Study and subjective evaluation on MPEG-4 narrowband CELP coding under mobile communication conditions

This paper evaluates MPEG-4 narrowband (NB) CELP speech coding under various mobile communication conditions, such as clean, background noise and transmission errors. In order to make the codec robust against the errors with minimum increase of redundant bits, a CRC error correction code is attached into the codec as well as an error concealment is included in the decoder. Subjective evaluation results demonstrate that the speech quality for MPEG-4 speech coding at above 8.3 kb/s is higher than that for the ITU-T G.726 ADPCM at 32 kb/s in the clean speech condition. Further, the speech quality degradation is less than 0.1 in MOS under 10/sup -3/ bit error conditions, and still comparable to or higher than that for G.726 at 32 kb/s without error.