I have a .mp4 movie (it's an .mp4 file, and the "video codec" is Xvid, and the "audio codec" is mp3) that I want to play, but when I try to open it in MPlayer, it says "The steam is encrypted and decryption is not supported." I tried to apply the answer from this question and this wiki page, but neither worked.

Any suggestions?

The file came from an [apparently] less than reputable site, which I guess I can't link to. :(

I've tried:

sudo apt-get install ubuntu-restricted-extras
sudo apt-get install libdvdread4
sudo /usr/share/doc/libdvdread4/install-css.sh
sudo apt-get install gstreamer0.10-ffmpeg
sudo apt-get install w64codecs
sudo apt-get update