在用解码器解码音频数据得到PCM音频数据块之后,可以在将数据送给声卡播放之前调节其音量大小,具体的实现函数如下:
void RaiseVolume(char* buf, UINT32 size, UINT32 uRepeat, double vol)//buf为需要调节音量的音频数据块首地址指针,size为长度,uRepeat为重复次数,通常设为1,vol为增益倍数,可以小于1 { if (!size) { return; } for (int i = 0; i < size;) { signed long minData = -0x8000; //如果是8bit编码这里变成-0x80 signed long maxData = 0x7FFF;//如果是8bit编码这里变成0xFF signed short wData = buf[i + 1]; wData = MAKEWORD(buf[i], buf[i + 1]); signed long dwData = wData; for (int j = 0; j < uRepeat; j++) { dwData = dwData * vol; if (dwData < -0x8000) { dwData = -0x8000; } else if (dwData > 0x7FFF) { dwData = 0x7FFF; } } wData = LOWORD(dwData); buf[i] = LOBYTE(wData); buf[i + 1] = HIBYTE(wData); i += 2; } }