[mythtv-users] Sandy Bridge Graphics w/MythTV
Michael T. Dean
mtdean at thirdcontact.com
Fri Jul 22 16:54:01 UTC 2011
On 07/22/2011 11:58 AM, jzigpublic wrote:
> I came across the following solution for Sandy Bridge Video Tearing in
> MythTV. The quote was pulled from this site:
> It worked for me with an i3 CPU and an Intel motherboard with Intel
> HD2000 on-board graphics. No more tearing. I'm using MythBuntu 11.04.
>> In order to play 1080i video content on my system running mythbuntu-11.04, I
>> created a new playback profile modeled after the "High Quality" playback
>> profile. The new profile differs in that it uses xshm for the video renderer
>> (as opposed to xv-blit). Please note that xshm says that it cannot scale video
>> in case this a problem for your setup
FWIW, Xshm is a terrible renderer to use for video. It's extremely
inefficient and, as mentioned, has issues such as lack of scaling, etc.
Xv, which is likely what you were using when you noticed the tearing,
should automatically prevent tearing, though some video drivers do
require flipping a switch--probably labeled something like, "Work
properly," or "Do the right thing," or, "Sync to vblank" (OK, really,
not like the first two, but...) in some configuration program. But, it
is possible that the drivers for the new Sandy Bridge graphics are
broken and don't properly handle sync for Xvideo.
That said, Xv is a 20+ year old API that shouldn't be the focus of
modern hardware/drivers. Instead, you may want to try the OpenGL
renderer (which is a much more modern approach to video--rather than
Xshm, which is a step back even from Xv). Again, you may need to set
some driver-specific video-syncing switch to prevent tearing (and your
drivers may have a different switch for Xv and OpenGL video).
With the OpenGL renderer, you'll also get additional benefits, such as a
full-resolution (rather than video-resolution) OSD (meaning the OSD
won't be squished to fit in a 4:3 video you're playing back with
letterboxing on your widescreen display, and OSD fonts will look pretty
even on standard definition video played back on your high-definition
display). The Sandy Bridge graphics should have sufficiently-powerful
OpenGL capabilities to allow use of the OpenGL video renderer.
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