Intra prediction mode mapping method and device using the method
The present invention relates to an intra prediction mode mapping method and a device using the method. The intra prediction mode includes: decoding flag information providing information regarding whether an intra prediction mode of a plurality of candidate intra prediction modes for the current block is the same as the intra prediction mode for the current block, and decoding a syntax component including information regarding the intra prediction mode for the current block in order to induce the intra prediction mode for the current block if the intra prediction mode from among the plurality of candidate intra prediction modes for the current block is not the same as the intra prediction mode for the current block. Thus, it is possible to increase the efficiency with which are images are decoded.
1. A decoding method of an intra-prediction mode, the method comprising:
decoding flag information indicating whether one of candidate intra-prediction modes with respect to a current block and an intra-prediction mode of the current block are identical;
when the one of the candidate intra-prediction modes with respect to the current block and the intra-prediction mode of the current block are identical, deriving the intra prediction mode of the current block by decoding a syntax element of information regarding the candidate intra-prediction modes with respect to the current block;
when the candidate intra-prediction modes with respect to the current block and an intra-prediction mode of the current block are not identical, deriving the intra-prediction mode of the current block by decoding a syntax element of remaining intra-prediction mode information comprising information regarding the intra-prediction mode of the current block; and
generating a prediction block of the current block based on the derived intra-prediction mode of the current block,
wherein, the deriving the intra-prediction mode of the current block is performed based on a table comprising intra-prediction mode information, the table mapping intra-prediction modes and index information of the intra-prediction modes, wherein when an intra-prediction mode is a planar mode, the intra-prediction mode is mapped to an index 0, when an intra-prediction mode is a DC mode, the intra-prediction mode is mapped to an index 1, and when intra-prediction modes are directional intra-prediction modes, the intra-prediction modes are mapped to indices 2 to 34 according to directivity of the intra-prediction modes,
wherein a codeword length of an index of the candidate intra-prediction modes with respect to the current block is shorter than a codeword length of an index of the remaining intra-prediction mode information,
wherein the candidate intra-prediction modes with respect to the current block are modes for predicting luminance information of the current block,
wherein chrominance information of the current block is predicted based on intra-prediction mode information according to the predicting luminance information of the current block, and
wherein the syntax element of the remaining intra-prediction mode information is a value coded using fixed 5 bits.
2. An encoding method of an intra-prediction mode, the method comprising:
determining and encoding flag information indicating whether one of candidate intra-prediction modes with respect to a current block and an intra-prediction mode of the current block are identical;
when the one of the candidate intra-prediction modes with respect to the current block and the intra-prediction mode of the current block are identical, encoding a syntax element of information regarding the candidate intra-prediction modes with respect to the current block;
when the candidate intra-prediction modes with respect to a current block and an intra-prediction mode of the current block are not identical, encoding a syntax element of remaining intra-prediction mode of the current block including information regarding the intra-prediction mode of the current block; and
generating a prediction block of the current block based on the intra-prediction mode of the current block,
wherein the intra-prediction mode of the current block is mapped to index information of the intra-prediction modes based on a table, wherein when an intra-prediction mode is a planar mode, the intra-prediction mode is mapped to an index 0, when an intra-prediction mode is a DC mode, the intra-prediction mode is mapped to an index 1, and when intra-prediction modes are directional intra-prediction modes, the intra-prediction modes are mapped to indices 2 to 34 according to directivity of the intra-prediction modes,
wherein a codeword length of an index of the candidate intra-prediction modes with respect to the current block is shorter than a codeword length of an index of the remaining intra-prediction mode information,
wherein the candidate intra-prediction modes with respect to the current block are modes for predicting luminance information of the current block,
wherein chrominance information of the current block is predicted based on intra-prediction mode information according to the predicting luminance information of the current block, and
wherein the syntax element of the remaining intra-prediction mode information is a value coded using fixed 5 bits.
3. A non-transitory computer-readable storage medium storing a bitstream which is encoded by an encoding method, the encoding method comprising:
determining and encoding flag information indicating whether one of candidate intra-prediction modes with respect to a current block and an intra-prediction mode of the current block are identical;
when the one of the candidate intra-prediction modes with respect to the current block and the intra-prediction mode of the current block are identical, encoding a syntax element of information regarding the candidate intra-prediction modes with respect to the current block;
when the candidate intra-prediction modes with respect to a current block and an intra-prediction mode of the current block are not identical, encoding a syntax element of remaining intra-prediction mode of the current block including information regarding the intra-prediction mode of the current block; and
generating a prediction block of the current block based on the intra-prediction mode of the current block,
wherein the intra-prediction mode of the current block is mapped to index information of the intra-prediction modes based on a table, wherein when an intra-prediction mode is a planar mode, the intra-prediction mode is mapped to an index 0, when an intra-prediction mode is a DC mode, the intra-prediction mode is mapped to an index 1, and when intra-prediction modes are directional intra-prediction modes, the intra-prediction modes are mapped to indices 2 to 34 according to directivity of the intra-prediction modes,
wherein a codeword length of an index of the candidate intra-prediction modes with respect to the current block is shorter than a codeword length of an index of the remaining intra-prediction mode information,
wherein the candidate intra-prediction modes with respect to the current block are modes for predicting luminance information of the current block,
wherein chrominance information of the current block is predicted based on intra-prediction mode information according to the predicting luminance information of the current block, and
wherein the syntax element of the remaining intra-prediction mode information is a value coded using fixed 5 bits.