| CPC H04N 19/619 (2014.11) [H04N 19/132 (2014.11); H04N 19/159 (2014.11); H04N 19/176 (2014.11)] | 3 Claims |

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1. A decoding apparatus for an image decoding, the decoding apparatus comprising:
a memory; and
at least one processor connected to the memory, the at least one processor configured to:
derive modified transform coefficients based on an inverse secondary transform using a transform kernel matrix for transform coefficients for a target block;
derive residual samples for the target block based on an inverse primary transform for the modified transform coefficients; and
generate a reconstructed picture based on the residual samples for the target block,
wherein the at least one processor is further configured to
derive the modified transform coefficients of a top-left 4×4 region, a top-right 4×4 region and a bottom-left 4×4 region of an 8×8 region by applying the transform kernel matrix to the transform coefficients of the top-left 4×4 region of the 8×8 region of the target block,
wherein the transform kernel matrix is a 48×16 matrix, and
wherein a matrix operation between the transform kernel matrix and the transform coefficients of the top-left 4×4 region is (48×16 matrix)*(16×1 transform coefficient vector).
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