Implement getMaxAmplitude for audio recordings

Question

I use audioRecord instead of mediarecorder, it works fine in my application, but I have logic that is very dependent on the maximum amplitude, which is very difficult to get with the audio editor, this is what I use when reading the buffer

private void writeAudioDataToFile(){ byte data[] = new byte[bufferSize]; String filename = getTempFilename(); FileOutputStream os = null; try { os = new FileOutputStream(filename); } catch (FileNotFoundException e) { // TODO Auto-generated catch block e.printStackTrace(); } int read = 0; max=0; if(null != os){ while(isRecording){ read = recorder.read(buffer, 0, bufferSize); int ab = (buffer[0] & 0xff) << 8 | buffer[1]; amplitude = Math.abs(ab); if(amplitude>0&&amplitude<25000) isSilence=true; else isSilence=false; //System.out.println(">>>>>>>>>>>"+amplitude); if(AudioRecord.ERROR_INVALID_OPERATION != read){ try { os.write(buffer); } catch (IOException e) { e.printStackTrace(); } } } try { os.close(); } catch (IOException e) { e.printStackTrace(); } } } 

but this does not work for me, as the value changes very quickly. I need to implement something like getMaxAmplitude () for audioRecord.

Answer 1

It does what you want and much more ... then it outputs the maximum points to a file that is read in excel. (I myself solved this problem, so the time is random.)

 package com.example.audiorecord; import java.io.BufferedWriter; import java.io.File; import java.io.FileWriter; import java.io.IOException; import java.text.SimpleDateFormat; import java.util.Calendar; import android.app.Activity; import android.media.AudioFormat; import android.media.AudioRecord; import android.media.MediaRecorder; import android.os.Bundle; import android.view.KeyEvent; import android.view.Menu; import android.view.View; import android.widget.Button; public class MainActivity extends Activity { private static final int RECORDER_SAMPLERATE = 44100; private static final int RECORDER_CHANNELS = AudioFormat.CHANNEL_IN_MONO; private static final int RECORDER_AUDIO_ENCODING = AudioFormat.ENCODING_PCM_16BIT; private AudioRecord recorder = null; private Thread recordingThread = null; private boolean isRecording = false; private String floatString = ""; Calendar c = Calendar.getInstance(); SimpleDateFormat df = new SimpleDateFormat("ddMMMyyyy_HHmmss"); String formattedDate = df.format(c.getTime()); @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); setButtonHandlers(); enableButtons(false); int bufferSize = AudioRecord.getMinBufferSize(RECORDER_SAMPLERATE, RECORDER_CHANNELS, RECORDER_AUDIO_ENCODING); } private void setButtonHandlers() { ((Button) findViewById(R.id.btnStart)).setOnClickListener(btnClick); ((Button) findViewById(R.id.btnStop)).setOnClickListener(btnClick); } private void enableButton(int id, boolean isEnable) { ((Button) findViewById(id)).setEnabled(isEnable); } private void enableButtons(boolean isRecording) { enableButton(R.id.btnStart, !isRecording); enableButton(R.id.btnStop, isRecording); } int BufferElements2Rec = 1024; // want to play 2048 (2K) since 2 bytes we use only 1024 int BytesPerElement = 2; // 2 bytes in 16bit format private void startRecording() { final File logFile = new File("sdcard/log_"+formattedDate+".txt"); if (!logFile.exists()) { try { logFile.createNewFile(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } recorder = new AudioRecord(MediaRecorder.AudioSource.MIC, RECORDER_SAMPLERATE, RECORDER_CHANNELS, RECORDER_AUDIO_ENCODING, BufferElements2Rec * BytesPerElement); recorder.startRecording(); isRecording = true; recordingThread = new Thread(new Runnable() { public void run() { writeAudioDataToFile(logFile); } }, "AudioRecorder Thread"); recordingThread.start(); } private void writeAudioDataToFile(File logFile) { // Write the output audio in byte short sData[] = new short[BufferElements2Rec]; while (isRecording) { // gets the voice output from microphone to byte format recorder.read(sData, 0, BufferElements2Rec); String sDataString = ""; double sDataMax = 0; for(int i=0; i<sData.length; i++){ if(Math.abs(sData[i])>=sDataMax){sDataMax=Math.abs(sData[i]);}; sDataString += "\n" + sDataMax; } try { //BufferedWriter for performance, true to set append to file flag BufferedWriter buf = new BufferedWriter(new FileWriter(logFile, true)); buf.append(sDataString); buf.newLine(); buf.close(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } } private void stopRecording() { // stops the recording activity if (null != recorder) { isRecording = false; recorder.stop(); recorder.release(); recorder = null; recordingThread = null; } } private View.OnClickListener btnClick = new View.OnClickListener() { public void onClick(View v) { switch (v.getId()) { case R.id.btnStart: { enableButtons(true); startRecording(); break; } case R.id.btnStop: { enableButtons(false); stopRecording(); break; } } } }; @Override public boolean onKeyDown(int keyCode, KeyEvent event) { if (keyCode == KeyEvent.KEYCODE_BACK) { finish(); } return super.onKeyDown(keyCode, event); } @Override public boolean onCreateOptionsMenu(Menu menu) { // Inflate the menu; this adds items to the action bar if it is present. getMenuInflater().inflate(R.menu.main, menu); return true; } } 

Answer 2

 int amplitude = (buffer[0] & 0xff) << 8 | buffer[1]; amplitude = Math.abs(ab); 

Are you wrong here? I think it should be

 int ab = (buffer[0] & 0xff) << 8 | buffer[1]; int amplitude = Math.abs(ab); 

Answer 3

If your encoding is ENCODING_PCM_16BIT , then you should use

 private int cAmplitude= 0; while(isRecording) { read = recorder.read(data, 0, bufferSize); for (int i=0; i<read/2; i++) { short curSample = getShort(data[i*2], data[i*2+1]); if (curSample > cAmplitude) { cAmplitude = curSample; } } Log.d("amplitude",Integer.toString(cAmplitude)); cAmplitude = 0; } private short getShort(byte argB1, byte argB2) { return (short)(argB1 | (argB2 << 8)); } 

For more information, see How to record a voice in the "wav" format in Android