# Bugs & Features **URL:** https://psychtoolbox.discourse.group/c/have-you-found-a-bug-or-wish-to-discuss-a-new-feature-then-post-here/7.md [Latest](https://psychtoolbox.discourse.group/latest.md) · [Categories](https://psychtoolbox.discourse.group/categories.md) · [Tags](https://psychtoolbox.discourse.group/tags.md) --- ## [About the Bugs & Features category](https://psychtoolbox.discourse.group/t/about-the-bugs-features-category/3054)
**Author:** [@Ian-Max-Andolina](https://psychtoolbox.discourse.group/u/Ian-Max-Andolina)\ **Replies:** 0
Please post bugs you think you may have found or potential feature requests here. But please be aware that PTB is open source and there is is only one main developer who contributes their spare time to this project–be ki… --- ## [Porting Psychtoolbox to Python](https://psychtoolbox.discourse.group/t/porting-psychtoolbox-to-python/5816)
**Author:** [@pscarfe](https://psychtoolbox.discourse.group/u/pscarfe)\ **Replies:** 4\ **Last updated:** [September 30, 2026, 9:35am UTC](https://psychtoolbox.discourse.group/t/porting-psychtoolbox-to-python/5816 "2026-09-30T09:35:14Z")
I broad question. Having grown up on Matlab and Psychtoolbox I am (for better or worse) using Python more and more these days. The primary reasons are the vast push behind Python development in academia and beyond. Some… --- ## [Recommended install on Linux? Neurodebian cannot handle licenses, libLexActivator missing](https://psychtoolbox.discourse.group/t/recommended-install-on-linux-neurodebian-cannot-handle-licenses-liblexactivator-missing/5815)
**Author:** [@uliwannek](https://psychtoolbox.discourse.group/u/uliwannek)\ **Replies:** 1\ **Last updated:** [September 25, 2026, 3:37pm UTC](https://psychtoolbox.discourse.group/t/recommended-install-on-linux-neurodebian-cannot-handle-licenses-liblexactivator-missing/5815 "2026-09-25T15:37:05Z")
Background: Debian Trixie (13.7), PsychToolbox (3.0.22.3 from neurodebian), license available. install: apt-get install matlab-psychtoolbox-3 fetches matlab-psychtoolbox-3 matlab-psychtoolbox-3-nonfree starting ptb3… --- ## [Experimental direct OpenGL-to-Metal presentation backend for Psychtoolbox on Apple Silicon](https://psychtoolbox.discourse.group/t/experimental-direct-opengl-to-metal-presentation-backend-for-psychtoolbox-on-apple-silicon/5811)
**Author:** [@keith](https://psychtoolbox.discourse.group/u/keith)\ **Replies:** 11\ **Last updated:** [September 21, 2026, 7:15pm UTC](https://psychtoolbox.discourse.group/t/experimental-direct-opengl-to-metal-presentation-backend-for-psychtoolbox-on-apple-silicon/5811 "2026-09-21T19:15:24Z")
Motivation I have been investigating the presentation-timing problems affecting Psychtoolbox on Apple Silicon under recent macOS versions. In particular, ordinary drawing and unscheduled flips can appear to work, while s… --- ## [Not using pageflips on recent AMD RDNA 4 gpu's on Ubuntu 24.04, Debian 13](https://psychtoolbox.discourse.group/t/not-using-pageflips-on-recent-amd-rdna-4-gpus-on-ubuntu-24-04-debian-13/5806)
**Author:** [@uwtuebingen](https://psychtoolbox.discourse.group/u/uwtuebingen)\ **Replies:** 6\ **Last updated:** [June 11, 2026, 6:16pm UTC](https://psychtoolbox.discourse.group/t/not-using-pageflips-on-recent-amd-rdna-4-gpus-on-ubuntu-24-04-debian-13/5806 "2026-06-11T18:16:34Z")
Disclaimer Yes, I am willing to contribute by testing with the new hardware. Yes, I am willing to use the payed support if needed. We do have payed licenses. Describe the bug New computer with new GPU “Navi RX 9060 … --- ## [Screen GetImage](https://psychtoolbox.discourse.group/t/screen-getimage/5805)
