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Sound capture for frequency analysis and visualization in Android

I'm new to Android, and I'm trying to make a program that captures sound, and then displays the frequencies that exist inside it. I found an example that draws the graphic part of a graphic equalizer. This example uses an object of type AudioRecord to record sound. The technique used to break the audio signal into frequency components uses a mathematical transform called Discrete Fourier Transform (DFT), and uses Fast Fourier Transform (FFT) to perform DFT. This example uses a package that implements FFT. The package is linked here www.netlib.org/fftpack/jfftpack.tgz . The problem is that after starting this example, the graphic equalizer does not appear on the display after pressing the start button.

Here is the source code for the activity class:

package com.audio.processing; import android.app.Activity; import android.graphics.Bitmap; import android.graphics.Canvas; import android.graphics.Color; import android.graphics.Paint; import android.media.AudioFormat; import android.media.AudioRecord; import android.media.MediaRecorder; import android.os.AsyncTask; import android.os.Bundle; import android.util.Log; import android.view.View; import android.view.View.OnClickListener; import android.widget.Button; import android.widget.ImageView; import ca.uol.aig.fftpack.RealDoubleFFT; public class AudioProcessing extends Activity implements OnClickListener{ int frequency = 8000; int channelConfiguration = AudioFormat.CHANNEL_CONFIGURATION_MONO; int audioEncoding = AudioFormat.ENCODING_PCM_16BIT; private RealDoubleFFT transformer; int blockSize = 256; Button startStopButton; boolean started = false; RecordAudio recordTask; ImageView imageView; Bitmap bitmap; Canvas canvas; Paint paint; /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); startStopButton = (Button) this.findViewById(R.id.StartStopButton); startStopButton.setOnClickListener(this); transformer = new RealDoubleFFT(blockSize); imageView = (ImageView) this.findViewById(R.id.ImageView01); bitmap = Bitmap.createBitmap((int)256,(int)100,Bitmap.Config.ARGB_8888); canvas = new Canvas(bitmap); paint = new Paint(); paint.setColor(Color.GREEN); imageView.setImageBitmap(bitmap); } private class RecordAudio extends AsyncTask<Void, double[], Void> { @Override protected Void doInBackground(Void... params) { try { int bufferSize = AudioRecord.getMinBufferSize(frequency, channelConfiguration, audioEncoding); AudioRecord audioRecord = new AudioRecord( MediaRecorder.AudioSource.DEFAULT, frequency, channelConfiguration, audioEncoding, bufferSize); short[] buffer = new short[blockSize]; double[] toTransform = new double[blockSize]; audioRecord.startRecording(); while (started) { int bufferReadResult = audioRecord.read(buffer, 0, blockSize); for (int i = 0; i < blockSize && i < bufferReadResult; i++) { toTransform[i] = (double) buffer[i] / 32768.0; // signed 16 bit } transformer.ft(toTransform); publishProgress(toTransform); } audioRecord.stop(); } catch (Throwable t) { Log.e("AudioRecord", "Recording Failed"); } return null; } } protected void onProgressUpdate(double[]... toTransform) { canvas.drawColor(Color.BLACK); for (int i = 0; i < toTransform[0].length; i++) { int x = i; int downy = (int) (100 - (toTransform[0][i] * 10)); int upy = 100; canvas.drawLine(x, downy, x, upy, paint); } imageView.invalidate(); } public void onClick(View v) { if (started) { started = false; startStopButton.setText("Start"); recordTask.cancel(true); } else { started = true; startStopButton.setText("Stop"); recordTask = new RecordAudio(); recordTask.execute(); } } }

Here is main.xml:

 <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent" > <TextView android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="@string/hello" /> <ImageView android:id="@+id/ImageView01" android:layout_width="wrap_content" android:layout_height="wrap_content"></ImageView><Button android:text="Start" android:id="@+id/StartStopButton" android:layout_width="wrap_content" android:layout_height="wrap_content"></Button> </LinearLayout>

In AndroidManifest.xml, I set the RECORD_AUDIO permission. Thanks in advance!

