Adaptive filtering based upon boundary strength

• US 7,613,240 B2
• Filed: 04/03/2006
• Issued: 11/03/2009
• Est. Priority Date: 09/14/2001
• Status: Expired due to Term

• Current Assignee: Dolby Laboratories Licensing Corporation (Dolby Laboratories Incorporated)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Katata, Hiroyuki, Sun, Shijun, Lei, Shawmin
• Primary Examiner(s): LEE, Y YOUNG
• Application Number:
  US11/395,181
• Publication Number:
  US 20060171472A1
• Time in Patent Office: 1,310 Days
• Field of Search: 375/240.01, 375/240.12, 375/240.26, 375/240.29
• US Class Current: 375/240.16
• 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. An encoder for encoding an image comprising:

an identifier for identifying a first region and a second region adjacent to each other in said image; and

a filter for selectively filtering at least a portion of said regions proximate a boundary between said regions based upon a boundary strength which is set for said boundary, wherein,

(a) a strength of said filter is controlled so that said strength increases as the boundary strength increases,

(b) said boundary strength is set to a first value when either one of said first region and said second region is intra-coded,

(c) said boundary strength is set to a second value when neither of said first region nor said second region is intra-coded and when either of said regions include non-zero coefficients,

(d) said boundary strength is set to a third value when neither of said first region nor said second region is intra-coded, when both of said regions do not include non-zero coefficients and

(1) when said regions are predicted based upon different reference images or

(2) when an absolute difference of motion vectors of said regions is equal to or greater than a non-zero threshold value in either vertical or horizontal directions,

(e) said boundary strength is set to a fourth value when neither of said first region nor said second region is intra-coded, when both of said regions do not include non-zero coefficients and

(1) when said regions are predicted based upon the same reference image and

(2) when an absolute difference of motion vectors of said regions is less than said non-zero threshold value in both vertical and horizontal directions,

(f) said first value being larger than said second value, said second value being larger than said third value and said third value being larger than said fourth value, and

(g) said fourth value indicates that there is no filtering.

2. A decoder for decoding an image comprising:

an identifier for identifying a first region and a second region adjacent to each other in said image; and

a filter, for selectively filtering at least a portion of said regions proximate a boundary between said regions based upon a boundary strength which is set for said boundary, wherein,

(a) a strength of said filter is controlled so that said strength increases as the boundary strength increases,

(b) said boundary strength is set to a first value when either one of said first region and said second region is intra-coded,

(c) said boundary strength is set to a second value when neither of said first region nor said second region is intra-coded and when either of said regions include non-zero coefficients,

(d) said boundary strength is set to a third value when neither of said first region nor said second region is intra-coded, when both of said regions do not include non-zero coefficients and

(1) when said regions are predicted based upon different reference images or

(2) when an absolute difference of motion vectors of said regions is equal to or greater than a non-zero threshold value in either vertical or horizontal directions,

(e) said boundary strength is set to a fourth value when neither of said first region nor said second region is intra-coded, when both of said regions do not include non-zero coefficients and

(1) when said regions are predicted based upon the same reference image and

(2) when an absolute difference of motion vectors of said regions is less than said non-zero threshold value in both vertical and horizontal directions,

(f) said first value being larger than said second value and said second value being larger than said third value and said third value being larger than said fourth value, and

(g) said fourth value indicates that there is no filtering.