Reliable transmission of high-quality video over ATM networks

The development of broadband networks has led to the possibility of a wide variety of new and improved service offerings, Packetized video is likely t o be one of the most significant high-bandwidth users of such networks, The transmission of variable bit-rate (VBR) video offers the potential promise of constant video quality but is generally accompanied by packet loss whic h significantly diminishes this potential. In this paper, me study a class of error recovery schemes employing forward error-control (FEC) coding to r ecover from such losses. In particular, we show that a hybrid error recover y strategy involving the use of active FEC in tandem with simple passive er ror concealment schemes offers very robust performance even under high pack et losses. We discuss two different methods of applying FEC to alleviate the problem o f packet loss, The conventional method of applying FEC generally allocates additional bandwidth for channel coding while maintaining a specified avera ge video coding rate. Such an approach suffers performance degradations at high toads since the bandwidth expansion associated with the use of PEC cre ates additional congestion that negates the potential benefit in using FEC, In contrast, we study a more efficient FEC application technique in our hy brid approach, which allocates bandwidth for channel coding by throttling t he source coder rate (i.e., performing higher compression) while maintainin g a fixed overall transmission rate, More specifically, we consider the per formance of the hybrid approach where the bandwidth to accommodate the FEC overhead is made available by throttling the source coder rate sufficiently so that the overall rate after application of FEC is identical to that of the original unprotected system, We obtain the operational rate-distortion characteristics of such a scheme employing Selected FEC codes. In doing so, we demonstrate the robust performance achieved by appropriate use of FEC u nder moderate-to-high packet losses in comparison to the unprotected system .