Encoding and decoding image using sample adaptive offset with start band indicator
A method for image decoding includes receiving image information including filter coefficients, generating a restored block for a current block on the basis of the image information; and applying an adaptive loop filter to the restored block on the basis of the filter coefficients. Image encoding efficiency may be improved, and complexity may be reduced.
1. A video decoding method by a video decoding apparatus, comprising:
receiving video information including picture reconstruction information for reconstructing a picture and offset information for sample adaptive offset (SAO) process;
reconstructing the picture on the basis of the picture reconstruction information; and
applying an in-loop filtering process to the reconstructed picture,
wherein applying the in-loop filtering process includes
applying a deblocking filtering process to the reconstructed picture, and
applying the SAO process to a sample in the reconstructed picture to which the deblocking filtering process is completed,
wherein the offset information includes offset type information indicating whether an edge offset type is applied to the sample, or a band offset type is applied to the sample,
wherein when the offset type information indicating the band offset type is applied to the sample, the offset information includes an explicit band information indicating one of 32 bands as a starting band of a band group consisting of n bands among the 32 bands, the band group is determined based on the starting band, and an offset corresponding a band among the n bands is applied to the sample, wherein n is an integer.
2. The method of claim 1 , wherein when the offset type information indicating the edge offset type is applied to the sample, applying the SAO process comprises calculating the difference between the sample and the neighboring samples based on a direction of an edge specifying locations of the sample and the neighboring samples and determining the category of the sample based on the difference.
3. The method of claim 1 , wherein the offset is applied to the sample based on the offset information which is transmitted for a largest coding unit to which the sample belongs.
4. The method of claim 1 , wherein the band is determined as a predetermined sample value range to which the sample belongs.
5. The method of claim 1 , wherein the n bands are specified as the starting band and following bands according to sample value order,
wherein the offset is determined based on the band to which the sample belongs.
6. The method of claim 1 , wherein the n bands are bands for which information indicating offset values is transmitted.
7. The method of claim 1 , wherein the band information indicates a last band among the n bands.
8. The method of claim 7 , wherein the available bands are specified as the last band and bands followed by the last band according to sample value order,
wherein the offset is determined based on the band which the sample corresponds to.
9. The method of claim 1 , wherein the offset type information is obtained by context-adaptive arithmetic coding.
10. A video decoding apparatus, comprising:
an entropy decoding module configured to obtain video information including picture reconstruction information for reconstructing a picture and offset information for sample adaptive offset (SAO) process from a received bitstream;
an adder module configured to reconstruct the picture on the basis of the picture reconstruction information; and
an filtering module configured to apply an in-loop filtering process to the reconstructed picture, wherein applying the in-loop filtering process includes applying a deblocking filtering process to the reconstructed picture, and applying the SAO process to a sample in the reconstructed picture to which the deblocking filtering process is completed,
wherein the offset information includes offset type information indicating whether an edge offset type is applied to the sample, or a band offset type is applied to the sample,
wherein when the offset type information indicating the band offset type is applied to the sample, the offset information includes an explicit band information indicating one of 32 bands as a starting band of a band group consisting of n (n is integer) bands among the 32 bands, the band group is determined based on the starting band,
wherein the filtering module applies an offset corresponding a band among the n bands to the sample, wherein n is an integer.
11. The apparatus of claim 10 , wherein the offset is applied to the sample based on the offset information which is signaled for a largest coding unit to which the sample belongs.
12. The apparatus of claim 10 , wherein the band is determined as a predetermined sample value range to which the sample belongs.
13. The apparatus of claim 10 , wherein the n bands are specified as the starting band and following bands according to sample value order,
wherein the offset is determined based on the band to which the sample belongs.
14. The apparatus of claim 10 , wherein the n bands are bands for which information indicating offset values is signaled.
15. The apparatus of claim 10 , wherein the band information indicates a last band among the n bands.
16. The apparatus of claim 10 , wherein the offset type information is obtained by context-adaptive arithmetic coding.
17. The apparatus of claim 6 , wherein the available bands are specified as the last band and bands followed by the last band according to sample value order,
wherein the offset is determined based on the band which the sample corresponds to.