Bit-rate control for digital TV and HDTV codecs

摘要

This paper intends to present an optimum control algorithm for digital television and high-definition television codecs. Transmissions at either constant or variable bit-rates will be taken into consideration with the purpose of transmitting on ATM networks. Two main goals are expected to be achieved in a codec which controls its output bit-rates. The first deals with realizing graceful commands and degradations of image quality and the second with achieving an optimum use of the buffer in order to maximize the image quality and avoid any buffer overflow. Both actions on buffer content and image quality will turn out to be tightly related in the optimum algorithm. The image control is mainly applied during the non-stationary periods of the incoming information source, i.e. especially during the scene changes to produce smooth variations of image quality. The control of buffer level is performed during the stationary or predictable periods of the source, i.e. within the scenes. The optimum algorithm is adaptive and combines concepts originating from adaptive filtering theory and operations research and is based on three functions: a non-stationary source predictor to estimate a coming horizon of future bit-rates, a cost function to be minimized and an algorithmic search of the optimum policy aiming at minimizing the previous cost function.