How do you a film a Halo 3 movie in a custom multiplayer game

For either splitscreen, single player, or multiplayer online matches, go into theater mode, click recent videos. Select the one you want to make a "movie" out of.

On theater mode take the scenes put them on a camcorder, after you hook it up to your TV using wires that come with it like RGA cables. Edit them on your computer if you have a MAC Final cut is a GREAT program just expensive OR you can use Windows Movie Maker Free on PCs.

NOTE: if you have an older camera that doesn't hook up to a computer via firewire or USB you cannot make a movie and put it online.

The actual way that people record their matches is with a video capture card.