IMAGE DECODING APPARATUS, IMAGE DECODING METHOD AND COMPUTER PROGRAM

• US 20100119167A1
• Filed: 11/10/2009
• Published: 05/13/2010
• Est. Priority Date: 11/11/2008
• Status: Active Grant

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Shimauchi, Kazuhiro, Wada, Yuji, Ikeda, Hiroshi
• Granted Patent: US 8,406,542 B2
• Time in Patent Office: Days
• US Class Current: 382/233
• CPC Class Codes: H04N 19/18 the unit being a set of transform coefficients
• CPC Class Codes: H04N 19/184 the unit being bits, e.g. of the compressed video stream
• CPC Class Codes: H04N 19/44 Decoders specially adapted therefor, e.g. video decoders which are asymmetric with respect to the encoder
• CPC Class Codes: H04N 19/48 using compressed domain processing techniques other than decoding, e.g. modification of transform coefficients, variable length coding [VLC] data or run-length data motion estimation in a transform domain H04N19/547; processing of decoded motion vectors H04N19/513
• CPC Class Codes: H04N 19/647 using significance based coding, e.g. Embedded Zerotrees of Wavelets [EZW] or Set Partitioning in Hierarchical Trees [SPIHT]

Abstract

An image decoding apparatus includes an information acquisition section that acquires information of a bit-plane truncation position in an encoded stream from the encoded stream generated by performing bit-plane encoding on a transform coefficient, a decoding process section that performs a decoding process on the encoded stream and generates a transform coefficient, and a significant coefficient detection section that detects whether the transform coefficient generated in the decoding process section is significant. The image decoding apparatus includes a correction value acquisition section that acquires a correction value corresponding to the bit-plane truncation position in the transform coefficient detected to be significant, from a correction value table, and a coefficient correction processing section that performs coefficient correction processing on the transform coefficient using the correction value acquired in the correction value acquisition section only for the transform coefficient detected to be significant in the significant coefficient detection section.

Claims

1. An image decoding apparatus comprising:

an information acquisition section that acquires information of a bit-plane truncation position in an encoded stream, from the encoded stream generated by performing a bit-plane encoding process on a transform coefficient obtained by frequency conversion of image data;

a decoding process section that performs a decoding process on the encoded stream and generates a transform coefficient;

a significant coefficient detection section that detects whether the transform coefficient generated in the decoding process section is significant;

a correction value acquisition section that acquires a correction value, which corresponds to the bit-plane truncation position in the transform coefficient detected to be significant in the significant coefficient detection section, from a correction value table where a correction value, previously prepared by statistically processing a coefficient value truncated by the bit-plane truncation, is stored for each bit-plane truncation position; and

a coefficient correction processing section that performs coefficient correction processing on the transform coefficient using the correction value acquired in the correction value acquisition section only for the transform coefficient detected to be significant in the significant coefficient detection section.

2. The image decoding apparatus according to claim 1, wherein the correction value is stored in the correction value table for each context which is characteristics of the image data, and

wherein the correction value acquisition section acquires a correction value corresponding to the bit-plane truncation position and the context from the correction value table.

3. The image decoding apparatus according to claim 2, wherein the context is a significant bit position of the transform coefficient,

wherein a significant bit detection section, that detects the significant bit position of the transform coefficient obtained in the decoding process section, is further provided, and

wherein the correction value acquisition section acquires the correction value using the significant bit position detected in the significant bit detection section.

4. The image decoding apparatus according to claim 2, wherein the context is any one of color component information representing which color component coefficient that the transform coefficient corresponds to, and frequency component information representing which frequency component coefficient that the transform coefficient corresponds to, or a combination thereof,

wherein the information acquisition section performs acquisition on the color component information or the frequency component information from the encoded stream, and

wherein the correction value acquisition section acquires the correction value using the color component information or the frequency component information acquired in the information acquisition section.

5. The image decoding apparatus according to claim 1, wherein a central value, that is representative of the distribution of the coefficient value truncated by the bit-plane truncation, is stored in the correction value table for each bit-plane truncation position.

6. An image decoding method comprising the steps of:

acquiring information of a bit-plane truncation position in an encoded stream by an information acquisition section, from the encoded stream generated by performing a bit-plane encoding process on a transform coefficient obtained by frequency conversion of image data;

performing a decoding process on the encoded stream and generating a transform coefficient by a decoding process section;

detecting whether the transform coefficient generated in the decoding process section is significant by a significant coefficient detection section;

acquiring a correction value, which corresponds to the bit-plane truncation position in the transform coefficient detected to be significant in the significant coefficient detection section by a correction value acquisition section, from a correction value table where a correction value, previously prepared by statistically processing a coefficient value truncated by the bit-plane truncation, is stored for each bit-plane truncation position; and

performing coefficient correction processing on the transform coefficient by a coefficient correction processing section using the correction value acquired in the correction value acquisition section only for the transform coefficient detected to be significant in the significant coefficient detection section.

7. A computer program causing a computer to function as functional means for:

acquiring information of a bit-plane truncation position in an encoded stream from the encoded stream generated by performing a bit-plane encoding process on a transform coefficient obtained by frequency conversion of image data;

performing a decoding process on the encoded stream and generating a transform coefficient;

detecting whether the transform coefficient generated by performing a decoding process on the encoded stream is significant;

acquiring a correction value, which corresponds to the bit-plane truncation position in the transform coefficient detected to be significant in a significant coefficient detection section, from a correction value table where a correction value, previously prepared by statistically processing the coefficient value truncated by the bit-plane truncation, is stored for each bit-plane truncation position; and

performing coefficient correction processing on the transform coefficient using the correction value acquired from the correction value table only for the transform coefficient detected to be significant.