Voice Over IP

PARAMETER SPEECH CODERS: 2.4-KBIT/S MIXED-EXCITATION LPC (MELP)

Parametric speech coders assume a generic speech model with a simplified excitation signal and thus are able to operate at the lowest bit rates. All of the speech coders discussed previously can be described as waveform following. Their output signals are similar in shape and phase to the input signal.

Parametric speech coders are different and do not exhibit waveform following. They are based on an analysis-synthesis model for speech signals that can be represented using relatively few parameters. These parameters are extracted and quantized, usually on a regular basis from every 20–40 ms. At the receiver, the parameters are used to create a synthetic speech signal. Under ideal ...