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c - 未调用消息“MM_WOM_DONE”

问题描述

我有一个问题：一旦音频块播放完毕，我就没有收到“MM_WOM_DONE”。

声音相关代码：

void initSound(HWND hwnd) {
    HWAVEOUT hWaveOut;
    WAVEFORMATEX wfx;

    wfx.nSamplesPerSec = 44100; /* sample rate */
    wfx.wBitsPerSample = 8; /* sample size */
    wfx.nChannels = 1; /* channels*/

    wfx.cbSize = 0;
    wfx.wFormatTag = WAVE_FORMAT_PCM;
    wfx.nBlockAlign = (wfx.wBitsPerSample >> 3) * wfx.nChannels;
    wfx.nAvgBytesPerSec = wfx.nBlockAlign * wfx.nSamplesPerSec;

    if(waveOutOpen(&hWaveOut, WAVE_MAPPER, &wfx, (DWORD)hwnd, 0, CALLBACK_WINDOW) != MMSYSERR_NOERROR) {
        printf("Wave out can't be opened!\n");
        ExitProcess(1);
    } else {
        printf("Wave out is now open!\n");
    }

    /* Building a block */
    DWORD size = 8192;
    int frequency = 523; // C note
    int volume = 20;
    float sinMul = 3.1415 * frequency / (wfx.nSamplesPerSec);
    unsigned char blockArray[size];
    for (int i = 0; i < size; i++) {
        blockArray[i] = 128 + (signed char)(sin(i * sinMul) * volume);
    }

    WAVEHDR header;
    ZeroMemory(&header, sizeof(WAVEHDR));
    header.dwBufferLength = size;
    header.lpData = (LPSTR)&blockArray;
    printf("Block was created!\n");

    /* Prepearing header */
    printf("Prepearing header for wave out...\n");
    waveOutPrepareHeader(hWaveOut, &header, sizeof(WAVEHDR));

    /* Playing a block */
    printf("Writing sound to wave out...\n");
    waveOutWrite(hWaveOut, &header, sizeof(WAVEHDR));
    printf("Waiting sound for finishing playing...\n");
}

LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam) {
    switch(msg) {
        case WM_CREATE:
            initSound(hwnd);
        break;
        case MM_WOM_DONE:
            printf("Sine wave stopped playing!");
            waveOutUnprepareHeader((HWAVEOUT)wParam, (LPWAVEHDR)lParam, sizeof(WAVEHDR));
            waveOutClose((HWAVEOUT)wParam);
        break;
    }
}

控制台输出：

Wave out is now open!
Block was created!
Prepearing header for wave out...
Writing sound to wave out...
Waiting sound for finishing playing...

正弦波播放良好且正确，但一旦播放完毕，一些短暂的白噪声就会开始播放很短的时间（接近 100-200 毫秒）。还有“正弦波停止播放！” 消息永远不会出现在控制台中，这意味着永远不会使用“MM_WOM_DONE”消息调用 WndProc 函数。如果我在“initSound”函数中处理所有内容，即使写入和关闭 waveOut 之间的延迟更大（超过一秒），正弦波最终也不会播放白噪声。

标签： cwindowswinapiwinmm

解决方案

Remy Lebeau 解决这个问题的功劳。我犯的错误是将波头和波头存储在堆栈而不是堆中。这导致出现噪音，因为数据被覆盖并且声卡开始读取无效数据。Wave out 标头也可能丢失或/和覆盖，因此我无法正确调用 MM_WOM_DONE 消息。所有这一切都只是为了在函数之外声明变量而解决。像这样：

HWAVEOUT hWaveOut;
WAVEFORMATEX wfx;
DWORD size = 8192;
WAVEHDR header;

void initSound(HWND hwnd) {
    /* Body of function */
}

因此，如果您遇到此问题，请确保与 waveout 相关的变量存在足够长的时间。

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