| CPC H04N 19/11 (2014.11) [H04N 19/105 (2014.11); H04N 19/159 (2014.11); H04N 19/176 (2014.11); H04N 19/184 (2014.11); H04N 19/593 (2014.11); H04N 19/96 (2014.11)] | 5 Claims |
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1. An image decoding method performed by an image decoding apparatus, the method comprising:
obtaining, through a bitstream, image information comprising information on quantized transform coefficient levels;
deriving transform coefficients of a current block based on the information on quantized transform coefficient levels;
determining a transform set for a secondary inverse-transform based on an intra prediction mode of the current block;
determining a transform kernel for the secondary inverse-transform based on the transform set and a size of the current block;
deriving modified transform coefficients by performing the secondary inverse-transform based on the transform coefficients and the transform kernel for the secondary inverse-transform;
deriving a reconstructed residual signal by performing a primary inverse-transform based on the modified transform coefficients; and
generating a reconstructed current block based on the reconstructed residual signal,
wherein the secondary inverse-transform is a non-separable inverse-transform, and the transform set includes a plurality of transform kernel candidates for the non-separable inverse-transform, and
wherein based on whether the intra prediction mode is a non-directional prediction mode, the transform kernel for the secondary inverse-transform is determined differently.
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