Method and device for storing a compression ratio indication in a pixel value buffer in tile encoding

A device for encoding a tile of pixels each having a respective pixel value, said device comprising:

• a variable length encoder configured to variable length encode multiple blocks of pixels constituting respective subsets of said tile to form multiple sequences of symbols as encoded representations of pixel values of said pixels in said multiple blocks;
• a compression rate determiner configured to determine, for each set of at least one block of said multiple blocks, a size indication representative of a compression ratio of a combined sequence corresponding to the at least one sequence of symbols obtained by variable length encoding said at least one block of said set by said variable length encoder;
• a sequence arranger configured to arrange said combined sequences in a pixel value buffer in a buffer memory;
• and
• an indication arranger configured to arrange, for each set, a size indication determined by said compression rate determiner for said set to precede, according to a reading order of said pixel value buffer, said combined sequence in said pixel value buffer in said buffer memory.

A device for encoding a pixel value buffer comprising multiple tiles of pixels each having a respective pixel value, said device comprising:

• a variable length encoder configured to variable length encode, for each tile of at least a portion of said multiple tiles multiple blocks of pixels constituting respective subsets of said tile to form multiple sequences of symbols as encoded representations of pixel values of said pixels in said multiple blocks;
• a compression rate determiner configured to determine, for each tile of said at least a portion of said multiple tiles and for each set of multiple blocks in said tile, a size indication representative of a compression ratio a combined sequence corresponding to multiple sequences of symbols obtained by variable length encoding said multiple blocks of said set by said variable length encoder;
• a sequence writer configured to write said combined sequences of said at least a portion of said multiple tile to said pixel value buffer in a buffer memory according to a reversed order selected from the group consisting of a reversed Morton order, a reversed Hilbert order and an order that is opposite to a reading order of said pixel value buffer;
• and
• an indication writer configured to write, for each tile of said at least a portion of said multiple tiles, said size indications determined by said compression rate determiner for said tile to said pixel value buffer in said buffer memory in connection with preceding combined sequences of a preceding tile preceding, according to said reading order of said pixel value buffer, said tile.

A method of encoding a pixel value buffer comprising multiple tiles of pixels each having a respective pixel value, said method comprising:

• variable length encoding, for each tile of at least a portion of said multiple tiles, multiple blocks of pixels constituting respective subsets of said tile to form multiple sequences of symbols as encoded representations of pixel values of said pixels in said multiple blocks;
• determining, for each tile of said at least a portion of said multiple tiles and for each set of multiple blocks in said tile, a size indication representative of a compression ratio a combined sequence corresponding to multiple sequences of symbols obtained by variable length encoding said multiple blocks of said set;
• writing said combined sequences of said at least a portion of said multiple tiles to said pixel value buffer in a buffer memory according to a reversed order selected from the group consisting of a reversed Morton order, a reversed Hilbert order and an order that is opposite to a reading order of said pixel value buffer;
• and
• writing, for each tile of said at least a portion of said multiple tiles, said size indications determined for said tile to said pixel value buffer in said buffer memory in connection with preceding combined sequences of a preceding tile preceding, according to said reading order of said pixel value buffer, said tile.