[mythtv-users] i915 IvyBridge issues with DRM playback

[Stephen Worthington]

On Mon, 23 Sep 2013 21:43:58 -0500, you wrote:

>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,

Have you checked out this page?

  http://www.mythtv.org/wiki/Frame_display_timing