Error resilience and recovery in streaming of embedded video

• Authors: Sungdae Cho;William A. Pearlman
• Venue: Signal Processing - Image and Video Coding beyond Standards
• Year: 2002

The three-dimensional (3-D) SPIHT coder is a scalable or embedded coder that has proved its efficiency and its real-time capability in compression of video. A forward-error-correcting (FEC) channel (RCPC) code combined with a single automatic repeat request (ARQ) proved to be an effective means for protecting the bitstream. There were two problems with this scheme: the noiseless reverse channel ARQ may not be feasible in practice; and, in the absence of channel coding and ARQ, the decoded sequence was hopelessly corrupted even for relatively clean channels. In this paper, we introduce a new method of partitioning wavelet coefficients into spatio-temporal (s-t) tree blocks to achieve error resilience. Each of these s-t blocks corresponds to the full 3-D image region, because roots of these trees are wavelet coefficients taken at fixed intervals in the root low-frequency subband. Previously, we reported on grouping contiguous root subband coefficients to generate s-t tree blocks that correspond to local 3-D regions. The new procedure brings higher error resilience, since lost coefficients can be concealed with the surrounding coefficients even if some of the coded s-t blocks are totally missing. The bitstreams of the coded s-t blocks are packetized and encoded with a channel code to correct errors and to prevent decoding of erroneous data after errors are detected. Because the separately encoded s-t blocks produce embedded bitstreams, the packets from the bitstreams are interleaved to generate an embedded composite bitstream. The embedded property, whereby successive compressed bits convey successively smaller value information, suggests unequal error protection, where earlier bits are more strongly protected by the channel code than later bits. Therefore, unequal error protection is also incorporated into our video bitstreams to bring an even higher degree of resilience to channel bit errors. Our claims are supported by extensive simulations with decoding of the various 3-D SPIHT bitstreams compared to each other and to MPEG-2. Superiority to MPEG-2 in noiseless and noisy channels, nnder equal conditions with or without FEC, is clearly demonstrated by the results of these simulations.