New preset transcoding breaks for some tmp-file paths

Okay, this issue is a bit weird.

Story time
I was working on a preset good for Android devices, so I checked how I could include an external preset in Video module without hacking it. It checks all modules for a video_preset folder. Fine I'll make my own module.
On my test-site everything worked well. On my project dev site it instantly died as it was converting. First I looked for video issues. Then I noticed at the bottom of the error detail:
sites/default/files/tmp/20100219_011.mp4

That site doesn't use standard /tmp for temporary files, in fact it uses the usually perfectly working sites/default/files/tmp
I imagine that the Video module simply isn't deeply tested with externally provided presets (from other modules) and that it is the different locations and all that causes havoc when using a relative temp path.

I attach my module for testing. The preset might be interesting for other's looking for Android-support with Baseline Profile H.264. I've copied it from a Ubuntu Tutorial that seemed sane and it works on my high end devices. Still untested for some devices that have had problems in the past.