Optimizing the image R/D coding performance by tuning quantization parameters

Uniform quantization schemas with dead zone are widely used in image and video codecs. The design of these quantizers affects to the final R/D performance, being two of the quantizer parameters the responsible for that variations: the dead zone size and the reconstruction point location inside each quantization step. In this work we tune the quantizer to obtain the optimum quantization parameters that provide the best R/D behavior for different quality metrics and rate ranges. Based on a representative image set, we provide the quantization parameters to encode general imagery, with a R/D performance close to the optimum one. The same study was done including the Contrast Sensitivity Function in the quantization stage. After an exhaustive experimental test, the results show that the estimated quantization parameters are able to provide bit rate savings up to 11% at low and moderate bit rates without additional computational cost.