Joint source-channel decoding for MPEG-4 coded video over wireless channels

MPEG-4 video coding standard [1] is one among the current state of the art techniques in video compression. This paper addresses the issue of reliable transmission of MPEG-4 video over wireless channels. This becomes an especially important issue for MPEG-4 video, because it uses variable length codes as part of its compression algorithm and although variable codes are often used for better compression, they are also extremely vulnerable to noise introduced by the channel. This paper presents a joint source-channel coding approach to achieving reliable transmission of MPEG-4 video over wireless channels. We present a maximum a posteriori probability based, joint source-channel decoder for the inter-coded macroblocks in an MPEG-4 encoded video stream. Although MPEG-4 contains several error resilience features like reversible variable length codes etc, we believe that our method could provide additional error resilience to the MPEG-4 stream. Our experiments indicate that the performance of the proposed decoder is superior to the standard MPEG-4 decoder both perceptually and in terms of the peak signal to noise ratio. In some case, our decoder does about 10 dB better in terms of PSNR.