Publications – Details
Error Concealment by Softbit Speech Decoding
- Authors:
- Tim Fingscheidt and Peter Vary
- Book Title:
- ITG-Fachtagung Sprachkommunikation
- Venue:
- Frankfurt a. M., Germany
- Event Date:
- 0.-0.9.1996
- Organization:
- ITG
- Date:
- Sept. 1996
- Pages:
- 7–10
- Language:
- English
Abstract
In digital mobile communication systems there is a need for reducing the subjective effects of residual bit errors by error concealment techniques. Due to the fact that most standards do not specify these algorithms bit exactly, there is room for new solutions to improve the decoding process. This contribution develops a new approach for optimum estimation of speech codec parameters using softbits. It can be applied to any speech codec standard if channel state information is provided by the demodulator (e.g. DECT), or by the channel decoder (e.g. soft-output Viterbi algorithm -- SOVA in GSM). The proposed method includes an inherent muting mechanism leading to a graceful degradation of speech quality in case of adverse transmission conditions. Particularly the additional exploitation of residual source redundancy, i.e. some a priori knowledge about codec parameters gives a significant enhancement of the output speech quality. In the case of an error free channel, bit exactness as required by the standards can be preserved.
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