>Psychtoolbox>PsychTests

PsychPortAudioDataPixxTimingTest([waitTime = 1][, exactstart=1][, deviceid=-1][, latbias=0][, triggerLevel=0.01][, reqlatencyclass=2])

Test script for sound onset timing reliability and sound onset latency of
the PsychPortAudio sound driver.

This script configures the driver for low latency and high timing
precision, then executes ten trials where it tries to emit a beep sound,
starting in exact sync to a black-white transition on the display.

You’ll need measurement equipment to use this: A DataPixx device from
VPixx technologies, connected to your computer via the USB connection
cable. Also a connection between the line-out jack of your soundcard and
the line-in jack of the DataPixx to transmit the sound data. The DataPixx
will receive the audio output of PsychPortAudio/Your Soundcard, timestamp
it and send the computed timing data to your computer via USB.

Some parameters may need tweaking, especially the ‘triggerLevel’
parameter.

Optional parameters:

‘waitTime’ = Time to wait (in seconds) before playing sound. Defaults
to 1 second if omitted.

‘exactstart’ = 0 – Start immediately, measure absolute latency.
= 1 – Test accuracy of scheduled sound onset. (Default)

‘deviceid’ = -1 – Auto-select optimal device (Default).
>=0 – Select specified output device. See
PsychPortAudio(‘GetDevices’) for a list of devices.

‘latbias’ = Hardware inherent latency bias. To be determined by
measurement - allows to PA to correct for it if provided.
Unit is seconds. Defaults to zero.

‘triggerLevel’ = Sound signal amplitude for DataPixx to detect sound
onset. Defaults to 0.01 = 1% of max amplitude if
exactstart == 0, otherwise it is auto-detected by
calibration. This will likely need tweaking on your
setup.

‘reqlatencyclass’ Override setting for reqlatencyclass parameter. By default,
reqlatencyclass = 2 is used, for exclusive device access for
low latency / high timing precision mode.