Adaptive filtering based upon boundary strength

• US 7,907,667 B2
• Filed: 12/20/2006
• Issued: 03/15/2011
• 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: Katata, Hiroyuki, Sun, Shijun, Lei, Shawmin
• Primary Examiner(s): LEE, Y YOUNG
• Application Number:
  US11/641,707
• Publication Number:
  US 20070098278A1
• Time in Patent Office: 1,546 Days
• Field of Search: 375/240.01, 375/240.18, 375/240.29
• US Class Current: 375/240.18
• 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 an image, comprising:

identifying adjacent regions in said image;

examining conditions of coding parameters for said adjacent regions;

determining boundary strength for at least one boundary between said adjacent regions; and

selectively filtering at least a portion of said regions proximate the at least one boundary between said adjacent regions based upon said conditions of coding parameters examined in said examining step, wherein

said conditions of coding parameters include whether at least one of said adjacent regions contains non-zero transform coefficients,

a strength of said selectively filtering is controlled by said boundary strength,

said boundary strength is set to a first predetermined fixed value when at least one of said adjacent regions contains non-zero transform coefficients, and

the boundary strength first predetermined fixed value is used to control a pixel value adaptation range in a loop filter to provide said step of selectively filtering.

2. The method of claim 1, wherein

said boundary strength is set to a second predetermined fixed value when the examining conditions step finds that said adjacent regions do not contain non-zero transform coefficients and are predicted based upon different reference frames, and

the strength of said selectively filtering for said second predetermined fixed value is smaller than the strength of said selectively filtering for said first predetermined fixed value.

3. An encoder for encoding an image, comprising:

an identifier portion configured to identify adjacent regions in said image;

a condition examiner portion configured to examine conditions of coding parameters for said adjacent regions;

a determiner portion configured to determine boundary strength for at least one boundary between said adjacent regions; and

a selective loop filter configured with at least pixel value adaption range to selectively filter at least a portion of said regions proximate the at least one boundary between said adjacent regions based upon said conditions of coding parameters examined by said condition examiner portion, wherein

said conditions of coding parameters include whether at least one of said adjacent regions contains non-zero transform coefficients,

a strength of said loop filter filtering is controlled by said boundary strength,

said boundary strength is set to a first predetermined fixed value when at least one of said adjacent regions contains non-zero transform coefficients, and

the boundary strength first predetermined fixed value is used to control the pixel value adaptation range in the loop filter to control the strength of the loop filter filtering.

4. The encoder of claim 3, wherein said boundary strength is set to a second predetermined fixed value when the condition examiner portion finds that said adjacent regions do not contain non-zero transform coefficients and are predicted based upon different reference frames, and

the strength of said loop filter filtering for said second predetermined fixed value is smaller than the strength of said loop filter filtering for said first predetermined fixed value.

5. A decoder for decoding an image, comprising:

an identifier portion configured to identify adjacent regions in said image;

a condition examiner portion configured to examine conditions of coding parameters for said adjacent regions;

a determiner portion configured to determine boundary strength for at least one boundary between said adjacent regions; and

a selective loop filter configured with at least pixel value adaption range to selectively filter at least a portion of said regions proximate the at least one boundary between said adjacent regions based upon said conditions of coding parameters examined by said condition examiner portion, wherein

said conditions of coding parameters include whether at least one of said adjacent regions contains non-zero transform coefficients,

a strength of said loop filter filtering is controlled by said boundary strength,

said boundary strength is set to a first predetermined fixed value when at least one of said adjacent regions contains non-zero transform coefficients, and

the boundary strength first predetermined fixed value is used to control the pixel value adaptation range in the loop filter to control the strength of the loop filter filtering.

6. The decoder of claim 5, wherein said boundary strength is set to a second predetermined fixed value when the condition examiner portion finds that said adjacent regions do not contain non-zero transform coefficients and are predicted based upon different reference frames, and

the strength of said loop filter filtering for said second predetermined fixed value is smaller than the strength of said loop filter filtering for said first predetermined fixed value.