Performance analysis of transcoding algorithms in packet-loss environments

This paper describes a robustness issue of the transcoder under packet loss channel environments. We briefly introduce the conventional transcoder between AMR and G. 729A speech coders, and analyze the performance of transcoder under frame erasure environments. In a tandem method even a single packet loss significantly affects to the parametric buffers of the successive frames because it should re-analyze the distorted signals. However, the propagation effect of the transcoding method is less severe because it uses a direct bitstream mapping method. By comparing the time delay of error propagation, spectral distortion of spectral information, magnitude spectral distance of excitation information and perceptual evaluation of speech quality (PESQ), we show that the transcoding algorithm is also a promising technology under packet loss channel environments.