Image encoder which determines whether to perform CIIP, image decoder, image encoding method, and image decoding method
An image encoder includes: circuitry; and a memory coupled to the circuitry. The circuitry, in operation: calculates first values of a current block using intra prediction, the intra prediction being limited to planar mode, the planar mode using multiple reference pixels for each pixel location of the current block; calculates second values of the current block using inter prediction; calculates third values of the current block by weighting the first values and the second values; and encodes the current block using the third values, and in the calculating of the third values, a first weight is applied to the first values and a second weight is applied to the second values, the second weight being different from the first weight.
1. An image encoder comprising:
circuitry; and
a memory coupled to the circuitry;
wherein the circuitry, in operation, determines whether to perform Combined Intra Inter Prediction (CIIP) on a current block,
when the CIIP is determined to be performed on the current block, the circuitry:
limits intra prediction to planar mode, the planar mode using multiple reference pixels for each pixel location of the current block;
calculates, for the entire current block, first values of the current block using the intra prediction;
calculates, for the entire current block, second values of the current block using inter prediction;
calculates, for the entire current block, third values of the current block by weighting the first values and the second values; and
encodes the current block using the third values, and
in the calculating of the third values, the circuitry:
determines a set of weights to be applied to the current block based on a variable, the set of weights including a first weight and a second weight;
applies the first weight to the first values; and
applies the second weight to the second values,
wherein candidates for the set of weights to be applied to the current block include a first set of weights and a second set of weights, the first weight and the second weight of the first set of weights having a same value, the first weight and the second weight of the second set of weights having different values from each other, and
the circuitry switches between different sets of weights for different blocks by determining the set of weights to be applied to the current block from among the candidates.
2. An image decoder comprising:
circuitry; and
a memory coupled to the circuitry;
wherein the circuitry, in operation, determines whether to perform Combined Intra Inter Prediction (CIIP) on a current block,
when the CIIP is determined to be performed on the current block, the circuitry:
limits intra prediction to planar mode, the planar mode using multiple reference pixels for each pixel location of the current block;
calculates, for the entire current block, first values of the current block using the intra prediction;
calculates, for the entire current block, second values of the current block using inter prediction;
calculates, for the entire current block, third values of the current block by weighting the first values and the second values; and
decodes the current block using the third values, and
in the calculating of the third values, the circuitry:
determines a set of weights to be applied to the current block based on a variable, the set of weights including a first weight and a second weight;
applies the first weight to the first values; and
applies the second weight to the second values,
wherein candidates for the set of weights to be applied to the current block include a first set of weights and a second set of weights, the first weight and the second weight of the first set of weights having a same value, the first weight and the second weight of the second set of weights having different values from each other, and
the circuitry switches between different sets of weights for different blocks by determining the set of weights to be applied to the current block from among the candidates.
3. A non-transitory computer readable medium storing a bitstream and a computer program having instructions for transmission thereof, the bitstream including information according to which a decoder determines whether to perform Combined Intra Inter Prediction (CIIP) on a current block,
when the CIIP is determined to be performed on the current block:
intra prediction being limited to planar mode, the planar mode using multiple reference pixels for each pixel location of the current block;
first values of the current block being calculated using the intra prediction for the entire current block;
second values of the current block being calculated using inter prediction for the entire current block;
third values of the current block being calculated by weighting the first values and the second values for the entire current block; and
the current block being decoded using the third values, and
in the calculating of the third values:
a set of weights to be applied to the current block being determined based on a variable, the set of weights including a first weight and a second weight;
the first weight being applied to the first values; and
the second weight being applied to the second values,
wherein candidates for the set of weights to be applied to the current block include a first set of weights and a second set of weights, the first weight and the second weight of the first set of weights having a same value, the first weight and the second weight of the second set of weights having different values from each other, and
the set of weights to be applied to the current block being determined among the candidates such that the decoder switches between different sets of weights for different blocks.