Not really. It is true for watching files on the computer, but the ATV has a much more restrictive list of files and codecs it supports. On a stock (not hacked) ATV, you can't simply install Perian, for example, to play more codecs.
To the OP, as you now know, just because a file plays in QT or iTunes on your computer does not mean it will play on your ATV. Are you trying to watch a DVD that you ripped, or a file you got from somewhere else? If it's the former, then it is likely that it's a framerate issue. Re-encode the movie in HandBrake, but this time manually select the proper framerate (don't leave it as "same as source").
If the latter, give HandBrake a try again, but this time go into audio and set the second audio track (I assume you are using the ATV preset?) to "none." I've had similar problems in the past, and that usually clears it up.
Right click on the file in iTunes and choose "Create Apple TV Version". It might take a while depending the size of the video. Once complete you should be able to sync this video onto your Apple TV or stream it.
Right click on the file in iTunes and choose "Create Apple TV Version". It might take a while depending the size of the video. Once complete you should be able to sync this video onto your Apple TV or stream it.
Not really. It is true for watching files on the computer, but the ATV has a much more restrictive list of files and codecs it supports. On a stock (not hacked) ATV, you can't simply install Perian, for example, to play more codecs.