[Intel-gfx] Tearing In Composite XVideo

Carl Worth cworth at cworth.org
Mon Jun 1 22:36:56 CEST 2009

On Sat, 2009-05-30 at 08:17 +0100, Garry Bodsworth wrote:
> On 28 May 2009, at 20:36, Garry Bodsworth wrote:
> > With the 2.7.1 driver compositing an xv surface using OpenGL works
> > flawlessly, but in the latest git version it has started tearing
> > again.  This is on an Intel 945GM, so I was wondering if the
> > commit  
> > 393abc15b76804580bfee0760ddbd1fb77e66c02 could have made this
> > change?
> > 
> > Thanks,
> > Garry Bodsworth
> And I also forgot to mention this commit which does not sync xv
> surfaces if they are rendered offscreen -
> 34660fd2df5d61b77ed7041d32ac29053fc94f5a.
> http://cgit.freedesktop.org/xorg/driver/xf86-video-intel/commit/?id=34660fd2df5d61b77ed7041d32ac29053fc94f5a
> It sounds a more likely culprit but I am not sure if that code is
> actually called on an Intel 945GM.

That commit may have cause problems, yes, but only because it reversed
the logic of the condition it added. When you tested, did you also have
this later commit which fixes it?

commit c3bf8b980134a2761701e4bc18235695a1cb07a4
Author: Eric Anholt <eric at anholt.net>
Date:   Thu May 21 11:05:01 2009 -0700

    Fix backwards logic on whether to sync to vblank or not.
    Thanks to Michel Dänzer for catching it.

If so, the next step would probably be to run a quick "git bisect" to
identify the actual commit which introduces the bug. If you can do that,
please let us know what you find. Or if you need any help with the git
bisect, we'll be happy to do that as well.

By the way, is there some easy way to replicate the bug you're having?
Running a video player with an OpenGL-based compositing manager or
something? Let me know what you're doing.

And, hmm... should that have even worked tear-free before? It seems like
only recently has Jesse been doing the work that would enable tear-free
operation in a mode like that.


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