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Record and Play Audio

Record Audio

To record data from an audio input device (such as a microphone connected to your system) for processing in MATLAB®:

  1. Create an audiorecorder object.

  2. Call the record or recordblocking method, where:

    • record returns immediate control to the calling function or the command prompt even as recording proceeds. Specify the length of the recording in seconds, or end the recording with the stop method. Optionally, call the pause and resume methods. The recording is performed asynchronously.

    • recordblocking retains control until the recording is complete. Specify the length of the recording in seconds. The recording is performed synchronously.

  3. Create a numeric array corresponding to the signal data using the getaudiodata method.

The following examples show how to use the recordblocking and record methods.

Record Microphone Input

This example shows how to record microphone input, play back the recording, and store the recorded audio signal in a numeric array. You must first connect a microphone to your system.

Create an audiorecorder object named recObj for recording audio input.

recObj = audiorecorder
recObj = 

  audiorecorder with properties:

          SampleRate: 8000
       BitsPerSample: 8
    NumberOfChannels: 1
            DeviceID: -1
       CurrentSample: 1
        TotalSamples: 0
             Running: 'off'
            StartFcn: []
             StopFcn: []
            TimerFcn: []
         TimerPeriod: 0.0500
                 Tag: ''
            UserData: []
                Type: 'audiorecorder'

audiorecorder creates an 8000 Hz, 8-bit, 1-channel audiorecorder object.

Record your voice for 5 seconds.

disp('Start speaking.')
recordblocking(recObj, 5);
disp('End of Recording.');

Play back the recording.

play(recObj);

Store data in double-precision array, y.

y = getaudiodata(recObj);

Plot the audio samples.

plot(y);

Record Two Channels from Different Sound Cards

To record audio independently from two different sound cards, with a microphone connected to each:

  1. Call audiodevinfo to list the available sounds cards. For example, this code returns a structure array containing all input and output audio devices on your system:

    info = audiodevinfo;

    Identify the sound cards you want to use by name, and note their ID values.

  2. Create two audiorecorder objects. For example, this code creates the audiorecorder object, recorder1, for recording a single channel from device 3 at 44.1 kHz and 16 bits per sample. The audiorecorder object, recorder2, is for recording a single channel from device 4 at 48 kHz:

    recorder1 = audiorecorder(44100,16,1,3); 
    recorder2 = audiorecorder(48000,16,1,4);
    
  3. Record each audio channel separately.

    record(recorder1);
    record(recorder2); 
    pause(5);

    The recordings occur simultaneously as the first call to record does not block.

  4. Stop the recordings.

    stop(recorder1);
    stop(recorder2); 

Specify the Quality of the Recording

By default, an audiorecorder object uses a sample rate of 8000 hertz, a depth of 8 bits (8 bits per sample), and a single audio channel. These settings minimize the required amount of data storage. For higher quality recordings, increase the sample rate or bit depth.

For example, typical compact disks use a sample rate of 44,100 hertz and a 16-bit depth. Create an audiorecorder object to record in stereo (two channels) with those settings:

myRecObj = audiorecorder(44100, 16, 2);

For more information on the available properties and values, see the audiorecorder reference page.

Play Audio

After you import or record audio, MATLAB supports several ways to listen to the data:

  • For simple playback using a single function call, use sound or soundsc. For example, load a sample MAT-file that contains signal and sample rate data, and listen to the audio:

    load chirp.mat;
    sound(y, Fs);
  • For more flexibility during playback, including the ability to pause, resume, or define callbacks, use the audioplayer function. Create an audioplayer object, then call methods to play the audio. For example, listen to the gong sample file:

    load gong.mat;
    gong = audioplayer(y, Fs);
    play(gong);

    For an additional example, see Record or Play Audio within a Function.

If you do not specify the sample rate, sound plays back at 8192 hertz. For any playback, specify smaller sample rates to play back more slowly, and larger sample rates to play back more quickly.

    Note:   Most sound cards support sample rates between approximately 5,000 and 48,000 hertz. Specifying sample rates outside this range can produce unexpected results.

Record or Play Audio within a Function

If you create an audioplayer or audiorecorder object inside a function, the object exists only for the duration of the function. For example, create a player function called playFile and a simple callback function showSeconds:

function playFile(myfile)
   load(myfile);
   
   obj = audioplayer(y, Fs);
   obj.TimerFcn = 'showSeconds';
   obj.TimerPeriod = 1;
   
   play(obj);
end

function showSeconds
   disp('tick')
end

Call playFile from the command prompt to play the file handel.mat:

playFile('handel.mat')

At the recorded sample rate of 8192 samples per second, playing the 73113 samples in the file takes approximately 8.9 seconds. However, the playFile function typically ends before playback completes, and clears the audioplayer object obj.

To ensure complete playback or recording, consider the following options:

  • Use playblocking or recordblocking instead of play or record. The blocking methods retain control until playing or recording completes. If you block control, you cannot issue any other commands or methods (such as pause or resume) during the playback or recording.

  • Create an output argument for your function that generates an object in the base workspace. For example, modify the playFile function to include an output argument:

    function obj = playFile(myfile)

    Call the function:

    h = playFile('handel.mat');

    Because h exists in the base workspace, you can pause playback from the command prompt:

    pause(h)
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