Voice encoder using a voice activity detector

Claim 1

A voice encoder comprising: input terminal means for receiving, for each sample, digital information of sampled values of an input voice signal; a subtractor for subtracting, for each sample, a prediction signal from the digital information of the sampled values to produce a difference signal; an adaptive quantizer for quantizing, for each sample, the difference signal to produce a quantized output; output terminal means for outputting, for each sample, the quantized output; an inverse adaptive quantizer for performing inverse-adaptive quantization, for each sample, of the quantized output to produce a quantized difference signal; an adder for adding, for each sample, the prediction signal and the quantized difference signal to obtain a reproduced signal; an adaptive predictor for producing, for each sample, the prediction signal and two predictive coefficients from the quantized difference signals and the reproduced signal; average calculator means for producing respective average values of the two predictive coefficients produced in the adaptive predictor for each framed period of the input voice signal; and decision means for holding respective ranges of predictive coefficient threshold values precalculated from respective distributions of the two predictive coefficients and for deciding whether said each framed period is a voice active period or a voice non-active period as a result of comparing the average values provided from said average calculator means with said respective ranges of predictive coefficient threshold values to obtain voice active/non-active flags in correspondence to said voice active period and said voice non-active period for voice operate switch exchange of the quantized output.