Unified Transform Type Signaling And Transform Type Dependent Transform Coefficient Level Coding

Abstract: An apparatus for decoding a picture using predictive coding and block-based transform residual coding, configured to subdivide the picture into transform bocks of different sizes. The apparatus is configured to select, for a predetermined transform block, a selected transformation by checking whether a size of the predetermined transform block exceeds a predetermined threshold size. If the size of the predetermined transform block exceeds the predetermined threshold size, the apparatus is configured to use a default way for selecting the selected transformation. If the size of the predetermined transform block does not exceed the predetermined threshold size, the apparatus is configured to use a transformation which is pointed to out of a predetermined list of transformations by an index transmitted in the data stream for the predetermined transform block as the selected transformation, the predetermined list of transformations comprising an identity transformation and non-identity transformations. Furthermore the apparatus is configured to decode, for the predetermined transform block, a block of coefficients from the data stream, if the selected transformation is the identity transformation, use the block of coefficients as residual sample array for the predetermined transform block, and if the selected transformation is not the identity transformation, subject the block of coefficients to an inverse transformation corresponding to the selected transformation to obtain the residual sample array for the predetermined transform block. Additionally the apparatus is configured to correct a prediction for the predetermined transform block using the residual sample array to reconstruct the predetermined transform block.

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