**Author:** [@pscarfe](https://psychtoolbox.discourse.group/u/pscarfe)\ **Replies:** 2\ **Last updated:** [May 19, 2026, 8:37pm UTC](https://psychtoolbox.discourse.group/t/screen-getimage/5805 "2026-05-19T20:37:00Z")
I am not sure if this is expected behaviour, but on macOS Screen(‘GetImage’, window) Gives the Psychtoolbox startup window with the frog, regardless of what is on the screen. Specifying the back or draw buffer results … --- ## [Quick fix for Mac Tahoe timing issues](https://psychtoolbox.discourse.group/t/quick-fix-for-mac-tahoe-timing-issues/5804)
**Author:** [@keith](https://psychtoolbox.discourse.group/u/keith)\ **Replies:** 18\ **Last updated:** [April 17, 2026, 2:19pm UTC](https://psychtoolbox.discourse.group/t/quick-fix-for-mac-tahoe-timing-issues/5804 "2026-04-17T14:19:44Z")
Hi all, I just wanted to report a trick that fixed the timing for me. So now I’ve upgraded to Mac OS 26.5 beta. I don’t know if this works on previous versions or not. I tested this using Octave 11.1 and PTB 3.0.22. My… --- ## [Windows 11 Compatibility - requesting a statement to show IT](https://psychtoolbox.discourse.group/t/windows-11-compatibility-requesting-a-statement-to-show-it/5794)
**Author:** [@Dagmar](https://psychtoolbox.discourse.group/u/Dagmar)\ **Replies:** 3\ **Last updated:** [March 4, 2026, 4:29am UTC](https://psychtoolbox.discourse.group/t/windows-11-compatibility-requesting-a-statement-to-show-it/5794 "2026-03-04T04:29:51Z")
Hey Mario! We have been trying to request Windows 10 LTSC Edition from our Central IT as a back up for our upcoming fleet of Ubuntu machines - this will enable legacy paradigm to run without tweaking - and sidesteps the… --- ## [Timing / Performance issues on macOS 26 Tahoe](https://psychtoolbox.discourse.group/t/timing-performance-issues-on-macos-26-tahoe/5767)
**Author:** [@keith](https://psychtoolbox.discourse.group/u/keith)\ **Replies:** 31\ **Last updated:** [December 21, 2025, 6:09pm UTC](https://psychtoolbox.discourse.group/t/timing-performance-issues-on-macos-26-tahoe/5767 "2025-12-21T18:09:22Z")
Something about Mac OS 26.1 seems to destroy the timing. Every frame flip is missed in VBLSyncTest and DotDemo, for example. Not sure if this is Matlab specific, because my Octave version had been updated to 10.3 and P… --- ## [Compatibility Issues Between PTB and MATLAB Versions](https://psychtoolbox.discourse.group/t/compatibility-issues-between-ptb-and-matlab-versions/5775)
**Author:** [@ziyuan](https://psychtoolbox.discourse.group/u/ziyuan)\ **Replies:** 1\ **Last updated:** [December 12, 2025, 4:00pm UTC](https://psychtoolbox.discourse.group/t/compatibility-issues-between-ptb-and-matlab-versions/5775 "2025-12-12T16:00:59Z")
Hello everyone in the community! I’m posting this request for help on behalf of a colleague—since he’s new to the community, his account is restricted from posting directly. Recently, they’ve been trying to install PTB… --- ## [Problems installing PTB on Linux](https://psychtoolbox.discourse.group/t/problems-installing-ptb-on-linux/5759)
**Author:** [@theprof07](https://psychtoolbox.discourse.group/u/theprof07)\ **Replies:** 19\ **Last updated:** [November 13, 2025, 1:35am UTC](https://psychtoolbox.discourse.group/t/problems-installing-ptb-on-linux/5759 "2025-11-13T01:35:15Z")
The NeuroDebian site is not working so I cannot install PsychToolbox. The line “After selecting a release the setup code will be shown here.” is not being replaced with the needed commands after selecting the OS release… --- ## [ASIO now dual licensed under GPLv3](https://psychtoolbox.discourse.group/t/asio-now-dual-licensed-under-gplv3/5764)
**Author:** [@aforren1](https://psychtoolbox.discourse.group/u/aforren1)\ **Replies:** 0\ **Last updated:** [October 22, 2025, 1:53pm UTC](https://psychtoolbox.discourse.group/t/asio-now-dual-licensed-under-gplv3/5764 "2025-10-22T13:53:05Z")
Maybe relevant to some? Press release, SDK page --- ## [Faint frame surrounding Gabor](https://psychtoolbox.discourse.group/t/faint-frame-surrounding-gabor/5762)
