Merging of multiple encoded audio-video streams into one program with source clock frequency locked and encoder clock synchronized

• US 20060248559A1
• Filed: 04/29/2005
• Published: 11/02/2006
• Est. Priority Date: 04/29/2005
• Status: Active Grant

• Current Assignee: The DIRECTV Group, Inc. (AT&T, Inc.)
• Original Assignee: The DIRECTV Group, Inc. (AT&T, Inc.)
• Inventors: Michener, James A., Stanger, Leon J.
• Granted Patent: US 7,735,111 B2
• Time in Patent Office: Days
• US Class Current: 725/67
• CPC Class Codes: H04N 21/233 Processing of audio elementary streams monitoring, identification or recognition of audio in broadcast systems H04H60/58
• CPC Class Codes: H04N 21/2368 Multiplexing of audio and video streams
• CPC Class Codes: H04N 21/242 Synchronization processes, e.g. processing of PCR [Program Clock References] arrangements for synchronising broadcast or distribution via plural systems in broadcast distribution systems H04H20/18
• CPC Class Codes: H04N 21/2665 Gathering content from different sources, e.g. Internet and satellite
• CPC Class Codes: H04N 21/8106 involving special audio data, e.g. different tracks for different languages

Abstract

A system and method for merging of multiple encoded audio and video streams into a single program in the transport stream enables playback of any audio stream with any video stream. This is accomplished by first locking the frequency of audio and video input streams for a plurality of different programs to a source clock, independently encoding each program with its own PCR and PTS into a program stream, multiplexing the program streams into a transport stream, and then synchronizing the PCR and PTS of the program streams to a declared master PCR.

Claims

1. A method, comprising:

frequency locking the audio and video streams from a plurality of programs;

separately encoding and multiplexing each program'"'"'s audio and video streams into a program stream, each program stream having an independent program clock reference (PCR) and presentation time stamps (PTS) in the audio and video streams;

multiplexing the program streams into a transport stream; and

synchronizing the programs'"'"' PCR and PTS in the transport stream off of a declared master PCR in one of the program streams to merge them into one program.

2. The method of claim 1, wherein the audio and video streams are frequency locked by providing a single source clock to capture the streams.

3. The method of claim 1, wherein the audio and video streams are frame synchronized to both frequency and phase lock the streams.

4. The method of claim 1, wherein the programs'"'"' PCR and PTS are synchronized by,

declaring one program and its PCR to be the master and the remaining programs and their PCRs to be slaves,

comparing each slave PCR to an interpolated value of the master PCR to compute an offset,

setting the slave PCR to the interpolated value, and

adding the offset to each occurrence of the slave'"'"'s PTS.

5. The method of claim 4, wherein the programs'"'"' PCR and PTS are synchronized sequentially.

6. The method of claim 4, wherein the offsets for each slave program are time averaged.

7. The method of claim 6, wherein, if a discontinuity is detected between the time-averaged offset and the current offset, resetting the time averaged offset to the current offset.

8. The method of claim 1, further comprising:

transmitting the transport stream to a customer site,

in response to a customer command selecting a video stream from a program stream and an audio stream from a different program stream, extracting the selected audio and video streams and the PCR from the transport stream,

decoding the selected audio and video streams, and

in accordance with the synchronized PTS with respect to the PCR, playing back the audio and video streams.

9. The method of claim 8, wherein the customer selects a plurality of video streams and/or a plurality of audio streams from different program streams for playback.

10. A method, comprising:

receiving a transport stream comprising multiplexed program streams each of which comprise an encoded video stream, an encoded audio stream, a program clock reference (PCR) and presentation time stamps (PTS) for the audio and video streams, wherein said video streams are source clock frequency locked and said PCR and PTS are encoder clock synchronized,

in response to a customer command selecting a video stream from a program stream and an audio stream from a different program stream, extracting the selected audio and video streams and the PCR from the transport stream,

decoding the selected audio and video streams, and

in accordance with the synchronized PTS with respect to the PCR, playing back the audio and video streams.

11. The method of claim 10, wherein the custom selects a plurality of video streams and/or a plurality of audio streams from different program streams for playback.

12. An apparatus, comprising:

a frequency locker that frequency locks the audio and video streams from a plurality of programs;

a plurality of encoders that respectively encode and multiplex the programs'"'"' audio and video streams into a respective plurality of program streams, each program stream having an independent program clock reference (PCR) and presentation time stamps (PTS) in the audio and video streams;

a transport multiplexer that multiplexes the program streams into a transport stream; and

an encoder clock synchronizer that synchronizes the programs'"'"' PCR and PTS in the transport stream off of a declared master PCR in one of the program streams to merge them into one program.

13. The apparatus of claim 12, wherein the frequency locker comprises a single source clock used to capture the audio and video streams.

14. The apparatus of claim 12, wherein the frequency locker comprises a plurality of frequency lockers that receive the respective programs and a common reference signal.

15. The apparatus of claim 12, wherein the encoder clock synchronizer declares one program and its PCR to be the master and the remaining programs and their PCRs to be slaves, compares each slave PCR to an interpolated value of the master PCR to compute an offset, sets the slave PCR to the interpolated value, and adds the offset to each occurrence of the slave'"'"'s PTS.

16. The apparatus of claim 15, wherein the encoder clock synchronizer synchronizes the programs'"'"' PCR and PTS sequentially.

17. The apparatus of claim 15, wherein the encoder clock synchronizer time averages the offsets for each slave program.

18. The apparatus of claim 17, wherein, if a discontinuity is detected between the time averaged offset and the current offset, the encoder clock synchronizer resets the time averaged offset to the current offset.