Wear-toll quality 4.8 kbps speech codec
US5307441A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Nov 29, 1989 |
| Grant date | Apr 26, 1994 |
| Priority date | — |
| Expiry date | Nov 29, 2009 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG10L2019/0014
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
A speech codec operating at low data rates uses an iterative method to jointly optimize pitch and gain parameter sets. A 26-bit spectrum filter coding scheme may be used, involving successive subtractions and quantizations. The codec may preferably use a decomposed multipulse excitation model, wherein the multipulse vectors used as the excitation signal are decomposed into position and amplitude codewords. Multipulse vectors are coded by comparing each vector to a reference multipulse vector and quantizing the resulting difference vector. An expanded multipulse excitation codebook and associated fast search method, optionally with a dynamically-weighted distortion measure, allow selection of the best excitation vector without memory or computational overload. In a dynamic bit allocation technique, the number of bits allocated to the pitch and excitation signals depend on whether the signals are "significant" or "insignificant". Silence/speech detection is based on an average signal energy over an interval and a minimum average energy over a predetermined number of intervals. Adaptive post-filter and the automatic gain control schemes are also provided. Interpolation is used for spe…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.