An image is split into a plurality of blocks of various sizes and a subdivision level counter is associated to each of the blocks. The value of this subdivision level counter for a block is representative of the size of the block and is used to determine the quantization parameter for the block. The value is propagated for each subdivision and incremented according the type of the subdivision. When the image is split, an analysis is done according to the subdivision level counter, a maximal value of subdivision and the type of split, in order to determine the start of a new quantization group and when it is the case, the current position of the partition is propagated to the further split partitions to be stored with these partition and serve in the prediction process when decoding.