I found a way to reproduce this on my i7-4790K. Unfortunately it involves the fluvadec GStreamer plugin which is not free software.
Still this is a case of an unprivileged process causing the kernel to crash, freezes the X server and prevents restarting it so it does prove there is a serious bug. Let me know if there is information I can provide. -- Francois Gouget <fgou...@codeweavers.com>