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Directly Accessing Media Foundation Objects

The ltmfPlay object implement the GetSubObject function so you can access Media Foundation specific objects directly.

Suppose for example, you wanted access to the ltmfPlay objects video processor in order to get its attribute store.

 

In C++, you would do the following:

   IltmfPlay *pPlay; // initialized elsewhere

   HRESULT hr;

   IUnknown *pUnk;

   IMFTransform *pTransform;

   // call the play object to retrieve the FilterGraph

   hr = m_player->GetSubObject(ltmfPlay_Object_SelVideoProcessor, &pUnk);

   if(SUCCEEDED(hr))

   {

      // retrieve the IMFTransform interface

      hr = pUnk->QueryInterface(IID_IMFTransform, (void**) &pTransform);

      if(SUCCEEDED(hr))

      {

         // get the attribute store

         IMFAttributes *pAttributes = NULL;

         pTransform->GetAttributes(&pAttributes);

         // do what you want with the attribute store

         

         pAttributes->Release();

         pTransform->Release();

      }

      pUnk->Release();

   }