Trellis decoding for MPEG-4 streams over wireless channels

Abstract

Most video coding standards, including MPEG-4, use variable length codes to encode the discrete cosine transform (DCT) coefficients of intra frames and inter frames, and the motion vector information. Although variable length codes can achieve good compression, they are very sensitive to channel errors, especially in wireless channels, which are characterized by bursty errors. Joint source-channel decoding (JSCD) is emerging as a potential alternative to traditional error resilience methods for dealing with this sensitivity to channel errors. This paper describes one such JSCD for the reliable transmission of MPEG-4 video over wireless channels. We apply the maximum a posteriori probability based JSCD developed for first order Markov sources to both inter and intra coded macroblocks. Experiments indicate that the proposed decoder gives significant improvements (9 dB in some cases) for MPEG-4 video with error resilience at various channel error rates.