如何为AMR播放填充AudioStreamBasicDescription

源数据为AMR-NB 5.9kbit/s(AMR\ U 5.90)

我试过下面的设置(和一打变化),但我得到的只是垃圾音频。有人知道AMR的正确设置吗?

 AudioStreamBasicDescription asbd;
 asbd.mSampleRate = 8000.0;
 asbd.mFormatID = kAudioFormatAMR;
 asbd.mFormatFlags = 0;
 asbd.mBytesPerPacket = 15;  // (118>>3)
 asbd.mFramesPerPacket = 1;
 asbd.mBytesPerFrame = 15;
 asbd.mChannelsPerFrame = 1;
 asbd.mBitsPerChannel = 118;  //tried also 0 and 13
 asbd.mReserved = 0;

基于维基百科的AMR信息:

数据结构描述如下:

http://developer.apple.com/iphone/library/documentation/MusicAudio/Reference/CoreAudioDataTypesRef/Reference/reference.html#//apple_ref/doc/c_ref/AudioStreamBasicDescription