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3 answers

Here is the working code. I tried it myself. It works great.

 package com.example.frequencytest; import android.app.Activity; import android.graphics.Bitmap; import android.graphics.Canvas; import android.graphics.Color; import android.graphics.Paint; import android.media.AudioFormat; import android.media.AudioRecord; import android.media.MediaRecorder; import android.os.AsyncTask; import android.os.Bundle; import android.util.Log; import android.view.Menu; import android.view.View; import android.view.View.OnClickListener; import android.widget.Button; import android.widget.ImageView; import ca.uol.aig.fftpack.RealDoubleFFT; public class MainActivity extends Activity implements OnClickListener { int frequency = 8000; int channelConfiguration = AudioFormat.CHANNEL_CONFIGURATION_MONO; int audioEncoding = AudioFormat.ENCODING_PCM_16BIT; private RealDoubleFFT transformer; int blockSize = 256; Button startStopButton; boolean started = false; RecordAudio recordTask; ImageView imageView; Bitmap bitmap; Canvas canvas; Paint paint; //AudioRecord audioRecord; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); startStopButton = (Button) this.findViewById(R.id.start_stop_btn); startStopButton.setOnClickListener(this); transformer = new RealDoubleFFT(blockSize); imageView = (ImageView) this.findViewById(R.id.imageView1); bitmap = Bitmap.createBitmap((int) 256, (int) 100, Bitmap.Config.ARGB_8888); canvas = new Canvas(bitmap); paint = new Paint(); paint.setColor(Color.GREEN); imageView.setImageBitmap(bitmap); } public class RecordAudio extends AsyncTask<Void, double[], Void> { @Override protected Void doInBackground(Void... arg0) { try { // int bufferSize = AudioRecord.getMinBufferSize(frequency, // AudioFormat.CHANNEL_IN_MONO, AudioFormat.ENCODING_PCM_16BIT); int bufferSize = AudioRecord.getMinBufferSize(frequency, channelConfiguration, audioEncoding); AudioRecord audioRecord = new AudioRecord( MediaRecorder.AudioSource.MIC, frequency, channelConfiguration, audioEncoding, bufferSize); short[] buffer = new short[blockSize]; double[] toTransform = new double[blockSize]; audioRecord.startRecording(); // started = true; hopes this should true before calling // following while loop while (started) { int bufferReadResult = audioRecord.read(buffer, 0, blockSize); for (int i = 0; i < blockSize && i < bufferReadResult; i++) { toTransform[i] = (double) buffer[i] / 32768.0; // signed // 16 } // bit transformer.ft(toTransform); publishProgress(toTransform); } audioRecord.stop(); } catch (Throwable t) { t.printStackTrace(); Log.e("AudioRecord", "Recording Failed"); } return null; } @Override protected void onProgressUpdate(double[]... toTransform) { canvas.drawColor(Color.BLACK); for (int i = 0; i < toTransform[0].length; i++) { int x = i; int downy = (int) (100 - (toTransform[0][i] * 10)); int upy = 100; canvas.drawLine(x, downy, x, upy, paint); } imageView.invalidate(); // TODO Auto-generated method stub // super.onProgressUpdate(values); } } @Override public boolean onCreateOptionsMenu(Menu menu) { getMenuInflater().inflate(R.menu.activity_main, menu); return true; } public void onClick(View arg0) { // TODO Auto-generated method stub if (started) { started = false; startStopButton.setText("Start"); recordTask.cancel(true); } else { started = true; startStopButton.setText("Stop"); recordTask = new RecordAudio(); recordTask.execute(); } } }
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Yes, I also had this project, and I had the same error as you, but after adding the permission below everything is fine. Most likely, you did not add it to the right place in the androidmanifest.xml file. This must be outside the application tag.

  <uses-permission android:name="android.permission.RECORD_AUDIO"> </uses-permission>
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The onProgressUpdate method must belong to RecordAudio, where, as in your code, it belongs to AudioProcessing. Check the braces, it should work based on the above correction

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