PTB BETA UPDATE "Timely Twinkler"

Ho Ho Ho, the “Timely Twinkler” arrived in time before christmas, so you can visually stimulate your loved ones under the christmas tree with more fine-grained timing than ever before! This release follows the pattern of substantial visual stimulation timing improvements: It brings another bunch of cool improvements to VRR/FreeSync/G-Sync support on Linux.There are also a few minor improvements in other areas for the less fortunate ones who can’t enjoy Linux.

New features and improvements:

All operating systems:

  • Adds PsychPhotodiode() driver for combining photo-diodes with sound cards for visual stimulus onset timestamping. Demonstrated in VRRTest.m as hwmeasurement=5 method.

  • UpdatePsychtoolbox() will now resolve potential file conflicts automatically by forcing the updated files from the upstream server, simply overwriting/discarding user modifications.

  • Documentation updates. Among other minor things, point to the new user forum at Discourse:

  • Improve ability to do reproducible builds for Python, contributed by Bernhard Wiedemann on behalf of openSUSE.


  • Ship basic set of MEX files for Octave 4.4 on Linux, e.g., for easy use with Octave on Ubuntu 19.10. Currently missing, to be part of a later update: Eyelink.mex, PsychCV.mex.

  • Improved VRR support for fine-grained visual stimulus onset timing on Linux. The API has been reworked to allow for more future flexibility and future extensions without breaking backwards compatibility of user scripts. Most importantly, a more sophisticated multi-threaded VRR scheduler is now used, which should take hardware (gpu and display) and operating system/driver constraints into account to provide more precise and stable visual stimulus onset timing. Testing shows pretty good results on AMD FreeSync hardware, and some improvements on NVidia G-Sync hardware. AMD gpu’s and compatible “FreeSync” displays are strongly recommended over NVidia G-Sync for optimal current results and to take advantage of substantial improvements on Linux in the future.


1 Like

Hi @mariokleiner I asked this before the forum was properly working, but can you detail the actual type of photodiode and USB soundcard model (for Linux compatibility etc.) you use for this? It seems a cool lightweight way to test timing!

Thanks, Ian

I’ll answer that in your original question/post
PsychPhotodiode() Recommended Card?