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How do I interrupt a sound file that is currently being played?

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Joel Sieber
Joel Sieber on 15 Apr 2021
Answered: Jimmy Lapierre on 3 May 2021
I'm trying to write a program in appDesigner using Audio Toolbox that reads in midi keyboard input and plays an audio recording on repeat while a key is pressed. I've managed to get it to play the correct note, however it plays the sound file to completion and doesn't read anything in while it is playing. Here is my code for reading in messages and playing the notes:
% Read midi messages from keyboards and play the corresponding
% notes
while app.PowerSwitch.Value == "On"
% Example edited from https://uk.mathworks.com/help/audio/ug/midi-synthesizer.html
msgs = midireceive(app.device1);
for i = 1:numel(msgs)
msg = msgs(i);
if isNoteOn(msg) == true && msg.Velocity > 0
% select note file
if msg.Note == 48
app.fileReader = dsp.AudioFileReader('OrganArchive\Processed Audio\Swell\Oboe\Audio\Close\C1\S.wav');
else
app.fileReader = dsp.AudioFileReader('OrganArchive\Processed Audio\Swell\Oboe\Audio\Close\A2\S.wav');
end
% Play sound
while ~isDone(app.fileReader) && msg.Velocity > 0
audioData = app.fileReader();
app.deviceWriter(audioData);
drawnow;
if msg.Velocity == 0 || isNoteOff(msg) == true
break;
end
end
elseif isNoteOff(msg) == true
% end note
% Doesn't work but this is what I've tried:
release(app.fileReader);
release(app.deviceWriter);
break
end %end if
end % end for loop
drawnow;
if app.PowerSwitch.Value == "Off"
break
end
end % end of loop
function yes = isNoteOn(msg)
if msg.Type == midimsgtype.NoteOn && msg.Velocity > 0 && isNoteOff(msg) == false
fprintf('NoteOn \n');
yes = true;
else
yes = false;
end
end
function yes = isNoteOff(msg)
if msg.Type == midimsgtype.NoteOff || msg.Velocity == 0
fprintf('NoteOff \n')
yes = true;
else
yes = false;
end
end
I've also tried using stop(app.deviceWriter) to stop the note from playing but I get an error.
How can I get it to interrupt/stop the devicewriter so that it plays in real-time? Thanks in advance and if there are any questions please don't hesitate to ask.

Answers (1)

Jimmy Lapierre
Jimmy Lapierre on 3 May 2021
You should write your audio samples by smaller frames (such as 1024 samples per frame). That way, you can stop writing at any time to stop playback. Then, you might notice a delay, so if you want to reduce the latency, you can look at audioPlayerRecorder (even if you don't need the recording, that is setup in a way that latency is much smaller).

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