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PTB sound backend on Linux (virtual env): TypeError setting sound from array

I’ve come across a recurrent TypeError thrown by the psychtoolbox sound backend:

File “MYPATH/audiotest-ptb.py”, line 98, in
sound_1.setSound(‘A’, secs=5, hamming=True)
File “MYPATH/venv/lib/python3.8/site-packages/psychopy/sound/backend_ptb.py”, line 413, in setSound
_SoundBase.setSound(self, value, secs, octave, hamming, log)
File “MYPATH/venv/lib/python3.8/site-packages/psychopy/sound/_base.py”, line 178, in setSound
self._setSndFromNote(value.capitalize(), secs, octave,
File “MYPATH/venv/lib/python3.8/site-packages/psychopy/sound/_base.py”, line 213, in _setSndFromNote
self._setSndFromFreq(thisFreq, secs, hamming=hamming)
File “MYPATH/venv/lib/python3.8/site-packages/psychopy/sound/_base.py”, line 229, in _setSndFromFreq
self._setSndFromArray(outArr)
File “MYPATH/venv/lib/python3.8/site-packages/psychopy/sound/backend_ptb.py”, line 489, in _setSndFromArray
self.track.fill_buffer(self.sndArr, start_index=1)
TypeError: fill_buffer() got an unexpected keyword argument ‘start_index’

Experiment ended.

The attachment gives a minimal builder example.
audiotest-ptb.psyexp (3.4 KB)

The sound plays fine with the sounddevice backend.

Any help would be much appreciated.

Thanks for flagging this up! Removing , start_index=1 fixes the error in so much as it allows the sound to play, but I’ll have to look a bit further into what effect this has.