Mohammed Atta video emerges with no sound?

Intelligence sources this week released video of 9/11 terrorist Mohammed Atta, in what was described by authorities as a "martyrdom" video. Made 18 months prior to 9/11, the video had been in intelligence possession since 2002. In a strange (but increasingly familiar) twist, the video lacked sound.

Osama Bin Laden can't find a camcorder. These guys have a broken camcorder. Too bad they can't pool their collective technology.

With no audio, how do we know it's a martyrdom video? Looks like two guys sitting around having a good time.