2.4 kb/s low bit rate speech coding based on local cosine transform

A 2.4 kb/s low-bit rate speech coder based on the local cosine transform (LCT) algorithm is designed for the first time in the paper. Four segment vector quantizers of the local cosine transform coefficients are employed, and the LGB algorithm is applied to design the codebooks. A fast tree search technique is used to select the vector of the local cosine transform coefficients for each split vector. The evaluation using subjective informal listening tests and a few object parameters indicates that the reconstructed speech quality of the designed low bit rate speech coder is better than that of the FS 1015 coder in intelligibility and naturalness. The new coder is more robust than the FS 1015 coder, which is suitable for speech coding in any environment.