A psychologist's thoughts on how and why we play games

Friday, December 1, 2017

Adventures programming a Word Pronunciation Task in PsychoPy

I'm a new assistant professor trying to set up my research laboratory. I thought I'd try making the jump to PsychoPy as a way to make my materials more shareable, since not everybody will have a $750+ E-Prime or DirectRT license or whatever. (I'm also a tightwad.)

My department has a shared research suite of cubicles. Those cubicles are equipped with Dell Optiplex 960s running Windows 7. I'm reluctant to try to upgrade them since, as shared computers, other members of the department have stuff running on them that I'm sure they don't want to set up all over again.

In this process, I ran into a couple of bugs on these machines that I hadn't encountered while developing the tasks on my Win10 Dell Optiplex 7050s. These really made life difficult. I spent a lot of time wrangling with these errors, and I experienced a lot of stress wondering whether I'd fix them in five minutes or five months.

Here for posterity are the two major bugs I'd encountered and how they were resolved. I don't know anything about Python, so I hope these are helpful to the equally clueless.

"Couldn't share context" error

Initially, PsychoPy tasks of all varieties were crashing on startup. Our group couldn't even get the demos to run. The error message said pyglet.gl.ContextException: Unable to share contexts.

Didn't fix it:

Apparently this can be an issue with graphics drivers on some machines. Updating my drivers didn't fix the problem, perhaps in part because the hardware is kind of old.


This error was resolved by specifying an option for pyglet. I used PyschoPy's Builder View to compile the task. This made a file called Task.py. I opened up the .py file with notepad / wordpad / coder view / code writer and added two lines to the top of the script (here in bold):

from __future__ import absolute_import, division
# Trying to fix pyglet 'shared environment' error
import pyglet
# script continues as normal
from psychopy import locale_setup, sound, gui, visual, core, data, event, logging
from psychopy.constants import (NOT_STARTED, STARTED, PLAYING, PAUSED,
                                STOPPED, FINISHED, PRESSED, RELEASED, FOREVER)
This fixed my "Couldn't share context" error. If you're having trouble with "couldn't share context", consider opening up your .py file and adding these two lines just underneath from __future__ import.

Portaudio not initialized error

My Word Pronunciation Task requires the use of a microphone to detect reaction time. Apparently this was a simple task for my intellectual ancestors back in the 1990s -- they were able to handle this using HyperCard, of all things! But I have lost a lot of time and sleep and hair trying to get microphones to play nice with PsychoPy. It's not a major priority for the overworked developers, and it seems to rely on some other libraries that I don't understand.

Trying to launch my Word Pronunciation Task lead to the following error: PortAudio not initialized [...] The Server must be booted! [...] Need a running pyo server."

This was fixed by changing Windows' speaker playback frequency from 48000 Hz to 44100 Hz.

Right click on the Volume icon in the taskbar and open up "Playback devices."

Right click on your playback device and click "Properties."

Under the "Advanced" tab, switch the audio quality from a 48000Hz sampling rate (which Portaudio doesn't like) to a 44100 Hz sampling rate (which Portaudio does like, apparently).

This strangely oblique tweak was enough to fix my Portaudio problems.

Now that I can use all these computers, I'm looking forward to scaling up my data collection and getting this project really purring!

Thanks to Matt Craddock and Stephen Martin for help with the "shared context" bug. Thanks to Olivier Belanger for posting how to fix the Portaudio bug.

1 comment:

  1. Thanks Joe. The fix for the context error has given me an idea of how to fix this silently for future versions. For most people the shadow window thing won't be a big deal (I think it will matter to people using multiple stimulus windows together) so we could ask Python to try with that turned but then happily fall back to context sharing turned off if it doesn't work.

    So means hopefully you won't have to keep reapplying your fix in future experiments (from PsychoPy 1.86 onwards).

    Ah, the beauty of community fixes to community projects! :-)