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1974
Conference Paper
Titel
Adaptive quantizing in speech coding systems
Abstract
This paper deals with the problem of calculating a local estimate of the time dependent variance of speech signals. The estimation value controls an adaptive amplifier, placed in front of a quantizer, to maintain the quantizer input signal within a specified range. A forward and some backward estimation schemes have been studied and optimized. Results are given for various optimum 3 bit-quantizers. A nonadaptive 3 bit-quantizer has a signal-to-noise ratio (SNR) of approximately 8-9 dB; an adaptive scheme not only raises this value up to 14-15 dB, but leads to an additional subjective gain. DPCM systems offer an additional rise of SNR up to 19 dB.
Language
English