c++ - G726 ADPCM缓冲怎么玩？

Question

我想播放从网络摄像机接收到的音频。压缩后的音频数据格式为G726 ADPCM。

在网上找了几天，还没做。

我试过很多方法来播放它。尝试解码为 PCM 并构建 header 以创建 Wave 文件，但都失败了(也许我在执行此操作时犯了一些错误)。

但是今天，我找到了从PC录制和播放波形音频的代码。

代码如下:

// ADPCM.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include <iostream>
#include <Windows.h>
#include <MMSystem.h>
using namespace std;

int _tmain(int argc, _TCHAR* argv[])
{
    const int NUMPTS = 8000*10;//44100 * 10;
    int sampleRate = 8000;//44100;
    short int waveIn[NUMPTS];

    HWAVEIN hWaveIn;
    WAVEHDR WaveInHdr;
    MMRESULT result;
    HWAVEOUT hWaveOut;

    WAVEFORMATEX pFormat;
    pFormat.wFormatTag = WAVE_FORMAT_PCM;
    pFormat.nChannels = 1;
    pFormat.nSamplesPerSec = sampleRate;
    pFormat.nAvgBytesPerSec = 2 * sampleRate;
    pFormat.nBlockAlign = 2;
    pFormat.wBitsPerSample = 16;
    pFormat.cbSize = 0;

    result = waveInOpen(&hWaveIn, WAVE_MAPPER, &pFormat, 0, 0, WAVE_FORMAT_DIRECT);

    if(result)
    {
        char fault[256];
        waveInGetErrorTextA(result, fault, 256);
        MessageBoxA(NULL, fault, "Failed to open waveform input device.", MB_OK | MB_ICONEXCLAMATION);
        return 1;
    }

    WaveInHdr.lpData = (LPSTR)waveIn;
    WaveInHdr.dwBufferLength = 2 * NUMPTS;
    WaveInHdr.dwBytesRecorded = 0;
    WaveInHdr.dwUser = 0;
    WaveInHdr.dwFlags = 0;
    WaveInHdr.dwLoops = 0;
    waveInPrepareHeader(hWaveIn, &WaveInHdr, sizeof(WAVEHDR));

    result = waveInAddBuffer(hWaveIn, &WaveInHdr, sizeof(WAVEHDR));
    if(result)
    {
        MessageBoxA(NULL, "Failed to read block from device", NULL, MB_OK | MB_ICONEXCLAMATION);
        return 1;
    }

    result = waveInStart(hWaveIn);
    if(result)
    {
        MessageBoxA(NULL, "Failed to start recording", NULL, MB_OK | MB_ICONEXCLAMATION);
        return 1;
    }

    cout << "Recording..." << endl;
    Sleep((NUMPTS/sampleRate) * 1000); //Sleep while recording

    cout << "Playing..." << endl;

    if(waveOutOpen(&hWaveOut, WAVE_MAPPER, &pFormat, 0, 0, WAVE_FORMAT_DIRECT))
    {
        MessageBoxA(NULL, "Failed to replay", NULL, MB_OK | MB_ICONEXCLAMATION );
    }

    waveOutWrite(hWaveOut, &WaveInHdr, sizeof(WaveInHdr));
    Sleep((NUMPTS/sampleRate) * 1000); //Sleep for as long as there was recorded

    waveOutUnprepareHeader(hWaveOut, &WaveInHdr, sizeof(WAVEHDR));
    waveInUnprepareHeader(hWaveIn, &WaveInHdr, sizeof(WAVEHDR));
    waveInClose(hWaveIn);
    waveOutClose(hWaveOut);

    return 0;
}

我的缓冲区中存储了 PCM 数据，我想修改上面的代码来播放它，所以我将其编辑为以下代码:

const int NUMPTS = 4000;//44100 * 10;
    int sampleRate = 8000;//44100;
    CHAR waveIn[NUMPTS];

    HWAVEIN hWaveIn;
    WAVEHDR WaveInHdr;
    MMRESULT result;
    HWAVEOUT hWaveOut;

    WAVEFORMATEX pFormat;
    pFormat.wFormatTag = WAVE_FORMAT_PCM;
    pFormat.nChannels = 1;
    pFormat.nSamplesPerSec = sampleRate;
    pFormat.nAvgBytesPerSec = sampleRate/2;//2 * sampleRate;
    pFormat.nBlockAlign = 1;//2;
    pFormat.wBitsPerSample = 4;//16;
    pFormat.cbSize = 0;


    WaveInHdr.lpData = (LPSTR)waveIn;
    WaveInHdr.dwBufferLength = 2 * NUMPTS;
    WaveInHdr.dwBytesRecorded = 0;
    WaveInHdr.dwUser = 0;
    WaveInHdr.dwFlags = 0;
    WaveInHdr.dwLoops = 0;
    waveInPrepareHeader(hWaveIn, &WaveInHdr, sizeof(WAVEHDR));

    memcpy(WaveInHdr.lpData, myPCMBuffer, NUMPTS);

    waveOutWrite(hWaveOut, &WaveInHdr, sizeof(WaveInHdr));

    waveOutUnprepareHeader(hWaveOut, &WaveInHdr, sizeof(WAVEHDR));
    waveInUnprepareHeader(hWaveIn, &WaveInHdr, sizeof(WAVEHDR));
    waveInClose(hWaveIn);
    waveOutClose(hWaveOut);

但是当调用 waveOutUnprepareHeader() 时，它会抛出消息“Run-Time Check Failure #3 - The variable 'hWaveIn' is being used without being initialized”。

如何初始化hWaveIn？

这是我第一次使用波形音频，所以我很笨^^。

你能告诉我正确的做法吗？

Answer 1

初始化 hWaveIn open音频设备:

MMRESULT waveInOpen(
  LPHWAVEIN phwi, 
  UINT uDeviceID, 
  LPCWAVEFORMATEX pwfx, 
  DWORD dwCallback, 
  DWORD dwInstance, 
  DWORD fdwOpen 
);

Example :

result = waveInOpen(&hWaveIn, WAVE_MAPPER,&pFormat,
            0L, 0L, WAVE_FORMAT_DIRECT);
 if (result)
 {
  char fault[256];
  waveInGetErrorText(result, fault, 256);
  Application->MessageBox(fault, "Failed to open waveform input device.",
              MB_OK | MB_ICONEXCLAMATION);
  return;
 }