In a continuous presence multipoint control unit, the multiple video sequences of the high spatial resolution are decoded and downconversed, then composed into an output video sequence. When the bandwidth to transmit the composed sequence is fixed, if the bit rate for each low spatial resolution sequence within the composed sequence is independently allocated, then the degradation of subjective picture quality among the low spatial resolution sequences is severe due to the different video characteristics. An adaptive bit-rate control method to maintain the uniform picture quality among the low spatial resolution sequences is presented. We first find a relationship of bit rate and quantizer parameter for the video manipulation and composition environments. Then we obtain the bit rate for each low spatial resolution sequence to have same quantizer parameter among the sequences by adaptively using the coded results of low or high spatial resolution sequences while considering the scene change of each sequence. We show by simulation that the proposed adaptive bit-rate control method can maintain almost uniform picture quality among the low spatial resolution sequences and almost constant picture quality within the composed sequence in comparison to an independent bit-rate control method.
"Bit-rate control for uniform picture quality within composed video sequence," Optical Engineering 37(11), (1 November 1998). http://dx.doi.org/10.1117/1.601977