Buffer-constrained coding of video sequences with quasi-constant quality

The problem of controlling a video coder in order to adapt its variable output bit-rate to the input requirements of the communication channel has received a lot of attention. While in the reported work the performance of the control system is mainly measured in terms of the resulting average coding distortion and its degree of variability, only the minimization of the first has received enough attention as a case for systematic optimization, while the joint minimization of the two terms has only received a heuristic treatment. This paper investigates the compromise between average distortion and distortion variability within the frame of the model-based optimal control for overflow-safe operation of the coder. For this purpose, the systematic obtaining of control policies which optimize a general measure of the dynamical performance of the system is addressed as an extension of the classical formulation of the buffer control problem. By obtaining optimal solutions for different parts of the general performance measure, the compromise between the average value of the distortion and its average variability is made explicit and its qualitative aspects analyzed. Results are provided for an ITU-standard hybrid video coder