Question

Hi I’ve been writing a chat client and wanted to test the Java Sound API. I’ve managed to get sound working from the mic to the speakers on different computers via UDP. However the sound isn’t very clear. To check whether this was because of lost packets etc in the UDP protocol I wrote a small test for the sound to go to the speakers on the same machine as the mic. The sound isn’t any different which makes me think I have some settings wrong for reading or writing the sound. Can anybody have a look at my code and tell me how to make the sound clearer?

package test;

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

@SuppressWarnings("serial")
public class VoiceTest extends JFrame {
    private JButton chat = new JButton("Voice");
    private GUIListener gl = new GUIListener();
    private IncomingSoundListener isl = new IncomingSoundListener();
    private OutgoingSoundListener osl = new OutgoingSoundListener();
    private boolean inVoice = true;
    private boolean outVoice = false;
    AudioFormat format = getAudioFormat();
    ByteArrayOutputStream baos = new ByteArrayOutputStream();

public VoiceTest() throws IOException {
    super ("Test");
    //new Thread(tl).start();
    new Thread(isl).start();
    Container contentPane = this.getContentPane();
    this.setSize(200,100);
    this.setLocationRelativeTo(null);
    this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    chat.setBounds(10,10,80,30);
    chat.addActionListener(gl);
    contentPane.add(chat);
    this.setVisible(true);
}

private AudioFormat getAudioFormat() {
    float sampleRate = 8000.0F;
    int sampleSizeBits = 16;
    int channels = 1;
    boolean signed = true;
    boolean bigEndian = false;
    //AudioFormat.Encoding.ULAW
    return new AudioFormat(sampleRate, sampleSizeBits, channels, signed, bigEndian);
}

class GUIListener implements ActionListener {

    public void actionPerformed(ActionEvent actionevent) {
        String action = actionevent.getActionCommand();
        switch (action) {
            case "Mute":
                outVoice = false;
                chat.setText("Voice");
                break;
            case "Voice":
                new Thread(osl).start(); 
                outVoice = true;
                chat.setText("Mute");
                break;
        }
    }
}

class IncomingSoundListener implements Runnable {
    @Override
    public void run() {
        try {
            System.out.println("Listening for incoming sound");
            DataLine.Info speakerInfo = new DataLine.Info(SourceDataLine.class, format);
            SourceDataLine speaker = (SourceDataLine) AudioSystem.getLine(speakerInfo);
            speaker.open(format);
            speaker.start();
            while(inVoice) { 
                byte[] data = baos.toByteArray();
                baos.reset();
                ByteArrayInputStream bais = new ByteArrayInputStream(data);
                AudioInputStream ais = new AudioInputStream(bais,format,data.length);
                int numBytesRead = 0;
                if ((numBytesRead = ais.read(data)) != -1) speaker.write(data, 0, numBytesRead);
                ais.close();
                bais.close();
            }
            speaker.drain();
            speaker.close();
            System.out.println("Stopped listening for incoming sound");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

class OutgoingSoundListener implements Runnable {
    @Override
    public void run() {
        try {
            System.out.println("Listening for outgoing sound");
            DataLine.Info micInfo = new DataLine.Info(TargetDataLine.class, format);
            TargetDataLine mic = (TargetDataLine) AudioSystem.getLine(micInfo);
            mic.open(format);
            byte tmpBuff[] = new byte[mic.getBufferSize()/5];
            mic.start();
            while(outVoice) {
                int count = mic.read(tmpBuff,0,tmpBuff.length);
                if (count > 0) baos.write(tmpBuff, 0, count);
            }
            mic.drain();
            mic.close();
            System.out.println("Stopped listening for outgoing sound");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

}

/**
 * @param args
 * @throws IOException 
 */
public static void main(String[] args) throws IOException {
    new VoiceTest();    
}
}

Answer 1

You should try higher sampling rates and try to find acceptable quality/size ratio for your audio stream.

Checking the AudioFormat reference is also a good start for getting the idea.

Try changing local variables in your getAudioFormat() method to this:

private AudioFormat getAudioFormat() {
    float sampleRate = 16000.0F;
    int sampleSizeBits = 16;
    int channels = 1;
    ...
}

This is equivalent to a 256 kbps Mono audio file.