Adaptive filtering based upon boundary strength

• US 8,891,634 B2
• Filed: 12/20/2006
• Issued: 11/18/2014
• Est. Priority Date: 09/14/2001
• Status: Expired due to Fees

• Current Assignee: Dolby Laboratories Licensing Corporation (Dolby Laboratories Incorporated)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Sun, Shijun, Lei, Shawmin, Katata, Hiroyuki
• Primary Examiner(s): LEE, Y YOUNG
• Application Number:
  US11/641,910
• Publication Number:
  US 20070098077A1
• Time in Patent Office: 2,890 Days
• Field of Search: 375/240.01, 375/240.12, 375/240.18, 375/240.29
• US Class Current: 375/240.29
• CPC Class Codes: H04N 19/105 Selection of the reference unit for prediction within a chosen coding or prediction mode, e.g. adaptive choice of position and number of pixels used for prediction
• 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 19/124 Quantisation
• CPC Class Codes: H04N 19/136 Incoming video signal characteristics or properties
• CPC Class Codes: H04N 19/137 Motion inside a coding unit, e.g. average field, frame or block difference
• CPC Class Codes: H04N 19/139 Analysis of motion vectors, e.g. their magnitude, direction, variance or reliability
• 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 19/15 by monitoring actual compressed data size at the memory before deciding storage at the transmission buffer
• CPC Class Codes: H04N 19/159 Prediction type, e.g. intra-frame, inter-frame or bidirectional frame prediction
• CPC Class Codes: H04N 19/167 Position within a video image, e.g. region of interest [ROI]
• 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 19/196 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 19/197 including determination of the initial value of an encoding parameter H04N19/56 takes precedence
• CPC Class Codes: H04N 19/43 Hardware specially adapted for motion estimation or compensation
• CPC Class Codes: H04N 19/46 Embedding additional information in the video signal during the compression process H04N19/517, H04N19/68, H04N19/70 take precedence
• CPC Class Codes: H04N 19/51 Motion estimation or motion compensation
• 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 19/58 Motion compensation with long-term prediction, i.e. the reference frame for a current frame not being the temporally closest one H04N19/23 takes precedence
• CPC Class Codes: H04N 19/60 : using transform coding
• CPC Class Codes: H04N 19/61 : in combination with predictive coding
• CPC Class Codes: H04N 19/615 : using motion compensated temporal filtering [MCTF]
• CPC Class Codes: H04N 19/82 : involving filtering within a prediction loop
• CPC Class Codes: H04N 19/85 : using pre-processing or post-processing specially adapted for video compression
• CPC Class Codes: H04N 19/86 : involving reduction of coding artifacts, e.g. of blockiness

Abstract

Adjacent regions are identified in an image. Coding parameters for the adjacent regions are identified. Selective filtering is performed at the region between the identified adjacent regions.

Claims

1. A method for at least one of encoding and decoding a digital image with an encoding or decoding apparatus, comprising:

identifying adjacent regions in said digital image;

determining, for said adjacent regions, whether each region is intra coded;

determining whether or not to filter, with a filter of said apparatus, at least a portion of digital image data in said regions proximate a boundary between said adjacent regions based on whether at least one of said adjacent regions is intra coded, where said determining whether or not to filter includes determining whether or not to filter said portion of digital image data based on motion vectors associated with said adjacent regions;

establishing a boundary strength of said boundary by

setting said boundary strength to a first value in response to at least one of said adjacent regions being intra coded; and

setting said boundary strength to a a second value, which is less than the first value in response to

both said adjacent regions being not intra coded;

neither of said adjacent regions having a non-zero transform coefficient; and

either the absolute value of the difference of horizontal components of motion vectors in said adjacent regions or the absolute value of the difference of vertical components of motion vectors in said adjacent regions being greater than or equal to a predetermined threshold value; and

controlling a strength of said filter according to said boundary strength such that, in response to at least one of said adjacent regions being intra coded, the strength of the filter for the boundary is always stronger than the filter for other cases.

2. The method of claim 1, establishing further comprising setting boundary strength to a third value when said adjacent regions are inter coded and at least one of said adjacent regions contains non zero transform coefficients.

3. The method of claim 1, where filtering includes selectively adjusting pixel values of non-correlated image pixels within said regions.

4. The method of claim 1, where controlling a strength of said filter includes controlling a permitted range of adjustment to pixel values of non-correlated image pixels within said regions.

5. An encoder for encoding an image, comprising:

an identifier portion that identifies adjacent regions in said image;

a condition examiner portion that determines whether each of said adjacent regions is intra coded;

a selective filter that determines whether or not to filter at least a portion of said regions proximate a boundary between said adjacent regions based on whether at least one of said adjacent regions is intra coded, where said determining whether or not to filter includes determining whether or not to filter said portion of digital image data based on motion vectors associated with said adjacent regions; and

a determiner portion that determines a boundary strength of said boundary such that

the boundary strength is a first value when at least one of said adjacent regions are intra coded; and

the boundary strength is a second value. which is less than the first value when;

both said adjacent regions are not intra coded;

neither of said adjacent regions has a non-zero transform coefficient; and

either the absolute value of the difference of horizontal components of motion vectors in said adjacent regions or the absolute value of the difference of vertical components of motion vectors in said adjacent regions being greater than or equal to a predetermined threshold value; and

where the selective filter selectively filters with a strength based on the boundary strength such that when at least one of said adjacent regions is intra coded. the filter for the boundary is always stronger than the filter for other cases.

6. The encoder of claim 5, wherein said boundary strength is a third value when said adjacent regions are inter coded and at least one of said adjacent regions contains non zero transform coefficients.

7. The encoder of claim 5, wherein said selective filter adjusts pixel values of non-correlated image pixels within said regions.

8. The encoder of claim 5, where the strength of the selective filter determines the permitted range of adjustment to pixel values of non-correlated image pixels within said regions.

9. A decoder for decoding an image, comprising:

an identifier portion that identifies adjacent regions in said image;

a condition examiner portion that determines whether each of said adjacent regions is intra coded; and

a selective filter that determines whether or not to filter at least a portion of said regions proximate a boundary between said adjacent regions based on whether at least one of said adjacent regions is intra coded, where said determining whether or not to filter includes determining whether or not to filter said portion of digital image data based on motion vectors associated with said adjacent regions; and

a determiner portion that determines a boundary strength of said boundary such that said boundary strength is a first value when at least one of said adjacent regions are intra coded; and

the boundary strength is a second value, which is less than the first value when;

both said adjacent regions are not intra coded;

neither of said adjacent regions has a non-zero transform coefficient; and

either the absolute value of the difference of horizontal components of motion vectors in said adjacent regions or the absolute value of the difference of vertical components of motion vectors in said adjacent regions greater than or equal to a predetermined threshold value; and

where the selective filter selectively filters with a strength based on the boundary strength such that when at least one of said adjacent regions is intra coded, the filter for the boundary is always stronger than the filter for other cases.

10. The decoder of claim 9, wherein said boundary strength is a third value when said adjacent regions are inter coded and at least one of said adjacent regions contains non zero transform coefficients.

11. The decoder of claim 9, wherein said selective filter adjusts pixel values of non-correlated image pixels within said regions.

12. The decoder of claim 9, where the strength of the selective filter determines the permitted range of adjustment to pixel values of non-correlated image pixels within said regions.