How can i make an Audio File loop continuously?

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Matlab_Beginner 2022-8-27

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评论： Matlab_Beginner 2022-8-28

Hello, im trying to make a simple Code, which allows me to loop an Audio File continuously.

i made a endless while loop, so that the Audio gets repeated, but it doesnt reload it and after the first Play, it get silenced.

Second Problem occur when the sound gets repeated via: ('Playcount=5' as an Exemple), i hear a millisecond cut between the replays, and i want to avoid that.

Any Ideas how can i solve this?

Thanks in advance.

Input = dsp.AudioFileReader('Sine_wave.wav',SamplesPerFrame=1024,PlayCount=5);
Output= audioDeviceWriter('SampleRate',Input.SampleRate);
while true
    
    audio = Input();
    Output(audio);
    
   
end 
release(Input); 
release(Output); 
 

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Walter Roberson 2022-8-27

Is it a 1 ms cut? Or would it just happen to be time equivalent to padding the end of the file to meet the SamplesPerFrame boundary?

That is, I wonder if it happens to work like buffer, buffer, buffer, final short buffer + padding to buffer boundary, buffer1, buffer2, ...

Matlab_Beginner 2022-8-28

编辑：Matlab_Beginner 2022-8-28

Hey walter, i think that may be the case that this happens to be time equivalent to padding the end of the file to meet the SamplesPerFrame boundary. However Mr Michael has posted a perfect solution. now it loops without any cuts.

Im wondering if i could stop this infinite loop with a keystroke when matlab in running and the sound is going out(Esc, Enter..)?

Thanks in advance!

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Answer 1

Michael 2022-8-27

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https://ww2.mathworks.cn/matlabcentral/answers/1788390-how-can-i-make-an-audio-file-loop-continuously#answer_1035475

编辑：Michael 2022-8-27

在 MATLAB Online 中打开

Have you read this article? Real-Time Audio in MATLAB It looks like your code is similar to what they show for real-time file to audio output, which is good. Have you checked your audio file to be sure the 1ms isn't at the end of the file? I'd graph the samples to check that.

The more likely culprit is an underrun of sample in the buffer. See this article for a discussion on how to reduce underrun errors. https://www.mathworks.com/help/audio/gs/audio-io-buffering-latency-and-throughput.html

One more thing...it looks like you are reading from the file each loop. If the file isnt too big you could do the read before the loop and keep it in memory as a variable.

Input = dsp.AudioFileReader('Sine_wave.wav',SamplesPerFrame=1024,PlayCount=5);
Output= audioDeviceWriter('SampleRate',Input.SampleRate);
Audio = Input()
while true
  Output(audio);
end
release(Input);
release(Output);

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Michael 2022-8-27

在 MATLAB Online 中打开

Here is the problem: This seems to be related to the audio file reader reaching the end of the file. As you can see in the code below, when it gets to the end and has to loop back to the beginning on the next iteration throug the loop, it takes 1.88 ms rather than the 0.22-0.23 ms that it typically takes. Not sure on a solution yet....

Fs = 48000;
dt = 1/Fs;
t = 0:dt:3;
y = sin(440*2*pi*t);
audiowrite('Sine_wave.wav',y,Fs)
%Input = dsp.AudioFileReader('Sine_wave.wav',SamplesPerFrame=1024,PlayCount=5);
fileReader = dsp.AudioFileReader('Sine_wave.wav',PlayCount=2);
deviceWriter = audioDeviceWriter('SampleRate',fileReader.SampleRate);
i= 1;
while ~isDone(fileReader)
    [mySignal, eof(i)] = fileReader();
    time(i) = toc;
    deviceWriter(mySignal);
    tic
    i = i+1
end
release(fileReader)
release(deviceWriter)
find(eof==true)
% ans =
% 
%    141   282
format long
time(138:145)'
% ans =
% 
%    0.000224349000000   <===== 138
%    0.000222358000000   <===== 139
%    0.000227631000000   <===== 140
%    0.000228241000000   <===== 141 (End of file
%    0.001844279000000   <===== 142
%    0.000227445000000   <===== 143
%    0.000227968000000   <===== 144
%    0.000235695000000   <===== 145

Michael 2022-8-28

No problem. See this on stopping execution: https://www.mathworks.com/help/matlab/matlab_env/stop-execution.html

Please don't forget to accept the answer.

Matlab_Beginner 2022-8-28

Thanks a lot!

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