Picture coding device, picture coding method, and picture coding program
There is provided a picture coding device that performs intra prediction coding of a picture signal including a luma signal and a chroma signal in units of blocks and codes information relating to an intra prediction mode. When the intra prediction of a picture signal is made in units of coding blocks, in a case where a chroma format is 4:2:2, in a mode for setting a chroma intra prediction mode in accordance with the luma intra prediction mode, an intra prediction unit sets the chroma intra prediction mode based on the luma intra prediction mode and the chroma format and makes an intra prediction of the chroma signal.
1. A picture coding device that performs intra prediction coding of a picture signal including a luma signal and a chroma signal in units of blocks and codes information relating to an intra prediction mode, the picture coding device comprising:
when a chroma format is 4:2:0, and a partition mode is a mode indicating that a coding target block in a luma signal is partitioned to first to fourth blocks of luma signals horizontally and vertically, and the coding target block in a chroma signal is a minimum size without being partitioned,
a luma signal intra prediction unit configured to set the first to fourth blocks of luma signals acquired by partitioning the coding target block of luma signals horizontally and vertically and predict a luma signal based on a coded neighboring block of luma signals in accordance with luma intra prediction modes of the first to fourth blocks of luma signals;
a chroma signal intra prediction unit configured to set a fifth block of chroma signals without partitioning the coding target block of chroma signals and predict a chroma signal based on a coded neighboring block of chroma signals in accordance with a chroma intra prediction mode;
a syntax element calculating unit relating to a luma intra prediction mode configured to calculate each of a syntax element relating to the luma intra prediction mode of the first to fourth blocks of luma signals from each of a value of the luma intra prediction mode of the first to fourth blocks of luma signals, respectively;
a syntax element calculating unit relating to a chroma intra prediction mode configured to calculate a syntax element relating to the chroma intra prediction mode of the fifth block of chroma signals; and
a bitstream constructing unit configured to code the syntax element relating to the luma intra prediction mode of the first block of luma signals, and subsequently code the syntax element relating to the chroma intra prediction mode of the fifth block of chroma signals, and subsequently code the syntax element relating to the luma intra prediction mode of the second block of luma signals, the syntax element relating to the luma intra prediction mode of the third block of luma signals, and the syntax element relating to the luma intra prediction mode of the fourth block of luma signals,
wherein the chroma signal intra prediction unit is further configured to be able to set a value indicating horizontal prediction in which a prediction direction is a horizontal direction as one of predefined values of the chroma intra prediction mode of the prediction block of the chroma signals, in accordance with the value of the syntax element relating to the chroma intra prediction mode of the prediction block of chroma signals.
2. A picture coding method for performing intra prediction coding of a picture signal including a luma signal and a chroma signal in units of blocks and coding information relating to an intra prediction mode, the picture coding method comprising:
when a chroma format is 4:2:0, and a partition mode is a mode indicating that a coding target block in a luma signal is partitioned to first to fourth blocks of luma signals horizontally and vertically, and the coding target block in a chroma signal is a minimum size without being partitioned,
a luma signal intra prediction step of setting the first to fourth blocks of luma signals acquired by partitioning the coding target block of luma signals horizontally and vertically and predicting a luma signal based on a coded neighboring block of luma signals in accordance with luma intra prediction modes of the first to fourth blocks of luma signals;
a chroma signal intra prediction step of setting a fifth block of chroma signals without partitioning the coding target block of chroma signals and predicting a chroma signal based on a coded neighboring block of chroma signals in accordance with a chroma intra prediction mode;
a syntax element calculating step relating to a luma intra prediction mode of calculating each of a syntax element relating to the luma intra prediction mode of the first to fourth blocks of luma signals from each of a value of the luma intra prediction mode of the first to fourth blocks of luma signals, respectively;
a syntax element calculating step relating to a chroma intra prediction mode of calculating a syntax element relating to the chroma intra prediction mode of the fifth block of chroma signals; and
a bitstream constructing step of coding the syntax element relating to the luma intra prediction mode of the first block of luma signals, and subsequently coding the syntax element relating to the chroma intra prediction mode of the fifth block of chroma signals, and subsequently coding the syntax element relating to the luma intra prediction mode of the second block of luma signals, the syntax element relating to the luma intra prediction mode of the third block of luma signals, and the syntax element relating to the luma intra prediction mode of the fourth block of luma signals,
wherein the chroma signal intra prediction step is operable to be able to set a value indicating horizontal prediction in which a prediction direction is a horizontal direction as one of predefined values of the chroma intra prediction mode of the prediction block of the chroma signals, in accordance with the value of the syntax element relating to the chroma intra prediction mode of the prediction block of chroma signals.
3. A non-transitory computer-readable recording medium having embodied thereon a picture coding program for performing intra prediction coding of a picture signal including a luma signal and a chroma signal in units of blocks and coding information relating to an intra prediction mode, the picture coding program causing a computer to execute:
when a chroma format is 4:2:0, and a partition mode is a mode indicating that a coding target block in a luma signal is partitioned to first to fourth blocks of luma signals horizontally and vertically, and the coding target block in a chroma signal is a minimum size without being partitioned,
a luma signal intra prediction step of setting the first to fourth blocks of luma signals acquired by partitioning the coding target block of luma signals horizontally and vertically and predicting a luma signal based on a coded neighboring block of luma signals in accordance with luma intra prediction modes of the first to fourth blocks of luma signals;
a chroma signal intra prediction step of setting a fifth block of chroma signals without partitioning the coding target block of chroma signals and predicting a chroma signal based on a coded neighboring block of chroma signals in accordance with a chroma intra prediction mode;
a syntax element calculating step relating to a luma intra prediction mode of calculating each of a syntax element relating to the luma intra prediction mode of the first to fourth blocks of luma signals from each of a value of the luma intra prediction mode of the first to fourth blocks of luma signals, respectively;
a syntax element calculating step relating to a chroma intra prediction mode of calculating a syntax element relating to the chroma intra prediction mode of the fifth block of chroma signals; and
a bitstream constructing step of coding the syntax element relating to the luma intra prediction mode of the first block of luma signals, and subsequently coding the syntax element relating to the chroma intra prediction mode of the fifth block of chroma signals, and subsequently coding the syntax element relating to the luma intra prediction mode of the second block of luma signals, the syntax element relating to the luma intra prediction mode of the third block of luma signals, and the syntax element relating to the luma intra prediction mode of the fourth block of luma signals,
wherein the chroma signal intra prediction step is operable to be able to set a value indicating horizontal prediction in which a prediction direction is a horizontal direction as one of predefined values of the chroma intra prediction mode of the prediction block of the chroma signals, in accordance with the value of the syntax element relating to the chroma intra prediction mode of the prediction block of chroma signals.