I am trying to develop a video player using Qt and DirectShow. When I use queryInterface( ) from mpVideoPlayer which is a QAxWidget, I get NULL pointers. Whenever I use CoCreateInstance to create the first pointer, I get valid pointers for all my subsequent pointers, but this creates the video playing window in a separate window instead of inside my Qt GUI. So how do I get the UUID for a DirectShow inside Qt? How do I use setControl to act like CoCreateInstance( )? Any help and/or examples would be greatly appreciated. Below is my code for setting up the different pointers and running the video. Thanks!!!

Qt Code: 
  1. bool VideoViewerWindow::createVideo( QString filename )
  2. {
  3.    int length = filename.size( ) + 1;
  4.    WCHAR* wfile = new WCHAR[length];
  5.    int i = 0;
  6.    for( i = 0 ; i < filename.size( ) ; i++ )
  7.    {
  8.       wfile[i] = filename[i].toAscii( );
  9.    }
  10.    wfile[i] = '\0';
  11.  
  12.    //mpVideoPlayer->setControl( "DirectShow" );   
  13.  
  14.     // Get the interface for DirectShow's GraphBuilder
  15.    //CoCreateInstance(CLSID_FilterGraph, NULL, CLSCTX_INPROC_SERVER, 
  16.      //               IID_IGraphBuilder, (void **)&pGraphBuilder);
  17.    mpVideoPlayer->queryInterface( QUuid( IID_IGraphBuilder ), (void**) &pGraphBuilder );
  18.  
  19.    pGraphBuilder->RenderFile( wfile, NULL );
  20.  
  21.    // Query for the media control interfaces
  22.    //mpVideoPlayer->queryInterface( QUuid( IID_IMediaControl ), (void **)&pMediaControl );
  23.    pGraphBuilder->QueryInterface( IID_IMediaControl, (void **)&pMediaControl );
  24.    pGraphBuilder->QueryInterface( IID_IMediaEventEx, (void **)&pMediaEvent );
  25.    pGraphBuilder->QueryInterface( IID_IMediaSeeking, (void **)&pMediaSeeking );
  26.    pGraphBuilder->QueryInterface( IID_IMediaPosition, (void **)&pMediaPosition );
  27.  
  28.    // Query for video interfaces, which may not be relevant for audio files
  29.    pGraphBuilder->QueryInterface( IID_IVideoWindow, (void **)&pVideoWindow );
  30.    pGraphBuilder->QueryInterface( IID_IBasicVideo, (void **)&pBasicVideo );
  31.  
  32.    // Query for audio interfaces, which may not be relevant for video-only files
  33.    pGraphBuilder->QueryInterface( IID_IBasicAudio, (void **)&pBasicAudio );
  34.  
  35.    getFrameStepInterface( );
  36.  
  37.    pMediaControl->Run( );
  38.  
  39.    return true;
  40. }
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