Resynchronization of the Adaptive Codebook in a Constrained celp Codec After a Frame Erasure

The adaptive codebook used in CELP (code excited linear prediction) codecs to model the pitch excitation allows the attainment of a high quality of synthesized speech but introduces a strong inter-frame dependency and consequently causes error propagation in case of frame erasure. In a previous work we showed that the error propagation can be greatly reduced by constraining, at the encoder side, the innovative codebook to partially model the pitch excitation. In this paper we extend this work by exploiting, at the decoder side, the pitch-related information present in the innovative excitation to speed up the recovery of the decoder. The method consists in adequately shifting the last pitch pulse present within the corrupted adaptive codebook memory so that it is resynchronized with the excitation parameters of the frame that follows the erased one