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我从网上获取了一个代码来从视频文件中捕获一帧并修改为捕获所有帧并将其存储为 bmp 图像。

HRESULT GrabVideoBitmap(PCWSTR pszVideoFile)
{
    IGraphBuilder *pGraph = NULL;
    IMediaControl *pControl = NULL;
    IMediaEventEx *pEvent = NULL;
    IBaseFilter *pGrabberF = NULL;
    ISampleGrabber *pGrabber = NULL;
    IBaseFilter *pSourceF = NULL;
    IEnumPins *pEnum = NULL;
    IPin *pPin = NULL;
    IBaseFilter *pNullF = NULL;

    long evCode;

    wchar_t temp[10];
    wchar_t framename[50] = IMAGE_FILE_PATH;    // L"D:\\sampleframe";

    BYTE *pBuffer = NULL;
    HRESULT hr = CoInitialize(NULL);
    if (FAILED(hr))
        return 0;

    hr = CoCreateInstance(CLSID_FilterGraph, NULL, CLSCTX_INPROC_SERVER, 
                          IID_PPV_ARGS(&pGraph));

    hr = pGraph->QueryInterface(IID_PPV_ARGS(&pControl));

    hr = pGraph->QueryInterface(IID_PPV_ARGS(&pEvent));

    // Create the Sample Grabber filter.
    hr = CoCreateInstance(CLSID_SampleGrabber, NULL, CLSCTX_INPROC_SERVER, 
                          IID_PPV_ARGS(&pGrabberF));

    hr = pGraph->AddFilter(pGrabberF, L"Sample Grabber");

    hr = pGrabberF->QueryInterface(IID_PPV_ARGS(&pGrabber));


    // Displays the metadata of the file
    DisplayFileInfo((wchar_t*)pszVideoFile); // to display video information

    AM_MEDIA_TYPE mt;
    ZeroMemory(&mt, sizeof(mt));
    mt.majortype = MEDIATYPE_Video;
    mt.subtype = MEDIASUBTYPE_RGB24;

    hr = pGrabber->SetMediaType(&mt);

    hr = pGraph->AddSourceFilter(pszVideoFile, L"Source", &pSourceF);

    hr = pSourceF->EnumPins(&pEnum);

    while (S_OK == pEnum->Next(1, &pPin, NULL))
    {
        hr = ConnectFilters(pGraph, pPin, pGrabberF);
        SafeRelease(&pPin);
        if (SUCCEEDED(hr))
        {
            break;
        }
    }

    hr = CoCreateInstance(CLSID_NullRenderer, NULL, CLSCTX_INPROC_SERVER,  
                          IID_PPV_ARGS(&pNullF));

    hr = pGraph->AddFilter(pNullF, L"Null Filter");

    hr = ConnectFilters(pGraph, pGrabberF, pNullF);

    hr = pGrabber->SetOneShot(TRUE);

    hr = pGrabber->SetBufferSamples(TRUE);

    hr = pControl->Run();


    hr = pEvent->WaitForCompletion(INFINITE, &evCode);

    for (int i = 0; i < 10; i++)
    {
        // Find the required buffer size.
        long cbBuffer;
        hr = pGrabber->GetCurrentBuffer(&cbBuffer, NULL);

        pBuffer = (BYTE*)CoTaskMemAlloc(cbBuffer);

        hr = pGrabber->GetCurrentBuffer(&cbBuffer, (long*)pBuffer);

        hr = pGrabber->GetConnectedMediaType(&mt);

        // Examine the format block.
        if ((mt.formattype == FORMAT_VideoInfo) &&
            (mt.cbFormat >= sizeof(VIDEOINFOHEADER)) &&
            (mt.pbFormat != NULL))
        {

            swprintf(temp, 5, L"%d", i);
            wcscat_s(framename, temp);
            wcscat_s(framename, L".bmp");

            VIDEOINFOHEADER *pVih = (VIDEOINFOHEADER*)mt.pbFormat;
            hr = WriteBitmap((PCWSTR)framename, &pVih->bmiHeader,  
                  mt.cbFormat - SIZE_PREHEADER, pBuffer, cbBuffer);
            wcscpy_s(framename, IMAGE_FILE_PATH);
        }
        else
        {
            // Invalid format.
            hr = VFW_E_INVALIDMEDIATYPE;
        }

        FreeMediaType(mt);
    }
done:
    CoTaskMemFree(pBuffer);
    SafeRelease(&pPin);
    SafeRelease(&pEnum);
    SafeRelease(&pNullF);
    SafeRelease(&pSourceF);
    SafeRelease(&pGrabber);
    SafeRelease(&pGrabberF);
    SafeRelease(&pControl);
    SafeRelease(&pEvent);
    SafeRelease(&pGraph);
    return hr;
}

输入视频文件有 132 帧。但只生成了 68 张图像。还为最后 38 张图像捕获视频的最后一帧。

我认为 directshow 图表正在连续运行，并且 WriteBitmap() 缺少帧。

如何让directX中的控件捕获一帧并将其写入bmp文件并捕获下一帧，从而将所有帧捕获为bmp图像。

谢谢阿伦

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1 回答 1

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你的方法是错误的。目前，您将样本采集器设置为一次，然后等待图形完成。这种方式仅适用于捕获单个帧。您需要在 pGrabber 的 ISampleGrabberCB 回调中捕获帧。您需要实现 ISampleGrabberCB 接口并在 pGrabber 过滤器上使用 ISampleGrabber::SetCallback 将其指向您的实现。之后，您可以在 SampleCB 或 BufferCB 方法中捕获帧。http://www.infognition.com/blog/2013/accessing_raw_video_in_directshow.html

于 2016-11-14T13:32:40.147 回答