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

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 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 apparatus for decoding an image comprising:

a storing means for storing two or more reference images for motion compensation prediction of an image to be decoded;

a motion compensation prediction means for deriving a reference block from the reference image according to a motion vector;

a decoding means for obtaining an image by decoding the reference blocks and decoded difference blocks;

a filtering means for de-block filtering a plurality of borders owned by a block in the reference image; and

a judging means for judging whether de-block filtering for each of the borders is performed, wherein

the judging means estimates whether a first motion vector and a second motion vector are similar to each other, which are respectively used in process of decoding a first block and a second block adjacent to the border, estimates whether the numbers of a first reference image and a second reference image are identical with each other, which are respectively used in process of decoding a first block and a second block,

performs de-block filtering the border on the condition that the motion vectors are not similar to each other or the numbers of the reference images are different from each other, and

does not perform de-block filtering the border on the condition that the motion vectors are similar to each other and the numbers of the reference images are identical with each other.

19. A method for decoding an image comprising steps of:

storing two or more reference images for motion compensation prediction of an image to be decoded;

deriving a reference block from the reference image according to a motion vector;

obtaining an image by decoding the reference blocks and decoded difference blocks;

de-block filtering a plurality of borders owned by a block in the reference image; and

judging whether de-block filtering for each of the borders is performed, wherein

the judging step estimates whether a first motion vector and a second motion vector are similar to each other, which are respectively used in process of decoding a first block and a second block adjacent to the border, estimates whether the numbers of a first reference image and a second reference image are identical with each other, which are respectively used in process of decoding a first block and a second block,

performs de-block filtering the border on the condition that the motion vectors are not similar to each other or the numbers of the reference images are different from each other, and

does not perform de-block filtering the border on the condition that the motion vectors are similar to each other and the numbers of the reference images are identical with each other.