VOCODER FOR CODING SPEECH BY USING A CORRELATION BETWEEN SPECTRAL MAGNITUDES AND CANDIDATE EXCITATIONS

A vocoder according to the present invention includes an analyzer portion and a synthesizer portion. The analyzer portion encodes an input frame of speech on the basis of a candidate excitation selected from a group of candidate excitations stored in memory. Instead of transmitting the actual candidate excitation to the synthesizer portion, the analyzer portion generates and provides to the synthesizer portion a variable length index code that identifies the selected candidate excitation. The synthesizer portion stores in memory the same plurality of candidate excitations as the analyzer portion. The synthesizer portion uses the variable length index code to obtain from its memory the candidate excitation originally selected by the analyzer portion. The synthesizer portion reconstructs the input frame of speech on the basis of the obtained candidate excitation.