Method and device for picture encoding and decoding
An encoding method is presented. Transform coefficients of a block are first obtained. They are then scanned according to a scan pattern for entropy coding. The scan pattern is determined responsive to a shape of the block. FIG. 5
1. An encoding method comprising:
obtaining transform coefficients of a residual block of a current block of samples; and
scanning the coefficients according to a scan pattern for entropy coding;
wherein responsive to a transform with constant low frequency basis function is applied both horizontally and vertically, the coefficients are scanned according to a diagonal scan pattern, and wherein responsive to one of horizontal and vertical transforms is not a transform with constant low frequency basis function, the coefficients are scanned according to a scan pattern selected by an exhaustive rate-distortion search among a set of patterns and wherein the selected scan pattern is encoded.
2. A decoding method comprising:
entropy decoding transform coefficients of a current block ordered according to a scan pattern; and
obtaining a residual block for the current block from the transform coefficients and the scan pattern;
wherein responsive to the transform having a constant low frequency basis function applied both horizontally and vertically, the scan pattern is diagonal and wherein responsive to one transform applied horizontally or vertically is not a transform with constant low frequency basis function, the scan pattern is decoded from a bitstream portion representative of the block.
3. An encoding apparatus comprising one or more processors configured to perform:
obtaining transform coefficients of a residual block of a current block; and
scanning the coefficients according to a scan pattern for entropy coding;
wherein responsive to the transform having a constant low frequency basis function applied both horizontally and vertically, the coefficients are scanned according to a diagonal scan pattern, and wherein responsive to one of horizontal and vertical transforms is not a transform with constant low frequency basis function, the coefficients are scanned according to a scan pattern selected by an exhaustive rate-distortion search among a set of patterns and wherein the selected scan pattern is encoded.
4. A decoding apparatus comprising one or more processors configured to perform:
entropy decoding transform coefficients of a current block ordered according to a scan pattern; and
obtaining a residual block for the current block from the transform coefficients and the scan pattern;
wherein responsive to the transform having a constant low frequency basis function applied both horizontally and vertically, the scan pattern is diagonal and wherein responsive to one transform applied horizontally or vertically is not a transform with constant low frequency basis function, the scan pattern is decoded from a bitstream portion representative of the block.
5. Non-transitory Information storage means storing program code instructions for implementing the method according to claim 1 .
6. Non-transitory Information storage means storing program code instructions for implementing the method according to claim 2 .