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This question seems poor but i really facing this problem (I am new to ubuntu). I install Ubuntu 12.04 on my HP laptop. I also upgraded all its packages using sudo apt-get update && sudo apt-get upgrade. But when I play any video file through media player (default and smplayer), i can only hear audio but no video is seen, screen becomes blanks. All types of video file can be played but only audio can be heard, no video.