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

• US RE46,482 E1
• Filed: 10/10/2014
• Issued: 07/18/2017
• Est. Priority Date: 03/26/2001
• Status: Expired due to Term

• Current Assignee: Dolby Laboratories Licensing Corporation (Dolby Laboratories Incorporated)
• Original Assignee: Dolby Laboratories Licensing Corporation (Dolby Laboratories Incorporated)
• Inventors: Sun, Shijun, Lei, Shawmin
• Primary Examiner(s): Basehoar, Adam L
• Application Number:
  US14/512,165
• Time in Patent Office: 1,012 Days
• Field of Search: 37524016, 37524018, 37524025, 37524029, 382233, 382236, 382239, 382254, 382264, 382266, 382268, 382269
• CPC Class Codes: G06T 5/001 Image 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 spatially adjacent blocks in a same frame of the image;

identifying transform coefficients for the spatially adjacent blocks in the same frame of the image;

comparing the transform coefficients between the spatially adjacent blocks in the same frame of the image;

skipping deblock filtering for removing image residuals to caused by encoding the image when the comparison indicates that the spatially adjacent blocks in the same frame of the image have same or similar transform coefficients; and

deblock filtering to remove image residuals between the identified spatially adjacent blocks when the comparison between the transform coefficients for the identified spatially adjacent blocks in the same frame of the image indicate that the spatially adjacent blocks do not have the same or similar transform coefficients.

2. A method according to claim 1 including:

identifying D.C. components in the transform coefficients;

comparing the D.C. components for the spatially adjacent blocks with each other; and

skipping deblock filtering between the spatially adjacent blocks when the D.C. components for the compared spatially adjacent blocks have same or similar values relative to each other.

3. A method according to claim 1 including:

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

comparing the D.C. components for adjacent blocks and A.C. components for adjacent blocks; and

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

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

5. 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.

6. 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.

7. 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.

8. An encoder for encoding an image, comprising:

a processor adapted to;

compare blocks in a same image frame with reference frames;

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

compare are the similarities between the transform coefficients for spatially adjacent transformed blocks within the same image frame; and

skipping deblock filtering between spatially adjacent transformed blocks in the image that have the same or similar transform coefficients.

9. An encoder according to claim 8 wherein the processor is adapted to

identify motion vectors and associated reference frames for the adjacent blocks and skip deblock filtering between the spatially adjacent blocks according to the identified motion vectors and reference frames.

10. An encoder according to claim 8 wherein the processor is adapted to

identify residual coefficients for the spatially adjacent blocks and skip deblock filtering according to the identified residual coefficients.

11. An encoder according to claim 8 wherein the processor is adapted to skip deblock filtering according to both D.C. and A.C. components in the residual coefficients.

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

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

identify coding parameters including D.C. coefficients for the spatially adjacent blocks within a same encoded image frame;

compare the identified D.C. coefficients between the identified spatially adjacent blocks; and

enable or disable filtering of blocking artifacts between the spatially adjacent blocks according to the comparison of the D.C. coefficients between the spatially adjacent blocks within the same encoded image frame.

13. A decoder according to claim 12 wherein the processor is adapted to identify both D.C. coefficients and A.C. coefficients for the spatially adjacent blocks within a same encoded image frame;

compare the identified D.C. coefficients between the identified spatially adjacent blocks and corn are the identified A.C. coefficients between the identified spatially adjacent blocks; and

enable or disable filtering of blocking artifacts between the spatially adjacent blocks according to the comparison of the D.C. coefficients between the adjacent blocks within the same encoded image frame and according to the comparison of the A.C. coefficients between the adjacent blocks within the same encoded image frame.

14. A decoder according to claim 12 wherein the processor is adapted to

identify residual coefficients for the spatially adjacent blocks and skip deblock filtering between the spatially adjacent blocks according to the identified residual coefficients.

15. A decoder according to claim 12 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 spatially adjacent blocks in the reconstructed image according to the coding parameters for the spatially adjacent blocks.

16. A decoder according to claim 15 wherein the coding parameters include transform coefficients, motion vectors, and reference frame information and the processor skips deblock filtering when the transform coefficients, motion vectors, and reference frame information for the spatially adjacent blocks are the same or similar.

17. A decoder according to claim 12 wherein the processor is adapted to

skip deblock filtering in one or both of a loop filter and a post filter.

18. An image decoding apparatus, comprising one or more processors configured to:

store reference images for an image to be decoded, the stored reference images being for motion compensation prediction of the image to be decoded;

obtain a reference block from the stored reference images according to a motion vector;

decode an image from the reference block and a decoded difference block;

generate a reconstructed image based on the decoding; and

judge whether or not to execute deblock filtering for each boundary between adjacent blocks in the reconstructed image with respect to each of a luminance channel and a chrominance channel for the adjacent blocks, wherein

the judging includes determining, with respect to one of the luminance channel or the chrominance channel for the adjacent blocks, whether or not motion vectors of the adjacent blocks are equal to each other as well as whether or not the motion vectors of the adjacent blocks point to the same reference image, and

in response to determining that the motion vectors of the adjacent blocks are equal to each other and point to the same reference image, deblock filtering is not executed for a boundary of the adjacent blocks in the reconstructed image corresponding to the luminance channel and a boundary of the adjacent blocks in the reconstructed image corresponding to the chrominance channel.

19. An image decoding method, comprising:

storing reference images for an image to be decoded, the stored reference images being for motion compensation prediction of the image to be decoded;

obtaining a reference block from the stored reference images according to a motion vector;

decoding an image from the reference block and a decoded difference block;

generating a reconstructed image based on the decoding; and

judging whether or not to execute deblock filtering for each boundary between adjacent blocks in the reconstructed image with respect to each of a luminance channel and a chrominance channel for the adjacent blocks, wherein

the judging includes determining, with respect to one of the luminance channel or the chrominance channel for the adjacent blocks, whether or not motion vectors of the adjacent blocks are equal to each other as well as whether or not the motion vectors of the adjacent blocks point to the same reference image, and

in response to determining that the motion vectors of the adjacent blocks are equal to each other and point to the same reference image, deblock filtering is not executed for a boundary of the adjacent blocks in the reconstructed image corresponding to the luminance channel and a boundary of the adjacent blocks in the reconstructed image corresponding to the chrominance channel.