Reduced codebook search arrangement for CELP vocoders

摘要

A new way of CELP coding speech simplifies the recursive loop used to poll code adaptive book vectors by reducing the number of autocorrelation operations that must be performed with the K vectors of the codebook each having N entries. Autocorrelation is initially performed for only a small number P N autocorrelation coefficients in each codebook vector and the values found are used to scan through all the codebook vectors looking for those S vectors (S K) which give the best match to the input speech. The autocorrelation function for the S vectors is then recalculated for R entries (P RN) in the codebook vectors to determine which of the S codebook vectors and associated gain gives the best match to the input speech.