Patent ID: 8139882

Claim:
Method for adjusting locally a quantization step in the images of a sequence of n images relative to a setpoint quantization step, said image comprising at least one region of interest and one potential masking region, each of said regions possibly comprising a number of disjoint groups of pixels, said region of interest and potential masking region being respectively encoded in a first and a second number of bits when they are quantized with said setpoint quantization step, wherein it comprises the following steps: calculating, for each image of the sequence, a first difference of bits between said second number of bits and the number of bits used to encode said potential masking region quantized with a first quantization step higher than or equal to the setpoint quantization step, and a second difference of bits between the number of bits used to encode said region of interest quantized with a second quantization step lower than or equal to the setpoint quantization step and said first number of bits; and in each image of the sequence, assigning to the potential masking region said first quantization step and if, over said n images of the sequence, the sum of the n first differences of bits is higher than the sum of the n second differences of bits, assigning said second quantization step to said region of interest and otherwise assigning to said region of interest a third quantization step higher than or equal to said second quantization step such that the sum of said n first differences of bits is distributed between the regions of interest of the images of the sequence according to a reconstruction quality criterion calculated for each image.