Statistics for variable bit-rate digital television sources

摘要

Several categories of networks allow the users to transmit at variable bit-rates on their channels. DQDB and ATM networks can be mentioned as such examples. This paper will be concerned with describing the digital television and the high-definition television coders as variable bit-rate sources to be transmitted on ATM networks. The variable bit-rates will be studied and modeled bottom up, starting at the sub image level with time scale orders of a few microseconds, and ending up at the program level with time scales of several hours. To validate the theoretical approach, an experiment has been set up to process 25 h of actual television images with digital television coders at different image quality levels. Bit-rates and cell inter-arrival times have been collected allowing statistics to be carried out. As a matter of fact, the television coders involved in variable bit-rate applications are designed to encode images with a quasi-constant quality and to take an optimum benefit from the offered variability. The levels of image quality considered in this paper range from secondary distribution quality up to contribution quality.