Method and apparatus for correcting corrupted digital video transport streams

Abstract

A digital video system, method, and computer program product for correcting corrupted digital video transport streams is described. The digital video system may include a digital cable, digital broadcast satellite (DBS), high definition television (HDTV), or video-on demand (VOD) system. In a VOD system, a VOD client at each receiver is capable of subscribing to one or more VOD sessions. The headend includes a video server and a control server that is coupled to the video server. The video server transmits one or more VOD sessions to one or more receivers over a transport stream. The control server can also cause the video server to transmit one or more dummy sessions to maintain a predetermined minimum bandwidth of content over the transport stream. Alternatively, the headend can transmit one or more null packets having a randomized payload, as necessary, to maintain a constant bit rate over the transport stream.

1 . A video-on-demand (VOD) system, comprising:
 a headend coupled to a transmission channel, said headend comprising:
 a video server that transmits, over the transmission channel, one or more VOD sessions to one or more receivers, where each receiver comprises a VOD client capable of subscribing to one or more VOD sessions over a transport stream; and 
 a control server coupled to the video server, the control server is adapted to dynamically allocate and terminate VOD sessions over the transport stream as VOD clients are added and terminated, and to cause the video server to transmit one or more dummy sessions over the transport stream such that a bandwidth over the transport stream is substantially constantly maintained above a predefined minimum bandwidth of content. 
   
   
   
       2 . The VOD system of  claim 1 , wherein the control server is further adapted to transmit one or more dummy sessions over the transport stream to maintain the minimum bandwidth of content over the transport stream to ensure that each receiver can synchronize to a subscribed VOD session. 
   
   
       3 . The VOD system of  claim 1 , wherein the control server is adapted to determine whether the bandwidth of content over the transport stream is below a predetermined threshold, and to cause the video server to transmit the one or more dummy sessions to maintain the bandwidth of content over the transport stream at or above the predetermined threshold. 
   
   
       4 . The VOD system of  claim 1  wherein each receiver includes a demodulator, decoder, and an MPEG frame synchronizer. 
   
   
       5 . The VOD system of  claim 1  wherein said headend further comprises a transmitter having an MPEG frame synchronizer, encoder, and modulator. 
   
   
       6 . The VOD system of  claim 1  wherein the transport stream is transmitted over a radio frequency channel. 
   
   
       7 . The VOD system of  claim 1  wherein the video server is further configured to transmit the one or more VOD sessions over one or more radio frequency (RF) channels each associated with a different transport stream, and wherein said control server is configured to cause the video server to transmit one or more dummy sessions over each transport stream to substantially constantly maintain the predetermined minimum bandwidth of content over each of the one or more transport streams. 
   
   
       8 . A video-on-demand (VOD) server, comprising:
 a server that receives requests from one or more VOD clients for one or more VOD sessions, causes transmission of one or more VOD sessions over a transport stream to the one or more VOD clients, determines whether the number of VOD sessions transmitted over the transport stream is below a minimum threshold, and causes transmission of one or more padding sessions over the transport stream if the number of VOD sessions transmitted over the transport stream is below the minimum threshold to maintain the number of VOD sessions at or above the minimum threshold.   
   
   
       9 . The VOD server of  claim 8  wherein the server causes transmission of VOD sessions over a plurality of radio frequency channels each associated with a transport stream, the server determines, for each transport stream, whether the number of VOD sessions is below the minimum threshold, and, for each transport stream, causes transmission of one or more padding sessions if the number of VOD sessions transmitted over the respective transport stream is below the minimum threshold to substantially constantly maintain the number of VOD sessions at or above the minimum threshold. 
   
   
       10 . The VOD server of  claim 8  wherein when the server receives a request for a new VOD session from a VOD client, the control server terminates one or more of the one or more padding sessions, and causes transmission of the new VOD session. 
   
   
       11 . A video-on-demand (VOD) system, comprising:
 a transmission channel;   a plurality of receivers coupled to the transmission channel, a VOD client at each receiver capable of subscribing to one or more VOD sessions over a transport stream; and   a headend coupled to the transmission channel, said headend including a video server than can transmit one or more VOD sessions to one or more receivers, and a control server coupled to the video server, the control server to dynamically allocate and terminate VOD sessions over the transport stream as VOD clients are added and terminated, said headend to transmit one or more stuffing packets to maintain a substantially constant bit rate over the transport stream, said one or more stuffing packets including a randomized payload.   
   
