Variable-subframe-length speech-coding classes derived from wavelet-transform parameters
US5781881A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Oct 21, 1996 |
| Grant date | Jul 14, 1998 |
| Priority date | — |
| Expiry date | Oct 21, 2016 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG10L2025/786
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
A method and a device are described for classifying speech on the basis of the wavelet transformation for low-bit-rate speech coding processes. The method and the device permit a more robust classifier of speech signals for signal-matched control of speech coding processes in order to reduce the bit rate without affecting the speech quality or to increase the quality at the same bit rate. The method provides that, after segmenting the speech signal, a wavelet transformation is calculated for each frame, from which a set of parameters is determined with the help of adaptive thresholds. The parameters control a finite-state model, which subdivides the frames into shorter subframes if required, and classifies each subframe into one of several classes typical for speech coding. The speech signal is classified on the basis of the wavelet transformation for each time frame. Thus both a high time resolution (location of pulses) and frequency resolution (good mean values) can be achieved. This method and the classifier are therefore especially well suited for the control and selection of code books in a low-bit-rate speech coder. They also have a low sensitivity to background noise and low…
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