High quality glottal LPC-vocoding

This paper presents an analysis procedure for a parametric coder, capable of coding speech at 2-3 kbit/s. The production model used is essentially that of the LPC-vocoder, however augmented with a variable glottal pulse model for voiced excitation. Starting with formulating a suitable error criterion, a scheme is discussed in detail for extracting close to optimal synthesis parameters. The error measure is in the time-domain essentially defined as for waveform coders. A medium size data base has been used to evaluate the coder. For high quality input speech the resulting speech quality is far above that of standard vocoders. For most of the data base, even trained listeners cannot tell the coded signal from the original signal when listening over loudspeakers.