Re: Analyse the amplitude while recording a sound

From:

Knute Johnson <nospam@rabbitbrush.frazmtn.com>

Newsgroups:

comp.lang.java.programmer

Date:

Sat, 09 Jan 2010 09:47:49 -0800

Message-ID:

<9j32n.19574$0U1.15003@newsfe16.iad>

On 1/9/2010 4:55 AM, S?l?nissime wrote:

Hello
I would like to record a sound (from the microphone) and, at the same
time, be able to analyse the sound amplitude.
For example, I want to be able to display (in real time) a number
indicating how high is the volume recorded from microphone.

I've looked at javax.sound.sampled API. I could read bytes from the
input Stream, by the method TargetDataLine.read, but I don't how I
could analyse these bytes.
I've looked at JMF API, but it doesn't seem to do what I want.

Thank you in advance for your help

---
Cedric (from France)

Cedric:

That's actually pretty easy if you know the format of the audio data.
If the data for example were encoded PCM_UNSIGNED in 8 bit you could
just use the 8 bit value directly. If it is 16 bit signed you would
need to read two bytes and convert it to a short or int value. With PCM
encoding the value of the data is the volume.

Here are the beginnings of some code I wrote to display the peak values.
  It is configured for PCM_SIGNED 16 bit audio data. Pass it the byte
buffer that you used to read the data from the TargetDataLine and the
number of bytes of data in the buffer.

import java.awt.*;
import java.awt.event.*;
import java.io.*;
import javax.swing.*;

public class PeakMeter extends JPanel {
     volatile int peak;
     volatile double previousLevel;

     public void draw(byte[] b, int len) {
         int n = 0;

         peak = 0;
         for (int i=0; i<len; i+=2) {
             n = Math.abs((b[i] << 8) | b[i+1]);
             if (n > peak)
                 peak = n;
         }
         repaint();
     }

     public void paintComponent(Graphics g2d) {
         Graphics2D g = (Graphics2D)g2d;
         g.rotate(Math.PI,getWidth()/2,getHeight()/2);

         double level = peak / 32768.0;
         if (level < previousLevel)
             level = previousLevel * 0.80;
         previousLevel = level;

         g.setColor(Color.WHITE);
         g.fillRect(0,0,getWidth(),getHeight());

         g.setColor(Color.GREEN);
         int h = Math.min((int)(level * getHeight()),(int)(0.70 *
getHeight()));
         g.fillRect(0,0,getWidth(),h);

         if (level > 0.70) {
             g.setColor(Color.YELLOW);
             h = Math.min((int)((level - 0.70) * getHeight()),
              (int)(0.20 * getHeight()));
             g.fillRect(0,(int)(0.70 * getHeight()),getWidth(),h);
         }

         if (level > 0.90) {
             g.setColor(Color.RED);
             h = (int)((level - 0.90) * getHeight());
             g.fillRect(0,(int)(0.90 * getHeight()),getWidth(),h);
         }
     }
}

--

Knute Johnson
email s/nospam/knute2010/