dirctshow编程实现视频采集

DirectShow是一个应用程序编程接口（API），它被用于Windows操作系统中的多媒体架构。在DirectShow中，视频采集是通过使用视频捕获过滤器来实现的。视频捕获过滤器是一个DirectShow过滤器，它可以从摄像头或视频设备中捕获视频流。以下是使用DirectShow编程实现视频采集的一般步骤：

1. 引入DirectShow库文件和头文件。
2. 创建一个图形渲染器过滤器，并将其添加到Filter Graph中。
3. 创建一个视频捕获过滤器，并将其添加到Filter Graph中。
4. 从视频捕获过滤器中获取视频捕获设备。
5. 设置视频捕获设备的属性，例如分辨率、帧速率等。
6. 将视频捕获过滤器连接到图形渲染器过滤器。
7. 开始视频捕获并显示采集的视频流。
8. 停止视频捕获并释放资源。

下面是一个使用DirectShow库实现视频采集的示例代码：

#include <dshow.h>

int main()
{
    HRESULT hr;
    ICaptureGraphBuilder2* pCaptureGraphBuilder = NULL;
    IGraphBuilder* pGraphBuilder = NULL;
    IBaseFilter* pVideoCaptureFilter = NULL;
    IBaseFilter* pVideoRendererFilter = NULL;
    IMoniker* pVideoCaptureMoniker = NULL;
    IEnumMoniker* pEnumMoniker = NULL;
    ULONG cFetched;

    // Initialize COM
    CoInitialize(NULL);

    // Create the capture graph builder
    hr = CoCreateInstance(CLSID_CaptureGraphBuilder2, NULL, CLSCTX_INPROC_SERVER, IID_ICaptureGraphBuilder2, (void**)&pCaptureGraphBuilder);
    if (FAILED(hr)) {
        return hr;
    }

    // Create the filter graph manager
    hr = CoCreateInstance(CLSID_FilterGraph, NULL, CLSCTX_INPROC_SERVER, IID_IGraphBuilder, (void**)&pGraphBuilder);
    if (FAILED(hr)) {
        return hr;
    }

    // Enumerate the video capture devices
    hr = EnumerateDevices(CLSID_VideoInputDeviceCategory, &pEnumMoniker);
    if (FAILED(hr)) {
        return hr;
    }

    // Get the first video capture device
    hr = pEnumMoniker->Next(1, &pVideoCaptureMoniker, &cFetched);
    if (FAILED(hr) || cFetched != 1) {
        return hr;
    }

    // Create the video capture filter
    hr = pVideoCaptureMoniker->BindToObject(NULL, NULL, IID_IBaseFilter, (void**)&pVideoCaptureFilter);
    if (FAILED(hr)) {
        return hr;
    }

    // Add the video capture filter to the filter graph
    hr = pGraphBuilder->AddFilter(pVideoCaptureFilter, L"Video Capture Filter");
    if (FAILED(hr)) {
        return hr;
    }

    // Create the video renderer filter
    hr = CoCreateInstance(CLSID_VideoRenderer, NULL, CLSCTX_INPROC_SERVER, IID_IBaseFilter, (void**)&pVideoRendererFilter);
    if (FAILED(hr)) {
        return hr;
    }

    // Add the video renderer filter to the filter graph
    hr = pGraphBuilder->AddFilter(pVideoRendererFilter, L"Video Renderer Filter");
    if (FAILED(hr)) {
        return hr;
    }

    // Connect the video capture filter to the video renderer filter
    hr = pCaptureGraphBuilder->RenderStream(&PIN_CATEGORY_CAPTURE, &MEDIATYPE_Video, pVideoCaptureFilter, NULL, pVideoRendererFilter);
    if (FAILED(hr)) {
        return hr;
    }

    // Start the video capture
    hr = pCaptureGraphBuilder->ControlStream(&PIN_CATEGORY_CAPTURE, &MEDIATYPE_Video, pVideoCaptureFilter, NULL, 0, 0);
    if (FAILED(hr)) {
        return hr;
    }

    // Run the filter graph
    hr = pGraphBuilder->QueryInterface(IID_IMediaControl, (void**)&pMediaControl);
    if (FAILED(hr)) {
        return hr;
    }

    hr = pMediaControl->Run();
    if (FAILED(hr)) {
        return hr;
    }

    // Wait for the user to stop the video capture
    getchar();

    // Stop the filter graph
    hr = pMediaControl->Stop();
    if (FAILED(hr)) {
        return hr;
    }

    // Release resources
    pGraphBuilder->Release();
    pCaptureGraphBuilder->Release();
    pVideoCaptureFilter->Release();
    pVideoRendererFilter->Release();
    pVideoCaptureMoniker->Release();
    pEnumMoniker->Release();

    // Uninitialize COM
    CoUninitialize();

    return 0;
}

HRESULT EnumerateDevices(REFGUID category, IEnumMoniker** ppEnumMoniker)
{
    HRESULT hr;
    IMoniker* pMoniker = NULL;
    ICreateDevEnum* pCreateDevEnum = NULL;

    // Create the system device enumerator
    hr = CoCreateInstance(CLSID_SystemDeviceEnum, NULL, CLSCTX_INPROC_SERVER, IID_ICreateDevEnum, (void**)&pCreateDevEnum);
    if (FAILED(hr)) {
        return hr;
    }

    // Create an enumerator for the specified category
    hr = pCreateDevEnum->CreateClassEnumerator(category, ppEnumMoniker, 0);
    if (hr == S_FALSE) {
        return E_FAIL;
    }

    // Release resources
    pCreateDevEnum->Release();

    return S_OK;
}

这个示例程序列举了所有视频捕获设备，并选择第一个设备进行视频捕获。它还创建了一个图形渲染器过滤器，并将其连接到视频捕获过滤器。用户可以通过按下Enter键来停止视频捕获。