This should solve at least one of the pause race condition.

Pause can be toggled until every single ClipWorkflow of every single TrackWorkflow has been paused.

src/Workflow/ClipWorkflow.cpp

@@ -188,14 +188,14 @@ void    ClipWorkflow::pauseAfterPlaybackStarted()
     disconnect( m_mediaPlayer, SIGNAL( positionChanged() ), this, SLOT( pauseAfterPlaybackStarted() ) );
     disconnect( m_mediaPlayer, SIGNAL( playing() ), this, SLOT( pauseAfterPlaybackStarted() ) );
 
-    connect( m_mediaPlayer, SIGNAL( paused() ), this, SLOT( pausedMediaPlayer() ), Qt::DirectConnection );
+    connect( m_mediaPlayer, SIGNAL( paused() ), this, SLOT( initializedMediaPlayer() ), Qt::DirectConnection );
     m_mediaPlayer->pause();
 
 }
 
-void    ClipWorkflow::pausedMediaPlayer()
+void    ClipWorkflow::initializedMediaPlayer()
 {
-    disconnect( m_mediaPlayer, SIGNAL( paused() ), this, SLOT( pausedMediaPlayer() ) );
+    disconnect( m_mediaPlayer, SIGNAL( paused() ), this, SLOT( initializedMediaPlayer() ) );
     setState( Ready );
 }
 
@@ -373,3 +373,8 @@ QMutex*     ClipWorkflow::getSleepMutex()
 {
     return m_condMutex;
 }
+
+LibVLCpp::MediaPlayer*       ClipWorkflow::getMediaPlayer()
+{
+    return m_mediaPlayer;
+}

src/Workflow/ClipWorkflow.h

@@ -45,15 +45,15 @@ class   ClipWorkflow : public QObject
         enum        State
         {
             None = -1,
-            Stopped,
-            Initializing,
-            Ready,
-            Rendering,
-            Sleeping,
-            Pausing,
-            Paused,
-            Stopping,
-            EndReached,
+            Stopped,        //0
+            Initializing,   //1
+            Ready,          //2
+            Rendering,      //3
+            Sleeping,       //4
+            Pausing,        //5
+            Paused,         //6
+            Stopping,       //7
+            EndReached,     //8
         };
        int                     debugId;
 
@@ -154,6 +154,8 @@ class   ClipWorkflow : public QObject
         void                    waitForPausingState();
         QMutex*                 getSleepMutex();
 
+        LibVLCpp::MediaPlayer*  getMediaPlayer();
+
 //        void                    activateOneFrameOnly();
 
     private:
@@ -206,7 +208,7 @@ class   ClipWorkflow : public QObject
 
     private slots:
         void                    pauseAfterPlaybackStarted();
-        void                    pausedMediaPlayer();
+        void                    initializedMediaPlayer();
         void                    setPositionAfterPlayback();
 
     public slots:

src/Workflow/MainWorkflow.cpp

@@ -45,6 +45,7 @@ MainWorkflow::MainWorkflow( int trackCount ) :
     {
         m_tracks[i].setPtr( new TrackWorkflow( i ) );
         connect( m_tracks[i], SIGNAL( trackEndReached( unsigned int ) ), this, SLOT( trackEndReached(unsigned int) ) );
+        connect( m_tracks[i], SIGNAL( trackPaused() ), this, SLOT( trackPaused() ) );
     }
     m_renderStartedLock = new QReadWriteLock;
     m_renderMutex = new QMutex;
@@ -127,10 +128,14 @@ void        MainWorkflow::pause()
     QMutexLocker    lock( m_renderMutex );
 
     qDebug() << "Pausing.......................";
+    m_nbTracksToPause = 0;
     for ( unsigned int i = 0; i < m_trackCount; ++i )
     {
         if ( m_tracks[i].activated() == true )
+        {
+            m_nbTracksToPause.fetchAndAddAcquire( 1 );
             m_tracks[i]->pause();
+        }
     }
     qDebug() << "Pausing completed <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<\n\n";
 }
@@ -249,3 +254,13 @@ void        MainWorkflow::activateOneFrameOnly()
             m_tracks[i]->activateOneFrameOnly();
     }
 }
+
+void        MainWorkflow::trackPaused()
+{
+    m_nbTracksToPause.fetchAndAddAcquire( -1 );
+    if ( m_nbTracksToPause == 0 )
+    {
+        emit mainWorkflowPaused();
+        qDebug() << "Emitted mainworkflow paused";
+    }
+}

src/Workflow/MainWorkflow.h

@@ -98,12 +98,14 @@ class   MainWorkflow : public QObject, public Singleton<MainWorkflow>
         QReadWriteLock*                 m_renderStartedLock;
 
