C代码实现的AMR语音编解码。AMR多速率编解码技术相比原有的GSM语音编码器采用固定的编码速率，AMR语音编码器则可根据无线信道和传输状况来自适应地选择一种最佳信道模式（全速率或半速率）和信源编码模式（以比特率来区分）进行编码传输。-C code to achieve AMR voice codec. AMR multi rate coding and decoding technology of GSM speech coder is compared to the original fixed code rate, AMR speech coder can be based on the wireless channel and the transmission state to adaptively　an optimal channel mode (full rate or half rate) and source coding mode (to distinguish between the transmission with a bit rate).