OT: Video tearing

OT: Video tearing

[Oliver Seitz]

Hi, perhaps one of the experts can answer this in a few words...

SandyBridge can prevent tearing only by using pageflipping.

pageflipping on Xorg always flips the whole framebuffer, so it can only 
be synced to one output device.

The vaapi-enabled MPlayer plays nice in fullscreen mode (via vaapi or 
gl), but sometimes tears in windowed mode.

Is this a MPlayer, Xorg, intel driver or SandyBridge problem? It's clear 
that pageflipping can not be syncronized to two displays at once, but I 
see no theoretical need for a video being fullscreen to make use of 
pageflipping.

Thank you for any hints!

Greets,
Kiste

Re: OT: Video tearing

[Jesse Barnes]

On Fri, 11 May 2012 11:06:37 +0200
Oliver Seitz <info@vtnd.de> wrote:

> Hi, perhaps one of the experts can answer this in a few words...
> 
> SandyBridge can prevent tearing only by using pageflipping.
> 
> pageflipping on Xorg always flips the whole framebuffer, so it can only 
> be synced to one output device.
> 
> The vaapi-enabled MPlayer plays nice in fullscreen mode (via vaapi or 
> gl), but sometimes tears in windowed mode.
> 
> Is this a MPlayer, Xorg, intel driver or SandyBridge problem? It's clear 
> that pageflipping can not be syncronized to two displays at once, but I 
> see no theoretical need for a video being fullscreen to make use of 
> pageflipping.
> 
> Thank you for any hints!

It's partly a hardware limitation, but it's really a bug in
xf86-video-intel since we don't work around it properly.

It should be possible for us to use flipping in the DDX all the time by
rendering everything to an offscreen buffer, but that involves some
surgery to the DDX we haven't done yet.

-- 
Jesse Barnes, Intel Open Source Technology Center