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function BasicSoundChannelHoppingDemo(nrChannels, device)
% BasicSoundChannelHoppingDemo([nrChannels][, device])
%
% Opens a multi-channel sound card for output, then uses audio slave devices to
% output a mono beep tone to each audio output channel in succession, "sweeping"
% or "hopping" over all speakers / output channels of the sound card.
%
% Press and hold a key to exit.
%
% Optional parameters:
%
% nrChannels = Number of channels to hop over. Tries to open first suitable audio
% device with nrChannels output channels if 'device' is omitted.
%
% device = Sound device index to choose. Will select 'device' by matching 'nrChannels'
% if omitted, or first audio device if both 'nrChannels' and 'device' are omitted.
%
% History:
% 02-Oct-22 mk Written.
if nargin < 1
nrChannels = [];
end
if nargin < 2
device = [];
end
% Initialize sound:
InitializePsychSound;
% Try to find suitable device for nrChannels, if specific count requested:
if isempty(device) && ~isempty(nrChannels)
devs = PsychPortAudio('GetDevices');
for i=1:length(devs)
if devs(i).NrOutputChannels == nrChannels
device = devs(i).DeviceIndex;
break;
end
end
end
% Open 'device' as playback master (1+8) with requested 'nrChannels' at default
% frequency [], in high timing precision / low latency mode 1:
pamaster = PsychPortAudio('Open', device, 1+8, 1, [], nrChannels);
% Start it: This is a master, so won't playback any sound by itself, only
% sound provided by potentially started slave devices:
PsychPortAudio('Start', pamaster);
% Query which device was chosen in the end:
status = PsychPortAudio('GetStatus', pamaster);
devinfo = PsychPortAudio('GetDevices', [], status.OutDeviceIndex);
fprintf('\nWill use following output device:\n');
disp(devinfo);
% And the actual number of channels that device has, assuming nrChannels was
% not already specified by the user:
if isempty(nrChannels)
nrChannels = devinfo.NrOutputChannels;
end
% Create a 1 second 400 Hz mono beep tone, usable by any [] open audio device via bufferHandle:
bufferHandle = PsychPortAudio('CreateBuffer', [], 0.8 * MakeBeep(400, 1, status.SampleRate));
fprintf('\nStarting infinite channel hopping loop over %i channels. Press and hold any key to exit.\n', nrChannels);
% Ready to do the thing - "trial loop"
KbReleaseWait;
while ~KbCheck
% Do a sweep over all output channels:
for i=1:nrChannels
% Open paout, for mono output attached to master channel i:
% Note: This is fast, but one could also open nrChannels separate paout
% devices, each attached to one master channel, prep them, and then inside
% the trial loop just call 'Start' on the one one wants, instead of doing
% a OpenSlave->FillBuffer->...->Close over and over again...
paout = PsychPortAudio('OpenSlave', pamaster, 1, 1, i);
PsychPortAudio('FillBuffer', paout, bufferHandle);
% Start playback, wait for start:
PsychPortAudio('Start', paout, 1, [], 1);
% Wait until end of playback:
PsychPortAudio('Stop', paout, 1);
% Close device:
PsychPortAudio('Close', paout);
% Next speaker, unless key pressed:
if KbCheck
break;
end
end
end
% Close all audio devices:
PsychPortAudio('Close');
fprintf('Done. Bye!\n');
end
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