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

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.

Answer 1

[Jimmy Lapierre]

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).