METHOD AND APPARATUS FOR ENCODING RESIDUAL BLOCK, AND METHOD AND APPARATUS FOR DECODING RESIDUAL BLOCK

• US 20110096834A1
• Filed: 10/28/2010
• Published: 04/28/2011
• Est. Priority Date: 10/28/2009
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: MIN, Jung-hye, HAN, Woo-jin, CHEON, Min-su
• Granted Patent: US 8,811,479 B2
• Time in Patent Office: Days
• US Class Current: 375/240.12
• CPC Class Codes: H04N 19/109 among a plurality of temporal predictive coding modes
• CPC Class Codes: H04N 19/119 Adaptive subdivision aspects, e.g. subdivision of a picture into rectangular or non-rectangular coding blocks
• CPC Class Codes: H04N 19/13 Adaptive entropy coding, e.g. adaptive variable length coding [AVLC] or context adaptive binary arithmetic coding [CABAC]
• CPC Class Codes: H04N 19/136 Incoming video signal characteristics or properties
• CPC Class Codes: H04N 19/176 the region being a block, e.g. a macroblock
• CPC Class Codes: H04N 19/18 the unit being a set of transform coefficients
• 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 19/46 Embedding additional information in the video signal during the compression process H04N19/517, H04N19/68, H04N19/70 take precedence
• CPC Class Codes: H04N 19/60 using transform coding
• CPC Class Codes: H04N 19/61 in combination with predictive coding
• CPC Class Codes: H04N 19/63 using sub-band based transform, e.g. wavelets
• CPC Class Codes: H04N 19/635 characterised by filter definition or implementation details
• CPC Class Codes: H04N 19/70 characterised by syntax aspects related to video coding, e.g. related to compression standards
• CPC Class Codes: H04N 19/96 Tree coding, e.g. quad-tree coding

Abstract

Methods and apparatuses for encoding and decoding a residual block are provided. The method of encoding the residual block includes: generating a prediction block of a current block; generating a residual block based on a difference between the prediction block and the current block; generating a transformation residual block by transforming the residual block to a frequency domain; splitting the transformation residual block into frequency band units; and encoding effective coefficient flags indicating frequency band units, of the frequency band units, in which nonzero effective transformation coefficients exist.

Claims

1. A method of encoding a residual block, the method comprising:

generating a prediction block of a current block;

generating a residual block based on a difference between the prediction block and the current block;

generating a transformation residual block by transforming the residual block to a frequency domain;

splitting the transformation residual block into frequency band units; and

encoding effective coefficient flags indicating frequency band units, of the frequency band units, in which nonzero effective transformation coefficients exist.

2. The method of claim 1, wherein the splitting the transformation residual block comprises splitting the transformation residual block such that a unit size split in a low frequency band is smaller than a unit size split in a high frequency band.

3. The method of claim 1, wherein the splitting the transformation residual block comprises quadrisecting the transformation residual block, and quadrisecting a lowest frequency band of the quadrisected transformation residual blocks.

4. The method of claim 1, wherein the splitting the transformation residual block comprises splitting the transformation residual block into frequency band units having a same size.

5. The method of claim 1, wherein the splitting the transformation residual block comprises splitting the transformation residual block by connecting a horizontal frequency and a vertical frequency having a same value at predetermined intervals.

6. The method of claim 1, wherein the splitting the transformation residual block comprises:

determining an image characteristic of the transformation residual block by using transformation coefficients of the transformation residual block;

determining a split size according to frequency bands of the transformation residual block by using the determined image characteristic; and

splitting the transformation residual block according to the determined split size.

7. The method of claim 6, wherein the determining the image characteristic comprises determining the image characteristic using at least one of a number and a distribution of transformation coefficients existing in each frequency band of the transformation residual block.

8. The method of claim 1, wherein the encoding the effective coefficient flags comprises not separately encoding an effective coefficient flag with respect to a smallest low frequency band unit from among the frequency band units.

9. The method of claim 1, further comprising encoding a significance map indicating locations of the effective transformation coefficients existing in the frequency band units having the nonzero effective transformation coefficients, from among the frequency band units.

10. The method of claim 9, wherein the encoding the significance map comprises encoding a flag indicating the locations of the effective transformation coefficients existing in the frequency band units having the nonzero effective transformation coefficients by reading the effective transformation coefficients according to a predetermined scanning order independent for each of the frequency band units.

11. The method of claim 9, wherein the encoding the significance map comprises encoding a flag indicating the locations of the effective transformation coefficients existing in the frequency band units having the nonzero effective transformation coefficients by reading all of the effective transformation coefficients in the transformation residual block according to a predetermined scanning order.

