Voice coder/decoder and methods of coding/decoding
US5189701A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Oct 25, 1991 |
| Grant date | Feb 23, 1993 |
| Priority date | — |
| Expiry date | Oct 25, 2011 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG10L25/90
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
The pitch frequency of voice signals in successive time frames at a voice coder may be determined as by (1) Cepstrum analysis (time between successive peak amplitudes in each time frame), (2) harmonic gap analysis (amplitude differences between peaks and troughs of the peak amplitude signals in the frequency spectrum) (3) harmonic matching, (4) filtering of the frequency signals in successive pairs of time frames and the performance of (1)-(3) on the filtered signals to provide pitch interpolation on the first frame in the pair and (5) pitch matching. The amplitude and phase of the pitch frequency and harmonic signals are determined by refined techniques to provide amplitude and phase signals with enhanced resolution. Such amplitudes are simplified digitally by (a) taking the logarithm of the frequency signals, (b) selecting the signal with the peak amplitude, (c) offsetting the amplitudes of the logarithmic signals relative to such peak amplitude, (d) companding the offset signals, (e) reducing the number of harmonics to a particular limit by eliminating selective harmonics, (f) taking a discrete cosine transform of the remaining signals and (g) digitizing the transformed signals.…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.