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This paper investigates the use of joint source-channel coding for reliable transmission of MPEG-4 video over wireless channels. We present a maximum a posteriori probability (MAP) based, joint source-channel decoder (JSCD) for variable length coded intra macroblocks 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 MPEG-4 error resilience tools such as reversible variable length codes (RVLC), resynchronization markers, and data partitioning, with and without forward error controls (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 (RS) 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 2.2 and 7.5 dB, respectively, when the MAP decoder is used in conjunction with the RS codes.
Date of Publication: Dec. 2003