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IMediaEvent.GetEventHandle

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Microsoft DirectShow 9.0

IMediaEvent.GetEventHandle

  • Note   This topic is deprecated. It applies to Visual Basic 6.0. DirectShow is not supported for Visual Basic .NET or C#.

The GetEventHandle method retrieves a handle to a manual-reset event that remains signaled while the queue contains event notifications.

Syntax

  objMediaEvent
  .GetEventHandle(
    ByRef 
  hEvent As 
  Long)

Parameters

hEvent

Variable that receives the event handle.

Return Values

This method does not return a value.

Remarks

The Filter Graph Manager keeps a manual-reset event that reflects the state of the event queue. If the queue contains event notifications, the manual-reset event is signaled. If the queue is empty, the IMediaEvent.GetEvent method resets the event. An application can use this event to determine the state of the queue.

To use this event in Visual Basic, your application must call into a Microsoft® Windows® function such as WaitForSingleObject or WaitForMultipleObjects. You must declare the function in a module, as shown in the example code. However, it might be easier in Visual Basic simply to create a timer and periodically call GetEvent.

Example Code

First declare the WaitForSingleObject and GetEvent methods in a module, as follows:

Public Const WAIT_ABANDONED& = &H80&
Public Const WAIT_OBJECT_0& = 0
Public Const WAIT_OBJECT_1& = 1
Public Const WAIT_TIMEOUT& = &H102&
Public Const INFINITE = &HFFFF
Public Declare Function WaitForSingleObject Lib "kernel32"  _
         (ByVal hHandle As Long, ByVal dwMilliseconds As Long) As Long
Declare Function CreateEvent _
          Lib "kernel32" _
          Alias "CreateEventA" _
          (lpEventAttributes As Long, _
          ByVal bManualReset As Long, _
          ByVal bInitialState As Long, _
          ByVal lpName As String) As Long

Then call GetEventHandle to retrieve the event handle, and use the WaitForSingleObject method to wait for the event to be signaled:

Dim hEvent As Long, wait_result As Long
Dim EvCode As Long, Param1 As Long, Param2 As Long

mEvent.GetEventHandle hEvent

wait_result = WaitForSingleObject(hEvent, 1000)
If wait_result = WAIT_OBJECT_0 Then
    On Error Resume Next
    Do
        mEvent.GetEvent EvCode, Param1, Param2, 0
        If Err.Number = 0 Then
            ' Handle event. (Not shown.)
            mEvent.FreeEventParams EvCode, Param1, Param2
    Loop While Err.Number = 0
End If
Err.Clear

Requirements

Reference: Add a reference to ActiveMovie control type library.

Library: Quartz.dll.

See Also