SMV(Selectable Mode Vocoder):Selectable Mode Vocoder (SMV) is variable bitrate speech coding standard used in CDMA2000 networksfull rate at 8.5 kbit/shalf rate at 4 kbit/squarter rate at 2 kbit/s eighth rate at 800 bit/s
全速率下：3.6 MOS分支持3G2文件