Publications – Details
Softbit Speech Decoding with Re-Quantization
- Authors:
- Stefan Heinen, Marc Adrat, Peter Vary, and Wen Xu
- Book Title:
- Proceedings of International ITG Conference on Source and Channel Coding (SCC)
- Venue:
- Munich, Germany
- Date:
- Jan. 2000
- Pages:
- 187–192
- Language:
- English
Abstract
In digital mobile communication usually speech decoding algorithms are closely combined with error concealment techniques to reduce the subjective effects of residual bit errors. In general these error concealment techniques require reliability information which is provided by the channel decoder. The amount of additional informationmay vary from 1 bit per received frame, e.g. in GSM a BFI (bad frame indicator) for a speech frame of 260 bits (Full Rate (FR) codec) or for a frame of 244 bits (Enhanced Full Rate (EFR) codec), up to several bits per received bit for Softbit Speech Decoding. In applications such as the GSM infrastructure where the channel decoder and the speech decoder are placed at spatially distant locations, the additional data rate required to transmit the reliability information might not be available. Therefore, we break up the close connection between error concealment and speech decoding and move the error concealment unit to the base transceiver station where the channel decoder is located. As the error concealment algorithm produces estimated speech parameters with high amplitude resolution a re-quantization of these estimated speech parameters is required which implies a loss in estimation quality. In this paper it is shown that this loss in quality is negligible in most practical cases. In addition, methods for a reduction of the requantization loss are discussed.
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