[visionlist] Sync problems

[Nicolas Brunet]

Dear vision community,

we are seeking help for a video sync problem with PTB for UBUNTU".
To achieve fast frame rate, we are running our experiments on a DELL (Precision Tower 5810) with a NVidiaG96GL (Quadro FX 580) graphic card using a Ubuntu 64-bit OS, in Psychtoolbox-3 for GNU/Linux X11 (version 3.0.13), under MATLAB R2017a (64 bit) with a dual monitor setup: for stimulus display, we use a Barco monitor connected to the HDMI port (using a HDMI to VGA converter), and for control a regular monitor plugged into a DVI port.
We managed to achieve a refresh rate of 160 frames per second, but 1-2 % of the frames are skipped. A screentest reveals poor synchronization; one of the psychtoolbox warning messages recommends installation of the most recent graphic card driver, and another one suggest that the problems are caused because the program runs into a virtual machine (which is, to my knowledge, not the case). Unfortunately, updating the Nvidia driver added a problem instead of solving one, because the Nvidia control panel now only recognizes both monitors when they are in mirror mode (as opposed to extended mode). Although the problem is mentioned on Ubuntu forums, I couldn't find a solution that works; neither did reinstalling older versions of the Nvidia driver. Any advice is greatly appreciated!


Nic


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