从扬声器录制并通过按键而不是等待指定的时间来结束录制过程

Question

根据How to record wav sound from mic using Windows API?问题的答案，我转到了答案中提供链接的页面，并找到了一个记录麦克风音频的示例代码。

我想知道如何将代码更改为：

1 - 从扬声器录制而来。 2 - 如果可能，按一个键停止录制，而不是等待作为函数参数给出的时间量。

#include <Windows.h>

#pragma comment (lib, "Winmm.lib")


DWORD recordWAVEFile(DWORD dwMilliSeconds)
{
    UINT wDeviceID;
    DWORD dwReturn;
    MCI_OPEN_PARMS mciOpenParms;
    MCI_RECORD_PARMS mciRecordParms;
    MCI_SAVE_PARMS mciSaveParms;
    MCI_PLAY_PARMS mciPlayParms;

    mciOpenParms.lpstrDeviceType = "waveaudio";
    mciOpenParms.lpstrElementName = "";

    if (dwReturn = mciSendCommand(0, MCI_OPEN,
                                  MCI_OPEN_ELEMENT | MCI_OPEN_TYPE,
                                  (DWORD)(LPVOID)&mciOpenParms))
    {
        return (dwReturn);
    }

    wDeviceID = mciOpenParms.wDeviceID;

    mciRecordParms.dwTo = dwMilliSeconds;

    if (dwReturn = mciSendCommand(wDeviceID, MCI_RECORD,
        MCI_TO | MCI_WAIT, (DWORD)(LPVOID)&mciRecordParms))
    {
        mciSendCommand(wDeviceID, MCI_CLOSE, 0, NULL);
        return (dwReturn);
    }

    mciPlayParms.dwFrom = 0L;
    if (dwReturn = mciSendCommand(wDeviceID, MCI_PLAY,
        MCI_FROM | MCI_WAIT, (DWORD)(LPVOID)&mciPlayParms))
    {
        mciSendCommand(wDeviceID, MCI_CLOSE, 0, NULL);
        return (dwReturn);
    }
    if (MessageBox(NULL, "Do you want to save this recording?",
        "", MB_YESNO) == IDNO)
    {
        mciSendCommand(wDeviceID, MCI_CLOSE, 0, NULL);
        return (0L);
    }

    mciSaveParms.lpfilename = "tempfile.wav";
    if (dwReturn = mciSendCommand(wDeviceID, MCI_SAVE,
        MCI_SAVE_FILE | MCI_WAIT, (DWORD)(LPVOID)&mciSaveParms))
    {
        mciSendCommand(wDeviceID, MCI_CLOSE, 0, NULL);
        return (dwReturn);
    }

    return (0L);
}


LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);


int WINAPI WinMain(
    HINSTANCE hInstance,
    HINSTANCE hPrevInstance,
    PSTR szCmdLine,
    int iCmdShow)
{
    char szAppName[] = "App";
    char szWinName[] = "App";

    WNDCLASS wndclass;
    wndclass.style = CS_HREDRAW | CS_VREDRAW | CS_OWNDC;
    wndclass.lpfnWndProc = WndProc;
    wndclass.cbClsExtra = 0;
    wndclass.cbWndExtra = 0;
    wndclass.hInstance = hInstance;
    wndclass.hIcon = LoadIcon(NULL, IDI_APPLICATION);
    wndclass.hCursor = LoadCursor(NULL, IDC_ARROW);
    wndclass.hbrBackground = (HBRUSH)GetStockObject(WHITE_BRUSH);
    wndclass.lpszMenuName = NULL;
    wndclass.lpszClassName = szAppName;

    if (!RegisterClass(&wndclass))
    {
        MessageBox(
            NULL,
            TEXT("Failed to register window class."),
            szAppName,
            MB_ICONERROR);
        return 0;
    }

    HWND hwnd;
    hwnd = CreateWindow(
        szAppName,
        szWinName,
        WS_OVERLAPPEDWINDOW,
        CW_USEDEFAULT,
        CW_USEDEFAULT,
        CW_USEDEFAULT,
        CW_USEDEFAULT,
        NULL,
        NULL,
        hInstance,
        NULL);

    if (!hwnd)
    {
        return 0;
    }

    ShowWindow(hwnd, iCmdShow);
    UpdateWindow(hwnd);

    MSG msg;
    while (GetMessage(&msg, NULL, 0, 0))
    {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }
    return msg.wParam;
}

LRESULT CALLBACK WndProc(
    HWND hwnd,
    UINT message,
    WPARAM wParam,
    LPARAM lParam)
{
    switch (message)
    {
    case WM_KEYDOWN:
        switch (wParam)
        {
        case VK_RETURN:
            recordWAVEFile(4000);
            break;
        default:
            break;
        }
        return 0;
    case WM_DESTROY:
        PostQuitMessage(0);
        return 0;
    }
    return DefWindowProc(hwnd, message, wParam, lParam);
}

Answer 1

使用MCI，您无法选择默认值以外的来源。您必须使用waveIn *函数（waveInOpen()接受一个参数来选择输入源）。

另一种选择是使用（可怕的）Mixer API将默认输入设置为可用的东西，因此MCI使用它。

但是，并非所有声卡都支持从扬声器录制（“你听到的”输入）。实际上，现在大多数与主板一起出售的廉价卡都没有这样的选择。

另一个问题是，为了停止录制，waveIn函数这些都是异步的，因此当按下某个键时，您可以使用waveInStop（），waveInReset（）和waveInClose（）停止录制。

一般来说，Windows中的声音业务不是通过MCI完成的，MCI是一个非常简单的快速播放和录制界面。