Table controlled dynamic bit allocation in a variable rate sub-band speech coder
US4899384A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Aug 25, 1986 |
| Grant date | Feb 6, 1990 |
| Priority date | — |
| Expiry date | Aug 25, 2006 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG10L19/24
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
A sub-band coder utilizes one or more bit allocation tables to dynamically distribute the channel bit capacity bandwidth among the frequency bands according to the desired output quality of speech rather than by means of complex algorithms or simulation techniques. Multiple bit assignment tables are provided to allow various quality levels to be traded off as increasing bit rate demands are placed upon the transmission system. The technique is used for a single coder to achieve a minimum bit rate for a desired given level of subjective quality in speech output or may be used in a shared bit resource to maintain equal and minimum quality degradation for all users. The quality tables determine the number of bits to be dropped from the encoded representation of each signal sample to minimize the transmission load for a given coder without sacrificing speech quality to an unacceptable degree. Table entries are arranged based on the overall band peak energy level and on the sub-band peak energy distribution or spectrum as it is known in the field.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.