**Author:** [@Ghu](https://psychtoolbox.discourse.group/u/Ghu)\ **Replies:** 2\ **Last updated:** [October 3, 2025, 7:04am UTC](https://psychtoolbox.discourse.group/t/faint-frame-surrounding-gabor/5762 "2025-10-03T07:04:22Z")
Hello! Our lab is working on an experiment that involves the presentation of Gabors, but we are noticing a frame-like structure around all four sides of the Gabor that doesn’t fully blend in with the background. It is fa… --- ## [PsychPortAudio('Start', ...) returns timestamp with large offset](https://psychtoolbox.discourse.group/t/psychportaudio-start-returns-timestamp-with-large-offset/5756)
**Author:** [@skjerns](https://psychtoolbox.discourse.group/u/skjerns)\ **Replies:** 1\ **Last updated:** [August 28, 2025, 6:45pm UTC](https://psychtoolbox.discourse.group/t/psychportaudio-start-returns-timestamp-with-large-offset/5756 "2025-08-28T18:45:42Z")
We’re using a loop to play several audio stimuli withlastStim = PsychPortAudio('Start', handle, 1, 0, 1);. However, the first value returned by the function is offset by a very large number, e.g. it has an offset of last… --- ## [PTB-ERROR: IMAGINGPIPE\_FLIPTWHEN variable assignment failed on macOS (works on Windows)](https://psychtoolbox.discourse.group/t/ptb-error-imagingpipe-fliptwhen-variable-assignment-failed-on-macos-works-on-windows/5685)
**Author:** [@ntcog](https://psychtoolbox.discourse.group/u/ntcog)\ **Replies:** 10\ **Last updated:** [April 28, 2025, 3:20pm UTC](https://psychtoolbox.discourse.group/t/ptb-error-imagingpipe-fliptwhen-variable-assignment-failed-on-macos-works-on-windows/5685 "2025-04-28T15:20:26Z")
Hi everyone, I’m encountering an issue when running my experiment code on macOS using Psychtoolbox. The error message is: PTB-ERROR: PsychPipelineProcessMacros: IMAGINGPIPE\_FLIPTWHEN variable assignment failed in runti… --- ## [Endless loop during installation](https://psychtoolbox.discourse.group/t/endless-loop-during-installation/5656)
**Author:** [@jskim628](https://psychtoolbox.discourse.group/u/jskim628)\ **Replies:** 7\ **Last updated:** [March 7, 2025, 1:06am UTC](https://psychtoolbox.discourse.group/t/endless-loop-during-installation/5656 "2025-03-07T01:06:37Z")
When running SetupPsychtoolbox.m, I see the error below. I have installed the necessary runtime libraries, but this still continues, thus I am stuck in an endless loop. I am using MATLAB2024B, Psychtoolbox 3.0.20.3, on a… --- ## [PTB's rendering is jumbled on Intel Arc graphics on MS-Windows](https://psychtoolbox.discourse.group/t/ptbs-rendering-is-jumbled-on-intel-arc-graphics-on-ms-windows/5652)
**Author:** [@JAQuent](https://psychtoolbox.discourse.group/u/JAQuent)\ **Replies:** 9\ **Last updated:** [February 26, 2025, 9:59am UTC](https://psychtoolbox.discourse.group/t/ptbs-rendering-is-jumbled-on-intel-arc-graphics-on-ms-windows/5652 "2025-02-26T09:59:50Z")
Background info I am trying to use PTB 3.0.19 on a Huawei laptop with Intel graphics that I bought for data collection. Currently I am running Windows 11 on it but it also persist on Windows 10. When I set the display t… --- ## [PsychPortAudio freezes after first sound](https://psychtoolbox.discourse.group/t/psychportaudio-freezes-after-first-sound/5639)
**Author:** [@baptiste](https://psychtoolbox.discourse.group/u/baptiste)\ **Replies:** 3\ **Last updated:** [February 11, 2025, 9:36pm UTC](https://psychtoolbox.discourse.group/t/psychportaudio-freezes-after-first-sound/5639 "2025-02-11T21:36:05Z")
Hello. I experience an issue with PsychPortAudio on Ubuntu 22.04.4 LTS. I use the PTB 3.0.19.64715640, and PsychPortAudio 3.0.19.64657228. When running an experiment that used to work fine on another system, PsychPortA… --- ## [Invalid screen MEX file](https://psychtoolbox.discourse.group/t/invalid-screen-mex-file/5615)
