Revert rev. ddcfc435 and 307be698 to fix a regression in the QT4L plugin (fixes #233).

plugins/filmQT4L/filmQT4L.cpp

@@ -103,7 +103,7 @@ bool filmQT4L :: open(const std::string&filename,
     // Get the number of tracks
     m_numTracks = quicktime_video_tracks(m_quickfile);
     // Get the length of the movie (on track current track)
-    m_numFrames = quicktime_video_length(m_quickfile, m_curTrack);
+    m_numFrames = quicktime_video_length(m_quickfile, m_curTrack) - 1;
     // Get the frame-rate
     m_fps = quicktime_frame_rate(m_quickfile, m_curTrack);
     // Get the video dimensions
@@ -176,10 +176,10 @@ pixBlock* filmQT4L :: getFrame()
 
 film::errCode filmQT4L :: changeImage(int imgNum, int trackNum)
 {
-  if(trackNum>=0 && trackNum < m_numTracks) {
-    if (m_curTrack != trackNum) {
-      m_numFrames = quicktime_video_length(m_quickfile, trackNum);
-    }
+  if  (imgNum>0) {
+    m_curFrame=imgNum;
+  }
+  if(trackNum>0) {
     m_curTrack=trackNum;
   }
   if(imgNum>=m_numFrames || imgNum<0) {