Efficient LPC vocoder

An LPC vocoder of CADM of residual random components

A mixed and code excitation LPC vocoder at 1.76 kb/s

This paper describes a speech-coding algorithm that we develop recently. We call it M&CELP VOCODER. It is based on the traditional linear prediction vocoder. The excitation is constructed by not usually one of either periodic pulse or white noise, but the mixture of periodic feature-waveform (from predict error) and periodic pulse and white noise passed high pass filter in voiced speech section...

High quality split band LPC vocoder operating at low bit rates

LPC based speech coders operating at bit rates below 3.0 kbits/sec are usually associated with buzzy or metallic artefacts in the synthetic speech. These are mainly attributable to the simplifying assumptions made about the excitation source, which are usually required to maintain such low bit rates. In this paper a new LPC vocoder is presented which splits the LPC excitation into two frequency...

Efficient cross-fade windows for transitions between LPC-based and non-LPC based audio coding

The reference model selected by MPEG for the forthcoming unified speech and audio codec (USAC) switches between a non-LPC based coding mode (based on AAC) operating in the transform domain and an LPC-based coding mode (derived from AMR-WB+) operating either in the time domain (ACELP) or in the frequency domain (wLPT). Seamlessly switching between these different coding modes required the design...

COMPANDED LATTICE VQ FOR EFFICIENT PARAMETRIC LPC QUANTIZATION (ThuPmPO1)

Source coding based on Gaussian Mixture Models (GMM) has been recently proposed for LPC quantization. We address in this paper the related problem of designing efficient codebooks for Gaussian vector sources. A new technique of ellipsoidal lattice vector quantization (VQ) is described, based on 1) scalar companding optimized for Gaussian random variables and 2) rectangular lattice codebooks wit...