[mythtv-users] i915 IvyBridge issues with DRM playback

[Steve Magnani]

Hi,

I am running 0.27 built from the GIT source, on a laptop with one of the
IvyBridge i915 variants (PCI ID 0x0166). This is a remote frontend
running Fedora 18.

Until a few weeks ago, playback of recorded TV was fine, except that the
very first recording I attempted to play would grind horribly (extremely
jerky and not at all viewable). If I <ESC>d out of this mode, subsequent
playbacks would be fine. 

This was with Fedora kernel 3.9.6-200.fc18.x86_64.

Then Fedora released a kernel upgrade, to 3.10.10-100. In this new,
improved world, playback seems to run at the same speed whether it's the
first attempt or not. Unfortunately, the speed seems to be something
like 5x normal. Video is fast, and audio is only disjointed snatches of
sound at what appears to be normal speed (not "chipmunk-y"). 

I did some investigation and discovered that under the 3.9.6 kernel, the
first (grinding) playback would use DRM video timing, and subsequent
playbacks would use usleep. Under 3.10, playback always seems to use DRM
timing. And, there are lots of messages about "doubling video frame
interval to slow down" - except that playback never seems to slow down.
The reported frame rate is in the 140 - 208 ballpark, so it seems
mythfrontend is well aware it is speeding...only its brakes don't seem
to work.

If I recompile libmythtv to disable DRM timing as an option, playback is
fine.

Unfortunately, the i915 driver seems to be under heavy development, so
there's not a "smoking gun" that's obvious to me by diffing the source
for the two driver versions. 

I can run my home-built version of mythfrontend, so this is not
something that needs an immediate fix, but I am wondering whether there
is anything mythfrontend should be doing differently, or whether to try
my luck reporting a bug to the kernel driver developers. Any advice?

Thanks,
------------------------------------------------------------------------
Steven J. Magnani               "I claim this network for MARS!
www.digidescorp.com              Earthling, return my space modulator!"

#include <standard.disclaimer>