Compressed digital video can be transported on ATM networks using either a constant bit rate (CBR) or a variable bit rate (VBR) network transport service. The use of VBR transport is generally considered to offer some potentially attractive advantages over more traditional CBR transport. These potential advantages include the expectation of improved reconstructed video quality, shorter end-to-end delays and improved statistical multiplexing performance. Unfortunately, most evaluations of the relative end-to-end performance of VBR versus CBR transport of digital video fail to adequately take into account the effects of lost cells in transporting multiple VBR streams which compete for limited network resources. These effects can be avoided with CBR transport using appropriate call admission control (CAC) procedures. Furthermore, these relative performance evaluations are generally not provided under comparable levels of network resource utilizations. Indeed, no methodology presently exists for fairly assessing the relative end-to-end performance of CBR and VBR encoded video at the same level of resource utilization. In this paper, we develop and illustrate a methodology for comparing the relative performance, in terms of the corresponding end-to-end distortion, of CBR and VBR encoded digital video transport for fixed network resources and at identical multiplexing levels. The approach is an extension of a previously developed joint source-channel coding approach for VBR digital video transport on ATM networks. Our objective in this paper is to provide a common comparison framework for CBR and VBR video streams.
ASJC Scopus subject areas
- Electrical and Electronic Engineering