Source and joint source-channel decoding of variable length codes

Several publications have shown that joint source-channel decoding (JSCD) could be a powerful technique for taking advantage of residual source redundancy. Furthermore, it appeared that the principle could also be successfully applied to variable length codes (VLCs). This paper gives an in-depth analysis of a new method proposed by Guivarch, Carlach and Siohan (see Data Compression Conference (DCC), Snowbird, Utah, USA, Mar. 2000, p.83-92) and Guivarch, Siohan and Carlach (see International Communication Conference (ICT), Acapulco, Mexico, May 2000, p.872-76) to provide a low complexity soft decoding of VLCs with and without channel coding. Furthermore we also present new results obtained in a video coding context, using a VLC table from the MPEG4 video standard. Compared to separated decoding systems, the gain in signal to noise ratio varies from 0.3 dB up to 2 dB.