12. The method of claim 9, wherein the encoding the significance map comprises:

setting a flag indicating a last effective transformation coefficient existing in a frequency band unit, from among the frequency band units, by reading the effective transformation coefficients in the frequency band units according to a predetermined scanning order; and

setting a flag indicating a last effective transformation coefficient existing in the transformation residual block.

13. The method of claim 1, wherein:

the splitting the transformation residual block comprises splitting the transformation residual block into the frequency band units according to a split form selected from a plurality of split forms that are predetermined according to sizes and shapes of the frequency band units; and

split form index information indicating the selected split form from among the plurality of split forms is added to an encoded bitstream comprising the effective coefficient flags.

28. A computer readable recording medium having recorded thereon a program executable by a computer for performing the method of claim 1.

14. An apparatus for encoding a residual block, the apparatus comprising:

a predictor which generates a prediction block of a current block;

a subtractor which generates a residual block based on a difference between the prediction block and the current block;

a transformer which generates a transformation residual block by transforming the residual block to a frequency domain;

an entropy encoder which splits the transformation residual block into frequency band units, and encodes effective coefficient flags indicating frequency band units, of the frequency band units, in which nonzero effective transformation coefficients exist.

15. A method of decoding a residual block, the method comprising:

extracting an effective coefficient flag from an encoded bitstream, the effective coefficient flag indicating a frequency band unit in which a nonzero effective transformation coefficient exists, from among frequency band units obtained by splitting a transformation residual block of a current block;

splitting the transformation residual block into the split frequency band units; and

determining the frequency band unit having the effective transformation coefficient from among the frequency band units obtained by splitting the transformation residual block, by using the extracted effective coefficient flag.

16. The method of claim 15, wherein the splitting the frequency band unit comprises splitting the transformation residual block such that a unit size split in a low frequency band is smaller than a unit size split in a high frequency band.

17. The method of claim 15, wherein the splitting the transformation residual block comprises quadrisecting the transformation residual block, and quadrisecting a lowest frequency band of the quadrisected transformation residual blocks.

18. The method of claim 15, wherein the splitting the transformation residual block comprises splitting the transformation residual block into frequency band units having a same size.

19. The method of claim 15, wherein the splitting the transformation residual block comprises splitting the transformation residual block by connecting a horizontal frequency and a vertical frequency having a same value at predetermined intervals.

20. The method of claim 15, wherein the splitting the transformation residual block comprises:

extracting split form index information from the encoded bitstream, the split form index information indicating a split form used to split the transformation residual block, from among a plurality of split forms that are predetermined according to sizes and shapes of the frequency band units; and

splitting the transformation residual block into the frequency band units according to the extracted split form index information.

21. The method of claim 15, further comprising:

extracting a significance map from the encoded bitstream, the significance map indicating locations of nonzero effective transformation coefficients existing in frequency band units having the nonzero effective transformation coefficients, from among the frequency band units; and

determining the locations of the nonzero effective transformation coefficients existing in the frequency band units having the nonzero effective transformation coefficients by using the significance map.

22. The method of claim 21, wherein the significance map indicates the locations of the effective transformation coefficients in the frequency band units according to a predetermined scanning order independent for each of the frequency band units.

23. The method of claim 21, wherein the significance map indicates the locations of the effective transformation coefficients in the frequency band units according to a predetermined scanning order for an entirety of the transformation residual block.

24. The method of claim 21, wherein the significance map comprises a flag indicating a last effective transformation coefficient existing in a frequency band unit, from among the frequency band units, by reading the effective transformation coefficients in the frequency band units according to a predetermined scanning order, and a flag indicating a last effective transformation coefficient existing in the transformation residual block.

29. A computer readable recording medium having recorded thereon a program executable by a computer for performing the method of claim 15.

25. An apparatus for decoding a residual block, the apparatus comprising:

a parser which extracts an effective coefficient flag from an encoded bitstream, the effective coefficient flag indicating a frequency band unit in which a nonzero effective transformation coefficient exists, from among frequency band units obtained by splitting a transformation residual block of a current block; and

an entropy decoder which splits the transformation residual block into the frequency band units, and determines the frequency band unit having the effective transformation coefficient from among the frequency band units obtained by splitting the transformation residual block, by using the extracted effective coefficient flag.

26. A method of encoding a residual block, the method comprising:

generating a transformation residual block by transforming a residual block to a frequency domain;

splitting the transformation residual block into frequency band units; and

encoding effective coefficient flags indicating frequency band units, of the frequency band units, in which nonzero effective transformation coefficients exist.

27. The method of claim 26, wherein the generating transformation residual block has a size of 16×

16 or larger.

30. A computer readable recording medium having recorded thereon a program executable by a computer for performing the method of claim 26.