Method and apparatus for determining the excitation signal in VSELP coders
US5307460A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Feb 14, 1992 |
| Grant date | Apr 26, 1994 |
| Priority date | — |
| Expiry date | Feb 14, 2012 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG10L25/06
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
A new basis vector search process that directly results in an optimal linear weighting for a VSELP (Vector Sum Excited Linear Prediction) coder, thus avoiding the need to perform an extensive search. In the present invention, the conventional search process is replaced by a direct formula, thus avoiding the time consuming searching procedure. Using a simple mathematical relationship, the process of filtering the basis signals with an impulse response filter h(n) every subframe is avoided. A simple theorem has been developed to reduce the computation involved in carrying out the filtering of the basis signals with h(n), and is referred to as the switching convolution theorem. As a result, the computation time necessary to produce the optimal weighting is reduced by a factor of from 3 to 4, while maintaining the output quality of the coder. The new apparatus and method are based upon a set of equations that includes several experimentally justified assumptions. The apparatus and method have been implemented successfully for use in a digital cellular telephone. The present invention reduces of the complexity of VSELP coders while maintaining voice quality comparable to conventional fu…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.