Are the following packages installed?: ffmpeg x264 libx264-dev
I originally thought "How can I tell? Is there a shell command I can use?" Then I remembered Synaptic and searched for x264 and libx264-dev in there. Neither were installed. However, after installing both and rebooting, mplayer still will not play these H.264/AVC Videos. If I try playing them from the Shell, I get screens of error messages, most of them telling me I don't have the codec for it...
You refer to ffmpeg - is this mplayer by another name?