ADAPTIVE SPEECH CODER HAVING CODE EXCITED LINEAR PREDICTION WITH MULTIPLE CODEBOOK SEARCHES

摘要

Methods and apparatus for determining codevectors in response to a speech signal including an adaptivestochastic codebook search combination. Each stochastic codebook search is made up of BPC and SHC search components (124). The speech signal is used as the input to each of the two possible codebook searches LTP-CB1 and CB0-CB1. The codebook target vector is computed at (120). The present invention determines when it is desirable to dispense with the adaptive LTP analysis (122) of the target vector and instead use the bits freed up by foregoing the LTP to add another code vector obtained from a second stochastic codebook to the modeling process. A first synthesized speech signal can be determined from the first and second codevectors and a second synthesized speech can be determined from the first and second codewords. The error between the synthesized and the input speech signals is computed (126), concurrently the SHC/BPC search for codebook is performed (128). The resultant vector is searched in the SHC/BPC (124) search for codebook 1 (130).