   
       12 . The VOD system of  claim 11  wherein the headend generates the one or more randomized payloads using one of a random number generator, pseudo-random number generator, and predetermined static payload. 
   
   
       13 . The VOD system of  claim 11  wherein the video server can transmit one or more VOD sessions over one or more radio frequency (RF) channels each associated with a transport stream, and wherein said headend to transmit one or more stuffing packets for each transport stream to maintain the substantially constant bit rate over the one or more transport streams, said one or more stuffing packets including a randomized payload. 
   
   
       14 . The VOD system of  claim 13  wherein the headend includes a random number generator that generates a plurality of random numbers, said plurality of random numbers being used to fill the payloads of the one or more stuffing packets. 
   
   
       15 . A video on demand (VOD) method, comprising:
 receiving requests from one or more VOD clients for one or more VOD sessions;   transmitting one or more VOD sessions to the one or more VOD clients over a transport stream having a substantially constant bit rate; and   transmitting one or more null packets to maintain the substantially constant bit rate over the transport stream, said null packets including a randomized payload.   
   
   
       16 . The VOD method of  claim 15 , wherein transmitting one or more null packets comprises transmitting one or more null packets to maintain the substantially constant bit rate over the transport stream, said null packets each including a randomized payload populated using one of a pseudo-random number generator, random number generator, and one of a plurality of predetermined static payloads. 
   
   
       17 . The VOD method of  claim 15 , further comprising dynamically allocating and terminating VOD sessions over the transport stream as VOD clients are added and terminated, respectively. 
   
   
       18 . A digital video system, comprising:
 a headend coupled to one or more transmission channels, said headend comprising:
 a video server that transmits one or more video sessions over a transport streams on a transmission channel to one or more receivers, where the one or more receivers are capable of subscribing to one or more video sessions, and 
 a control server coupled to the video server, the control server adapted to cause the video server to transmit one or more dummy sessions over the transport stream to substantially constantly maintain a predetermined minimum bandwidth of content over the transport stream. 
   
   
   
       19 . The digital video system of  claim 18 , wherein the control server further determines whether the bandwidth of content over the transport stream is below a predetermined threshold, and causes the video server to transmit the one or more dummy sessions to ensure that the bandwidth of content is substantially continuously maintain at or above the predetermined threshold, wherein the dummy sessions comprise non-null data and cannot be accessed by the one or more receivers. 
   
   
       20 . The digital video system of  claim 18 , further comprising:
 the transmission channel; and   the one or more receivers coupled to the transmission channel, where a client at each receiver is configured to subscribe to the one or more video sessions over the transport stream;   wherein the headend transmits digital video programming in accordance to one of a digital broadcast satellite (DBS) system, digital cable system, high definition television (HDTV) system, and video-on-demand (VOD) system.   
   
   
       21 . A computer program product, comprising:
 a computer usable medium having computer readable program code embodied therein to minimize a possibility of an erroneous MPEG frame synchronization in a digital video receiver, the computer readable program code in said computer program product comprising:   first computer readable program code to transmit one or more video sessions to the one or more clients over a transport stream having a substantially constant bit rate; and   second computer readable program code to transmit one or more null packets to maintain the substantially constant bit rate over the transport stream, said null packets including a randomized payload.   
   
   
       22 . The computer program product of  claim 21 , wherein the first computer readable program code comprises first computer readable program code to transmit one or more video sessions in accordance to one of a digital broadcast satellite (DBS) system, digital cable system, high definition television (HDTV) system, and video-on-demand (VOD) system. 
   
   
       23 . A digital video receiver, comprising:
 a demodulator to demodulate analog signals received over a transmission channel;   decoder to decode signals from the demodulator;   an MPEG framer to synchronize to a video session in a transport stream;   a memory including one or more instructions;   a processor, coupled to the memory, demodulator, decoder, and framer, the processor, in response to the one or more instructions, to,   detect a checksum error from the MPEG framer indicative of a false synchronization to the video session, and   responsive to detecting a checksum error, resynchronize the MPEG framer to the transport stream.