AudioRecord buffer values - audio

Question

Hi I am building an app that will use incoming audio from the MIC and compare it with a stored sound file. At the moment I am trying to get to grips with what the data from the AudioRecord function looks like when saved to a array of bytes. My problem is that the values that are returned are all zero. I don't know if I am maybe not using/setting up the AudioRecord function properly. Here is my code:
import android.app.Activity;
import android.media.AudioRecord;
import android.media.MediaRecorder;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;
public class SnoreAlarmActivity extends Activity implements OnClickListener {
/** Called when the activity is first created. */
Button start, stop;
TextView display;
Boolean rec = false;
AudioRecord snore;
byte[] arrayOfByte = new byte[16 * 1024 / 8];
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
start = (Button) findViewById(R.id.bStart);
stop = (Button) findViewById(R.id.bStop);
display = (TextView) findViewById(R.id.tAnswer);
start.setOnClickListener(this);
stop.setOnClickListener(this);
int i = AudioRecord.getMinBufferSize(44100, 16, 2);
snore = new AudioRecord(MediaRecorder.AudioSource.MIC, 44100, 16, 2, i);// From
// MIC,Sample
// Rate
// of
// 44100,
// Channel_IN_MONO,16Bit
// Encoding,buffer
// size
// i
new Record().start();
}
#Override
public void onClick(View arg0) {
// TODO Auto-generated method stub
switch (arg0.getId()) {
case R.id.bStart:
rec = true;
break;
case R.id.bStop:
rec = false;
snore.stop();
snore.release();
for (int i = 0; i < 100; i++) {
int x = (int) arrayOfByte[i];
Log.w("Tag", "" + x);
}
break;
}
}
class Record extends Thread {
Record() {
}
#Override
public void run() {
// TODO Auto-generated method stub
while (rec) {
snore.startRecording();
snore.read(arrayOfByte, 0, (16 * 1024 / 8));
}
}
}
}
So my question is, why am I getting zero's?
*Also I know I should store the data in a short because of 16Bit encoding, will do that later, just trying to understand the values returned from the AudioRecord function at the moment.

Answer 1

Recording through MIC give me headache :)
Hope this will help because I lost whole day playing with it.
Here are steps which must be satisfied for MIC to work
Maniefst.xml MUST contains:
< uses-permission android:name="android.permission.RECORD_AUDIO" />
AudioRecord buffer should be set with AudioRecord.getMinBufferSize (you did it right)
If MIC wasn't released, you WON'T be able to bind to MIC again!
Restarting your phone will reset MIC.
Here is short example how I did it.
private android.media.AudioRecord aRecorder = null;
private Boolean breakLoop = false;
private byte[] buffer;
public Boolean StartRecording()
int freq = 22050;
try
{
prepareWaveFile(MyRandomAccessFile); //open file and writes WAV header
int bufferSize = android.media.AudioRecord.getMinBufferSize(freq, android.media.AudioFormat.CHANNEL_IN_MONO, android.media.AudioFormat.ENCODING_PCM_16BIT);
buffer = new byte[bufferSize];
if(bufferSize == AudioRecord.ERROR_BAD_VALUE){
Log.e(LOG_TAG, "Min buff size error");
return false;
}
aRecorder = new android.media.AudioRecord(MediaRecorder.AudioSource.MIC, freq, android.media.AudioFormat.CHANNEL_IN_MONO, android.media.AudioFormat.ENCODING_PCM_16BIT, bufferSize);
aRecorder.startRecording();
breakLoop = false;
int TotalSize=0; //koliko je snimljeno podataka
while (TotalSize < freq * 2 * 1 * 30) { //SampleRate * BytesPerSample * NumberOfChannels * seconds
int bufferReadResult = aRecorder.read(buffer, 0, bufferSize);
TotalSize+=bufferReadResult; // filesize failsafe
if (breakLoop) break; //if other thread stops recording
if (bufferReadResult>0) MyRandomAccessFile.write(buffer, 0, bufferReadResult); //write into some file ...
}
aRecorder.stop();
aRecorder.release(); //this is mandatory !
updateWaveFile(MyRandomAccessFile); //updates wave header
MyRandomAccessFile.close();
return true;
} catch (Exception e)
{
Log.e(LOG_TAG, "StartRecording: LOOP " + e);
try
{
aRecorder.stop();
} catch(Exception ex) {}
try
{
aRecorder.release();
} catch(Exception ex) {}
try
{
randomAccessWriter.close();
} catch(Exception ex) {}
return false;
}

Answer 2

are you on the Emulator? I heard that the Mic doesn't work on that.