1. An apparatus for decoding a significance map indicating positions of significant transform coefficients within a transform coefficient block from a data stream comprising: a decoder configured to extract a significance map indicating positions of significant transform coefficients within the transform coefficient block, and then the values of the significant transform coefficients within the transform coefficient block from a data stream, with, in extracting the significance map, sequentially extracting first-type syntax elements from the data stream by context-adaptive entropy decoding, the first-type 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; and an associator configured to sequentially associate the sequentially extracted first-type syntax elements to the positions of the transform coefficient block in a scan order determined from among a plurality of scan orders, wherein the decoder is configured to use, in context-adaptively entropy decoding the first-type syntax elements, contexts which are individually selected for each of the first-type syntax elements based at least on the scan order and a number of positions at which, according to the previously-extracted first-type syntax elements, significant transform coefficients are situated, in a neighborhood of the position with which a current first-type syntax element is associated, wherein different contexts for the first-type syntax elements relate to different combinations of the scan order and the number of positions.
1. An apparatus for decoding a significance map indicating positions of significant transform coefficients within a transform coefficient block from a data stream comprising: a decoder configured to extract a significance map indicating positions of significant transform coefficients within the transform coefficient block, and then the values of the significant transform coefficients within the transform coefficient block from a data stream, with, in extracting the significance map, sequentially extracting first-type syntax elements from the data stream by context-adaptive entropy decoding, the first-type 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; and an associator configured to sequentially associate the sequentially extracted first-type syntax elements to the positions of the transform coefficient block in a scan order determined from among a plurality of scan orders, wherein the decoder is configured to use, in context-adaptively entropy decoding the first-type syntax elements, contexts which are individually selected for each of the first-type syntax elements based at least on the scan order and a number of positions at which, according to the previously-extracted first-type syntax elements, significant transform coefficients are situated, in a neighborhood of the position with which a current first-type syntax element is associated, wherein different contexts for the first-type syntax elements relate to different combinations of the scan order and the number of positions. 2. The apparatus according to claim 1 , wherein the decoder is further configured such that the neighborhood of the position with which the respective first-type syntax element is associated merely comprises positions directly adjacent to, or positions either directly adjacent to or separated from the position with which the respective first-type syntax element is associated, at at least one of one position in vertical direction and one position in the horizontal direction at the maximum, wherein the size of the transform coefficient clock is equal to or greater than 8×8 block.