Transcoding Scheme between AMR-WB and VMR-WB

The adaptive multirate wideband (AMR-WB) speech codec and variable-rate multimode wideband (VMR-WB) speech codec are two coding standards based on CELP model for processing wideband input speech. When communication occurs between them, transcoding must be performed to translate the encoding format from one standard to another one. In this paper, an effective transcoding scheme is presented which makes full use of the interoperability between AMR-WB and VMR-WB, and also the encoding similarity between the bit-rates from 12.65 kb/s to 23.85 kb/s in AMR-WB. When transcoded from the non-interoperable modes in AMR-WB to VMR-WB, the speech frames of the non-interoperable modes are first translated to the interoperable 12.65 kb/s mode, then the AMR-WB interoperable 12.65 kb/s mode is mapped into the corresponding mode in VMR-WB. Algorithm evaluation indicates that the proposed transcoding scheme has less computational complexity and similar or higher quality compared to the traditional tandem transcoding method.