Adding duration for the render preview.

There's still some problems on the workflow rendering if we specify a
length.

src/WorkflowFileRenderer.cpp

@@ -42,6 +42,8 @@ void        WorkflowFileRenderer::run()
     m_media->addOption( buffer );
     m_media->addOption( ":no-audio" );
     m_media->addOption( ":fake" );
+    sprintf(buffer, ":fake-duration=%lli", m_mainWorkflow->getLength() );
+//    m_media->addOption( buffer );
 
     QString     transcodeStr = "sout=#transcode{vcodec=mp4v,vb=800,acodec=mpga,ab=128}"
                                ":standard{access=file,mux=ps,dst=\""

src/gui/RenderPreviewWidget.cpp

@@ -108,9 +108,13 @@ void        RenderPreviewWidget::stopPreview()
 
 void        RenderPreviewWidget::startPreview( Media* )
 {
+    char        buff[128];
+
     connect( m_mainWorkflow, SIGNAL( frameChanged(qint64) ),
              Timeline::getInstance()->tracksView()->tracksCursor(), SLOT( updateCursorPos( qint64 ) ) );
     m_mainWorkflow->startRender();
+    sprintf( buff, ":fake-duration=%lli", m_mainWorkflow->getLength() / FPS * 1000 );
+    m_media->addOption( buff );
     m_mediaPlayer->play();
     m_isRendering = true;
     m_paused = false;