how to record the voice and get the fft data in both android and ios?

Question

I want to get the fft data and draw it .

I am trying platform on android:

mediaRecorder.SetAudioSource(AudioSource.Mic);
mediaRecorder.SetOutputFormat(OutputFormat.ThreeGpp);
mediaRecorder.SetAudioEncoder(AudioEncoder.AmrNb);
var file = Java.IO.File.CreateTempFile("audio", ".3gp");
mediaRecorder.SetOutputFile(file);
file.DeleteOnExit();
mediaRecorder.Prepare();
visualizer = new Visualizer(Visualizer.GetCaptureSizeRange()[1]);
visualizer.SetCaptureSize(visualizer.CaptureSize);
visualizer.SetDataCaptureListener(new DataCaptureListener(), Visualizer.MaxCaptureRate / 2, false, true);
visualizer.SetEnabled(true);
mediaRecorder.Start();

but it is not work it is recording and the visualizer data of fft and waveform is all zero .

how to do it?

Answer 1

If I understand correctly, the recording is working but the visualizer is not. If that is the case, then what might be the issue is that the Visualizer was not properly instantiated.

The Visualizer class has one public constructor and it calls for an audioSession not a captureSizeRange. See here Visualizer**
**
MediaRecorder does not have a method to get the audioSession from what I can see. In fact it looks like only MediaPlayer or AudioTrack audioSessions can be passed to the Visualizer

From the Visualizer reference docs

• If the session is not 0, the audio from a particular MediaPlayer or AudioTrack using this audio session is visualized

You might be able to get away with using a MediaRecorder if you pass a 0 to the Visualizer. No guarantees, but according to the Visualizer reference docs

• If the session is 0, the audio output mix is visualized

So I would try changing this line

visualizer = new Visualizer(Visualizer.GetCaptureSizeRange()[1]);

to

visualizer = new Visualizer(0);

This might allow you to see the audio output from the MediaRecorder.