https://bugs.freedesktop.org/show_bug.cgi?id=89987
James Le Cuirot chewi@gentoo.org changed:
What |Removed |Added ---------------------------------------------------------------------------- Status|NEW |RESOLVED Resolution|--- |NOTOURBUG
--- Comment #9 from James Le Cuirot chewi@gentoo.org --- Sincere apologies for this but it looks like this is actually a bug in VLC. Several factors threw me off, namely that mplayer isn't playing ball either (don't know why yet), that I upgraded the kernel around the same time, that UVD was introduced in 3.18, and the error in dmesg, all of which made it look like a kernel problem.
Doesn't that mean it would have still been broken when going back to 3.17? Actually it kinda was but not nearly as badly so I guess I didn't notice when filing this bug. Under that kernel version, it looks as though it drops every other frame in a smooth manner. Under recent kernels, it barely moves at all. I started downgrading various userspace components like libvdpau, Mesa, and xf86-video-ati to see whether any of those made a difference but it wasn't until I downgraded VLC from 2.2 to 2.1 that the problem went away, both under 3.17 and 4.1. I also tried VLC git master under 4.1 and strangely it behaves like 2.2 does under 3.17, dropping every other frame. Very confusing.
I am now bisecting to track down the precise cause.