image slower than sound!!!!

As you can see at the topic title i am having problems with my real player[10].although not something too serious...but wouldn’t you get upset if you were watching a video file and than all of a sudden the image doesn’t keep up with the sound or worst it freezes for a couple of seconds!i heard that i could luck a video codec.COULD YOU PLEASE HELP ME??????p.s.i’m a newbie so i wouldn’t mind a few extra details