Method and device for entropy coding/decoding
The present invention relates to an entropy decoding method which includes: generating context related to a bin that forms a codeword of a syntax element; and performing arithmetic decoding of the bin based on the context.
1. An entropy decoding method comprising the steps of:
deriving context information on a bin constituting a codeword of a syntax element cbf_luma that specifies whether a luma residual other than 0 is present in a current luma transform block; and
deriving a value of the syntax element cbf_luma by performing an arithmetic decoding operation on the bin on the basis of the derived context information,
wherein the step of deriving the context includes deriving the context information on the basis of information on a depth of the current luma transform block,
wherein a luma residual other than 0 is not present in the current luma transform block when the derived value of the syntax element cbf_luma is 0, and
wherein at least one luma residual other than 0 is present in the current luma transform block when the derived value of the syntax element cbf_luma is 1.
2. The entropy decoding method according to claim 1 , wherein the context information in the step of deriving the context information on the bin is indicated by the sum of a context index offset and a context index by the bin, and
wherein the context index offset is determined depending on whether a current slice is an I slice, a P slice, or a B slice.
3. The entropy decoding method according to claim 2 , wherein the value of the context index offset is 0 when the current slice is an I slice, is 2 when the current slice is a P slice, and is 4 when the current slice is a B slice.
4. The entropy decoding method according to claim 2 , wherein
in the step of deriving the context information on the bin,
the bin is a first bin of the codeword to which a bin index having a value of 0 is allocated, and
a value of 1 is allocated to the context index by the bin when the depth of the transform block is 0.
5. The entropy decoding method according to claim 2 , wherein
in the step of deriving the context information on the bin,
the bin is a first bin of the codeword to which a bin index having a value of 0 is allocated, and
a value of 0 is allocated to the context index by the bin when the depth of the transform block is not 0.
6. The entropy decoding method according to claim 2 , wherein in the step of deriving the context information on the bin,
the bin is a first bin of the codeword to which a bin index having a value of 0 is allocated,
a context index of 1 is allocated to the bin when the depth of the transform block is not 0 and the size of the transform block is equal to a maximum transform size of a current sequence, and
a context index of 0 is allocated to the bin when the size of the transform block is not equal to the maximum transform size.
7. The entropy decoding method according to claim 1 , wherein the context information is specified by the sum of a context index offset determined on the basis of a slice type of a current slice and a context index by the bin,
wherein the value of a bin index indicating the bin in the syntax element cbf_luma is 0, and
wherein the value of the context index offset is 0 when the current slice is an I slice, is 2 when the current slice is a P slice, and is 4 when the current slice is a B slice.
8. The entropy decoding method according to claim 7 , wherein in the step of deriving the context information on the bin,
the bin is a first bin of the codeword to which a bin index having a value of 0 is allocated,
a value of 1 is allocated to the context index by the bin when the depth of the transform block is 0, and
a value of 0 is allocated to the context index by the bin when the depth of the transform block is not 0.
9. The entropy decoding method according to claim 7 , wherein in the step of deriving the context information on the bin,
the bin is a first bin of the codeword to which a bin index having a value of 0 is allocated,
a value of 1 is allocated to the context index by the bin when the depth of the transform block is 0, and
a value of 1 is allocated to the context index by the bin when the depth of the transform block is not 0 and the size of the transform block is equal to a maximum transform size of a current sequence, and a value of 0 is allocated to the context index by the bin when the size of the transform block is not equal to the maximum transform size.
10. The entropy decoding method according to claim 1 , wherein in the step of deriving the context, the context information is derived on the basis of information on a depth of the current luma transform block only.
11. The entropy decoding method according to claim 1 , wherein in the step of deriving the context, the context information is derived on the basis of the depth of the current luma transform block regardless a size of the current luma transform block.