[Fwd: Re: How To Reduce/Eliminate Horizontal Tearing]

Nick Nobody me at nikosapi.org
Wed Dec 10 21:34:47 PST 2008

Forgot to "reply to all" :S

---------------------------- Original Message ----------------------------
Subject: Re: How To Reduce/Eliminate Horizontal Tearing
From:    "Nick Nobody" <me at nikosapi.org>
Date:    Thu, December 11, 2008 00:30
To:      "Keith Packard" <keithp at keithp.com>

On Thu, December 11, 2008 00:11, Keith Packard wrote:
> On Wed, 2008-12-10 at 23:14 -0500, Nick Nobody wrote:
>> Hello,
>> I'm using Ubuntu 8.10 with a GM945 (at 1920x1080) for my media center
>> PC.
>> The problem I'm running into is a bunch of horizontal tearing on higher
>> resolution videos (720p or greater). From what I can tell it's not a CPU
>> limitation but rather something related to the graphics card...
>> Are there any options that I can enable in my xorg.conf to help
>> reduce/eliminate this tearing? Or is this simply a hardware limitation?
>> Can XvMC somehow help me here?
> There aren't any options at this point, but I'm wondering -- is this
> full-screen? If we made full-screen Xv operations block until vblank
> (which would lock up the X server), would that be an acceptable option?
> It's actually very easy to do, just stick a 'wait for vblank' command
> into the ring right before the 'copy the new picture' command in the Xv
> extension code. It's just annoying when you're watching a tiny movie and
> your whole session stops responding.
> --
> keith.packard at intel.com

Hi Keith!

That would be really cool, I obviously have no idea how to implement it
though... At the moment I'm using XBMC to play back videos and it does
have a "Vertical Blank Sync" option but I'm not sure of how it's
implemented (it clearly doesn't work as advertised). I doubt they're using
Xv anyway so that's irrelevant.

Seeing as this is a media center PC, I really don't care if the system has
to wait for the next vblank, it's only being used to watch videos. And at
at a 60Hz vsync I doubt it would even be noticeable

I just wanted to make sure that my hardware is capable of playing back
this content. I got quite worried when I noticed the tearing on this new
box that I bought :)



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