Video decoding apparatus and video coding apparatus
A video decoding apparatus includes: a matrix reference pixel derivation unit configured to derive, as a reference image, an image obtained by down-sampling an image adjacently above a target block and an image adjacently leftward of the target block; a weight matrix derivation unit configured to derive a matrix of weighting factors in accordance with an intra prediction mode and a target block size; a matrix prediction image derivation unit configured to derive a prediction image by using a product of elements of the reference image and elements of the matrix of the weighting factors; and a matrix prediction image interpolation unit deriving, as a prediction image, the prediction image or an image obtained by interpolating the prediction image, wherein the weight matrix derivation unit derives a matrix with a size of a width equal to or smaller than a width of the target block size and a height equal to or smaller than a height of the target block size.
1. A video decoding apparatus for decoding an encoded image, the video decoding apparatus comprising:
a matrix reference pixel derivation circuitry that derives reference samples by using top neighboring samples and left neighboring samples of a current block, wherein each of the top neighboring samples and left neighboring samples is derived by performing a down-sampling process;
a weight matrix derivation circuitry that derives a weight matrix, which is defined by using a prediction size, based on an intra prediction mode and a size index;
a matrix prediction image derivation circuitry that derives a prediction image, which is defined by using the prediction size, by using a product-sum operation using sample values in the reference samples and elements in the weight matrix; and
a matrix prediction image interpolation circuitry that derives a predicted image by using the prediction image,
wherein:
the size index is derived according to a value of a transform block width and a value of a transform block height,
the prediction size is derived using the size index,
in a case that a first condition, that both the value of the transform block width and the value of the transform block height are equal to 4, is true, the size index is set equal to 0 and the prediction size is set equal to 4, and
in a case that the first condition is false and a second condition, that (i) the value of the transform block width is equal to 4 and the value of the transform block height is greater than 8 or (ii) the value of the transform block width is greater than 8 and the value of the transform block height is equal to 4, is true, the size index is set equal to 1 and the prediction size is set equal to 4.
2. The video decoding apparatus of claim 1 , wherein the prediction image is defined as a square matrix.
3. A video encoding apparatus for encoding an image data, the video encoding apparatus comprising:
a matrix reference pixel derivation circuitry that derives reference samples by using top neighboring samples and left neighboring samples of a current block, wherein each of the top neighboring samples and left neighboring samples is derived by performing a down-sampling process;
a weight matrix derivation circuitry that derives a weight matrix, which is defined by using a prediction size, based on an intra prediction mode and a size index;
a matrix prediction image derivation circuitry that derives a prediction image, which is defined by using the prediction size, by using a product-sum operation using sample values in the reference samples and elements in the weight matrix; and
a matrix prediction image interpolation circuitry that derives a predicted image by using the prediction image,
wherein:
the size index is derived according to a value of a transform block width and a value of a transform block height,
the prediction size is derived using the size index,
in a case that a first condition, that both the value of the transform block width and the value of the transform block height are equal to 4, is true, the size index is set equal to 0 and the prediction size is set equal to 4, and
in a case that the first condition is false and a second condition, that (i) the value of the transform block width is equal to 4 and the value of the transform block height is greater than 8 or (ii) the value of the transform block width is greater than 8 and the value of the transform block height is equal to 4, is true, the size index is set equal to 1 and the prediction size is set equal to 4.
4. A video decoding method for decoding an encoded image, the video decoding method including:
deriving reference samples by using top neighboring samples and left neighboring samples of a current block, wherein each of the top neighboring samples and left neighboring samples is derived by performing a down-sampling process;
deriving a weight matrix, which is defined by using a prediction size, based on an intra prediction mode and a size index;
deriving a prediction image, which is defined by using the prediction size, by using a product-sum operation using sample values in the reference samples and elements in the weight matrix; and
deriving a predicted image by using the prediction image,
wherein:
the size index is derived according to a value of a transform block width and a value of a transform block height,
the prediction size is derived using the size index,
in a case that a first condition, that both the value of the transform block width and the value of the transform block height are equal to 4, is true, the size index is set equal to 0 and the prediction size is set equal to 4, and
in a case that the first condition is false and a second condition, that (i) the value of the transform block width is equal to 4 and the value of the transform block height is greater than 8 or (ii) the value of the transform block width is greater than 8 and the value of the transform block height is equal to 4, is true, the size index is set equal to 1 and the prediction size is set equal to 4.