Waiting for the end of media

Waiting for an end

You can use WaitForCompletion in IMediaEvent, to wait for the media file to end. WaitForCompletion is a blocking method. The first argument of WaitForCompletion is a timeout value. For example, if you put "2" as the first argument, WaitForCompetion will block for maximum of 2 seconds. If you use "-1" as the first argument, WaitForCompletion will wait forever until the playback reaches an end.

Sample code

The following sample code shows how to use WaitForCompletion.

#include <stdio.h>

#include <dshow.h>

// change here
#define	FILENAME L"c:\\DXSDK\\Samples\\Media\\butterfly.mpg"

int
main()
{
 IGraphBuilder *pGraphBuilder;
 IMediaControl *pMediaControl;
 IMediaEvent *pMediaEvent;
 long eventCode;

 CoInitialize(NULL);

 CoCreateInstance(CLSID_FilterGraph,
	NULL,
	CLSCTX_INPROC,
	IID_IGraphBuilder,
	(LPVOID *)&pGraphBuilder);

 pGraphBuilder->QueryInterface(IID_IMediaControl,
	(LPVOID *)&pMediaControl);

 pGraphBuilder->QueryInterface(IID_IMediaEvent,
	(LPVOID *)&pMediaEvent);

 pMediaControl->RenderFile(FILENAME);

 pMediaControl->Run();

 // The first argument is timeout value.
 // If you change the "-1" part into "2",
 // WaitForCompletion will timeout after 2 seconds.
 pMediaEvent->WaitForCompletion(-1, &eventCode);
 switch (eventCode) {
 case 0:
	printf("timeout\n");
	break;
 case EC_COMPLETE:
	printf("complete\n");
	break;
 case EC_ERRORABORT:
	printf("errorabort\n");
	break;
 case EC_USERABORT:
	printf("userabort\n");
	break;
 }

 pMediaControl->Release();
 pGraphBuilder->Release();
 CoUninitialize();

 return 0;
}

WaitForCompletion is a blocking method. Therefore, if you want to do something else while playing the MPEG file, you would have to create a new thread.

You can also use GetState() in IMediaEvent instead of using WaitForCompletion. You can create a busy loop that lookup the state of the Graph using GetState().

Using a window event to notify the end of playback is another option. This might be the best way if you are using MFC, etc.