GENERALIZED ANALYSIS-BY-SYNTHESIS SPEED CODING METHOD, AND CODER IMPLEMENTING SUCH METHOD

摘要

An improved EX-CELP or RCELP encoding scheme is proposed, in which, at the encoder side, a speech signal is perceptually weighted signal prior to entering a time scale modification module, then the modified signal is transformed into another domain, such as the speech or LP short-term residua l domain, using the corresponding inverse filtering operation directly or possibly combined with another processing, for instance a short-term LP filtering. A shift function is calculated in the time scale modification process to associate t he position of each sample in the modified signal with its original position before the modification. The positions of the samples in the modified signal that correspond to sub-frame boundaries of the original signal are evaluated to switch filters for the inverse filtering at the appropriate instants. Therefore, the synchronization between the inverse filters and the modified signal is maintained.