Slight ripping of video when compiz is enabled

[Kyle M Weller]

Binary package hint: compiz

While watching movies I see slight ripping during fast video playback with any player only when compiz is enabled

[sp8472 (sp8472)]

This may be a duplicate of bug #212587.

[Nicholas Xenakis (xnicholas)]

I am running windows xp nvidia 7600gs, with the latest drivers. Forced
Vsync option enabled. I get 100% vsync when I move windows around
rapidly and take screenshot.

I get 0% vsync doing same thing on latest kubuntu, with latest
proprietary nvidia drivers, and open source "nv" driver, with all
vsync options enabled. Strangely, I do have fps cap at 60 fps on glx
gears. Yet applications visibly tears apart if I move them around too
fast, movies also tear apart mid frame, even though my pc is more than
fast enough to handle full hd video playback without tearing on
windows xp.

What really is the issue perhaps might be, there is no concrete way of
testing if vsync is working besides high speed window movement and
printscreen. Most other bugs are easily verified, yet vsync is hard to
confirm on a stationary screen. Anyone care to develop a program that
reads the framebuffer and determines if vsync is working?

Nick

On Tue, Jun 23, 2009 at 3:03 AM, Robert
Ancell<email address hidden> wrote:
> *** This bug is a duplicate of bug 212587 ***
>    https://bugs.launchpad.net/bugs/212587
>
> ** This bug has been marked a duplicate of bug 212587
>   Vsync setting has no effect
>
> --
> Slight ripping of video when compiz is enabled
> https://bugs.launchpad.net/bugs/288822
> You received this bug notification because you are a direct subscriber
> of the bug (via bug 212587).
>
> Status in “compiz” source package in Ubuntu: New
>
> Bug description:
> Binary package hint: compiz
>
> While watching movies I see slight ripping during fast video playback with any player only when compiz is enabled
>

[Tessa (unit3)]

Nick:

You can't check the framebuffers for vsync problems, because it's not an issue that'll show up in the framebuffer. Typically, in applications that attempt to do vsync, there are two complete, correct buffers. The app then swaps the inactive (back) buffer to screen when the monitor is doing its vertical sync, (ie, not drawing to the screen) so that screen updates aren't visible to the user. If there's a problem with that code, it swaps the buffers in the middle of drawing the screen, and you see the "tearing" effect.

So there's really nothing to check in the buffers, as they'll likely always be correct. The problem is a matter of timing: when is compiz or whatever window manager you're using swapping the buffers? And why isn't it doing it during the monitor vsync?

[Nicholas Xenakis (xnicholas)]

Graeme:

Hai, can you think of any test to determine if vsync is working? When
I move windows rapidly, and then do printscreen, i get massively
distorted images. Fedora also seems to be effected, yet this glitch?
never happens on windows xp.

http://i44.tinypic.com/24l6kgx.png ( pretty fast)

http://i43.tinypic.com/13ygg41.png ( very slow movement)

What do you think?

On Tue, Jun 23, 2009 at 10:04 AM, Graeme Humphries<email address hidden> wrote:
> *** This bug is a duplicate of bug 212587 ***
>    https://bugs.launchpad.net/bugs/212587
>
> Nick:
>
> You can't check the framebuffers for vsync problems, because it's not an
> issue that'll show up in the framebuffer. Typically, in applications
> that attempt to do vsync, there are two complete, correct buffers. The
> app then swaps the inactive (back) buffer to screen when the monitor is
> doing its vertical sync, (ie, not drawing to the screen) so that screen
> updates aren't visible to the user. If there's a problem with that code,
> it swaps the buffers in the middle of drawing the screen, and you see
> the "tearing" effect.
>
> So there's really nothing to check in the buffers, as they'll likely
> always be correct. The problem is a matter of timing: when is compiz or
> whatever window manager you're using swapping the buffers? And why isn't
> it doing it during the monitor vsync?
>
> --
> Slight ripping of video when compiz is enabled
> https://bugs.launchpad.net/bugs/288822
> You received this bug notification because you are a direct subscriber
> of the bug (via bug 212587).
>
> Status in “compiz” source package in Ubuntu: New
>
> Bug description:
> Binary package hint: compiz
>
> While watching movies I see slight ripping during fast video playback with any player only when compiz is enabled
>

[Tessa (unit3)]

That's very interesting. Your problem definitely appears in the framebuffer, which indicates 2 things to me:

 - Your install isn't doing double buffering, as double buffering would never have this issue visually appear in the framebuffer.
 - Your install isn't even attempting to vsync, as if it was, it would be doing double buffering.

This makes me suspect this may not be a dupe of #212587. For some reason, your window manager or copy of X isn't doing proper double buffering.

With the proprietary NV drivers, can you enable compiz effects, and see if this changes things at all?

[Nicholas Xenakis (xnicholas)]

Ok, sorry for the delay. I did as you asked, I took one screenshot
using medium compiz settings. and one using extra compiz settings.
Although the medium seemed to have visably less tearing when i moved
my windows around, the screenshots still are completely distorted.

http://i39.tinypic.com/ejdk5y.png (medium settings, slow movement)

http://i43.tinypic.com/35lrfpd.png (extra settings, slow movement)

I might later try to record video of monitor and check for tearing,
just to confirm this isn't some printscreen glitch.

On Tue, Jun 23, 2009 at 11:21 AM, Graeme Humphries<email address hidden> wrote:
> *** This bug is a duplicate of bug 212587 ***
>    https://bugs.launchpad.net/bugs/212587
>
> That's very interesting. Your problem definitely appears in the
> framebuffer, which indicates 2 things to me:
>
>  - Your install isn't doing double buffering, as double buffering would never have this issue visually appear in the framebuffer.
>  - Your install isn't even attempting to vsync, as if it was, it would be doing double buffering.
>
> This makes me suspect this may not be a dupe of #212587. For some
> reason, your window manager or copy of X isn't doing proper double
> buffering.
>
> With the proprietary NV drivers, can you enable compiz effects, and see
> if this changes things at all?
>
> --
> Slight ripping of video when compiz is enabled
> https://bugs.launchpad.net/bugs/288822
> You received this bug notification because you are a direct subscriber
> of the bug (via bug 212587).
>
> Status in “compiz” source package in Ubuntu: New
>
> Bug description:
> Binary package hint: compiz
>
> While watching movies I see slight ripping during fast video playback with any player only when compiz is enabled
>

[Tessa (unit3)]

Yeah, if it does that on the monitor as well as in the buffer when doing printscreen, then there's definitely some sort of rendering path problem on your system, that isn't the same as the missing vsync from bug #212587. At most, a vsync issue (with double buffering) should only have a single tear in a window, not a ton like you're seeing here.