develop FFT real time in matlab

Hello,

I have a microphone in front of a cooler because my goal is to define the RPM of the cooler. I have to develop a SCADA with this system.

Well, I don't know very much about the processing of the signal in Matlab and I found this code:

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

It worked very well, but know, I would like to listen de song in real time and not hold on the matlab process the signal read the line

play(recObj);

What I need is REAL TIME!

cheers!

Answer 1

[Geoff Hayes]

yogan - you could use the non-blocking record function instead and just assign a callback to the TimerFcn of your recorder. Then whenever the callback fires, you can grab the latest set of audio samples and process them. A very crude example is the following piece of code

function myRecorder = nonBlockingAudioRecorder

      figure;
      hPlot = plot(NaN,NaN);
      sampleRate = 8192;
      myRecorder = audiorecorder(sampleRate,8,1);
      set(myRecorder, 'TimerFcn', @myRecorderCallback, 'TimerPeriod', 1);
      atSecond = 1; 
      record(myRecorder);

      function myRecorderCallback(~, ~)
          allSamples = getaudiodata(myRecorder);
          newSamples = allSamples((atSecond - 1) * sampleRate + 1:atSecond * sampleRate);

          xdata = get(hPlot, 'XData');
          ydata = get(hPlot, 'YData');
          if isnan(xdata)
             xdata = linspace(0, atSecond - 1/sampleRate,sampleRate);
             ydata = [];
          else
              xdata = [xdata linspace(atSecond, atSecond + 1 - 1/sampleRate, sampleRate)];
          end
          ydata = [ydata newSamples'];
          set(hPlot, 'XData', xdata, 'YData', ydata);

          atSecond = atSecond + 1;

          if atSecond > 10
              stop(myRecorder);
          end
      end
  end

The above code records about a little over eleven seconds of data. Whenever the callback fires (about every one second), we grab the latest 8192 samples and plot them.