An efficient transcoding algorithm between AMR-NB and G.729ab
In this paper, an efficient transcoding algorithm between AMR-NB and G.729ab is proposed. The proposed algorithm further elaborates on solutions when a DTX function is adopted between the source and destination coding systems. When neither, either or both of the source and destination coding systems adopt the DTX function, the proposed algorithm can carry out the transcoding operation between the two coding systems efficiently. When neither of the two coding systems adopts the DTX function, transcoding methods in different domains are proposed. A scalable distortion measure method based on parameter domain, specifically related to codebook gain conversion, is proposed to keep the amplitude of synthesized speech. The effect on subjective speech quality due to the amplitude of synthesized speech is cancelled out by using the proposed method and the computational complexity is reduced as well. When either or both of the two coding systems adopt the DTX function, depending on the type of the destination frame, transcoding methods between speech frames and non-speech frames are proposed. When the frame is declared as an erased frame, a linear prediction-based pitch recovery and transcoding method is used in this paper. By employing the proposed algorithm in transcoders, complexity is reduced by about 2682% and quality is also improved compared to the conventional DTE method.
amr-nb g.729ab speech coding speech transcoding celp