital reproducer  200 P and digital replicator  200 R, which requires execution of copy control responses determined by the bits reproduced by reproducer  200 P. Clearly in both FIGS. 3A and 3B, reproducer  200 P transduces copy  210  for differing signal destinations and uses, namely decoding and viewing in FIG.  3 A and replication in FIG.  3 B. As described with respect to FIG. 1, digital replicator  200 R may demultiplex copy control bits from the exemplary superpacket, depicted at block  203  and communicate the required copy control action to controller  208 . Thus as described for FIG. 1, copying may be permitted, prohibited or a single copy allowed with that copy&#39;s respective copy control bit amended to prohibit further copying. 
     The differing signal destinations and consequential uses of transduced copy  210  may be advantageously determined by reproducer  200 P by means of serial data control line CRL. For example, during reproduction of copy  210 , demultiplexor  203  may extract and interprit CGMS-D bits  6  and  7  of the exemplary packet header. When bits  6  and  7  prohibit copying, controller  208  may poll via control line CRL to determine the destination of the transport packets or superpackets about to be coupled via the serial data bus. Control via a data bus is well known and may be implemented in various forms, for example, controller  208  may generate a message requiring responses from all bus nodes thereby identifying apparatus coupled to the control bus. Thus transport packets or superpackets may be coupled for decoding and viewing but may be inhibited from bus coupling to a recording device. Alternatively controller  208  may specifically address the transport packets or superpackets to a non-replicating destination, for example decoder  100 / 109 . Thus copy  210 , with copying prohibited, may be coupled for decoding and viewing but may be inhibited from bus coupling responsive to a determination of the apparatus present on the bus, for example digital replicator  200 R. 
     In the discussion of FIGS. 1,  3 A and  3 B, it was assumed that the recording or replicating devices are capable of demultiplexing the exemplary copy control word from the exemplary packet header. However, in replicating devices which may fail, or be incapable of demultiplexing copy control data, copy control management may be facilitated by means of the control line CRL. As discussed for FIG. 1, copy control data may be filtered or demultiplexed from the selected program stream at block  104 . The copy control data may be coupled to controller  111  for periodic bus transmission via control line CRL. Thus copy control data may be coupled to replicator controller  208  thereby facilitating the required copy management. In replicating devices incapable of amending the copy control bits when required by single copy authorization, the replicating device will transmit via the control line the correct copy control data, namely copying prohibited. The control line copy control data will be transmitted periodically, for example at least once per second. When a replicating device determines a difference between copy control data received via control line CRL and that demuxed from the packet header, the device inhibits recording or replication. However, in the eventuality that copy control data is absent from control line CRL for a predetermined time period, for example 10 seconds, the packet header CGMS data is then assumed correct and copy management is facilitated. 
     FIG. 4 depicts an analog recorder/replicator  300  coupled to an analog signal AS, decoded from a digital signal source by integrated receiver decoder  100 . An analog taping flag is demultiplexed, for example by block  104 , from an exemplary DSS™ electronic program guide. The demuxed taping or copy control data is coupled to controller  111  which in turn invokes the required copy management control by means of anti-copying device  110 , for example a MACROVISION™ apparatus. As shown in Table 1, analog CGMS-A provides the same three copying conditions as CGMS-D, namely, unlimited copying, copying prohibited and one copy permitted. 
     In the unlimited copying condition analog output signal AS passes through anti-copy block  110  without signal modification or addition. When copying is prohibited, anti-copy block  110  modifies the decoded analog signal AS such as to render a copy unusable but still permit direct viewing of the decoded analog signal on display  99 . The third control condition, namely one copy only, requires that analog signal AS be modified prior to copying to indicate that copy contains material for which copying is prohibited. The recording prohibition may be encoded during a vertical blanking interval of the analog signal, for example by use of line  21 . In FIG. 4 the demultiplexed CGMS-A may be encoded as described on exemplary line  21  of the vertical blanking interval or signal AS. When analog signal AS is received by replicator  300  line  21  is demultiplexed at block  301 . When the third copy management condition is read from the copy control data controller  311  enables multiplexor adder  302  which modifies the data on line  21  to reflect a recording prohibited status.