Unable to use WaitForCompletion() in #include <dshow.h> - c++

Question

I am using Qt patch in visual studio 2008. I am trying to run a video using #include <dshow.h>. I can run video successfully, but on using WaitForCompletion() my video gets hang. here is my code:-
MediaPlayer = new Media(ui.stackedWidget->currentWidget());
connect(ui.stackedWidget->currentWidget(), SIGNAL(videograph()), MediaPlayer,SLOT(HandleGraphEvent()));
MediaPlayer->pMediaControl->Run();
long evCode;
MediaPlayer->g_pEvent1->WaitForCompletion(INFINITE,&evCode);
My header file:-
Media.cpp
#include <dshow.h>
#include <commctrl.h>
#include <commdlg.h>
#include <stdio.h>
#include <tchar.h>
//#include <atlbase.h>
#include "Media.h"
#include <qtconcurrentrun.h>
Media::Media(QWidget *parent)
{
HRESULT hr;
CoInitialize(NULL);
hr = CoCreateInstance(CLSID_VideoMixingRenderer, NULL, CLSCTX_INPROC, IID_IBaseFilter, (void**)&pVmr);
hr = pVmr->QueryInterface(IID_IVMRFilterConfig, (void**)&pWc);
hr = pWc->SetNumberOfStreams(2);
hr = pVmr->QueryInterface(IID_IVMRMixerBitmap,(void **)&pBitMAp);
if(SUCCEEDED(hr))
{
hr = pWc->SetRenderingMode(VMRMode_Windowless);
hr = pWc->SetRenderingPrefs( RenderPrefs_ForceOffscreen| RenderPrefs_AllowOffscreen );
pWc->Release();
}
if(SUCCEEDED(hr))
{
hr = pVmr->QueryInterface(IID_IVMRWindowlessControl, (void**)&pWl);
if(SUCCEEDED(hr))
hr = pWl->SetVideoClippingWindow(parent->winId());
}
CoCreateInstance(CLSID_FilterGraph, NULL, CLSCTX_INPROC, IID_IGraphBuilder, (void **)&pGraph);
pGraph->QueryInterface(IID_IMediaControl, (void **)&pMediaControl);
pGraph->QueryInterface(IID_IMediaEventEx, (void **)&g_pEvent);
pGraph->QueryInterface(IID_IBasicAudio,(void **)&pAudio);
pGraph->QueryInterface(IID_IMediaSeeking, (void **)&pMediaSeeking );
pGraph->QueryInterface( IID_IMediaPosition, (void **) &pMediaPosition);
hr = pGraph->AddFilter(pVmr, L"Video Mixing Renderer");
g_pEvent->SetNotifyWindow((OAHWND)parent->winId(), WM_GRAPHNOTIFY, 0);
RECT grc;
GetWindowRect(parent->winId(), &grc);
pGraph->RenderFile(L"/FlashDisk/test.mp4", NULL);
long lWidth, lHeight;
hr = pWl->GetNativeVideoSize(&lWidth, &lHeight, NULL, NULL);
if (SUCCEEDED(hr))
{
SetRect(&g_rcSRc, 0, 0, lWidth, lHeight);
GetWindowRect(parent->winId(), &g_rcDest);
SetRect(&g_rcDest, 0, 0, g_rcDest.right, g_rcDest.bottom);
}
video_rendered = 1;
pWl->SetVideoPosition(&g_rcSRc, &g_rcDest);
}
Media::~Media()
{
CleanUp();
}
void Media::HandleGraphEvent()
{
if (g_pEvent == NULL)
return;
long evCode;
LONG_PTR param1, param2;
while (SUCCEEDED(g_pEvent->GetEvent(&evCode, &param1, &param2, 0)))
{
g_pEvent->FreeEventParams(evCode, param1, param2);
switch (evCode)
{
case EC_STATE_CHANGE: //ADDED for state change from pause to play to indiacte video paused.
//SetEvent(sync_event);
return;
case EC_COMPLETE: // Fall through.
CleanUp();
return;
case EC_USERABORT: // Fall through.
case EC_ERRORABORT:
CleanUp();
//media.play_next_file();
return;
}
}
}
/*#######################################################################################
CleanUp
#######################################################################################*/
void Media::CleanUp(void)
{
video_rendered = 0;
g_pEvent->SetNotifyWindow(NULL, 0, 0);
g_pEvent->Release();
g_pEvent = NULL;
pMediaControl->Release();
pAudio->Release();
pGraph->Release();
}
Media.h
#ifndef MEDIA_H
#define MEDIA_H
//#define max(a,b) (((a) > (b)) ? (a) : (b))
//#define min(a,b) (((a) < (b)) ? (a) : (b))
#include <windef.h>
#include <QObject>
#include <QDebug>
#include <QFile>
#include <QMessageBox>
#include <QTimer>
#include <windows.h>
#include <math.h>
#include <stdlib.h>
#include <Phonon>
#include <dshow.h>
#include <commctrl.h>
#include <commdlg.h>
#include <stdio.h>
#include <tchar.h>
//#include <atlbase.h>
#include <qtconcurrentrun.h>
#pragma comment (lib, "strmiids.lib")
#define WM_GRAPHNOTIFY WM_APP + 1
#define WM_AUDIOGRAPHNOTIFY WM_APP + 2
class Media: public QObject
{
Q_OBJECT
public:
Media(QWidget *parent);
~Media();
IMediaControl *pMediaControl;
IMediaEventEx *g_pEvent;
IMediaEvent *g_pEvent1;
IVideoWindow *pVidWin;
IVMRMixerBitmap *pBitMAp;
IVMRMixerBitmap *pBitMAp1;
IMediaSeeking *pMediaSeeking;
IMediaPosition *pMediaPosition;
IVMRFilterConfig *pWc;
IBaseFilter *pVmr;
IVMRWindowlessControl *pWl;
RECT g_rcSRc;
RECT g_rcDest;
IBasicAudio *pAudio;
IVMRMixerControl *pVmc;
IGraphBuilder *pGraph;
DWORD width;
unsigned char video_rendered;
void CleanUp(void);
public slots:
void HandleGraphEvent(void);
};
#endif
Please suggest me what i am missing here.

Answer 1

On a COM STA thread you are responsible to dispatch window messages and WaitForCompletion is a blocking call without a promise to implement message loop.
See DShow Sample Code for playing video does not play the video
An easy way to find out if #2 is the problem is placing MessageBox call between Run and WaitForCompletion. MessageBox dispatches messages for you and as long as you keep the box open, video plays as well (or start playing well and keeps playing even after you close the box). Proper solution is to wait and displach messages in the same time (WaitDispatchingMessages, this SO question or similar).
This applies to your case as well, change to finite timeout, dispatch messages and get back to another wait attempt.