MPEG over ATM DBR service class for high quality transmission and effective bandwidth usage

Abstract

The highly bursty nature of the moving picture experts group (MPEG) determines the bandwidth when it is applied to the asynchronous transfer mode (ATM) deterministic bit rate (DBR) service class. Furthermore, the MPEG source must declare peak cell rate (PCR), one of the traffic descriptors used in the call admission control (CAC) procedure, before actual transmission in ATM networks. However, the real-time encoding of the MPEG video introduces a difficulty in predicting a maximum picture size of the video, which is necessary to determine PCR. When an MPEG source can be equipped with the capability to adjust the encoding rate to the allocated bandwidth, the burstiness of the MPEG video can be lowered and the uncertainty in predicting PCR is avoided to some extent. In this case, a problem is apparently quality degradation caused by introducing such a rate adaptation mechanism, which is the main subject of this study. For the rate adaptation method, we consider a priority control method, a space reduction method, a time reduction method and a bandwidth renegotiation method. Quality of the video is evaluated and compared in terms of signal-to-noise ratio (SNR) as well as mean opinion score (MOS) because users' perception becomes an important measure of the quality of video transmissions. Through experimental results, it is shown that the space reduction method is useful for real-time transmission, whereas the time reduction method can be applicable if the users' application can tolerate the relatively large delay between source and destination. Furthermore, the applicability of the bandwidth renegotiation method is also validated. © 1997 by John Wiley & Sons, Ltd.