How can I view an .mp4 video on my MacPro?
Use vlc player is probably the easiest way.
Maybe if you install Perian (which I recommend you install anyway) you could play them in quicktime but I never tried since I think vlc is a superior player to quicktime player.
MPEG-4 video files should be natively supported by Quicktime Player. If Quicktime gives you a codec error, you can try installing Perian (which adds more codecs to Quicktime) or VLC (a standalone video player)
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