Study of MPEG VBR sequen ality transmitte rt-VBR and A contracts
Slim Gara, Guy Pujolle · 1997
In this paper, we study the impact of resource allocation protocol on the quality of a MPEC sequence encoded in a Variable Bit Rate mode (MPEC VBR). The transmission of the video with real-time constraints will be made through one of the following contracts : Constant Bit-Rate (CBR), real-time Variable Bit Rate(rt-VBKJ, ATM Block Transfer (ABT). CBR contract leads either to an under-utilization of resources or a greater end-to- end delay. rt-VBR contract allows statistical multiplexing but induces inevitably cell losses in the network. Fast reservation protocol (FRP) having given birth to the ABT contract is based on a preliminary resource reservation. The reserved bandwidth can be less than the bandwidth requested by the application. We propose a method to estimate the quality degradation caused by image size reduction. It is shown that the sequence quality is less damaged by reducing image size at the encoder level with ABT contract than by a random cell loss inside the network with rt-VBR contract. Finally, we present a novel mechanism for real-time video transmission over ATM networks based on ABT contract.