When attempting to play a video with an ".avi" extension in Totem with the
GStreamer backend, the following series of error dialogs appears:
Totem could not play '<filename>'.
Internal GStreamer error: negotiation problem.  File a bug.
Internal GStreamer error: pad problem.  File a bug.
Could not get/set settings from/on resource.

I had first suspected this was due to a locking problem between Totem/GStreamer
and another application also attempting to access the sound device, however it
seems many DivX/MPEG-4 encoded movies have this problem.  After experimenting
with many files, it seems to only occur when the audio codec is "A/52 5.1".

File properties of one such file (from Nautilus right click menu):
640 x 368
ISO MPEG-4 (DivX5, ffmpeg)
25 frames per second
384 kbps
A/52 5.1

Contents of ALSA configuration file, /etc/asound.conf:
pcm.!default
{
    type plug
    slave.pcm "dmixer"
}
pcm.dmixer
{
    type dmix
    ipc_key 1025
    slave
    {
        pcm "hw:0,0"
        period_time 0
        period_size 4096
        buffer_size 16384
        periods 128
        rate 44100
    }
    bindings
    {
        0 0
        1 1
    }
}