When watching movies with totem, I often noticed a small delay between the video and the sound. I'm not 100% sure but it seems to occur only when watching video with AC-3 audio.

For example I got this problem with an avi file containing a XVID MPEG-4 25 fps video and AC-3 surround 5.1 audio. Totem was also displaying an external .srt subtitle file.
I also noticed this problem with AC-3 stereo files.

I'm using Ubuntu Hardy with the following packages:
root@cass-wks:~# dpkg -l | grep gstreamer
ii  gstreamer-tools                            0.10.18-4ubuntu1                                   Tools for use with GStreamer
ii  gstreamer0.10-alsa                         0.10.18-3                                          GStreamer plugin for ALSA
ii  gstreamer0.10-ffmpeg                       0.10.3-6                                           FFmpeg plugin for GStreamer
ii  gstreamer0.10-gnomevfs                     0.10.18-3                                          GStreamer plugin for GnomeVFS
ii  gstreamer0.10-pitfdll                      0.9.1.1+cvs20080215-1                              GStreamer plugin for using MS Windows binary
ii  gstreamer0.10-plugins-base                 0.10.18-3                                          GStreamer plugins from the "base" set
ii  gstreamer0.10-plugins-base-apps            0.10.18-3                                          GStreamer helper programs from the "base" se
ii  gstreamer0.10-plugins-farsight             0.12.7-1~ppa8.04+1                                 plugins for GStreamer for Audio/Video confer
ii  gstreamer0.10-plugins-good                 0.10.8-2~ppa8.04+1                                 GStreamer plugins from the "good" set
ii  gstreamer0.10-plugins-ugly                 0.10.7-3                                           GStreamer plugins from the "ugly" set
ii  gstreamer0.10-plugins-ugly-multiverse      0.10.7-1                                           GStreamer plugins from the "ugly" set (Multi
ii  gstreamer0.10-pulseaudio                   0.9.7-2                                            GStreamer plugin for PulseAudio
ii  gstreamer0.10-tools                        0.10.18-4ubuntu1                                   Tools for use with GStreamer
ii  gstreamer0.10-x                            0.10.18-3                                          GStreamer plugins for X11 and Pango
ii  libgstreamer-plugins-base0.10-0            0.10.18-3                                          GStreamer libraries from the "base" set
ii  libgstreamer-plugins-base0.10-dev          0.10.18-3                                          GStreamer development files for libraries fr
ii  libgstreamer0.10-0                         0.10.18-4ubuntu1                                   Core GStreamer libraries and elements
ii  libgstreamer0.10-dev                       0.10.18-4ubuntu1                                   GStreamer core development files
ii  totem-gstreamer                            2.22.1-0ubuntu2                                    A simple media player for the Gnome desktop