libvlc is unable to stop streaming & causes crash in Qt Application

Question

I am creating a streaming application in QT using libvlc, which will play the RTSP streaming coming from any source. I have created it and it is working fine for me except that whenever i want to close it my application crashes. My code is as below.

ThreadVlc.h

<pre>
#ifndef THREADVLC_H
#define THREADVLC_H
#include <vlc\vlc.h>
#include <vlc\libvlc.h>
#include <QtGui>
#include <QWidget>
#include <QThread>
#include <QApplication>
class vlcOnQtPlayer : public QThread
{
Q_OBJECT
	bool isVideoPlayingCheck;
    libvlc_instance_t *libvlcInstance;
    libvlc_media_player_t *libvlcMediaPlayer;
    libvlc_media_t *libvlcMedia;
	QString rtspLink;
	QMutex mmutex;

public:
    vlcOnQtPlayer(WId parentWinId);
    void stop();
protected:
	void run();

public slots:
	void vlcOnQtSetLink(QString link);
	//void playRtspLink();
	int onVlcStreamCapture(QString imageSavePath);
private:
	WId windowId;
};
#endif

</pre>

ThreadVlc.cpp

<pre>

#include "ThreadVlc.h"
#include <QVBoxLayout>
#include <QPushButton>
#include <QFrame>
#include<iostream>
#include<QMessageBox>
using namespace std;
vlcOnQtPlayer::vlcOnQtPlayer(WId parentWinId) : QThread()
{

	mmutex.lock();
	windowId=parentWinId;
	mmutex.unlock();
	isVideoPlayingCheck=false;
}

void vlcOnQtPlayer::stop()
{
	//QMessageBox::warning(0,"Warning", "before libvlc_media_player_stop");
    libvlc_media_player_stop (libvlcMediaPlayer);
	QMessageBox::warning(0,"Warning", "After libvlc_media_player_stop");
	libvlc_media_player_release (libvlcMediaPlayer);
    libvlc_release (libvlcInstance);
	
}

void vlcOnQtPlayer::run()
{
	if(rtspLink!=NULL)
	{

	const char * const vlc_args[] = { "--no-audio","-vv" };
	libvlcInstance=libvlc_new(sizeof(vlc_args)/sizeof(vlc_args[0]), vlc_args);          
    
     //Create a new LibVLC media descriptor
	libvlcMedia = libvlc_media_new_location(libvlcInstance, rtspLink.toAscii());
    
    libvlcMediaPlayer=libvlc_media_player_new_from_media (libvlcMedia);


    // Get our media instance to use our window 
     libvlc_media_player_set_hwnd(libvlcMediaPlayer, windowId);//vlcOnQtVideoFrame->winId());
    
    // Play 
    libvlc_media_player_play (libvlcMediaPlayer);
	   
    isVideoPlayingCheck=true;   
	//return 0;
	}
	else
		isVideoPlayingCheck=false;
		//return 1;
}

int vlcOnQtPlayer::onVlcStreamCapture(QString imageSavePath)
{
	const char *file_Path=imageSavePath.toLocal8Bit().constData();
	//Function to take the snap shot of the screen
	int i=libvlc_video_take_snapshot(libvlcMediaPlayer,0,file_Path,0,0);
	return i;
}


void vlcOnQtPlayer::vlcOnQtSetLink(QString link) 
{ 
	mmutex.lock();
	rtspLink=link;
	mmutex.unlock();
}



</pre>

ThreadVlcMainWindow.h

<pre>

		
	#ifndef THREADVLCMAINWINDOW_H 
	#define THREADVLCMAINWINDOW_H
	 /* Including necessary classes*/
	 #include <QtGui>
	 #include <QMainWindow> 
	 #include <QApplication>
	 #include <ThreadVlc.h>
	 #include <QThread>
	 #include <QEvent>
	/* Proto type for the Main Window Class*/	
	class streamParentClass : public QMainWindow 
	{ 
		Q_OBJECT 
	public: 
		int count,noOfCam; // Variables for munber of cameras and counter
		streamParentClass(QWidget *parent = 0);
		~streamParentClass();
		QWidget *centralWidgetWindow; //Window to be set as central widget (central widget of main window)
		QGridLayout *streamIfaceLayout;
		QFrame * streamFrame;
		vlcOnQtPlayer * streamPlayerInstance;

		//QList <QPushButton *>btn;
		void guiDesign(); //For basic design of controls
		void addStreamWin(int); // To add vlc instances to main window
		void closeEvent(QCloseEvent *);
	};

#endif



</pre>

ThreadVlcMainWindow.cpp

<pre>

#include "ThreadVlcMainWindow.h" 
	#include <QtGui>
	#include <QToolBar> 
	#include <QIcon> 
	#include <QAction> 
	streamParentClass::streamParentClass(QWidget *parent) : QMainWindow(parent) 
    {
		noOfCam=1;
		guiDesign();     //Initializing controls
		addStreamWin(noOfCam);
	}

	
	streamParentClass::~streamParentClass()
	{
		for(int i=0;i<noOfCam;i++)
		{
			streamPlayerInstance->stop();
			streamIfaceLayout->removeWidget(streamFrame);

		}
		
		qApp->quit();
	}
	void streamParentClass::guiDesign()
	{
		centralWidgetWindow=new QWidget(this);
		streamIfaceLayout=new huffnetInterfaceLayout(centralWidgetWindow,4);
		centralWidgetWindow->setLayout(streamIfaceLayout);
		setCentralWidget(centralWidgetWindow);

	}
	void streamParentClass::addStreamWin(int n)
	{				
			for(int i=0;i<n;i++)
			{   
		    	streamFrame=new QFrame(centralWidgetWindow);
				streamFrame->setWindowFlags(Qt::FramelessWindowHint);
				streamPlayerInstance= new vlcOnQtPlayer(streamFrame->winId());
				streamIfaceLayout->addWidget(streamFrame,0,0);
				connect(streamPlayerInstance,SIGNAL(finished()),streamPlayerInstance,SLOT(deleteLater()));
				streamPlayerInstance->vlcOnQtSetLink("rtsp://:8554/strm");
				streamPlayerInstance->start();
			}
				
	}
	
	
	void streamParentClass::closeEvent(QCloseEvent *event)
		{
			
			for(int i=0;i<noOfCam;i++)
			{
				streamPlayerInstance->stop();//~vlcOnQtPlayer();
				delete streamFrame;
				delete centralWidgetWindow;
			//QMessageBox::warning(0,"Warning", "Inside for ");	
			}	

			qApp->quit();
		}
				 

</pre>

Main.cpp

<pre>

#include "ThreadVlcMainWindow.h"
#include <QApplication>
int main(int argc, char *argv[])
{
	QApplication app(argc,argv);
	streamParentClass mp;
	mp.resize(500,400);
	mp.show();
	return app.exec();
}

</pre>

I am using Qt 4.8 and Microsoft visual studio 2010 to build it. It is streaming fine from server. I am using Vlc Media player to create a streaming server that is streaming a video. But when i try to close this it is crashing down my window. I have checked for several errors & fond that libvlc is unable to process command libvlc_media_player_stop() . Thanks for any suggestions.

Answer 1

Found the mainProblem in the code. The main problem was due to multithreading because multiple threads were unable to communicate while we called libvlc_media_player_stop() in threadVLC.cpp. So we have to forcefully terminate the thread either, or we have to skip threading. libvlc_media_player_stop() is working fine. I have searched about it on the videoLAN forums. https://forum.videolan.org/viewtopic.php?t=106415

Thanks RSATom for suggesting me about Forums.