[Interest] QML animation flickering on Ubuntu

[Sean Harmer]

On Tuesday 13 January 2015 23:06:40 Dmitry Volosnykh wrote:
> Sean, thanks for your input.
> 
> I have NVidia GeForce 9800M GTX, and VSync is enabled. Double-checked that.
> Another enabled options: Allow Flipping and Use Conformant Texture
> Clamping. Do not know what are they for...
> 
> Regarding your question about monitor's refresh rate. Here is xrandr's
> output:
> $ xrandr
> Screen 0: minimum 8 x 8, current 1680 x 1050, maximum 8192 x 8192
> DVI-D-0 disconnected (normal left inverted right x axis y axis)
> LVDS-0 connected 1680x1050+0+0 (normal left inverted right x axis y axis)
> 331mm x 207mm
>    1680x1050      59.9*+
> DVI-D-1 disconnected (normal left inverted right x axis y axis)
> HDMI-0 disconnected (normal left inverted right x axis y axis)
> 
> I guess, it means runs on 60Hz refresh rate.

Hmm OK if that didn't work, can you try this trick. Try setting

export __GL_YIELD="USLEEP"

for your X environment. I have this set in /etc/profile.d/tearing.sh on Gentoo. 
Not sure where the correct place is on Ubuntu. If this is set when X starts 
this solves the tearing for me on nVidia when using a compositing window 
manager.

Cheers,

Sean

> 
> On Tue, Jan 13, 2015 at 9:35 PM, Sean Harmer <sean.harmer at kdab.com> wrote:
> > On Tuesday 13 January 2015 17:02:40 Dmitry Volosnykh wrote:
> > > I've tried to capture the issue: see http://youtu.be/KUNyk2YWBaY
> > > The flickering is more obvious in this video since capturing software
> > > affecting performance. When running application with no video recording
> > > there's no visual artifacts for about 15 seconds. Then the top of the
> > 
> > green
> > 
> > > bar visually looks like be shifted leftwards by a small offset which
> > 
> > holds
> > 
> > > on form the moment of its appearance. The height of this 'cap' may
> > 
> > slightly
> > 
> > > increase over time. This issue reproduces constantly.
> > 
> > Sounds like a lack of v-sync is causing tearing and over time the offset
> > between the swapbuffers and screen refresh is changing. Is your monitor
> > running
> > at a standard refresh rate?
> > 
> > Try forcing vsync in the control panel for your graphics card driver. At
> > least
> > nVidia provide an option for this. I'm not sure about AMD and Intel.
> > 
> > Cheers,
> > 
> > Sean
> > --
> > Dr Sean Harmer | sean.harmer at kdab.com | Managing Director UK
> > Klarälvdalens Datakonsult AB, a KDAB Group company
> > Tel. Sweden (HQ) +46-563-540090, USA +1-866-777-KDAB(5322)
> > KDAB - Qt Experts - Platform-independent software solutions
> > _______________________________________________
> > Interest mailing list
> > Interest at qt-project.org
> > http://lists.qt-project.org/mailman/listinfo/interest

--
Dr Sean Harmer | sean.harmer at kdab.com | Managing Director UK
Klarälvdalens Datakonsult AB, a KDAB Group company
Tel. Sweden (HQ) +46-563-540090, USA +1-866-777-KDAB(5322)
KDAB - Qt Experts - Platform-independent software solutions