当我试图将IMA ADPCM解码为16位有符号PCM时，我得到了半垃圾PCM
我尝试在WAV文件（22050采样/秒，4位/采样，36（！）byte（？）align（？！），1个通道）。

int16_t decodeImaAdpcmSampleUIS(struct AdpcmState* state, const uint8_t sample){
int diff;
int8_t si=state->stepindex;
int step=i_step_table[si];
int cur=state->current;

diff=step>>3;
if( sample&0x04 ) diff += step;
if( sample&0x02 ) diff += step>>1;
if( sample&0x01 ) diff += step>>2;
if( sample&0x08 ){
cur -= diff;
if(cur<-32768)
    cur=-32768;
}else{
cur += diff;
if(cur>32767)
    cur=32767;
}
//predictor: cur, state.current
//step_index: si, stepindex
si+=ima_index_table[sample&0b111];
if(si < 0)
    si = 0;
if(si > 88)
    si = 88;
state->stepindex=si;

return state->current=cur;
}

void decodeImaAdpcm(uint8_t* src, int16_t* dst, size_t srcLen){
    struct AdpcmState state={0,0};

    for(size_t i=0; i<srcLen; i++){
        *(dst++)=decodeImaAdpcmSampleUIS(&state, (*src)&0xf);
        *(dst++)=decodeImaAdpcmSampleUIS(&state, (*src)>>4);
        src++;
    }
}

带有WAV文件的完整项目：https://drive.google.com/open?id=1xuxwXj3Y_QhPDWhrQY7nmz8ycBE1cgyL
转换为PCM WAV的ADPCM WAV文件包含一些垃圾，但ffmpeg正常转换。PCM WAV到ADPCM WAV的转换当前未实现。