Adaptive intra-refresh for digital video encoding

• US 20060078051A1
• Filed: 12/28/2004
• Published: 04/13/2006
• Est. Priority Date: 10/12/2004
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: El-Maleh, Khaled Helmi, Liang, Yi, Manjunath, Sharath
• Granted Patent: US 8,948,266 B2
• Time in Patent Office: Days
• US Class Current: 375/240.240
• CPC Class Codes: H04N 19/107 between spatial and temporal predictive coding, e.g. picture refresh
• CPC Class Codes: H04N 19/14 Coding unit complexity, e.g. amount of activity or edge presence estimation H04N19/146 takes precedence
• CPC Class Codes: H04N 19/147 according to rate distortion criteria rate-distortion as a criterion for motion estimation H04N19/567
• CPC Class Codes: H04N 19/164 Feedback from the receiver or from the transmission channel
• CPC Class Codes: H04N 19/172 the region being a picture, frame or field
• CPC Class Codes: H04N 19/176 the region being a block, e.g. a macroblock
• CPC Class Codes: H04N 19/61 in combination with predictive coding
• CPC Class Codes: H04N 19/89 involving methods or arrangements for detection of transmission errors at the decoder

Abstract

An adaptive Intra-refresh (IR) technique for digital video encoding adjusts IR rate based on video content, or a combination of video content and channel condition. The IR rate may be applied at the frame level or macroblock (MB) level. At the frame level, the IR rate specifies the percentage of MBs to be Intra-coded within the frame. At the MB level, the IR rate defines a statistical probability that a particular MB is to be Intra-coded. The IR rate is adjusted in proportion to a combined metric that weighs estimated channel loss probability, frame-to-frame variation, and texture information. The IR rate can be determined using a close-form solution that requires relatively low implementation complexity. For example, such a close-form does not require iteration or an exhaustive search. In addition, the IR rate can be determined from parameters that are available before motion estimation and compensation are performed.

Claims

1. A video encoding method comprising:

obtaining a measure of frame-to-frame variation between a current frame and another frame;

obtaining texture information for the current frame; and

generating an Intra-refresh (IR) rate for the current frame based on the frame-to-frame variation and the texture information.

2. The method of claim 1, wherein obtaining a measure of the frame-to-frame variation includes obtaining a sum of square difference (SSD) value between the current frame and the other frame, and the texture information characterizes texture complexity within the current frame.

3. The method of claim 1, wherein the texture information is based on pixel variation.

4. The video encoding method of claim 1, further comprising obtaining an estimate of channel loss probability, wherein generating an IR rate includes generating the IR rate for the current frame based on the channel loss probability estimate, the measure of frame-to-frame variation and the texture complexity.

5. The method of claim 4, wherein obtaining the estimate of channel loss probability includes obtaining the estimate using control messages received from a remote terminal or based on loss of information transmitted by a remote terminal.

6. The method of claim 1, further comprising selecting Inter-coding or Intra-coding for all macroblocks (MBs) within the current frame based on the IR rate.

7. The method of claim 1, further comprising selecting Inter-coding or Intra-coding for individual macroblocks (MBs) within the current frame based on the IR rate.

8. The method of claim 1, further comprising updating the IR rate on a frame-by-frame basis.

9. The method of claim 1, further comprising updating the IR rate on a macroblock-by-macroblock basis within the current frame.

10. The method of claim 1, further comprising:

selecting one of a plurality of grids within the current frame, each of the grids containing a subset of macroblocks (MBs) within the current frame; and

applying the IR rate to select Intra-coding for macroblocks (MBs) within the selected grid.

11. The method of claim 10, further comprising selecting different grids in each of a plurality of successive frames, wherein each of the grids contains a substantially equal number of MBs.

12. The method of claim 10, further comprising selecting different grids in each of a plurality of successive frames, wherein the grids contain different numbers of MBs.

13. The method of claim 1, further comprising selecting Inter-coding or Intra-coding for macroblocks (MBs) within the current frame based on the IR rate and texture information associated with the MBs.