**Author:** [@S.Obika](https://psychtoolbox.discourse.group/u/S.Obika)\ **Replies:** 4\ **Last updated:** [January 20, 2025, 12:06pm UTC](https://psychtoolbox.discourse.group/t/invalid-screen-mex-file/5615 "2025-01-20T12:06:27Z")
Hello. I am facing the issue with screen mex file. I know there are several similar issues that were posted previously but still I could not find a way to solve it. I would be grateful if you could help us to find a so… --- ## [Text Bounding Boxes](https://psychtoolbox.discourse.group/t/text-bounding-boxes/5536)
**Author:** [@pscarfe](https://psychtoolbox.discourse.group/u/pscarfe)\ **Replies:** 9\ **Last updated:** [November 18, 2024, 6:56pm UTC](https://psychtoolbox.discourse.group/t/text-bounding-boxes/5536 "2024-11-18T18:56:20Z")
Hi all, I have been playing around with bounding boxes for text, prompted by a recent forum question. I have made a demo drawing the alphabet and the bounding boxes around the letters. I am getting some behavior that I … --- ## [Postdoctoral Research Position](https://psychtoolbox.discourse.group/t/postdoctoral-research-position/5542)
**Author:** [@pscarfe](https://psychtoolbox.discourse.group/u/pscarfe)\ **Replies:** 0\ **Last updated:** [November 11, 2024, 4:13pm UTC](https://psychtoolbox.discourse.group/t/postdoctoral-research-position/5542 "2024-11-11T16:13:46Z")
Have you just graduated with your PhD? Do you have less than 12 months postdoctoral research experience? Do you want to come work in my lab for a year? If you have answered yes to these questions look no further: https:… --- ## [Psychtoolbox SyncTests error (windows 11): Trouble with VBL syncing/VBL not working](https://psychtoolbox.discourse.group/t/psychtoolbox-synctests-error-windows-11-trouble-with-vbl-syncing-vbl-not-working/5540)
**Author:** [@Nora](https://psychtoolbox.discourse.group/u/Nora)\ **Replies:** 4\ **Last updated:** [November 9, 2024, 5:32pm UTC](https://psychtoolbox.discourse.group/t/psychtoolbox-synctests-error-windows-11-trouble-with-vbl-syncing-vbl-not-working/5540 "2024-11-09T17:32:41Z")
Hello everyone! I am programming a SSVEP experiment which is time-sensitive, so I cannot skip the SyncTest. The scripts worked well with SkipSyncTests=1, but when I tried to do the SyncTest, it reports warnings and the e… --- ## [Solved: Installation problem on Ubuntu 24.04-LTS with NeuroDebian matlab package](https://psychtoolbox.discourse.group/t/solved-installation-problem-on-ubuntu-24-04-lts-with-neurodebian-matlab-package/5523)
**Author:** [@theprof07](https://psychtoolbox.discourse.group/u/theprof07)\ **Replies:** 5\ **Last updated:** [October 25, 2024, 4:19pm UTC](https://psychtoolbox.discourse.group/t/solved-installation-problem-on-ubuntu-24-04-lts-with-neurodebian-matlab-package/5523 "2024-10-25T16:19:42Z")
I’m trying to install PTB on Ubuntu 24.04.1 LTS via NeuroDebian. I followed the procedure outlined on NeuroDebian, but accidentally did the one for Octave, so I did sudo apt-get remove octave-psychtoolbox-3 and then re… --- ## [Invalid mex file error on Windows](https://psychtoolbox.discourse.group/t/invalid-mex-file-error-on-windows/5468)
**Author:** [@vishalbharmauria](https://psychtoolbox.discourse.group/u/vishalbharmauria)\ **Replies:** 9\ **Last updated:** [September 4, 2024, 8:39pm UTC](https://psychtoolbox.discourse.group/t/invalid-mex-file-error-on-windows/5468 "2024-09-04T20:39:24Z")
I tried setting up the Psychtoolbox in the last two days but somehow the following error pops up everytime: Invalid MEX-file ‘D:\\Psychtoolbox\\Psychtoolbox-3-3.0.19.14\\Psychtoolbox\\PsychBasic\\MatlabWindowsFilesR2007a\\Scr… --- ## [No pageflipping on Ubuntu 24.04-LTS with Ubuntu/Gnome desktop GUI](https://psychtoolbox.discourse.group/t/no-pageflipping-on-ubuntu-24-04-lts-with-ubuntu-gnome-desktop-gui/5459)
