Psychtoolbox release "Virtuality!" SP2 released

Psychtoolbox 3.0.19 Beta update “Virtuality” SP2 was released at 21st April 2023.
As usual, the complete development history can be found in our GitHub repository.
The release tag is “”, with the full tree and commit logs under the URL:


  • PsychPaidSupportAndServices now handles users pressing Space or Enter too often.
    Reported by Giles Holland, thanks!

  • PsychDataPixx: Don’t blank top-left pixel anymore, so the “Viewpixx EEG trigger pixel”
    works better.


  • Our new OpenXR driver now has the ability to provide accurate and trustworthy visual
    stimulus onset timestamps for VR HMD’s - as tested with Oculus Rift CV-1 and HTC Vive Pro Eye and some photo-diode measurements. This however currently only works with Linux and only with Monado as OpenXR runtime, and only with a special set of Mesa Vulkan drivers for AMD and Intel gpu’s. It also comes at a performance cost.
    However, this combination of Psychtoolbox and modified Monado + Mesa is to my knowledge the only existing modern VR system that can actually provide accurate and trustworthy timing and timestamping for VR applications on modern VR HMD’s. Read “Help PsychOpenXR” for setup instructions. A proper non-hacky, easy to use solution to VR timing problems is still to be done and will require substantial amounts of work.

The Monado improvements needed for this timestamping hack have now been upstreamed and integrated into official Monado. A minor update to ‘help PsychOpenXR’ describes required tweaked setup instructions.


  • Verified quickly that Psychtoolbox for Octave also works with the new Octave 8.2 from HomeBrew on macOS 12.0, in addition to the supported Octave 8.1. Octave 7.x or 6.x may continue to work, but this is assumed, not tested.