how to remove the data (output of the function 'getaudiodata') from the memory buffer when I record an audio for long time and plot it at the same time?

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hoda kazemzadeh 2018-6-13

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评论： hoda kazemzadeh 2018-7-23

I record an audio signal from microphone and I plot it in real time. Simply I have:

 rObj=audiorecorder(fs, 24, 2);
 recordblocking(rObj)
 y=getaudiodata(rObj);

data accumulates in samples so it can not do recording for long time. Is it possible to remove data from the memory sometimes?

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Walter Roberson 2018-6-13

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No, it is not.

If you do not need to keep all of the data until the end, and the amount of data is not easily handled, then you should not be using audiorecorder: you should be using the Audio System Toolbox, probably with audioDeviceReader()

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Walter Roberson 2018-6-14

If you were to use the Audio System Toolbox or the DSP Toolbox, then you would be reading in a buffer of data at a time, which for your purposes here you would plot and then overwrite with the next buffer-full.

Memory does not accumulate for those unless you specifically save the contents, and if you do specifically save them, then you would know how you are keeping track of it and so would know what you would have to do to release it or reuse it according to your own implementation.

audiorecorder() will release accumulated audio data in one circumstance: that you call stop() on the object and then call resume(). This will clear all the accumulated data, and of course with the stop() it stops recording. There is no method of releasing accumulated audio data while you are still recording.

If you do not have enough easily available memory to store the audio data for the entire maximum time period for which you might need to record, then you should not be using audiorecorder(). As usual, there are temporary copies of the audio data made while it is adding on samples, so really you should not use audiorecorder() if you do not have at least twice as much memory as would be needed for the entire maximum time period for which you might record.

hoda kazemzadeh 2018-7-17

编辑：hoda kazemzadeh 2018-7-17

在 MATLAB Online 中打开

what i was doing is that : I was using the audiorecorder function and a timer function that could fire every one second and plot the data captured in that last one second. Every one second, it grabs all of the samples collected then, we extract those new samples and plot the data on the time domain. On the next call to this function, the data is replaced with the next one second of data. So the samples collected at the buffer is going more and more at each second (48000×2×8 bytes).

As soon as the code runs, we have access to the audio recorder and the timer function to have access to the plots. The recording is started and that executes a function that reads in stereo data from the board and stores it in a MATLAB two column vector. Then the figures are displayed which correspond to the signal recorded. the samples of data are updated every second using this function:

 recorder = audiorecorder(FS,24,2);
 set(recorder,'TimerPeriod',1,'TimerFcn',{@audioTimer,hObject});
 samples  = getaudiodata(hObject);

Thta works perfect but the only problem is the memory. Now how can I replace dsp.audiorecorder with 'audiorecorder' function without loosing the real time recording and displaying?

hoda kazemzadeh 2018-7-18

编辑：Walter Roberson 2018-7-18

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I use GUI, it seems that it s not that easy to modify the code with this function.

my code is:

   handles.recorder=audiorecorder(48000,24,2)
   set(handles.recorder,'TimerPeriod',1,'TimerFcn',{@audioTimer,hObject}); 
   record(handles.recorder)
  ...
  function audioTimer(hObject,varargin)
   hGui = varargin{2};
   % get the handles structure to access the plots/axes
   handles = guidata(hGui);
   % get the audio samples
  handles.samples  = getaudiodata(hObject);
  %processes
  handles.X=....
  t=...
  plot(handles.axes1,t,handles.X)
% store and stopStore callback functions to store the data as wave file and stop storing.  
...
% stop callback to stop the recording and GUI.

Now I dont need to timer function and time period and instead of getaudiodata, I have to replace with step(handles.recorder). but nothing is displayed maybe because audiodevice only be opened once.

Also I have warning: Warning: dsp.AudioRecorder will be removed in a future release. Use audioDeviceReader from Audio System Toolbox instead.

another error is for stop(hanldes.recorder) function which I use as stop button is pressed the recording and the figures have to be stopped.but stop does not work for dsp.audiorecorder, does it?

Walter Roberson 2018-7-21

That BufferSize is too small, should be at least as large as SamplesPerFrame.

You should probably be telling animatedline to limit the number of points it displays.

hoda kazemzadeh 2018-7-23

在 MATLAB Online 中打开

I am trying to modify my code in GUI. I dont use audiotimer function now. In 'OutputFcn' I write the dsp.audiorecorder and step functions and display the signal. I get this error when it reaches the line of 'step' function :

A given audio device may only be opened once.

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