Encoder, decoder, encoding method, and decoding method
An encoder includes circuitry and memory coupled to the circuitry. In residual coding of a current block, the circuitry, in operation, encodes a subblock flag by Context-based Adaptive Binary Arithmetic Coding (CABAC) in both of a first type of residual coding where an orthogonal transform is performed and a second type of residual coding where the orthogonal transform is skipped, the subblock flag indicating whether a non-zero coefficient is included in a plurality of coefficients for a subblock within the current block, wherein a first syntax used for the first type of residual coding is different from a second syntax used for the second type of residual coding; and controls a number of CABAC processes, wherein the encoding of the subblock flag is not counted as the number of CABAC processes.
1 . A decoder comprising:
circuitry; and
memory coupled to the circuitry, wherein
in residual decoding of a current block, the circuitry, in operation,
determines whether a reverse-orthogonal transform is to be applied;
decodes, using a first syntax, a subblock flag by Context-based Adaptive Binary Arithmetic Coding (CABAC) decoding in a first type of residual decoding in a case where the circuitry determines that the reverse-orthogonal transform is to be applied, and decodes, using a second syntax different from the first syntax, the subblock flag by CABAC decoding in a second type of residual decoding in a case where the circuitry determines that the reverse-orthogonal transform is not to be applied, the subblock flag indicating whether a non-zero coefficient is included in a plurality of coefficients for a subblock within the current block; and
controls a number of CABAC decoding processes, wherein the decoding of the subblock flag is not counted as the number of CABAC decoding processes.
2 . A non-transitory computer readable medium storing a bitstream and a computer program having instructions for transmission of the bitstream, the bitstream including: information according to which a decoder performs residual decoding on a current block,
in the residual decoding of the current block:
whether a reverse-orthogonal transform is to be applied to the current block being determined based on information in the bitstream; and
a subblock flag indicating whether a non-zero coefficient is included in a plurality of coefficients for a subblock within the current block, being decoded by Context-based Adaptive Binary Arithmetic Coding (CABAC) decoding, using a first syntax, in a first type of residual decoding in a case where the reverse-orthogonal transform is to be applied, and the subblock flag being decoded by CABAC decoding, using a second syntax different from the first syntax, in a second type of residual decoding in a case where the reverse-orthogonal transform is not to be applied,
wherein the decoding of the subblock flag is not to be counted in a number of CABAC decoding processes to be controlled.