| CPC H04N 19/61 (2014.11) [H04N 19/11 (2014.11); H04N 19/122 (2014.11); H04N 19/124 (2014.11); H04N 19/129 (2014.11); H04N 19/132 (2014.11); H04N 19/159 (2014.11); H04N 19/176 (2014.11); H04N 19/18 (2014.11)] | 3 Claims |
|
1. An image decoding method performed by a decoding apparatus, the method comprising:
obtaining information on an intra prediction mode, information on quantized transform coefficients, and a transform index from a bitstream;
deriving prediction samples for a target block based on the intra prediction mode of the target block;
deriving transform coefficients of the target block based on a dequantization for the quantized transform coefficients of the target block;
deriving modified transform coefficients of the target block based on an inverse non-separable transform using a transform kernel matrix for the transform coefficients;
deriving residual samples for the target block based on an inverse primary transform for the modified transform coefficients; and
generating a reconstructed picture based on the prediction samples and the residual samples for the target block,
wherein the deriving of the modified transform coefficients comprises:
determining a transform set based on the intra prediction mode of the target block;
selecting the transform kernel matrix among two transform kernel matrices comprised in the transform set based on the transform index; and
deriving 16 modified transform coefficients by applying the transform kernel matrix to 8 transform coefficients in a 4×4 region of the target block,
wherein 65 directional modes among intra prediction modes are symmetric with respect to mode 34 which is an intra prediction mode in the top-left diagonal direction, and
wherein based on the intra prediction mode of the target block being one of mode 2 to the mode 34 in the left direction with respect to the mode 34, the 16 modified transform coefficients are two-dimensionally arranged in the 4×4 region according to a row-first direction.
|