HOW TO: Capture frames with PlayCtrl using LEAD Video Callback in VB.NET

#1 Posted : Tuesday, July 18, 2017 3:25:00 PM(UTC)

Walter

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The attached Visual Studio 2017 project illustrates the use of the LEAD Video Callback filter with the LEADTOOLS 19 PlayCtrl in VB.NET. The callback implementation waits until the user indicates they would like a frame, and saves that frame using the LEADTOOLS 19 .NET RasterCodecs class. This project assumes you have installed the LEADTOOLS Imaging Pro SDK and integrated the LEADTOOLS Multimedia SDK into the existing installation. To run the project, please extract it to the following location:

C:\LEADTOOLS 19\Examples\posts\t12246

Note: If you have changed the default installation location, you will need to update the output path to one of the following:

[LEADTOOLS 19]\Bin\Dotnet4\Win32
[LEADTOOLS 19]\Bin\Dotnet4\x64

The project uses a global instance of the callback implementation:

Code:

Private lmvMyUserCallBk As New CallbackFilterClass()
Private lmvMyCallBk As LMVCallbackLib.ILMVCallback

It sets some defaults in the main form load event:

Code:

lmvMyUserCallBk.codecsEngine = codecs
lmvMyUserCallBk.imageCounter = 1
lmvMyUserCallBk.SaveDirectory = txtSaveDirectory.Text

And then adds the callback filter to the PlayCtrl like this:

Code:

   Private Function insertCallbackFilter() As Boolean
      Dim success As Boolean = False
      Dim nIndex As Integer = -1
      Try
         _playctrl.SelectedVideoProcessors.Add(_playctrl.VideoProcessors.Callback)

         lmvMyCallBk = DirectCast(_playctrl.GetSubObject(PlayObject.SelVideoProcessor), LMVCallbackLib.LMVCallback)

         If lmvMyCallBk IsNot Nothing Then
            lmvMyCallBk.ReceiveProcObj = lmvMyUserCallBk
         End If

         success = True
      Catch addFilterException As Exception
         MessageBox.Show("An error has occured in adding the filter" & vbLf & vbLf & addFilterException.Message)
      End Try

      Return success
   End Function

The basic ILMVUserCallback filter implementation looks like this:

Code:

Friend Class CallbackFilterClass
   Implements ILMVUserCallback

   Public Sub ReceiveProc(ByVal pData As Integer, ByVal lWidth As Integer, ByVal lHeight As Integer, ByVal lBitCount As Integer, ByVal lSize As Integer, ByVal bTopDown As Integer) Implements LMVCallbackLib.ILMVUserCallback.ReceiveProc
   End Sub
End Class

A similar example using C# with the CaptureCtrl can be found here:
HOW TO: Capture to MPEG2 with Video Callback Filter for Stills

File Attachment(s):

VB.NET_PlayerCallback.zip (19kb) downloaded 203 time(s).

Walter Bates
Senior Support Engineer
LEAD Technologies, Inc.


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HOW TO: Capture frames with PlayCtrl using LEAD Video Callback in VB.NET