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

• US 7,352,812 B2
• Filed: 03/29/2002
• Issued: 04/01/2008
• Est. Priority Date: 03/26/2001
• Status: Expired due to Term

• 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
• Primary Examiner(s): An; Shawn S.
• Application Number:
  US10/112,683
• Publication Number:
  US 20020146072A1
• Time in Patent Office: 2,195 Days
• Field of Search: 375/240.16, 375/240.25, 375/240.12, 375/240.26, 375/240.14, 375/240.15, 375/240.18, 375/240.2, 348/699, 382/238, 382/268, 382/248, 382/236, 382/250
• 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 selective image filtering, said method comprising:

identifying a first block in an image;

identifying an adjacent block in said image, wherein said adjacent block shares a common interblock boundary with said first block, wherein said interblock boundary is located between boundary pixels in said first block and boundary pixels in said adjacent block that are immediately adjacent to said boundary pixels in said first block;

identifying a coding parameter for said first block;

identifying a coding parameter for said adjacent block; and

selectively deblock filtering only within a portion of said first block that is proximate to said interblock boundary when said first block coding parameter and said adjacent block coding parameter are not similar.

2. A method according to claim 1 wherein said identified coding parameters comprise motion vectors.

3. A method according to claim 1 wherein said identified coding parameters comprise reference image frames.

4. A method according to claim 1 wherein said identified coding parameters comprise transform coefficients.

5. A method according to claim 1 wherein said identified coding parameters comprise D.C. components in the transform coefficients.

6. A method according to claim 1 wherein said identified coding parameters comprise A.C. components in the transform coefficients.

7. A method according to claim 1 wherein said identified coding parameters comprise at least one parameter taken from the group consisting of motion vector data, reference image frame data, reference image block data, D.C. component data in a transform coefficient and A.C. component data in a transform coefficient.

8. A method for selective filtering of individual block boundaries, said method comprising:

selecting a target block in an image;

identifying a first adjacent block that is immediately adjacent to said target block;

identifying a second adjacent blocks that is immediately adjacent to said target block;

identifying a first interblock boundary along a line between a first set of pixels in said target block and pixels in said first adjacent block that are immediately adjacent to said first set of pixels in said target block;

identifying a second interblock boundary along a line between a second set of pixels in said target block and pixels in said second adjacent block that are immediately adjacent to said second set of pixels in said target block;

identifying a target coding parameter for said target block;

identifying a first coding parameter for said first adjacent block;

identifying a second coding parameter for said second adjacent block;

filtering only within a first portion of said target block and said first adiacent block that is proximate to said first interblock boundary when said target coding parameter and said first coding parameter are substantially dissimilar; and

filtering only within a second portion of said target block and said second adjacent block that is proximate to said second interblock boundary when said target coding parameter and said second coding parameter are substantially dissimilar.

9. A method according to claim 8 wherein said coding parameters comprise motion vectors and said substantial dissimilarity is achieved when said motion vectors point to different reference frames.

10. A method according to claim 8 wherein said coding parameters are transform coefficients.

11. A method according to claim 10 wherein said transform coefficients are D.C. coefficients.

12. A method according to claim 11 further comprising transform coefficients that are A.C. coefficients.

13. A method according to claim 10 wherein said coding parameters comprise motion vectors and transform coefficients.

14. A codec for at least one of encoding or decoding an image, said codec comprising:

a block identifier for identifying a target block, an adjacent block, and an interblock boundary along a line where pixels in said target block are immediately adjacent to pixels in said adjacent block;

a parameter identifier for identifying coding parameters that were previously used in an encoding process for said target block and said adjacent blocks;

a comparator for comparing said coding parameters; and

a filter selector for selective enablement of at least one filter to only within a portion of said target block and said adjacent block that is proximate to said interblock boundary, said selector operating in response to a comparison of the coding parameters; and

wherein said at least one filter is enabled when said coding parameters are not similar, and said at least one filter is disabled when said coding parameters are similar.

15. A codec according to claim 14 wherein said identified coding parameters comprise at least one parameter taken from the group consisting of motion vector data, reference image frame data, reference image block data D.C. component data in a transform coefficient and A.C. component data in a transform coefficient.

16. A method for selective image filtering, said method comprising:

dividing an original image into a plurality of channels, said channels comprising a luminance channel and a chrominance channel;

identifying a target block and an adjacent block in at least one of said channels, wherein said target block is immediately adjacent to said adjacent block;

identifying an interblock boundary along a line between pixels in said target block and pixels in said adjacent block that are immediately adjacent to said pixels in said target block;

identifying coding parameters for said target block and said adjacent block in said at least one channel;

comparing said coding parameters;

selectively filtering only within a portion of said target block and said adiacent block that is proximate to said interblock boundary when said coding parameters are dissimilar.

17. A method for selective image filtering, said method comprising:

dividing an original image into a plurality of channels, said channels comprising a luminance channel and at least one chrominance channel wherein each channel comprises a channel image;

identifying a target block and an adjacent block in one of said channel images;

identifying an interblock boundary along a line between boundary pixels in said target block and boundary pixels in said adjacent block that are immediately adjacent to said boundary pixels in said target block;

identifying coding parameters for said target block and said adjacent block in said at least one of said channels;

comparing said coding parameters; and

filtering only within a portion of said channel image, wherein said portion being proximate to said interblock boundary when said coding parameters for said target block and said adjacent block are dissimilar and skipping said filtering when said coding parameters are similar.

18. A method as described in claim 17 wherein said coding parameters are related to a luminance channel and said filtering is applied to all channels.

19. A method as described in claim 17 wherein said coding parameters are related to a luminance channel and said filtering is applied to a chrominance channel.

20. A method as described in claim 17 wherein said coding parameters are related to a luminance channel and said filtering is applied only to said luminance channel.

21. A method as described in claim 17 wherein said coding parameters are related to a chrominance channel and said filtering is applied to said chrominance channel.