[HELP] problem of ECHO during record.

Question

Hello experts,
I have used a java code for sound record and playback from one of the threads in this forum.
But i am hearing an ECHO while recording as well as playback. That means the echo is getting stored.
i'm attaching the code.can u please suggest me any method for ECHO Cancellation.thanks a lot in advance...
import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;
import javax.microedition.media.control.RecordControl;
import javax.microedition.media.Manager;
import javax.microedition.media.MediaException;
import javax.microedition.media.Player;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
public class recordMidlet extends MIDlet implements CommandListener
private Form init = new Form("info");
private Command rec = new Command("rec",Command.OK, 1),
stop = new Command("stop",Command.STOP, 0),
exit = new Command("exit",Command.EXIT, 0);
private byte[] recordedSoundArray;
private Player p;
private RecordControl rc;
private ByteArrayOutputStream output;
public void startApp()
init.addCommand(rec);
init.addCommand(stop);
//init.addCommand(exit);
init.setCommandListener(this);
Display.getDisplay(this).setCurrent(init);
public void pauseApp()
public void destroyApp(boolean unconditional)
class dorecord extends Thread
public void run()
try
init.append("record voice ...\n\n");
// Create a Player that captures live audio.
p = Manager.createPlayer("capture://audio?encoding=pcm&rate=8000&bits=16");
p.realize();
// Get the RecordControl, set the record stream,
rc = (RecordControl)p.getControl("RecordControl");
output = new ByteArrayOutputStream();
rc.setRecordStream(output);
rc.startRecord();
p.start();
catch (Exception ioe)
init.append(ioe.toString());
class stopplay extends Thread
public void run()
try
init.append("finish record... starting playback\n\n");
rc.stopRecord();
rc.commit();
p.stop();
p.close();
init.append("playing...\n");
recordedSoundArray = output.toByteArray();
init.append("recorded sound = " String.valueOf(recordedSoundArray.length)"\n\n");
ByteArrayInputStream recordedInputStream = new ByteArrayInputStream(recordedSoundArray);
Player p2 = Manager.createPlayer(recordedInputStream,"audio/x-wav");
p2.prefetch();
p2.start();
//init.append("finish playing...");
catch (Exception e)
init.append("stop command: "+e.toString());
public void recordaud()
new dorecord().start();
public void stopplaying()
new stopplay().start();
public void commandAction(Command com, Displayable dis)
if(com == exit)
notifyDestroyed();
else if(com == stop)
init.removeCommand(stop);
init.addCommand(exit);
stopplaying();
else if(com == rec)
recordaud();

Answer 1

The attached VI will take care of phase jumps in either direction. I developed this for another project and it may need modification for your application.
Have you tried a smoothing filter or sliding window averager to get rid of your noise? These often work better than a simple lowpass filter.
When the system is moving slowly or stopped recalling the last valid position and allowing only small adjustments to it may prevent the big jumps. In other words, if you can't beat the noise, ignore it. This can be easy to talk about but is not always so easy to implement.
Lynn
Attachments:
Phase Unwrapper.vi ‏51 KB