Seeking and getting the position snippets for DirectShow.NET

Introduction

Did you ever want to seek through your DirectShow movie? Or get the current position of your movie and want to show that using your trackbar?

Background

Please read the related articles here:

• CodeProject -> DirectShow examples
• Convert C# to VB.NET and back
• Informikon -> DirectShow
• MSDN forum DirectShow
• MSDN newsgroup DirectX Video
• Sourceforge Directshow.Net Forum
• The March Hare-> DirectShow
• TheZBuffer -> DirectShow + Direct3D

Using the code

When you have created your graph like this:

f_MediaPositioning = CType(f_GraphManager, IMediaSeeking) '(f_graphmanager is the base) 
Public Event Movie_Playhead_Moved(ByVal frame as long, duration as long)
Public Sub Graph_Seek(ByVal frame As Long)
    If FilterGraphState = FilterGraphStateEnum.Ready Then
        Try
            Dim hr As Integer
            Dim duration As Long
            hr = f_MediaPositioning.GetDuration(duration) : DsError.ThrowExceptionForHR(hr)
            hr = f_MediaPositioning.SetPositions(frame, _
                    AMSeekingSeekingFlags.AbsolutePositioning, _
                    duration, AMSeekingSeekingFlags.AbsolutePositioning)
            RaiseEvent Movie_Playhead_Moved(frame , duration)
            DsError.ThrowExceptionForHR(hr)
        Catch ex As Exception
            ThrowError("error sub graph_seek : ", ex)
            'throwerror is my custom messagehandler
        End Try
    Else
        ThrowError("not ready to do seeking")
    End If
End Sub

Private Sub HeANewPlayheadEvent(byval frame as long, _
            byval duration as long) handles me.Movie_Playhead_Moved
    Invoke_trackbar_playhead_update(frame, duration)
End Sub

Public Sub Invoke_trackbar_playhead_update(ByVal frame as long, duration as long)
    If Me.TrackbarPlayhead.InvokeRequired Then
        Dim del As New Delegate_Trackbar_Playhead_Update(_
                       AddressOf Process_Trackbar_playhead_update)
        del.Invoke(frame,duration)
    Else
        Process_Trackbar_playhead_update(frame,duration)
    End If
End Sub

Private Sub Process_Trackbar_playhead_update(ByVal frame As long, ByVal duration As long)
    If TrackbarPlayhead.Value <> frame Then
        TrackbarPlayhead.Maximum = Cint(duration / 1000)
        TrackbarPlayhead.Value = CInt(frame / 1000)
        TrackbarPlayhead.TickFrequency = CInt(duration / 10)
        TrackbarPlayhead.Update()
        Application.DoEvents()
    End If
End Sub

you can have a separate sub that is called by a timer (whenever your graph is loaded and is in play/pause mode):

Dim hr As Integer:Dim frame As Long
hr = f_MediaPositioning.GetCurrentPosition(frame) : DsError.ThrowExceptionForHR(hr)
hr = f_MediaPositioning.GetDuration(duration) : DsError.ThrowExceptionForHR(hr)
Invoke_trackbar_playhead_update(frame, duration)     

You can use the IMediaSeeking interface to control the rate of your movie.

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