An efficient transcoding algorithm for G.723.1 and EVRC speech coders

Interoperability is one the most important factors for a successful integration of the speech network. To operate speech networks employing different speech coders, but integrated as one, bitstreams generated by one coder should be translated seamlessly to those of the other coders. Connecting two coders in tandem may be the simplest way to accomplish this. However, coders in tandem connection often produce problems such as poor speech quality, high computational load, and additional transmission delay. We propose an efficient transcoding algorithm that can provide interoperability to the networks employing ITU-T G.723.1 and TIA IS-127 EVRC speech coders. Subjective and objective quality evaluation have confirmed that the speech quality produced by the proposed transcoding algorithm was equivalent to, or better than the tandem coding, while it had shorter processing delay and less computational complexity.