Method and device for selecting quantization parameters in a picture using side information

摘要

The invention concerns a method for selecting a quantization parameter for each pixel group in a picture. The quantization parameters are used for encoding the picture into a first number of bits (R). The method comprises: A first step (11, 12) for computing a preliminary quantization parameter ( q i max ) for each pixel group, the quantization parameters insuring a minimum picture quality when being used for encoding the picture into a second number of bits (R min ) lower than the first number of bits (R); and A second step (13, 14) for computing a final quantization parameter ( q i ˆ— ) lower that or equal to the preliminary quantization parameter for each pixel group by reallocating the bit difference (R-R min ) between the first and second bit numbers to the pixel groups depending on their perceptual relevancy.