Hello, I create object of CapDevice in Main window (WPF) , and try to call GetBrightness() but it failed with error: Unable to cast COM object of type 'System.__ComObject' to interface type 'DirectShowLib.IAMVideoProcAmp'. This operation failed because the QueryInterface call on the COM component for the interface with IID '{C6E13360-30AC-11D0-A18C-00A0C9118956}' failed due to the following error: No such interface supported (Exception from HRESULT: 0x80004002 (E_NOINTERFACE)).
When I call it inside worker thread everything is OK.
Something wrong with marshalling to another thread ?
public class CapDevice:DependencyObject, IDisposable
{
Thread worker;
IGraphBuilder graphBuilder = null;
ICaptureGraphBuilder2 captureGraphBuilder = null;
IBaseFilter sourceFilter = null,
CapGrabber capGrabber = null;
IAMVideoProcAmp videoProcAmp = null;
IMediaEventEx mediaEventEx = null;
DsDevice capDevice = null;
public void Start()
{
if (worker == null)
{
worker = new Thread(RunWorker);
worker.SetApartmentState(ApartmentState.MTA);
worker.Start();
}
}
public int GetBrightness()
{
int br = 0;
VideoProcAmpFlags CapsFlags;
if (videoProcAmp != null)
//THIS CALL FAILED WHEN GetBrightness() CALLED FROM ANOTHER WINDOW
videoProcAmp.Get(VideoProcAmpProperty.Brightness, out br, out CapsFlags);
return br;
}
void RunWorker()
{
// Create DirectShow interfaces
graphBuilder = (IGraphBuilder)new FilterGraph();
captureGraphBuilder = (ICaptureGraphBuilder2)new CaptureGraphBuilder2();
// Attach the filter graph to the capture graph
hr = captureGraphBuilder.SetFiltergraph(graphBuilder);
DsError.ThrowExceptionForHR(hr);
// create a video capture/preview device
sourceFilter = FindCaptureDevice(1);
videoProcAmp = (IAMVideoProcAmp)sourceFilter;
graphBuilder = (IGraphBuilder)new FilterGraph();
captureGraphBuilder = (ICaptureGraphBuilder2)new CaptureGraphBuilder2();
int br = GetBrightness(); //HERE EVERYTHING IS OK
//.....
//Do some work
}
}
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Gohil JayendrasinhPosted Jul 24, 2012, 9:56 AM
you must create com visible true in your project property.
http://www.c-sharpcorner.com/Blogs/7439/creating-com-components-in-net.aspx