Matlab parallel computing - Simultaneous play and record

Question

I want to play a pure tone and record from the default microphone simultaneously using Matlab.

%% Main code   
frequency = 500;
time = 5;

tic
parfor ii = 1:2
    if ii==1
        recording = test_record(time);
    elseif ii==2
        test_play(frequency,time);
    end
end
toc

size(recording)

This all works fine except that recording variable is not available after the parfor loop ends and I need it for further analysis. I'd appreciate suggestions of how to make the recorded sample available after the parforloop or even better - I'll be happy to learn if a better design is preferable.

Thanks!

Here are the two additional functions used for running the above code :

%% Play the given frequency
function test_play(frequency,recording_time)
fs = 8000; % Samples per second
t = 0:(1/fs):recording_time;
y =  sin(2*pi*frequency*t);
sound(y, fs);
end

%% Record from the microphone for given number of seconds
function recording = test_record(recording_time)
recObj = audiorecorder;
recordblocking(recObj, recording_time);
recording = getaudiodata(recObj);
end

Note - A related question's answer redirect to some program (Sox) that seem to do what I search for, however I want to write the Matlab code myself.

Daniel Daniel · Accepted Answer · 2014-05-25T13:53:20

In your case, recording is a local variable which remains on the worker. This code creates a sliced cell array which should fix it:

%% Main code   
frequency = 500;
time = 5;
recording=cell(2,1)
parfor ii = 1:2
    if ii==1
        recording{ii} = test_record(time);
    elseif ii==2
        test_play(frequency,time);
    end
end

Obviously, your data is recording{1}

Matlab parallel computing - Simultaneous play and record

1 Answers