Transport coding schemes for digital video transmission over asynchronous transfer mode networks

We investigate the use of forward error-control (FEC) for variable bit-rate (VBR) video transmission over Asynchronous Transfer Mode (ATM) networks. ATM has rapidly emerged as the appropriate transport technique for Broadband ISDN. Among the various services offered in future ATM networks, VBR video is likely to be one of the largest users of bandwidth. The transmission of VBR video offers the potential promise of constant video quality but is generally accompanied by packet loss. In particular, loss of crucial information such as motion vectors and headers can lead to poor reception quality. Furthermore, due to stringent delay constraints, such packet loss cannot be recovered through retransmission as in most currently used protocols.;This thesis focuses on the design and evaluation of efficient transport coding schemes employing FEC to provide robust transmission. First, the associated delay in using representative FEC schemes is evaluated and shown to be acceptable for codes of small-to-moderate complexity. Next, two different approaches to employing FEC are studied. The traditional approach increases the transmission bandwidth to accommodate FEC overheads while maintaining a fixed video coding rate. Consequently, packet loss is exacerbated under high network loads. We show that a better technique is to throttle the video coder rate to accommodate FEC overheads. Our results demonstrate that for a slight penalty in quality under very low losses, much better performance is achieved under moderate-to-heavy losses. Under heavy loads, such a scheme can potentially outperform an unthrottled FEC: application by as much as 6 dB.;A central issue associated with applying FEC is the design of an efficient code selection strategy. Poorly chosen codes not only waste transmission bandwidth but also lack the capability to adequately protect under loss. Therefore, we formulate a code selection strategy to optimize the performance using appropriate codes. Information-theoretic bounds are determined to assess the efficacy of the resulting performance. We demonstrate that moderate complexity codes are sufficient to ensure excellent performance even under moderate-to-heavy loss. This investigation which initially employed a subband coding scheme is extended to include the MPEG-2 coding standard.