Method and apparatus for controlling loop filtering or post filtering in block based motion compensationed video coding

• US 20020136303A1
• Filed: 03/26/2001
• Published: 09/26/2002
• Est. Priority Date: 03/26/2001
• Status: Active Grant

• Current Assignee: Dolby Laboratories Licensing Corporation (Dolby Laboratories Incorporated)
• Original Assignee: Sharp Laboratories of America Incorporated (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Sun, Shijun, Lei, Shawmin
• Granted Patent: US 6,931,063 B2
• Time in Patent Office: Days
• US Class Current: 375/240.16
• CPC Class Codes: G06T 5/00 Image enhancement or restoration
• CPC Class Codes: H04N 19/117 Filters, e.g. for pre-processing or post-processing sub-band filter banks H04N19/635
• CPC Class Codes: H04N 19/132 Sampling, masking or truncation of coding units, e.g. adaptive resampling, frame skipping, frame interpolation or high-frequency transform coefficient masking
• CPC Class Codes: H04N 19/136 Incoming video signal characteristics or properties
• CPC Class Codes: H04N 19/139 Analysis of motion vectors, e.g. their magnitude, direction, variance or reliability
• CPC Class Codes: H04N 19/176 the region being a block, e.g. a macroblock
• CPC Class Codes: H04N 19/196 being specially adapted for the computation of encoding parameters, e.g. by averaging previously computed encoding parameters processing of motion vectors H04N19/513
• CPC Class Codes: H04N 19/527 Global motion vector estimation
• CPC Class Codes: H04N 19/573 Motion compensation with multiple frame prediction using two or more reference frames in a given prediction direction
• CPC Class Codes: H04N 19/577 Motion compensation with bidirectional frame interpolation, i.e. using B-pictures
• CPC Class Codes: H04N 19/60 using transform coding
• CPC Class Codes: H04N 19/61 in combination with predictive coding
• CPC Class Codes: H04N 19/80 Details of filtering operations specially adapted for video compression, e.g. for pixel interpolation H04N19/635, H04N19/86 take precedence
• CPC Class Codes: H04N 19/82 involving filtering within a prediction loop
• CPC Class Codes: H04N 19/86 involving reduction of coding artifacts, e.g. of blockiness
• CPC Class Codes: H04N 19/895 in combination with error concealment

Abstract

Adjacent blocks are identified in an image. Coding parameters for the adjacent blocks are identified. Deblock filtering between the identified adjacent blocks is skipped if the coding parameters for the identified adjacent blocks are similar and not skipped if the coding parameters for the identified adjacent blocks are substantially different.

Claims

1. A method for encoding an image, comprising:

identifying adjacent blocks in the image;

identifying coding parameters for the adjacent blocks;

skipping deblock filtering between the identified adjacent blocks when the coding parameters for the identified adjacent blocks are similar; and

deblock filtering between the identified adjacent blocks when the coding parameters for the identified adjacent blocks are not similar.

2. A method according to claim 1 including skipping deblock filtering when the adjacent blocks have similar motion vectors pointing to a same reference image frame.

3. A method according to claim 1 including:

identifying transform coefficients for the adjacent blocks; and

skipping deblock filtering between the adjacent blocks when the transform coefficients are similar.

4. A method according to claim 3 including:

identifying D.C. components in the transform coefficients; and

skipping deblock filtering between the adjacent blocks when the D.C. components are the same or similar.

5. A method according to claim 4 including:

identifying A.C. components in the transform coefficients; and

skipping deblock filtering between the adjacent blocks when the D.C. and A.C. components are the same or similar.

6. A method according to claim 3 including transforming the adjacent blocks using a Discrete Cosine Transform to generate the transform coefficients.

7. A method according to claim 1 including:

comparing blocks in the image with reference frames;

transforming the result of the comparison between the reference frames and the blocks in the image into transformed blocks having transform coefficients;

comparing the similarities between the transform coefficients; and

skipping deblock filtering between adjacent blocks in the image according to the results of the comparison between the transform coefficients.

8. A method according to claim 7 wherein the transform coefficients include D.C. transform coefficients.

9. A method according to claim 1 including controlling deblock filtering for a loop filter in an image coder.

10. A method according to claim 1 including controlling deblock filtering in one or both of a loop filter and a post filter in an image decoder.

11. A method according to claim 1 including:

identifying similarities between coding parameters in a luminance channel of the adjacent blocks; and

controlling deblock filtering for both the luminance channel and a chrominance channel in the image according to identified similarities in the luminance channel.

12. A method according to claim 1 including selectively skipping deblock filtering in any one of a H.261, H.263, H263+, MPEG-1, MPEG-2, or H26L encoding standard according to encoding parameter similarities between adjacent image blocks.

14. An encoder according to claim 13 wherein the processor is adapted to identify motion vectors and associated reference frames for the adjacent blocks and skip deblock filtering between the adjacent blocks according to the identified motion vectors and reference frames.

15. An encoder according to claim 13 wherein the processor is adapted to identify residual coefficients for the adjacent blocks and skip deblock filtering according to the identified residual coefficients.

16. An encoder according to claim 13 wherein the processor is adapted to skip deblock filtering according to D.C. components in the residual coefficients.

17. An encoder according to claim 16 wherein the processor is adapted to skip deblock filtering D.C. and A.C. components in the residual coefficients.

18. An encoder according to claim 13 wherein the processor is adapted to compare blocks in the image with reference frames, transform the result of the comparison between the reference frames and the blocks into transformed blocks having transform coefficients, compare the transform coefficients and encoding parameters of adjacent blocks, and skip deblock filtering between adjacent blocks in the image according to the results of the comparison between the transform coefficients and encoding parameters.

19. An encoder according to claim 18 wherein the transform coefficients include D.C. transform components and the encoding parameters include motion vectors and reference frames.

13. An encoder for encoding an image, comprising:

a processor adapted to identify adjacent blocks in the input image;

compare coding parameters for the adjacent blocks; and

enable and disable filtering of blocking artifacts between the adjacent blocks according to the comparisons.

20. A decoder for decoding an encoded image, comprising:

a processor adapted to identify adjacent blocks in the encoded image;

identify coding parameters for the adjacent blocks; and

enable or disable filtering of blocking artifacts between the adjacent blocks according to the coding parameters for the adjacent blocks.

21. A decoder according to claim 20 wherein the processor is adapted to identify motion vectors and associated reference frames for the adjacent blocks and skip deblock filtering between the adjacent blocks according to the identified motion vectors and reference frames.

22. A decoder according to claim 20 wherein the processor is adapted to identify residual coefficients for the adjacent blocks and skip deblock filtering between the adjacent blocks according to the identified residual coefficients.

23. A decoder according to claim 22 wherein the processor is adapted to identify D.C. components in the residual coefficients and skip deblock filtering between the adjacent blocks according to the identified D.C. components.

24. A decoder according to claim 23 wherein the processor is adapted to identify similar A.C. components in the residual coefficients and skip deblock filtering between the identified adjacent according to the identified D.C. and A.C. components.

25. A decoder according to claim 20 wherein the processor is adapted to inverse transform the encoded image, compare blocks in the inverse transformed encoded image with reference frames, generate a reconstructed image from the comparison between the inverse transformed encoded image and the reference frame, and skip deblock filtering between adjacent blocks in the reconstructed image according to the coding parameters for the adjacent blocks.

26. A decoder according to claim 25 wherein the coding parameters include transform coefficients, motion vectors, and reference frame information.

27. A decoder according to claim 20 wherein the processor is adapted to skip deblock filtering in one or both of a loop filter and a post filter.