Rate control and buffer protection for variable bit rate video programs over a constant rate channel

• US 6,493,388 B1
• Filed: 04/19/2000
• Issued: 12/10/2002
• Est. Priority Date: 04/19/2000
• Status: Active Grant

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: General Instrument Corporation (CommScope Holding Company, Inc.)
• Inventors: Wang, Limin
• Primary Examiner(s): LEE, RICHARD J
• Application Number:
  US09/553,457
• Time in Patent Office: 965 Days
• Field of Search: H04/N.712, H04/N.758, 348/385.1, 348/388.1, 348/389.1, 370/465, 370/468, 370/477, 370/538, 375/240-1-2, 375/240-2-2, 375/240.24, 375/240.25, 382/232, 382/236, 382/238
• US Class Current: 375/240.12
• CPC Class Codes: H04N 19/114 Adapting the group of pictures [GOP] structure, e.g. number of B-frames between two anchor frames H04N19/107 takes precedence
• CPC Class Codes: H04N 19/115 Selection of the code volume for a coding unit prior to coding
• CPC Class Codes: H04N 19/124 Quantisation
• CPC Class Codes: H04N 19/152 by measuring the fullness of the transmission buffer
• CPC Class Codes: H04N 19/172 the region being a picture, frame or field
• CPC Class Codes: H04N 19/177 the unit being a group of pictures [GOP]
• CPC Class Codes: H04N 19/61 in combination with predictive coding
• CPC Class Codes: H04N 21/2365 Multiplexing of several video streams
• CPC Class Codes: H04N 21/23655 Statistical multiplexing, e.g. by controlling the encoder to alter its bitrate to optimize the bandwidth utilization
• CPC Class Codes: H04N 21/2401 Monitoring of the client buffer

Abstract

A system for rate control and buffer management during coding of multiple variable bit rate digital video programs over a constant bit rate channel. The system is suitable for use in a hierarchical bit allocation scheme that includes a super group of pictures (GOP) level, a super frame level, and a frame level. For each super GOP with a length N frames, for each video program, the transmission rate for the current frame is set according to an average number of compressed bits for at least N previous frames, including a frame starting at N′+N−1 frames before the current frame, a frame ending at N′ frames before the current frame, and intermediate frames therebetween. N′ is a decoding delay of a modeled decoder that receives a respective video program. Moreover, the transmission rates of future frames are pre-set so that the average input rate of each individual video stream to the respective decoder buffer is equal to the average output rate, and the total transmission rate of programs is equal to the channel rate.

Claims

1. A method for coding data of a plurality L of video programs at a variable bit rate, comprising the steps of:

allocating bits for coding the video programs according to a hierarchical scheme that includes at least;

(a) a super group of pictures (GOP) level, wherein a super GOP comprises at least one GOP from each of the video programs, and has a length of N frames, and (b) a frame level; and

for each program, setting a transmission rate for a respective current frame according to an average number of compressed bits for at least N previous frames, including a frame starting at N′

+N-1 frames before a current frame, a frame ending at N′

frames before the current frame, and intermediate frames therebetween;

wherein N′

is a decoding delay of a modeled decoder that receives a respective video program.

2. The method of claim 1, wherein:

the hierarchical bit allocation scheme includes a super frame level between the super GOP level and the frame level; and

each super frame comprises L pictures at a common frame instant, one from each video program.

3. The method of claim 1, wherein:

for each program, the transmission rates for the respective current frame and N′

future frames is predetermined at the time the current frame is coded.

4. The method of claim 1, wherein:

for each program, said N previous frames are the frames that are most recently moved out of a buffer of the modeled decoder.

5. The method of claim 1, wherein:

for each program, said N previous frames are the frames that are most recently moved out of a buffer of the modeled decoder at a start of a coding time of the current frame.

6. The method of claim 1, wherein:

for each program, the transmission rate that is set results in an average input rate to a buffer of the modeled decoder that is equal to an average output rate thereof.

7. The method of claim 1, wherein:

an aggregate of the transmission rates for the respective current frames of the video programs is maintained within a total available channel rate.

8. The method of claim 1, wherein:

the video programs are communicated over a broadband communication network to a decoder population.

9. The method of claim 1, wherein:

for each program, the transmission rate is set for the respective current frame according to an average number of compressed bits for N previous frames including said frame starting at N′

+N−

1 frames before the current frame, and said frame ending at N′

frames before the current frame.

10. The method of claim 1, wherein:

for each program, the transmission rate for the respective current frame is set according to an average number of compressed bits for an integer multiple of N previous frames.

11. The method of claim 1, wherein:

the video programs that are coded comprise uncompressed and compressed video data.

12. The method of claim 1, wherein:

the video programs that are coded comprise uncompressed video data.

13. An apparatus for coding data of a plurality L of video programs at a variable bit rate, comprising:

means for allocating bits for coding the video programs according to a hierarchical scheme that includes at least;

(a) a super group off pictures (GOP) level, wherein a super GOP comprises at least one GOP from each of the video programs, and has a length of N frames, and (b) a frame level; and

means for setting a transmission rate for a respective current frame for each program according to an average number of compressed bits for at least N previous frames, including a frame starting at N′

+N−

1 frames before a current frame, a frame ending at N′

frames before the current frame, and intermediate frames therebetween;

wherein N′

is a decoding delay of a modeled decoder that receives a respective video program.

14. The apparatus of claim 13, wherein:

the hierarchical bit allocation scheme includes a super frame level between the super GOP level and the frame level; and

each super frame comprises L pictures at a common frame instant, one from each video program.

15. The apparatus of claim 13, wherein:

for each program, the transmission rates for the respective current frame and N′

future frames is predetermined at the time the current frame is coded.

16. The apparatus of claim 13, wherein:

for each program, said N previous frames are the frames that are most recently moved out of a buffer of the modeled decoder.

17. The apparatus of claim 13, wherein:

for each program, said N previous frames are the frames that are most recently moved out of a buffer of the modeled decoder at a start of a coding time of the current frame.

18. The apparatus of claim 13, wherein:

for each program, the transmission rate that is set results in an average input rate to a buffer of the modeled decoder that is equal to an average output rate thereof.

19. The apparatus of claim 13, wherein:

an aggregate of the transmission rates for the respective current frames of the video programs is maintained within a total available channel rate.

20. The apparatus of claim 13, wherein:

the video programs are communicated over a broadband communication network to a decoder population.

21. The apparatus of claim 13, wherein:

for each program, the transmission rate is set for the respective current frame according to an average number of compressed bits for N previous frames including said frame starting at N′

+N−

1 frames before the current frame, and said frame ending at N′

frames before the current frame.

22. The apparatus of claim 13, wherein:

for each program, the transmission rate for the respective current frame is set according to an average number of compressed bits for an integer multiple of N previous frames.

23. The apparatus of claim 13, wherein:

the video programs that are coded comprise uncompressed and compressed video data.

24. The apparatus of claim 13, wherein:

the video programs that are coded comprise uncompressed video data.