How can i make an Audio File loop continuously?

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); 
 

[Walter Roberson]

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]

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!

Answer 1

[Michael]

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);

[Matlab_Beginner]

Hey Michael, first thanks for ur quick Answer. I'v checked my file and im sure that the file does not have that 1ms silence in it, this comes from Matlab, when loading the file to replay it. i have read the articles and i still can't find a solution for my problems.

(The code u'v posted about reading the file before the loop and keep it in memory as a variable doesnt work correctly, it feels like the sound gets cut 1000 time per sec.)

So what i want to achieve is a perfect looping of my audio file without this cut? is this Possible to do?

i scoped the output of my Code to better visualize the problem.

Thanks in advance!

[Michael]

Can you upload the .wav file?

[Michael]

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]

Here you go. This will load the file in memory and then loop through that vector rather than reading the file:

[y Fs] = audioread('Sine_wave.wav');
totalSamps = numel(y);
seg = 0;
while true
    inds = 1+mod((0:1023)+1024*seg,totalSamps);
    deviceWriter(y(inds));
    seg = seg + 1;
end

[Matlab_Beginner]

Hello Michael, Thank u so much for ur effort that ur putting in here. It loops perfect!!!

One last question, as u know the while loop in this Code is infinite. Is it possible to stop it with a keystroke while matlab is running? for exemple with ESC Key.

Thanks a lot in advance

[Michael]

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]

Thanks a lot!