Utility or method for joining MP4 files I have two MP4 files that I generated with Camtasia Studio. I need to join them together post rendering with Camtasia (it can't be done during the Camtasia rendering process). Looking for a utility or technique that will work to join these, preferably that doesn't require re-rendering all the video again.

Update: Either Windows (preferred) or Mac. Doesn't need a GUI if it is a good command-line app.
I think the simplest way to this is to use MP4Box.

./MP4Box -add file1.mp4 -cat file2.mp4 -cat file3.mp4 output.mp4