Playing audio

This demo will load an audio file and play it on your device.
To playback audio, we write the file in the audio buffer. When we load the audio, we need to make sure we obtain the frequency, otherwise the playback will be distorted. Once the audio buffer is written Datapixx('WriteAudioBuffer', waveData, 0);, we must again create a schedule for proper playback. As you can see, most functions are executed through a schedule.

Datapixx('SetAudioSchedule', 0, freq, nTotalFrames*repetitions, lrMode, 0, nTotalFrames);

Again, the first zero is the delay, freq is the audio frequency acquired when loading the audio file. If you want to repeat the sound, you need to know how many frames your sound file possesses. lrMode can take values [0 1 2 3], signifying respectively mono, left only, right only and stereo. The second zero is the address of the audio stimulus and the final argument is the number of frames.

MATLAB

function DatapixxAudioDemo(wavFilename, repetitions)
% DatapixxAudioDemo([wavFilename=funk.wav] [, repetitions=0])
%
% Demonstrates how to play an audio waveform using the Datapixx CODEC.
%
% Optional arguments:
%
% wavFilename = Name of a .wav sound file to load and play.
%               Otherwise the funk.wav provided with PsychToolbox is used.
%
% repetitions = Number of times to play the sound.
%               0 means play until the sun goes nova
%               (or a keypress, whichever comes first)
%
% Also see: DatapixxAudioStreamDemo
%
% History:
%
% Oct 1, 2009  paa     Written
% Oct 29, 2014 dml     Revised 

AssertOpenGL;   % We use PTB-3

% Get the .wav filename
if nargin < 1
    wavFilename = [];
end
if isempty(wavFilename)
    wavFilename = [PsychtoolboxRoot 'PsychDemos' filesep 'SoundFiles' filesep 'funk.wav'];
end

% Get the number of repetitions
if nargin < 2
    repetitions = [];
end
if isempty(repetitions)
    repetitions = 0;
end

% Load the .wav file
[waveData, freq] = audioread(wavFilename);
waveData = waveData';               % Transpose so that each row has 1 channel
nChannels = size(waveData, 1);
nTotalFrames = size(waveData, 2);

% Open Datapixx, and stop any schedules which might already be running
Datapixx('Open');
Datapixx('StopAllSchedules');
Datapixx('InitAudio');
Datapixx('SetAudioVolume', 1.00);    % Not too loud
Datapixx('RegWrRd');    % Synchronize Datapixx registers to local register cache

% Download the entire waveform to address 0.
Datapixx('WriteAudioBuffer', waveData, 0);

% Configure the Datapixx to play the buffer at the correct frequency.
% If the .wav file has a single channel, it will play to both ears in mono mode,
% otherwise it will play in stereo mode.
if (nChannels == 1)
    lrMode = 0;
else
    lrMode = 3;
end
if (repetitions > 0)    % Play a fixed number of reps
    Datapixx('SetAudioSchedule', 0, freq, nTotalFrames*repetitions, lrMode, 0, nTotalFrames);
else                    % Play forever
    Datapixx('SetAudioSchedule', 0, freq, 0, lrMode, 0, nTotalFrames);
end

% Start the playback
Datapixx('StartAudioSchedule');
Datapixx('RegWrRd');    % Synchronize Datapixx registers to local register cache

% Wait until schedule stops, or until a key is pressed.
fprintf('\nWaveform playback starting, press any key to abort.\n');
if (exist('OCTAVE_VERSION'))
    fflush(stdout);
end
while 1
    Datapixx('RegWrRd');   % Update registers for GetAudioStatus
    status = Datapixx('GetAudioStatus');
    if ~status.scheduleRunning
        break;
    end
    if KbCheck
        Datapixx('StopAudioSchedule');
        Datapixx('RegWrRd');    % Synchronize Datapixx registers to local register cache
        break;
    end
end

% Show final status of audio scheduler
fprintf('\nStatus information for audio scheduler:\n');
Datapixx('RegWrRd');   % Update registers for GetAudioStatus
disp(Datapixx('GetAudioStatus'));

% Job done
Datapixx('Close');
fprintf('\nDemo completed\n\n');