Look-Ahead Transition Detection for Quantizer Adaptation in Sub-Band Coders
Original Publication Date: 1987-Jul-01
Included in the Prior Art Database: 2005-Feb-01
The quantization of non-stationary signals like speech requires the continuous adaptation of the quantizers. This adaptation can be implemented either in a forward or a backward way. This general rule applies to sub-band coding of speech, where the sub-band quantizers are adapted either forwardly or backwardly. In forwardly-adapted quantizers, like block companded PCM (BCPCM), one determines the quantizer characteristics C(i) and, optionally, the bit allocation n(i) for sub-band i. This information is encoded and transmitted along with the coded sub-band samples as side information. This technique gives good performances but introduces a long end-to-end delay due to the necessity of processing the samples by blocks. Attempts to avoid this drawback have been made by using quantizers with one sample backward adaptation.