Use EVR to display frames captured by camera device directly

Hi,

I am trying to write a small app that display video frames captured by camera device directly onto a window. I am using "Source Reader" + "Sink Writer" architecture rather than "Media Session" as I have to deal with those captured samples directly. I have created Source Reader successfully but when I tried to create EVR to display frames, I met some problems... following is my code:

HRESULTCCapture::CreatePreviewEVR(HWNDhWindow)

{

//m_pPreviewSink,m_pPreviewStream,m_pPresentationClock,andm_pPresentationTimeSource

//arealldefinedasClassmembers

HRESULThr=S_OK;

DWORDsinkCharacteristics=NULL;

IMFActivate*pPreviewSinkActive=NULL;

IMFClockStateSink*pClockStateSink=NULL;

hr=MFCreateVideoRendererActivate(hWindow,&pPreviewSinkActive);

if(SUCCEEDED(hr))

{

hr=pPreviewSinkActive->ActivateObject(IID_PPV_ARGS(&m_pPreviewSink));

}

if(SUCCEEDED(hr))

{

        hr=m_pPreviewSink->GetCharacteristics(&sinkCharacteristics);//sinkCharacteristicsis0x18

}

if(SUCCEEDED(hr))

{

hr=m_pPreviewSink->GetStreamSinkByIndex(0,&m_pPreviewStream);

}

if(SUCCEEDED(hr))

{

hr=MFCreatePresentationClock(&m_pPresentationClock);

}

if(SUCCEEDED(hr))

{

hr=MFCreateSystemTimeSource(&m_pPresentationTimeSource);

}

if(SUCCEEDED(hr))

{

hr=m_pPresentationTimeSource->QueryInterface(__uuidof(IMFClockStateSink),(void**)&pClockStateSink);

}

if(SUCCEEDED(hr))

{

hr=m_pPresentationClock->SetTimeSource(m_pPresentationTimeSource);

}

if(SUCCEEDED(hr))

{

hr=m_pPresentationClock->AddClockStateSink(pClockStateSink);

}

if(SUCCEEDED(hr))

{

hr=m_pPreviewSink->SetPresentationClock(m_pPresentationClock);

}

returnhr;

}

HRESULTCCapture::ConfigurePreviewEVR()

{

//ThisfunctionisimplementedtryingtodoEVRMediaTypeNegotiation

DWORDmediaTypeCount=0;

HRESULThr=S_OK;

IMFMediaType*pSourceReaderType=NULL;

IMFMediaType*pSourceReaderTypeValid=NULL;

IMFMediaType*pPreviewSinkMediaType=NULL;

IMFMediaTypeHandler*pPreviewSinkMediaTypeHandler=NULL;

hr=m_pReader->GetCurrentMediaType((DWORD)MF_SOURCE_READER_FIRST_VIDEO_STREAM,&pSourceReaderType);

if(SUCCEEDED(hr))

{

hr=MFCreateMediaType(&pPreviewSinkMediaType);

}

if(SUCCEEDED(hr))

{

hr=pPreviewSinkMediaType->SetGUID(MF_MT_MAJOR_TYPE,MFMediaType_Video);

}

if(SUCCEEDED(hr))

{

hr=pPreviewSinkMediaType->SetGUID(MF_MT_SUBTYPE,MFVideoFormat_H264);

}

if(SUCCEEDED(hr))

{

hr=pPreviewSinkMediaType->SetUINT32(MF_MT_AVG_BITRATE,14000000);

}

if(SUCCEEDED(hr))

{

hr=CopyAttribute(pSourceReaderType,pPreviewSinkMediaType,MF_MT_FRAME_SIZE);

}

if(SUCCEEDED(hr))

{

hr=CopyAttribute(pSourceReaderType,pPreviewSinkMediaType,MF_MT_FRAME_RATE);

}

if(SUCCEEDED(hr))

{

hr=CopyAttribute(pSourceReaderType,pPreviewSinkMediaType,MF_MT_PIXEL_ASPECT_RATIO);

}

if(SUCCEEDED(hr))

{

hr=CopyAttribute(pSourceReaderType,pPreviewSinkMediaType,MF_MT_INTERLACE_MODE);

}

if(SUCCEEDED(hr))

{

hr=m_pPreviewStream->GetMediaTypeHandler(&pPreviewSinkMediaTypeHandler);

    }

    if(SUCCEEDED(hr))

{

hr=pPreviewSinkMediaTypeHandler->GetMediaTypeCount(&mediaTypeCount);//derivedmediaTypeCountis0

}

if(SUCCEEDED(hr))

{

hr=pPreviewSinkMediaTypeHandler->IsMediaTypeSupported(pSourceReaderType,&pSourceReaderTypeValid);//FailedtogetsupportedMediaType

}

if(SUCCEEDED(hr))

{

hr=pPreviewSinkMediaTypeHandler->SetCurrentMediaType(pSourceReaderTypeValid);//ThisfunctionstillfailsifIusepSourceReaderTypedirectly

}

if(SUCCEEDED(hr))

{

SafeRelease(&pSourceReaderType);

SafeRelease(&pPreviewSinkMediaType);

SafeRelease(&pPreviewSinkMediaTypeHandler);

}

returnhr;

}

As the variable "sinkCharacteristics" gives 0x18, it seems I should be able to add a new stream with the media type I wish to use to the mediasink; however I tried AddStreamSink function but it returned error directly.

The "CCapture" Class inherits from IMFSourceReaderCallBack, and If my understanding is correct, I should use m_pPreviewStream->ProcessSample(pSample) in OnReadSample callback function.

Thanks a lot if anyone can help on this!

Best Regards