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Posted 11 May 2014

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Custom Media Sink for Use with Media Foundation Topologies and WinRT/WRL MediaCapture

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26 Dec 2015CPOL1 min read
Custom Media Sink for use with Media Foundation Topologies and WinRT/WRL MediaCapture


WinRT and WRL introduce the requirement that most Media Foundation interfaces can no longer be directly created. If one wants to record audio or video through a sink, the only way to do so is with quite literally hundreds to thousands of lines of code in a custom sink. This prototype will get someone started towards achieving that with greater ease. Native C++ and C++/CX compatible. This is also compatible with non-WinRT/non-WRL uses since custom sinks could also be used prior to Windows 8 but generally shortcut interfaces were used.


Knowledge of WinRT, WRL, C++, C++/CX, MediaCapture, Media Foundation, ATL and COM are recommended.

Using the Code

The block of code here is for all scenarios including non-WinRT/non-WRL cases where it is bound as an output node of a topology.

#ifdef _WINRT_DLL
#ifdef __cplusplus_winrt
Windows::Media::MediaProperties::VideoEncodingProperties^ vidProps;
Windows::Media::MediaProperties::AudioEncodingProperties^ audProps;
Windows::Media::MediaProperties::MediaEncodingProfile^ medEncProf = 
        ref new Windows::Media::MediaProperties::MediaEncodingProfile;
medEncProf->Video = vidProps;
medEncProf->Audio = audProps;
//set any properties to pass to the Custom Sink in a PropertySet as a best practice
Windows::Foundation::Collections::IPropertySet^ pSet = 
        ref new Windows::Foundation::Collections::PropertySet();
Windows::Media::Capture::MediaCapture^ medCap;
HRESULT hr = medCap->StartPreviewToCustomSinkAsync(medEncProf, 
    ref new Platform::String(RuntimeClass_TimeStamp_WebCamSecExtensions_MediaSink), pSet);
//when finished
hr = medCap->StopPreviewAsync();
ABI::Windows::Media::Capture::IMediaCapture* medCap;
ABI::Windows::Media::MediaProperties::IVideoEncodingProperties* vidProps;
ABI::Windows::Media::MediaProperties::IAudioEncodingProperties* audProps;
ABI::Windows::Foundation::IAsyncAction** pAction;
Microsoft::WRL::ComPtr<ABI::Windows::Media::Capture::IMediaCaptureVideoPreview> imedPrevCap;
if (pAction == nullptr) return E_POINTER;
hr = medCap->QueryInterface<ABI::Windows::Media::Capture::IMediaCaptureVideoPreview>(&imedPrevCap);
if (FAILED(hr)) return hr;
Microsoft::WRL::ComPtr<IActivationFactory> objFactory;
hr = Windows::Foundation::GetActivationFactory(Microsoft::WRL::Wrappers::HStringReference
    (RuntimeClass_Windows_Media_MediaProperties_MediaEncodingProfile).Get(), objFactory.ReleaseAndGetAddressOf());
if (FAILED(hr)) return hr;
Microsoft::WRL::ComPtr<IInspectable> medEncProf;
hr = objFactory->ActivateInstance(medEncProf.ReleaseAndGetAddressOf());
if (FAILED(hr)) return hr;
Microsoft::WRL::ComPtr<ABI::Windows::Media::MediaProperties::IMediaEncodingProfile> encProps;
hr = medEncProf.As<ABI::Windows::Media::MediaProperties::IMediaEncodingProfile>(&encProps);
if (FAILED(hr)) return hr;
hr = encProps->put_Video(vidProps);
if (FAILED(hr)) return hr;
//if audio desired must also set an audio sink stream
hr = encProps->put_Audio(audProps);
if (FAILED(hr)) return hr;
hr = Windows::Foundation::GetActivationFactory(Microsoft::WRL::Wrappers::HStringReference
    (RuntimeClass_Windows_Foundation_Collections_PropertySet).Get(), objFactory.ReleaseAndGetAddressOf());
if (FAILED(hr)) return hr;
Microsoft::WRL::ComPtr<IInspectable> pSet;
hr = objFactory->ActivateInstance(pSet.GetAddressOf());
if (FAILED(hr)) return hr;
Microsoft::WRL::ComPtr<ABI::Windows::Foundation::Collections::IPropertySet> pProps;
hr = pSet.As(&pProps);
if (FAILED(hr)) return hr;
Microsoft::WRL::ComPtr<ABI::Windows::Foundation::Collections::IMap<HSTRING, IInspectable *>> spSetting;
hr = pSet.As(&spSetting);
if (FAILED(hr)) return hr;
hr = Windows::Foundation::GetActivationFactory(Microsoft::WRL::Wrappers::HStringReference
    (RuntimeClass_Windows_Foundation_PropertyValue).Get(), objFactory.ReleaseAndGetAddressOf());
if (FAILED(hr)) return hr;
Microsoft::WRL::ComPtr<ABI::Windows::Foundation::IPropertyValueStatics> spPropVal;
hr = objFactory.As(&spPropVal);
if (FAILED(hr)) return hr;
hr = imedPrevCap->StartPreviewToCustomSinkIdAsync(encProps.Get(), Microsoft::WRL::Wrappers::HStringReference
    (RuntimeClass_TimeStamp_WebCamSecExtensions_MediaSink).Get(), pProps.Get(), pAction);
//when finished
hr = imedPrevCap->StopPreviewAsync(pAction);
CComPtr<IMFTopologyNode> pNode; // Create the node.
HRESULT hr = MFCreateTopologyNode(MF_TOPOLOGY_OUTPUT_NODE, &pNode);
if (SUCCEEDED(hr)) {
CComPtr<IMFMediaSink> pSink;
hr = TimeStamp::WebCamSecExtensions::MediaSink::CreateInstance<IMFMediaSink>(&pSink);
if (FAILED(hr)) return hr;
CComPtr<IMFAttributes> pAttr;
hr = pSink->QueryInterface(&pAttr);
if (FAILED(hr)) return hr;
CComPtr<IMFMediaTypeHandler> pHandler; hr = pSD->GetMediaTypeHandler(&pHandler);
if (FAILED(hr)) return hr;
CComPtr<IMFMediaType> pMediaType;
hr = pHandler->GetCurrentMediaType(&pMediaType);
if (FAILED(hr)) return hr;
hr = pAttr->SetUnknown(MF_MEDIASINK_PREFERREDTYPE, pMediaType.Detach());
if (FAILED(hr)) return hr;
hr = pNode->SetObject(pSink);

