Issue 'COMException: HRESULT E_FAIL' in BlackMagic DeckLink

Hello Community,

I am currently facing a problem while working with the BlackMagic DeckLink SDK and I am seeking assistance to resolve it. I am encountering the following error:

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Unhandled Exception: System.Runtime.InteropServices.COMException: An HRESULT E_FAIL error was returned when calling a COM component.
   at DeckLinkAPI.IDeckLinkInput.EnableVideoInput(_BMDDisplayMode displayMode, _BMDPixelFormat pixelFormat, _BMDVideoInputFlags flags)
   at CapturePreviewCSharp.DeckLinkDevice.StartCapture(_BMDDisplayMode displayMode, IDeckLinkScreenPreviewCallback screenPreviewCallback, Boolean applyDetectedInputMode) in C:\Users\$username\Desktop\CapturePreviewCSharp\DeckLinkDevice.cs:Line 266.
   at CapturePreviewCSharp.MainWindow.<>cDisplayClass33_0.<startCapture>b0() in C:\Users\$username\Desktop\CapturePreviewCSharp\MainWindow.xaml.cs:Line 478.
   at CapturePreviewCSharp.MTAAction.MTAActionThreadPoolCallback(Object threadContext) in C:\Users\$username\Desktop\CapturePreviewCSharp\ApartmentHelper.cs:Line 62.
   at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   at System.Threading.QueueUserWorkItemCallback.System.Threading.IThreadPoolWorkItem.ExecuteWorkItem()
   at System.Threading.ThreadPoolWorkQueue.Dispatch())


I'm using Visual Studio 2022 Community edition. Any guidance or suggestions on how to resolve this issue would be greatly appreciated. Thank you in advance for your assistance.

[Cameron Nichols]

Hi Danil,

Check that your capture input hasn't already been enabled by another application, this is the common reason for exception on IDeckLinkInput.EnableVideoInput. I recommend adding try/catch block to handle this exception.

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try
{
   deckLinkInput.EnableVideoInput(displayMode, _BMDPixelFormat.bmdFormat8BitYUV, videoInputFlags);
}
catch (Exception)
{
   // Handle/forward exception, update UI, etc
}

Regards
Cameron