Efficient near-optimum softbit source decoding for sources with inter- and intra-frame redundancy

The source codec parameters determined by modern speech, audio, or video encoders are, especially at high compression rates, highly sensitive to transmission errors and they usually exhibit natural residual redundancy due to delay and complexity limitations in the encoding process. Error concealment techniques like softbit source decoding (SBSD) utilize the residual redundancy as a priori knowledge for parameter estimation. Therewith, the annoying artifacts of transmission errors can considerably be concealed. But, the optimal utilization of all terms of residual redundancy requires large computational complexity. In this paper, we derive a new efficient, nearly optimal version to SBSD. Significant complexity savings become possible by exploiting the intra-frame and inter-frame redundancy separately using two nested forward-backward algorithms. Compared to the optimal joint evaluation, the performance loss is negligibly small.