Influence of Dead Zone Quantization Parameters in the R/D Performance of Wavelet-Based Image Encoders

Uniform quantization schemas with dead zone are commonly 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: (a) the dead zone size and (b) the reconstruction point location inside each quantization step. We analyze how variations of these parameters, by means of a variable dead zone quantizer, affect to the R/D performance of wavelet-based image encoders, using three different quality metrics. We tune the quantizer for each image to obtain the optimum parameters that provide the best R/D behavior for each of the metrics for different rate ranges, without altering the rest of the encoder stages. We provide a general parameter set for each metric and rate range, to be used with other images to obtain important rate savings and better quality values for each metric.