Method of coding and decoding images, coding and decoding device and computer programs corresponding thereto
A method for coding includes; segmenting an image into blocks; grouping blocks into a number of subsets; coding, using an entropy coding module, each subset, by associating digital information with symbols of each block of a subset, including, for the first block of the image, initializing state variables of the coding module; and generating a data sub-stream representative of at least one of the coded subsets of blocks. Where a current block is the first block to be coded of a subset, symbol occurrence probabilities for the first current block are determined based on those for a coded and decoded predetermined block of at least one other subset. Where the current block is the last coded block of the subset: writing, in the sub-stream representative of the subset, the entire the digital information associated with the symbols during coding of the blocks of the subset, and implementing the initializing sub-step.
1. A computer-implemented method for entropy decoding, the method comprising:
receiving, by a decoder, a data stream representative of a coded image;
identifying, in the data stream, a plurality of rows of consecutive blocks of quantized coefficients of transformed residual values for the coded image;
initializing one or more state variables for entropy decoding a current block in a current row of the plurality of rows; and
entropy decoding the current block based on the one or more state variables for entropy decoding the current block,
wherein when the current block is a first block in the current row in a decoding order for decoding the coded image and the current row is not the first row of the plurality of rows in the decoding order, the one or more state variables for decoding the current block are initialized based on one or more state variables of a predetermined entropy decoded block,
wherein the predetermined entropy decoded block is a second block in the decoding order in a row of consecutive blocks other than the current row,
wherein entropy decoding a block comprises partitioning an interval into a plurality of sub-intervals where the sub-intervals represent probabilities of occurrence of symbols, and
wherein when the current block is a last block in the current row in decoding order, the interval is reinitialized.