Why doeas my voice capture midlet generates echo? please help

Question

This midlet is for recording voice but it generates an echo of the voice while recording.. and i can't understand why. is there anyone who has any idea? i'd really appreciate any help.. it is required for my term project..
package com.apress.chapter8;
import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;
import javax.microedition.media.*;
import javax.microedition.media.control.RecordControl;
public class SaveCapturedAudioMIDlet extends MIDlet
implements CommandListener {
// the display items
private Display display = null;
private Alert alert = null;
private Command exitCommand = null;
// players and controls
private Player capturePlayer = null;
private RecordControl rControl = null;
private boolean error = false;
public SaveCapturedAudioMIDlet() {
// create the display
display = Display.getDisplay(this);
alert = new Alert("Message");
alert.setTimeout(Alert.FOREVER);
alert.setString("Capturing for 10 seconds. Say something intelligent!");
exitCommand = new Command("Exit", Command.EXIT, 1);
alert.addCommand(exitCommand);
alert.setCommandListener(this);
try {
// create the capture player
capturePlayer = Manager.createPlayer("capture://audio");
if (capturePlayer != null) {
// if created, realize it
capturePlayer.realize();
// and grab the RecordControl
rControl = (RecordControl)capturePlayer.getControl(
"javax.microedition.media.control.RecordControl");
// set the alert as the current item
display.setCurrent(alert);
// if it is null throw exception
if(rControl == null) throw new Exception("No RecordControl available");
// and set the destination for this captured data
rControl.setRecordLocation("file:///test.wav");
} else {
throw new Exception("Capture Audio Player is not available");
} catch(Exception e) {
error(e);
public void startApp() {
if(error) return;
try {   
// first start the corresponding recording player
capturePlayer.start();
// and then start the RecordControl
rControl.startRecord();
// now record for 10 seconds
Thread.sleep(10000);
// stop recording after time is up
rControl.stopRecord();
// commit the recording
rControl.commit();
// stop the Player instance
capturePlayer.stop();
// and close it to release the microphone
capturePlayer.close();
// finally, create a Player instance to playback
// check your device documentation to find out the root.
// The following will work on devices that have the root
// specified as shown
// and start it
} catch(Exception e) {
error(e);
public void pauseApp() {
public void destroyApp(boolean unconditional) {
if(capturePlayer != null) capturePlayer.close();
public void commandAction(Command cmd, Displayable disp) {
if(cmd == exitCommand) {
destroyApp(true);
notifyDestroyed();
// general purpose error method, displays on screen as well to output
private void error(Exception e) {
alert.setString(e.getMessage());
alert.setTitle("Error");
display.setCurrent(alert);
e.printStackTrace();
error = true;
}

Answer 1

hi, i am trying to make a karaoke player with j2me and i want it to be able to record the user's voice while playing the background song.. how can i synchronize these two? what can i do to make it more efficient?