Multiband prototype waveform analysis synthesis for very low bit rate speech coding

Abstract

Prototype waveform interpolation is one of the most efficient compression techniques for coding the speech signal at bit rates below 4 kb/s. Most of the PWI coders employ prototype waveforms of the linear predictive residual signal for coding purpose. In the latest PWI systems, decomposition methods are used to separate the voiced and unvoiced components of the prototype waveforms prior to coding. This has resulted in high quality speech at very low bit rates. This paper presents a novel combination of the multiband voicing analysis and PWI coding system in which the multiband analysis is exploited to identify the voiced and unvoiced spectral components of the prototype waveforms of the original speech signal. To produce a high quality synthetic speech, the energy variation of the original signal is recovered by transmitting its energy envelope. This method resulted in a high quality and low complexity coder operating at 2.55 kb/s.