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Description
Plays sounds from the governing computer using an Asus Xonar DX, DSX or U7 sound cards.
Low latency and jitter (7-8ms) are achievable when running Bpod on Ubuntu 14.04 with the low-latency kernel and PsychToolbox installed. Comparable performance is possible on a Windows 7-10 computer (Core i7, >=8GB Ram) with only MATLAB running, no processing-intensive background processes, and the latest ASUS ASIO driver installed.
Sounds are sampled at 192kHz, 7 channel, with left and right speakers on channels 1 and 2 ("front/left" and "front/right").
By default, channels 3-5 output a 1ms TTL pulse at the onset of each sound. Connecting any of these channels to a BNC or wire input channel will provide a precise record of sound onset. On Linux, to ensure that the pulse can be read by Bpod, verify that you have configured ALSAmixer correctly during installation.
Up to 32 sounds can be loaded before each trial, and are known to the sound server as sounds 1-32. The number of sounds is currently limited in software to 32, but theoretically depends on available RAM. Sounds can be quickly re-loaded between trials to change their waveform.
Sounds are triggered by sending a soft code back to the governing computer from a trial's state matrix, and calling PsychToolboxSoundServer from a predetermined soft code handler function.
Syntax
To initialize:
PsychToolboxSoundServer('init')
To load a sound:
PsychToolboxSoundServer('load', SoundID, Waveform)
To play a sound:
PsychToolboxSoundServer('play', SoundID)
To stop playback:
PsychToolboxSoundServer('stop', SoundID)
To stop all playback:
PsychToolboxSoundServer('stopall')
To close the sound server:
PsychToolboxSoundServer('close')
Parameters
SoundID: A byte specifying which sound to load, play or clear (1-32).
Waveform: A vector containing the waveform of the sound to load. Samples must be between -1 and 1, and the sampling rate is 192kHz.
For mono, use a 1Xn vector. Both speakers will play the sound.
For stereo, use a 2Xn vector. Row 1 is the left channel, and row 2 is right.
Returns
-None
Example
% 1. This code creates a noise waveform, loads it to the sound server, plays it and then closes the server.
SoundDuration = 3; SamplingRate = 192000; % Set parameters
MyWaveform = rand(1,SoundDuration*SamplingRate); % Create waveform
PsychToolboxSoundServer('init'); % Initialize sound server
PsychToolboxSoundServer('load', 1, MyWaveform); % load the sound
PsychToolboxSoundServer('play', 1); % Play the sound
pause(3);
PsychToolboxSoundServer('close'); % Close sound server
% 2. This code loads a sound, sets a soft-code handler to play it, and sets a soft code to be sent from a state matrix.
%%-------In main protocol file-------
SoundDuration = 3; SamplingRate = 192000; % Set parameters
MyWaveform = rand(1,SoundDuration*SamplingRate); % Create waveform
PsychToolboxSoundServer('init'); % Initialize sound server
PsychToolboxSoundServer('load', 3, MyWaveform); % load the sound
sma = NewStateMatrix();
sma = AddState(sma, 'Name', 'State1', ...
'Timer', 1,...
'StateChangeConditions', {'Tup', 'exit'},...
'OutputActions', {'SoftCode', 3});
BpodSystem.SoftCodeHandlerFunction = 'SoftCodeHandler_PlaySound';
%%-------Soft code handler file in protocol folder (SoftCodeHandler_PlaySound.m)-------
function SoftCodeHandler_PlaySound(SoundID)
if SoundID ~= 255
PsychToolboxSoundServer('Play', SoundID);
else
PsychToolboxSoundServer('StopAll');
end