14. The method of claim 13, further comprising selecting Inter-coding or Intra-coding for macroblocks (MBs) within the current frame based on a combination of selection of a cyclical pattern of MBs and a selection of MBs based on texture information associated with the MBs.

15. The method of claim 1, further comprising adjusting the IR rate based on an Intra-frame period.

16. A video encoder comprising:

an Intra-refresh (IR) rate control unit to generate an IR rate for a current frame based on a measure of frame-to-frame variation between the current frame and another frame and a texture information for the current frame; and

a mode select unit to select Inter-coding or Intra-coding for macroblocks (MBs) within the current frame based on the IR rate.

17. The video encoder of claim 16, wherein the frame-to-frame variation is a sum of square difference (SSD) value between the current frame and the other frame, and the texture information characterizes texture complexity within the current frame.

18. The video encoder of claim 16, wherein the texture information is based on pixel variation.

19. The video encoder of claim 16, wherein the IR rate control unit generates the IR rate based on the measure of frame-to-frame variation between the current frame and another frame, the texture information for the current frame and an estimated channel loss probability.

20. The video encoder of claim 19, wherein the estimate of channel loss probability is based on control messages received from a remote terminal, or loss of information transmitted by a remote terminal.

21. The video encoder of claim 16, wherein the mode select unit selects Inter-coding or Intra-coding for all macroblocks (MBs) in the current frame based on the IR rate.

22. The video encoder of claim 16, wherein the mode select unit selects Inter-coding or Intra-coding for individual macroblocks (MBs) within the current frame based on the IR rate.

23. The video encoder of claim 16, wherein the IR rate control unit updates the IR rate on a frame-by-frame basis.

24. The video encoder of claim 16, wherein the IR rate control unit updates the IR rate on a macroblock-by-macroblock basis within the current frame.

25. The video encoder of claim 16, wherein the mode select unit selects one of a plurality of grids within the current frame, each of the grids containing a subset of macroblocks (MBs) within the current frame, and applies the IR rate to select Intra-coding for macroblocks (MBs) within the selected grid.

26. The video encoder of claim 25, wherein the mode select unit selects different grids in each of a plurality of successive frames, and each of the grids contains a substantially equal number of MBs.

27. The video encoder of claim 25, wherein the mode select unit selects different grids in each of a plurality of successive frames, and the grids contain different numbers of MBs.

28. The video encoder of claim 16, wherein the mode select unit selects Inter-coding or Intra-coding for macroblocks (MBs) within the current frame based on the IR rate and texture information associated with the MBs.

29. The video encoder of claim 16, wherein the mode select unit selects Inter-coding or Intra-coding for macroblocks (MBs) within the current frame based on a combination of selection of a cyclical pattern of MBs and a selection of MBs based on texture information associated with the MBs.

30. The video encoder of claim 16, wherein the IR rate control unit adjusts the IR rate based on an Intra-frame period.

31. A computer-readable medium comprising instructions to cause a processor within a video encoder to:

obtain a measure of frame-to-frame variation between a current frame and another frame;

obtain texture information for the current frame;

generate an Intra-refresh (IR) rate for the current frame based on the frame-to-frame variation and the texture information.

32. The computer-readable medium of claim 31, further comprising instructions to cause the processor to obtain the frame-to-frame variation as a sum of square difference (SSD) value between the current frame and the other frame, and the texture information characterizes texture complexity of the current frame.

33. The computer-readable medium of claim 31, wherein the texture information is based on pixel variation.

34. The computer-readable medium of claim 31, further comprising instructions to cause the processor to obtain an estimate of channel loss probability, and generate the IR rate based on the channel loss probability estimate, the frame-to-frame variation and the texture information.

35. A video encoding method comprising:

generating an Intra-refresh (IR) rate for a current video frame based on video content of the current video frame; and

selecting Inter-coding or Intra-coding for macroblocks (MBs) within the current frame based on the IR rate.

36. A video encoder comprising:

an Intra-refresh (IR) rate control unit to generate an IR rate for a current video frame based on video content of the current video frame; and

a mode select unit to select Inter-coding or Intra-coding for macroblocks (MBs) within the current frame based on the IR rate.