compiz team mailing list archive

[Daniel van Vugt <vanvugt@xxxxxxxxx>]

Public bug reported:

You might expect that with "Sync To VBlank" enabled in compiz that video
tearing doesn't happen. But it does, just less often.

This is normal, expected behaviour. The cause is that compiz (up to
0.9.6 at least) uses GLX_SGI_video_sync, which provides a rough way of
synchronizing with the video frame rate of the monitor. But it's not
reliable in most cases because if you take a little too long to render
the frame, then you can miss the frame deadline and tearing can still be
seen.

The solution to this bug is to modify compiz to use GLX_SGI_swap_control
instead, which provides a more reliable and more efficient way of
synchronizing with the refresh rate.

Speaking with smspillaz, he says a move to glXSwapBuffers is planned for
a future version of compiz, not least because it is required in order to
port compiz to OpenGLES. Once compiz uses glXSwapBuffers for every
frame, it will be possible to then use GLX_SGI_swap_control for reliable
synchronization.

More info: http://www.opengl.org/wiki/Swap_Interval

ProblemType: Bug
DistroRelease: Ubuntu 11.10
Package: compiz 1:0.9.6+bzr20110929-0ubuntu5
ProcVersionSignature: Ubuntu 3.0.0-12.20-generic 3.0.4
Uname: Linux 3.0.0-12-generic x86_64
.tmp.unity.support.test.0:
 
ApportVersion: 1.23-0ubuntu3
Architecture: amd64
CompizPlugins: [core,bailer,detection,composite,opengl,compiztoolbox,decor,mousepoll,place,gnomecompat,resize,imgpng,move,wall,regex,grid,vpswitch,animation,session,resizeinfo,unitymtgrabhandles,expo,workarounds,fade,scale,ezoom,unityshell]
CompositorRunning: compiz
Date: Mon Oct 24 16:01:07 2011
DistUpgraded: Fresh install
DistroCodename: oneiric
DistroVariant: ubuntu
GraphicsCard:
 Intel Corporation 2nd Generation Core Processor Family Integrated Graphics Controller [8086:0102] (rev 09) (prog-if 00 [VGA controller])
   Subsystem: Dell Device [1028:047e]
InstallationMedia: Ubuntu 11.10 "Oneiric Ocelot" - Release amd64 (20111012)
MachineType: Dell Inc. OptiPlex 990
PackageArchitecture: all
ProcEnviron:
 LANGUAGE=en_AU:en
 PATH=(custom, no user)
 LANG=en_AU.UTF-8
 SHELL=/bin/bash
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.0.0-12-generic root=UUID=c9a0c042-2d94-4c4b-bb7f-756faf723ada ro quiet splash intel_iommu=on vt.handoff=7
SourcePackage: compiz
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 05/28/2011
dmi.bios.vendor: Dell Inc.
dmi.bios.version: A05
dmi.board.name: 0D6H9T
dmi.board.vendor: Dell Inc.
dmi.board.version: A00
dmi.chassis.type: 15
dmi.chassis.vendor: Dell Inc.
dmi.modalias: dmi:bvnDellInc.:bvrA05:bd05/28/2011:svnDellInc.:pnOptiPlex990:pvr01:rvnDellInc.:rn0D6H9T:rvrA00:cvnDellInc.:ct15:cvr:
dmi.product.name: OptiPlex 990
dmi.product.version: 01
dmi.sys.vendor: Dell Inc.
version.compiz: compiz 1:0.9.6+bzr20110929-0ubuntu5
version.ia32-libs: ia32-libs N/A
version.libdrm2: libdrm2 2.4.26-1ubuntu1
version.libgl1-mesa-dri: libgl1-mesa-dri 7.11-0ubuntu3
version.libgl1-mesa-dri-experimental: libgl1-mesa-dri-experimental N/A
version.libgl1-mesa-glx: libgl1-mesa-glx 7.11-0ubuntu3
version.xserver-xorg: xserver-xorg 1:7.6+7ubuntu7
version.xserver-xorg-input-evdev: xserver-xorg-input-evdev 1:2.6.0-1ubuntu13
version.xserver-xorg-video-ati: xserver-xorg-video-ati 1:6.14.99~git20110811.g93fc084-0ubuntu1
version.xserver-xorg-video-intel: xserver-xorg-video-intel 2:2.15.901-1ubuntu2
version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 1:0.0.16+git20110411+8378443-1

** Affects: compiz (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: amd64 apport-bug compiz-0.9 oneiric running-unity ubuntu

-- 
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packagers, which is subscribed to compiz in Ubuntu.
https://bugs.launchpad.net/bugs/880707

Title:
  Video tearing still occurs in compiz (less so) when "Sync To VBlank"
  is enabled.

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