Coding of significance maps and transform coefficient blocks

摘要

A higher coding efficiency for coding a significance map indicating positions of significant transform coefficients within a transform coefficient block is achieved by the scan order by which the sequentially extracted syntax elements indicating, for associated positions within the transform coefficient block, as to whether at the respective position a significant or insignificant transform coefficient is situated, are sequentially associated to the positions of the transform coefficient block, among the positions of the transform coefficient block depends on the positions of the significant transform coefficients indicated by previously associated syntax elements. Alternatively, the first-type elements may be context-adaptively entropy decoded using contexts which are individually selected for each of the syntax elements dependent on a number of significant transform coefficients in a neighborhood of the respective syntax element, indicated as being significant by any of the preceding syntax elements.

主权项

1. An apparatus for decoding a transform coefficient block, the apparatus comprising:
a decoder configured to extract, from a data stream, a significance map indicating positions of significant transform coefficients within the transform coefficient block, and the significant transform coefficients within the transform coefficient block; and an associator configured to associate the extracted significant transform coefficients with their respective positions in the transform coefficient block in a coefficient scan order, wherein according to the coefficient scan order, a plurality of sub-blocks of the transform coefficient block are scanned in a sub-block scan order, wherein each sub-block includes more than one pixel, and the transform coefficients within each sub-block are scanned in a position sub-scan order, wherein the position sub-scan order is adaptively selected from a plurality of scan orders including a diagonal scan order, wherein the decoder is configured to use, in extracting the significant transform coefficients, context-adaptive entropy decoding wherein, for each sub-block, a selected set of contexts from a plurality of sets of contexts is determined based on a statistic of the transform coefficients within a previously traversed sub-block of the transform coefficient block, or a statistic of the transform coefficients of a co-located sub-block in a previously decoded transform coefficient block.