#0  gst_thumbnailer_play_start (cancellable=0x7f04a0006b30, play=0x0) at gst-thumbnailer.c:461
  456:     {
  457:       message = gst_bus_timed_pop_filtered (bus,
  458:                                             GST_CLOCK_TIME_NONE,
  459:                                             GST_MESSAGE_ASYNC_DONE | GST_MESSAGE_ERROR);
  460: 
  461:       switch (GST_MESSAGE_TYPE (message))
  462:         {
  463:         case GST_MESSAGE_ASYNC_DONE:
  464:           if (GST_MESSAGE_SRC (message) == GST_OBJECT (play))
  465:             {
  466:               async_received = TRUE;
#1  gst_thumbnailer_create (thumbnailer=0x7f04ae733de0, cancellable=0x7f04a0006b30, info=0x7f04ae7e3a80) at gst-thumbnailer.c:581
  576:   tumbler_thumbnail_flavor_get_size (flavor, &width, &height);
  577: 
  578:   /* prepare factory */
  579:   play = gst_thumbnailer_play_init (info);
  580: 
  581:   if (gst_thumbnailer_play_start (play, cancellable))
  582:     {
  583:       /* check for covers in the file */
  584:       pixbuf = gst_thumbnailer_cover (play, cancellable);
  585: 
  586:       /* extract cover from video stream */
#2  0x00007f04ae15b59c in tumbler_lifo_scheduler_thread (data=0x7f04ae7e3cd0, user_data=0x7f04a00050c0) at tumbler-lifo-scheduler.c:495
  490:       g_signal_connect (request->thumbnailers[n], "ready",
  491:                         G_CALLBACK (tumbler_lifo_scheduler_thumbnailer_ready),
  492:                         request);
  493: 
  494:       /* tell the thumbnailer to generate the thumbnail */
  495:       tumbler_thumbnailer_create (request->thumbnailers[n], 
  496:                                   request->cancellables[n],
  497:                                   request->infos[n]);
  498: 
  499:       /* disconnect from all signals when we're finished */
  500:       g_signal_handlers_disconnect_matched (request->thumbnailers[n],
#3  0x00007f04ad069a12 in g_thread_pool_new (func=<optimized out>, user_data=<optimized out>, max_threads=<optimized out>, exclusive=<optimized out>, error=<optimized out>) at /build/buildd/glib2.0-2.36.0/./glib/gthreadpool.c:513
  [Error: /build/buildd/glib2.0-2.36.0/./glib/gthreadpool.c was not found in source tree]
#4  0x00007f04acde6f8e in start_thread (arg=0x7f04a5614700) at pthread_create.c:311
  [Error: pthread_create.c was not found in source tree]
#5  0x00007f04acb10e1d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:113
  [Error: ../sysdeps/unix/sysv/linux/x86_64/clone.S was not found in source tree]