Application of reversible variable-length codes in robust speech coding

The performance of speech coders, such as the ITU-T G.722.1 wideband speech coder, that employ non-self-synchronising variable-length codes is greatly degraded when the received bit stream is in error. The authors study the use of reversible variable-length codes (RVLCs) to replace the Huffman codes recommended in the G.722.1 coder. A modified trellis-based scheme to decode the RVLCs-encoded bit stream is proposed and applied to the coder to improve its performance when bit errors occur. Simulation results show that the modified coder is much more robust in segmental SNR performance as compared to the original G.722.1 coder when bit errors occur.