https://bugs.freedesktop.org/show_bug.cgi?id=85613
--- Comment #8 from Andreas Boll andreas.boll.dev@gmail.com --- It seems Arthur is using shader-based decoding instead of UVD based decoding, which is less tested nowadays.
@Arthur: UVD based decoding for your card is available with linux kernel >= 3.18-rc1 and the corresponding UVD firmware [1].
[1] http://people.freedesktop.org/~agd5f/radeon_ucode/R600_uvd.bin