Watching an MP4 video on Totem
 

I'm trying to watch an mp4 video on Totem, but get an error "The playback of this movie requires a H.264 decoder plugin which is not installed." I find this strange as I do have libx264 installed and can work with the codec in other programs like Cinelerra.

I'm using Debian Wheezy 64 bit.

Did this not work for you?
http://www.videolan.org/developers/x264.html

Install the needed gstreamer plugins.

i A gstreamer0.10-ffmpeg
i A gstreamer0.10-plugins-bad
i A gstreamer0.10-plugins-base
i A gstreamer0.10-plugins-good
i A gstreamer0.10-plugins-ugly

It would appear the problem was a library conflict. To install either of the options mentioned would have meant the removal of current libraries that I wish to keep. The solution was quite simple though, just boot into any other of the Linux distro's I have installed on this computer, as the all have the required libraries in the right places to play the clip on Totem, or VLC, on the distro with that installed.