Points of Interest

Passing parameters is done through a PropertyBag in WinRT/WRL yet through the IMFAttribute interface in non-WinRT/non-WRL code which can be found through IUnknown QueryInterface on the Custom Sink object.

An object of type ICustomSinkCallback must be passed and the interface implemented to utilize the features including initialization, cleanup, property change notification, preparing for samples and sample processing.

When initializing the custom sink, if planning to reuse the MediaCapture object, then be sure to pass the activation name to StartPreviewToCustomSinkAsync and not an instance of a CustomSink object. There is a bug in the MediaCapture library which causes it to become in a bad state if not using the activation ID which is present in Windows 8 and Windows 8.1.

The code is compatible with Visual Studio 2012/2013/2015 and Windows 8/8.1/10.


  • Initial version


This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)


About the Author

Gregory Morse
Software Developer (Senior)
United States United States
No Biography provided

Comments and Discussions

QuestionMy Previous Post Pin
Eitan Barazani31-Oct-14 7:11
MemberEitan Barazani31-Oct-14 7:11 
QuestionReading RAW video stream from a Windows Phone/Tablet camera (in WinRT) Pin
Eitan Barazani29-Oct-14 10:25
MemberEitan Barazani29-Oct-14 10:25 
AnswerRe: Reading RAW video stream from a Windows Phone/Tablet camera (in WinRT) Pin
Gregory Morse29-Oct-14 11:34
MemberGregory Morse29-Oct-14 11:34 
GeneralRe: Reading RAW video stream from a Windows Phone/Tablet camera (in WinRT) Pin
Eitan Barazani29-Oct-14 12:25
MemberEitan Barazani29-Oct-14 12:25 
QuestionIs FTM a must have? Pin
zxli6-Jun-14 20:12
Memberzxli6-Jun-14 20:12 
AnswerRe: Is FTM a must have? Pin
Gregory Morse8-Jun-14 1:18
MemberGregory Morse8-Jun-14 1:18 
QuestionIs this something I would need given my requirement? Pin
Steven123456789026-May-14 9:56
MemberSteven123456789026-May-14 9:56 
Sorry this might be a bit offtopic (or not)...

I'm not sure whether I would need something like your sample code for my purposes. What I need to do is capture audio in realtime and do DSP processing on it while displaying analysis of the data (for example, think guitar tuner). The audio data would not be saved to file and will be discarded after it has been analyzed.

I've been struggling with MediaCapture but the documentation is so minimal at this point that I can't figure out how to do it. All the samples I found so far only saves captured audio to file, which is not what I want.

So at this point I'm trying to figure out whether I need to implement a custom sink or not. Your sample code is a great starting point, however:

- How would I use your code? Are there any usage samples?
- I would prefer to use C#, so is there a way to implement a C# class derived from your classes/interfaces, or would I need to create a C# wrapper around an actual C++ implementation that is based on your code?
- I want this to be compatible with Windows Store apps for both Windows 8.1 and WP 8.1.

EDIT: OK I just read through your article again... The code shown is the actual usage code so ignore the 1st question.
AnswerRe: Is this something I would need given my requirement? Pin
Gregory Morse26-May-14 13:47
MemberGregory Morse26-May-14 13:47 
QuestionThis is really helpful... Pin
zxli20-May-14 14:13
Memberzxli20-May-14 14:13 
AnswerRe: This is really helpful... Pin
Gregory Morse20-May-14 17:07
MemberGregory Morse20-May-14 17:07 

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