mesa 10.3.2 original debian package without changes and linux 3.18.0-rc5 crashed after a few minutes when playing the video. That is worse than before, it has usually crashed after four to six replays of the video. I'll start testing mesa 10.4.0-devel with rc5 again, probably it was a random fluke that it lasted ten replays, longest this far has been seven replays without the bypassed si_dma_copy_tile().