Region-of-interest video coding based on rate and distortion variations for H.263+

Region-of-interest (ROI) is an essential task that one must undertake in low bit-rate multimedia communications because of the limited bandwidth of the channels and the transcoder between different standards. In this paper, an effective ROI determination method is proposed. The skin-color extraction is first employed to determine the ROI macroblocks; then, the framework for the adjustment of the quantization parameters (QPs) of ROI macroblocks according to the distortion and bit-rate variations is proposed to fit the target bit rate. In view of the residual distortion information, the fuzzy logic controller proposed in our framework can adaptively adjust the weighting factor for corresponding QPs by the distortion variation in the macroblock layer. A linear prediction formula, derived from the rate variation, is proposed to allocate appropriate bits for each ROI macroblock and maintain the target bit rate and buffer fullness. Experiment results on TMN8 reveal that the proposed ROI video coding can significantly enhance the quality at ROIs. Furthermore, the proposed framework obtains about 0.5 dB gain in the objective performance and also provides the better subjective quality compared with previous works.