Method and apparatus for entropy-encoding and entropy-decoding video signal
The present invention relates to a method for performing entropy decoding on a video signal including a current block. The method comprises the steps of: deriving affine coding information and/or affine prediction mode information of a left block and/or an upper block which are adjacent to the current block; determining a context index of a syntax element associated with an affine prediction of the current block on the basis of at least one of the affine coding information and/or the affine prediction mode information of the left block and/or the upper block; and entropy decoding the syntax element associated with the affine prediction of the current block on the basis of the context index.
1. A method of performing entropy decoding on a video signal including a current block, the method comprising:
checking whether a left block and top block neighboring the current block are available;
deriving affine coding information and/or affine prediction mode information of the left block and/or the top block based on at least one of the left block and/or the top block being available;
determining a context index of an affine prediction-related syntax element of the current block based on at least one of the affine coding information and/or affine prediction mode information of the left block and/or the top block; and
entropy-decoding an affine prediction-related syntax element of the current block based on the context index,
wherein the affine coding information includes information indicating whether an affine motion prediction has been performed,
wherein the affine prediction mode information includes information indicating whether the affine motion prediction is performed based on a 4-parameter affine mode or 6-parameter affine mode,
wherein the 4-parameter affine mode indicates that an affine motion prediction is performed by four parameters,
wherein the 6-parameter affine mode indicates that an affine motion prediction is performed by six parameters,
wherein, based on the affine prediction-related syntax element including an affine flag, a context index of the affine flag is determined based on a sum of the affine coding information of the left block and the affine coding information of the top block, and
wherein the affine flag indicates whether an affine motion prediction has been performed.
2. The method of claim 1 ,
wherein, based on the affine prediction-related syntax element including an affine parameter flag, a context index of the affine parameter flag is determined based on a sum of a first value determined by the affine coding information and affine prediction mode information of the left block and a second value determined by the affine coding information and affine prediction mode information of the top block, and
wherein the affine parameter flag indicates whether an affine motion prediction is performed based on the 4-parameter affine mode or the 6-parameter affine mode.
3. The method of claim 2 ,
wherein an affine motion prediction is performed on the left block based on the affine flag, and
wherein the first value is determined as 1 when the left block is coded based on the 6-parameter affine mode based on the affine parameter flag, and the first value is determined as 0 when the left block is not coded based on the 6-parameter affine mode based on the affine parameter flag.
4. The method of claim 2 ,
wherein an affine motion prediction is performed on the top block based on the affine flag, and
wherein the second value is determined as 1 when the top block is coded based on the 6-parameter affine mode based on the affine parameter flag, and the second value is determined as 0 when the top block is not coded based on the 6-parameter affine mode based on the affine parameter flag.
5. The method of claim 1 ,
wherein, based on the affine prediction-related syntax element including an affine motion vector predictor index and/or a non-affine motion vector predictor index, the affine motion vector predictor index and the non-affine motion vector predictor index are defined by different tables,
wherein the affine motion vector predictor index indicates a candidate used for an affine motion prediction, and
wherein the non-affine motion vector predictor index indicates a candidate used for an inter prediction.
6. An apparatus performing entropy decoding on a video signal including a current block, the apparatus comprising:
a processor configured to check whether a left block and top block neighboring the current block are available, derive affine coding information and/or affine prediction mode information of the left block and/or the top block based on at least one of the left block and/or the top block is available, determine a context index of an affine prediction-related syntax element of the current block based on at least one of the affine coding information and/or affine prediction mode information of the left block and/or the top block, and
entropy-decode an affine prediction-related syntax element of the current block based on the context index,
wherein the affine coding information includes information indicating whether an affine motion prediction has been performed,
wherein the affine prediction mode information includes information indicating whether the affine motion prediction is performed based on a 4-parameter affine mode or a 6-parameter affine mode,
wherein the 4-parameter affine mode indicates that an affine motion prediction is performed by four parameters,
wherein the 6-parameter affine mode indicates that an affine motion prediction is performed by six parameters,
wherein, based on the affine prediction-related syntax element including an affine flag, a context index of the affine flag is determined based on a sum of the affine coding information of the left block and the affine coding information of the top block, and
wherein the affine flag indicates whether an affine motion prediction has been performed.
7. The apparatus of claim 6 ,
wherein, based on the affine prediction-related syntax element including an affine parameter flag, a context index of the affine parameter flag is determined based on a sum of a first value determined by the affine coding information and affine prediction mode information of the left block and a second value determined by the affine coding information and affine prediction mode information of the top block, and
wherein the affine parameter flag indicates whether an affine motion prediction is performed based on the 4-parameter affine mode or the 6-parameter affine mode.
8. The apparatus of claim 7 ,
wherein an affine motion prediction is performed on the left block based on the affine flag, and
wherein the first value is determined as 1 when the left block is coded based on the 6-parameter affine mode based on the affine parameter flag, and the first value is determined as 0 when the left block is not coded based on the 6-parameter affine mode based on the affine parameter flag.
9. The apparatus of claim 7 ,
wherein an affine motion prediction is performed on the top block based on the affine flag, and
wherein the second value is determined as 1 when the top block is coded based on the 6-parameter affine mode based on the affine parameter flag, and the second value is determined as 0 when the top block is not coded based on the 6-parameter affine mode based on the affine parameter flag.
10. The apparatus of claim 6 ,
wherein, based on the affine prediction-related syntax element including an affine motion vector predictor index and/or a non-affine motion vector predictor index, the affine motion vector predictor index and the non-affine motion vector predictor index are defined by different tables,
wherein the affine motion vector predictor index indicates a candidate used for an affine motion prediction, and
wherein the non-affine motion vector predictor index indicates a candidate used for an inter prediction.