         QMutex*                         m_renderMutex;
+        QAtomicInt                      m_nbTracksToPause;
 
     public slots:
         void                            clipMoved( QUuid, int, int, qint64 );
 
     private slots:
         void                            trackEndReached( unsigned int trackId );
+        void                            trackPaused();
 
     signals:
         /**
@@ -116,6 +118,7 @@ class   MainWorkflow : public QObject, public Singleton<MainWorkflow>
         void                    positionChanged( float pos );
 
         void                    mainWorkflowEndReached();
+        void                    mainWorkflowPaused();
 };
 
 #endif // MAINWORKFLOW_H

src/Workflow/TrackWorkflow.cpp

@@ -342,9 +342,13 @@ void            TrackWorkflow::pauseClipWorkflow( ClipWorkflow* cw )
          cw->getState() == ClipWorkflow::EndReached )
     {
         qDebug() << "Pausing a sleeping, ready or EndReached ClipWorkflow, state =" << cw->getState();
+        qDebug() << "getting condwait lock";
+        cw->getSleepMutex()->lock();
         cw->queryStateChange( ClipWorkflow::Pausing );
-        qDebug() << "Unlocked state mutex";
         cw->getStateLock()->unlock();
+        qDebug() << "Unlocked state mutex";
+        qDebug() << "Realeasing condwait lock";
+        cw->getSleepMutex()->unlock();
         cw->wake();
     }
     else if ( cw->getState() == ClipWorkflow::Rendering )
@@ -388,6 +392,7 @@ void                TrackWorkflow::pause()
 
     //FIXME: it's probably bad to iterate over every clip workflows.
     qDebug() << "Started track pause loop";
+    m_nbClipToPause = 0;
     for ( ; it != end; ++it )
     {
         ClipWorkflow*   cw = it.value();
@@ -401,6 +406,8 @@ void                TrackWorkflow::pause()
         if ( cw->getState() != ClipWorkflow::Paused )
         {
             cw->getStateLock()->unlock();
+            m_nbClipToPause.fetchAndAddAcquire( 1 );
+            connect( cw->getMediaPlayer(), SIGNAL( paused() ), this, SLOT( clipWorkflowPaused() ) );
             pauseClipWorkflow( cw );
         }
         else
@@ -467,3 +474,13 @@ void        TrackWorkflow::activateOneFrameOnly()
 {
     m_oneFrameOnly = 1;
 }
+
+void        TrackWorkflow::clipWorkflowPaused()
+{
+    m_nbClipToPause.fetchAndAddAcquire( -1 );
+    if ( m_nbClipToPause == 0 )
+    {
+        emit trackPaused();
+        qDebug() << "Emitted track paused";
+    }
+}

src/Workflow/TrackWorkflow.h

@@ -94,8 +94,14 @@ class   TrackWorkflow : public QObject
         bool                                    m_paused;
 
         QAtomicInt                              m_oneFrameOnly;
+        QAtomicInt                              m_nbClipToPause;
+
+    private slots:
+        void                                    clipWorkflowPaused();
+
     signals:
-        void            trackEndReached( unsigned int );
+        void                                    trackEndReached( unsigned int );
+        void                                    trackPaused();
 };
 
 #endif // TRACKWORKFLOW_H

src/renderer/WorkflowRenderer.cpp

@@ -149,6 +149,7 @@ void        WorkflowRenderer::startPreview()
 
     connect( m_mainWorkflow, SIGNAL( frameChanged(qint64) ),
              Timeline::getInstance()->tracksView()->tracksCursor(), SLOT( updateCursorPos( qint64 ) ) );
+    connect( m_mainWorkflow, SIGNAL( mainWorkflowPaused() ), this, SLOT( mainWorkflowPaused() ) );
     m_mainWorkflow->startRender();
     sprintf( buff, ":fake-duration=%lli", m_mainWorkflow->getLength() / FPS * 1000 );
     m_media->addOption( buff );
@@ -186,7 +187,12 @@ void        WorkflowRenderer::pauseMainWorkflow()
 {
     qDebug() << "In pause callback";
     m_mainWorkflow->pause();
+}
+
+void        WorkflowRenderer::mainWorkflowPaused()
+{
     m_paused = true;
+    emit paused();
 }
 
 void        WorkflowRenderer::togglePlayPause( bool forcePause )
@@ -252,7 +258,6 @@ void        WorkflowRenderer::__videoPaused()
         m_oneFrameOnly = 0;
     }
     pauseMainWorkflow();
-    emit paused();
 }
 
 void        WorkflowRenderer::__videoPlaying()

src/renderer/WorkflowRenderer.h

@@ -79,6 +79,8 @@ class   WorkflowRenderer : public GenericRenderer
         QReadWriteLock*     m_actionsLock;
 
     public slots:
+        void                mainWorkflowPaused();
+
         void                __positionChanged();
         void                __positionChanged( float pos );
         void                __videoPaused();