Method of use of voice message coder/decoder
AssigneeAT&T Bell Laboratories
InventorJuin-Hwey Chen
Life of this patent
Estimating the term…
Abstract
A code excited linear predictive coder and decoder well suited to speech recording, transmission and reproduction, especially in voice messaging systems, provides backward adaptive gain control of stored codevectors to be applied to a synthesis filter prior to being compared with sequences of input speech signals. Simplified linear predictive parameter quantization using efficient table lookup procedures, efficient codevector storage and search all contribute in an illustrative embodiment to high quality coding and decoding with reduced computational complexity.
Claims45
A method of processing a sequence of input samples comprising
- gain adjusting each of a plurality of codevectors in a backward adaptive gain controller to produce corresponding gain-adjusted codevectors, each of said codevectors being identified by a corresponding index,
- filtering each of said gain-adjusted codevectors in a synthesis filter characterized by a plurality of filter parameters to generate candidate codevectors, the synthesis filter comprising a short term synthesis filter and a long term synthesis filter, the long term synthesis filter being forward adaptive,
- comparing said sequence of input samples with each of said candidate codevectors to determine, for said sequence of input samples, a candidate codevector substantially approximating said sequence of input samples, and
- outputting
- (i) the index for the candidate codevector, and
- (ii) the parameters of said long term synthesis filter.
A method of processing a sequence of input samples comprising:
- (a) gain adjusting the sequence of input samples in a backward adaptive gain controller to produce a gain-adjusted sequence of input samples;
- (b) filtering each of a plurality of codevectors in a synthesis filter characterized by a plurality of filter parameters to generate a plurality of candidate codevectors, the synthesis filter comprising a short term synthesis filter and a long term synthesis filter, the long term synthesis filter being forward adaptive, each of the plurality of codevectors having an index associated therewith;
- (c) comparing the plurality of candidate codevectors with the gain-adjusted sequence of input samples to determine a candidate codevector substantially approximating the gain-adjusted sequence of input samples;
- and
- (d) outputting
- (i) the index associated with the candidate codevector substantially approximating the gain-adjusted sequence of input samples;
- and
- (ii) the parameters of said long term synthesis filter.
A method of processing a first signal by utilizing a set of second signals, the method comprising:
- (a) in a backward adaptive gain controller, producing a gain-adjusted first signal and a gain-adjusted set of second signals;
- (b) filtering the gain-adjusted set of second signals in a synthesis filter characterized by a plurality of filter parameters to generate a filtered set of second signals, the synthesis filter comprising a short term synthesis filter and a long term synthesis filter, the long term synthesis filter being forward adaptive, each signal in the filtered set of second signals having an index associated therewith;
- (c) comparing each signal in the filtered set of second signals with the gain-adjusted first signal to determine a filtered second signal substantially approximating the gain-adjusted first signal;
- and
- (d) outputting
- (i) the index associated with the filtered second signal;
- and
- (ii) the parameters of said long term synthesis filter.
Dependencies are inferred from the claim text.