Efficient drift-free signal-to-noise ratio scalability

Signal-to-noise ratio (SNR) scalability has been incorporated into the MPEG-2 video-coding standard to allow for the delivery of two services with the same spatial and temporal resolution but different levels of quality. In this paper, we begin by reviewing the performance of a single-loop SNR scalable encoder that is compliant with the MPEG-2 standard and demonstrate that its performance is limited by drift in the base layer. We also look at an alternative single-loop drift-free noncompliant SNR scalable encoder, but discover that its coding efficiency is poor, We then review the performance of an MPEG-compliant two-loop SNR scalable encoder. Finally, we propose a new two-loop noncompliant encoder which achieves improved coding performance at the expense of some increase in encoder and decoder complexity.