（原）Microsoft Source Reader的简单使用

感觉Microsoft Source Reader还是比较坑的，只是由于需要，不得不使用。其实按照Microsoft提供的示例，基本上可以正常的调试出程序来。

下面的例子，简单的给出了Source Reader的代码。同时，HRESULT CreateVideoDeviceSource(IMFMediaSource **ppSource)函数中，使用了指针的指针，能正确的传出ppSource，不是NULL。之前调试时，使用HRESULT CreateVideoDeviceSource(IMFMediaSource *ppSource)，出来后，ppSource依旧为NULL。后来直接把代码展开，没有继续深入考虑。感谢前两天@wuruifang  的建议，之后在网上搜了一下，指针的指针可以使得输入参数为NULL时输出正常。因而此处重新写成一个函数（以前不清楚为啥用指针的指针时出错，现在倒是没有）。

主要代码：

int _tmain(int argc, _TCHAR* argv[])
{
    IMFMediaSource *ppSource = NULL;
    CreateVideoDeviceSource(&ppSource);

//     hr = EnumerateCaptureFormats(ppSource);  // This can show the formats the camera support. Notice that output window of visual studio shows the infomation.
//     if (FAILED(hr))
//         abort();
    HRESULT hr;
    IMFSourceReader *pReader;
    hr = MFCreateSourceReaderFromMediaSource(ppSource, NULL, &pReader);
    if (FAILED(hr))
        abort();

    hr = SetDeviceFormat(ppSource, 6);   //I need to configure the camera to format 6.
    if (FAILED(hr))
        abort();

    ProcessSamples(pReader);

    SafeRelease(&pReader);
    SafeRelease(&ppSource);
    MFShutdown();
    CoUninitialize();
}

HRESULT ProcessSamples(IMFSourceReader *pReader)
{
    HRESULT hr = S_OK;
    IMFSample *pSample = NULL;
    size_t  cSamples = 0;

    _LARGE_INTEGER time_start;    /*begin time */
    _LARGE_INTEGER time_over;        /*end time*/
    double dqFreq;                /*timer frequence*/
    LARGE_INTEGER f;            /*timer frequence*/
    QueryPerformanceFrequency(&f);
    dqFreq = (double)f.QuadPart;

    QueryPerformanceCounter(&time_start);


    bool quit = false;
    while (!quit)
    {
        DWORD streamIndex, flags;
        LONGLONG llTimeStamp;

        hr = pReader->ReadSample(
            MF_SOURCE_READER_ANY_STREAM,    // Stream index.
            0,                              // Flags.
            &streamIndex,                   // Receives the actual stream index. 
            &flags,                         // Receives status flags.
            &llTimeStamp,                   // Receives the time stamp.
            &pSample                        // Receives the sample or NULL.
            );

        if (FAILED(hr))
            break;

        if (flags & MF_SOURCE_READERF_ENDOFSTREAM)
        {
            wprintf(L"	End of stream
");
            quit = true;
        }

        if (pSample)
        {
            BYTE* data;
            IMFMediaBuffer* buffer;
            DWORD max, current;

            //        printf(" cSamples = %d
", cSamples);
            ++cSamples;
            pSample->GetBufferByIndex(0, &buffer);
            buffer->Lock(&data, &max, &current);

        //    saveBMP(data, cSamples, IMGWIDTH, IMGHEIGHT);

            buffer->Unlock();
            SafeRelease(&buffer);
        
            QueryPerformanceCounter(&time_over);          //In order to find the frames per second of the camera.
            double usedtime = ((time_over.QuadPart - time_start.QuadPart) / dqFreq);
            if (usedtime>1)
            {
                printf(" cSamples = %d
", cSamples);
                cSamples = 0;
                QueryPerformanceCounter(&time_start);
            }
        }
        SafeRelease(&pSample);
    }

    SafeRelease(&pSample);
    return hr;
}

HRESULT CreateVideoDeviceSource(IMFMediaSource **ppSource)
{
    HRESULT hr;
    hr = CoInitialize(NULL);
    if (FAILED(hr))
        abort();
    hr = MFStartup(MF_VERSION, MFSTARTUP_NOSOCKET);
    if (FAILED(hr))
        abort();
        
    *ppSource = NULL;

    IMFMediaSource *pSource = NULL;
    IMFAttributes *pAttributes = NULL;
    IMFActivate **ppDevices = NULL;

    // Create an attribute store to specify the enumeration parameters.
    /*HRESULT*/ hr = MFCreateAttributes(&pAttributes, 1);
    if (FAILED(hr))
        abort();

    // Source type: video capture devices
    hr = pAttributes->SetGUID( MF_DEVSOURCE_ATTRIBUTE_SOURCE_TYPE,
        MF_DEVSOURCE_ATTRIBUTE_SOURCE_TYPE_VIDCAP_GUID );
    if (FAILED(hr))
        abort();

    // Enumerate devices.
    UINT32 count;
    hr = MFEnumDeviceSources(pAttributes, &ppDevices, &count);
    if (FAILED(hr))
        abort();
    if (count == 0)
    {
        hr = E_FAIL;
        return hr;
    }

    // Create the media source object.
    hr = ppDevices[0]->ActivateObject(IID_PPV_ARGS(&pSource));
    if (FAILED(hr))
        abort();

    *ppSource = pSource;
    (*ppSource)->AddRef();

    // release part
    SafeRelease(&pAttributes);

    for (DWORD i = 0; i < count; i++)
    {
        SafeRelease(&ppDevices[i]);
    }
    CoTaskMemFree(ppDevices);
    SafeRelease(&pSource);    //此处不确定，是否需要SafeRelease。
    return hr;
}

得到的图片（程序中保存的是BMP图片，由于cnblogs不支持BMP，因而转成jpg）：

完整代码（不会插入超链接，抱歉）见：https://github.com/darkknightzh/Microsoft-Source-Reader

参考（其他的记不清了，见谅）：

Microsoft ：http://msdn.microsoft.com/en-us/library/windows/desktop/dd389281(v=vs.85).aspx

指针的指针（详见4楼，14楼） ：http://bbs.csdn.net/topics/210076970