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

This paper investigates the use of joint sourcechannel coding for reliable transmission of MPEG-4 video over wireless channels. We present a maximum a posteriori probability (MAP) based, joint source-channel decoder for variable length coded intra and inter macroblocks in a MPEG-4 encoded video stream. We then provide a comprehensive evaluation of this paradigm as an alternative method for achieving error resilience. In particular our method is tested in conjunction with the MPEG4 error resilience tools such as reversible variable length codes (RVLC), resynchronization markers and data partitioning, with and without FECs and finally without the use of RVLCs (only variable length codes). In addition, the JSCD algorithm is tested with and without the use of FECs (Reed-Solomon codes). These tests show that the best performance at high channel bit error rate is obtained when all error resilience tools are co-opted. The maximum improvement due to the proposed decoder when used without FEC is about 7 dB for RVLC and 8 dB for VLCs. These numbers are about 2.2dB and 7.5dB respectively, when the MAP decoder is used in conjunction with the Reed-Solomon codes.