Importance

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Abstract

In a speech packet transmission system, a transmitter (speech terminal) first linearly predicts a speech signal input at a predetermined sample period from the input signal in the past and outputs the difference between the input speech signal and the prediction signal. A prediction coefficient used for linear prediction at this time is adapted with an output differential coded value at each predetermined sample period such that the prediction value is as close as possible to the value of the input waveform. The difference between the input speech signal and the prediction signal is converted to a differential code. A packet is prepared from a plurality of differential codes obtained during a frame period concerned and transmitted to a transmission line. A bit accuracy indicative of the differential code and a bit accuracy indicative of the differential coded value used for adaptation of the prediction coefficient are changed depending on the nature or property of the input speech signal.

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First Claim