mpeg2 files are not good for doing media servers.
mpeg2 support comes from the os.

there is no random frame access and looping playback control is very poor.

the other media servers are using mpeg2 but only with all i-frames. so you have to reencode anyway.

dv is much better for doing this kindof thing.
and its much more compatible with the production workflow - and is still editable.
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my suggestion for safe crashing - if that is a major concern... -always has to be something that completely stops the output from the computer - or divert it?
no software device will help here.
How about a black flap over the projector?
Or you could control the shutter of the projector?