How can I simultaneously play and record from the same audio device?

Hi guys,

I am trying to do a super simple operation of playing the signal and recording it at the same time through my RME audio interface. I have the DSP toolbox so I wanted to use the audioPlayerRecorder object to do that however my output is just a bunch of zeros with couple of non-zero values at the very end of the vector. I have been trying to figure out what would seem to be super simple operation for couple of days now and I just cannot figure it out. Please, any advice would be a lifesaver! My code so far is below

clear all
close all

%%DEFINE PARAMETERS FOR EXTERNAL SOUND CARD
internaldata.driver = 'ASIO';
internaldata.audio_device = 'ASIO Fireface USB';
internaldata.framesize = 30*2^13;
internaldata.samplerate = 48000;
internaldata.tfe_FFTLength = 512;
internaldata.spectral_averages = 1;
internaldata.input_channel_map = 5;
internaldata.output_channel_map = 5;

internaldata.deviceReader = audioDeviceReader('Driver',internaldata.driver,'SampleRate',internaldata.samplerate,...
    'Device',internaldata.audio_device,'ChannelMappingSource','Property','ChannelMapping',internaldata.input_channel_map);
internaldata.deviceWriter = audioDeviceWriter('Driver',internaldata.driver,'SampleRate',internaldata.samplerate,...
    'Device',internaldata.audio_device,'ChannelMappingSource','Property','ChannelMapping',internaldata.output_channel_map);

input = step(dsp.ColoredNoise('Color','pink','SamplesPerFrame',internaldata.framesize,'NumChannels',1));

aPR = audioPlayerRecorder('SampleRate',internaldata.samplerate,'PlayerChannelMapping',internaldata.output_channel_map,...
     'RecorderChannelMapping',internaldata.input_channel_map);

output=aPR(input);

figure
subplot 211
plot(input)
subplot 212
plot(output)

release(internaldata.deviceWriter)
release(internaldata.deviceReader)

Answer 1

[Sharan Paramasivam Murugesan]

1. Is your audio device capable of simultaneous playback and recording (Full duplex sound card)?

2. Following is an example on how to perform simultaneous playback and recording: https://www.mathworks.com/help/audio/ref/audioplayerrecorder-class.html#examples

Please take a look at the above example - especially the frame based loop. If you want to specify channel mapping manually, the section on "Specify non-default channel mapping" might help.