Now this is a problem which i was facing for a long time in both Ubuntu and Mandriva. I wasnt able to play .mp4 format files . Now i have a solution and i am sharing it with you. I stumbled upon this simple solution in http://ubuntuforums.org and the solution was posted by Fabián Rodríguez , whom i appreciate for his different thinking . Now to the solution…
Just convert the .mp4 file into a .ogv file and you will be able to play it in any video player in Linux. 🙂
The conversion can be done by installing ffmpeg2theora and using the following syntax in Terminal.
$ ffmpeg2theora filename.mp4
the output is a clone of filename.mp4 but with a .ogv extension (say filename.ogv). That video file is playable in a ll video players.
It took me 3 mins (approx) for converting a 18MB .mp4 video file and the video/audio quality didnt get affected in any way.