**Author:** [@prattems](https://psychtoolbox.discourse.group/u/prattems)\ **Replies:** 3\ **Last updated:** [August 29, 2024, 6:22pm UTC](https://psychtoolbox.discourse.group/t/no-pageflipping-on-ubuntu-24-04-lts-with-ubuntu-gnome-desktop-gui/5459 "2024-08-29T18:22:48Z")
I have a newly built PC with an Intel chip and integrated GPU (i7-13700K) running PTB (3.0.19) on Octave (8.4.0) on Ubuntu (24.04) with the low-latency kernel and a single monitor. Totally fresh install of OS and everyth… --- ## [Codecs in VideoRecordingDemo not working on Linux](https://psychtoolbox.discourse.group/t/codecs-in-videorecordingdemo-not-working-on-linux/5441)
**Author:** [@inichoson](https://psychtoolbox.discourse.group/u/inichoson)\ **Replies:** 12\ **Last updated:** [August 21, 2024, 10:19pm UTC](https://psychtoolbox.discourse.group/t/codecs-in-videorecordingdemo-not-working-on-linux/5441 "2024-08-21T22:19:01Z")
Comercial support token: 6R7X549H-202481111018:8517f9148012534acf6ae04e29b2b28cd5325a8e4a6cd5177b90073e7fc10268 Desktop (please complete the following information): OS: Ubuntu Linux 22.04 Runtime: Matlab R2022b Hardwa… --- ## [Recording and playback duration not the same using PsychPortAudio with full duplex](https://psychtoolbox.discourse.group/t/recording-and-playback-duration-not-the-same-using-psychportaudio-with-full-duplex/5428)
**Author:** [@Long](https://psychtoolbox.discourse.group/u/Long)\ **Replies:** 1\ **Last updated:** [July 12, 2024, 3:52pm UTC](https://psychtoolbox.discourse.group/t/recording-and-playback-duration-not-the-same-using-psychportaudio-with-full-duplex/5428 "2024-07-12T15:52:36Z")
Hi, I am trying to playback and capture audio at the same time, but in the end, I found that the audio recorded and the audio played do not have the same length. I loop through playing 100 audios with 15 seconds each; Wh… --- ## [Unable to set up in octave (version 9.1)](https://psychtoolbox.discourse.group/t/unable-to-set-up-in-octave-version-9-1/5359)
**Author:** [@Gonza](https://psychtoolbox.discourse.group/u/Gonza)\ **Replies:** 3\ **Last updated:** [May 20, 2024, 6:46am UTC](https://psychtoolbox.discourse.group/t/unable-to-set-up-in-octave-version-9-1/5359 "2024-05-20T06:46:54Z")
Hi I´m tring to install Psychtoolbox using Octave version 9.1. I followed all the steps outlined on the Psychtoolbox website for downloading: http://psychtoolbox.org/ The problem: When i type SetupPsychtool, it starts… --- ## [erro while packaging psychtoolbox into matlap app designer](https://psychtoolbox.discourse.group/t/erro-while-packaging-psychtoolbox-into-matlap-app-designer/5269)
**Author:** [@mfibm](https://psychtoolbox.discourse.group/u/mfibm)\ **Replies:** 1\ **Last updated:** [February 26, 2024, 12:46am UTC](https://psychtoolbox.discourse.group/t/erro-while-packaging-psychtoolbox-into-matlap-app-designer/5269 "2024-02-26T00:46:10Z")
Dear Team of psychtoolbox I am suing Matlab App Designer with PsychToolbox Version '3.0.19 - Flavor: beta - Corresponds to SVN Revision 13790. I developed a Matlab app designer to show an experiment using PsychToolbox,… --- ## [Matlab + Intel graphics plotting bug again (Was: X screen configuration doesn't work)](https://psychtoolbox.discourse.group/t/matlab-intel-graphics-plotting-bug-again-was-x-screen-configuration-doesnt-work/5177)
**Author:** [@Cemre](https://psychtoolbox.discourse.group/u/Cemre)\ **Replies:** 12\ **Last updated:** [February 16, 2024, 4:54pm UTC](https://psychtoolbox.discourse.group/t/matlab-intel-graphics-plotting-bug-again-was-x-screen-configuration-doesnt-work/5177 "2024-02-16T16:54:43Z")
Hello, PTB community! I have some issues with my setup. I have a Linux PC and I needed to reinstall everything due to a graphic cards issue (I don’t know what happened but the PC started refusing to turn on.). I have 2 … [Next page](https://psychtoolbox.discourse.group/c/have-you-found-a-bug-or-wish-to-discuss-a-new-feature-then-post-here/7.md?page=1)