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Connection between audio output device and Raspberry Pi hardware

Since R2019b

Add-On Required: This feature requires the MATLAB Support Package for Raspberry Pi Hardware add-on.


This object represents a connection between the audio output devices, such as speakers or headphones, and a Raspberry Pi® hardware. You can interact with the audio device using the functions listed in Object Functions.




audioPlayObj = audioplayer(mypi,DeviceName) creates an object that represents the connection to the audio output device, DeviceName, connected to the Raspberry Pi hardware, mypi. The Raspberry Pi hardware is represented by a raspi object.


audioPlayObj = audioplayback(mypi,DeviceName,Name,Value) sets Properties using name-value pairs. For example, audioPlayObj = audioplayback(mypi,'plughw:1,0','SampleRate',44100) plays audio data at a sample rate of 44100. You can specify multiple name-value pairs. Enclose each property name in single quotes.

Input Arguments

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Connection to the Raspberry Pi hardware board, specified as a raspi object.

The name of the audio output device attached to the hardware. To get the list of audio output devices connected to the hardware, use the listAudioDevices function, as described in List Available ALSA Audio Output Devices.

Example: audioPlayObj = audioplayback(mypi,'DeviceName','plughw:1,0');

Data Types: string


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The sample rate used by the audio output device to play audio. To find the sample rates supported by the audio output device, use the listAudioDevices function as described in List Available ALSA Audio Output Devices


>> audioCaptureObj.SampleRate
ans = 

Data Types: double

Object Functions

playPlay audio from audio device connected to Raspberry Pi


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Create a connection from the MATLAB® to the Raspberry Pi board. If you encounter errors after running the above command, try using additional arguments (as listed in raspi) or refer to Troubleshoot Connecting Issues to Raspberry Pi Hardware.


This example uses Audio Toolbox.

mypi = raspi;

Create a raspi_pitchshiftdeployment() function. In this function, connections to the audio input and output devices are created using the audiocapture and audioplayer objects. Modify the properties of the audio objects to match the properties of the device that you are using.

function raspi_pitchshiftdeployment()
% This function is used to deploy an audio processing application to a
% Raspberry Pi. The specific application of interest is pitch-shifting.
% This function takes audio input from a device connected to the Raspberry
% Pi, pitch-shifts this audio input to the desired pitch and then sends
% this output to the playback device connected to the Raspberry Pi

% Copyright 2019 The MathWorks, Inc.

% Create capture and playback system objects for audio processing on
% Raspberry Pi Hardware.

r = raspi();
captureObj = audiocapture(r,'plughw:2,0','SampleRate', 48000, 'SamplesPerFrame', 4800);

playbackObj = audioplayer(r,'plughw:2,0', 'SampleRate', 48000);

% Settings for pitch shifting operation
pitch = -5;         % Pitch shift in semi-tones
overlap = 0.2;      % Overlap of delay line
Fs = 8192;          % Sampling Frequency

pitchShifter = audiopluginexample.PitchShifter('PitchShift',8,'Overlap',0.3);

for k = 1:3000
    % capture audio input from the input device
    input = capture(captureObj);
    % pitch shift the audio input.
    % input is of type int16 and needs to be converted to type double
    % before processing the data. This is because the function shiftPitch
    % expects all its inputs to be of the same data type which in this case
    % is type double
    pitchShifted = zeros(size(double(input)),'like',double(input)); %#ok<PREALL>
    pitchShifter.PitchShift = pitch;
    pitchShifter.Overlap = overlap;
    [pitchShifted] = pitchShifter(double(input));
    % playback audio output using the output device
    % output data needs to be of type int16 and thus pitchShifted
    % which is a double is cast to be of type int16 before being sent to
    % the device

Create a Raspberry Pi configuration object, board.

[board = targetHardware('Raspberry Pi')
board = 
targetHardware with properties:

               Name: 'Raspberry Pi'
      DeviceAddress: ''
           Username: 'pi'
           Password: '*********'
           BuildDir: '/home/pi'
    EnableRunOnBoot: 0
        BuildAction: 'Build, load, and run'
        CoderConfig: [1×1 coder.CodeConfig]

Deploy the raspi_pitchshiftdeployment() function on Raspberry Pi using the configuration object, board. On successful deployment, hold the audio capture device close to your mouth and start speaking. You can hear your pitch shifted voice through the audio playback device.

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Extended Capabilities

Version History

Introduced in R2019b