Getting echo when capturing audio with JMF

Question

Hello.
I have just downloaded JMF 2.1.1 and have cribbed one of the examples to produce an application that will capture audio input, process it and pass it straight to the speakers. However, I am getting echo, i.e. the input signal appears twice at the speakers, shifted by about half a second.
Now, before you tell me that it is due to feedback from the speakers to the microphone, I must tell you that my audio signal is from a radio plugged into the mike socket of my PC, so there is no chance of any external feedback.
Below is the code:
import javax.media.*;
import javax.media.protocol.*;
import javax.media.control.*;
import javax.media.format.*;
public class ExampleClass2 implements ControllerListener {
     private Object waitSync = new Object();
private boolean stateTransitionOK = true;
     private Processor proc;
     public ExampleClass2 () {
          MediaLocator locator = getLocatorByName ("JavaSound audio capture");
          try {
               proc = Manager.createProcessor(locator);
               proc.addControllerListener(this);
               proc.configure();
               waitForState (Processor.Configured);
               proc.setContentDescriptor(null);
               proc.start();
//               waitForState(Processor.Started);
//          proc.getGainControl().setMute(true);
          } catch (Exception ex) {
               ex.printStackTrace();
               System.exit(1);
* Block until the processor has transitioned to the given state.
* Return false if the transition failed.
boolean waitForState(int state) {
     synchronized (waitSync) {
     try {
          while (proc.getState() != state && stateTransitionOK)
          waitSync.wait();
     } catch (Exception e) {}
     return stateTransitionOK;
* Controller Listener.
public void controllerUpdate(ControllerEvent evt) {
     if (evt instanceof ConfigureCompleteEvent ||
     evt instanceof RealizeCompleteEvent ||
     evt instanceof PrefetchCompleteEvent) {
     synchronized (waitSync) {
          stateTransitionOK = true;
          waitSync.notifyAll();
     } else if (evt instanceof ResourceUnavailableEvent) {
     synchronized (waitSync) {
          stateTransitionOK = false;
          waitSync.notifyAll();
     } else if (evt instanceof EndOfMediaEvent) {
     proc.close();
     System.exit(0);
     public static void main (String [] args) {
          ExampleClass2 two = new ExampleClass2();
Now, the really interesting thing is that if I uncomment the lines that mute the processor, I get only a single signal out of the speakers. It appears as if there is some connection between the mike input and speaker output.
Just to make sure, I tried this with JMStudio and got the same result. When I captured input, I got two signals output until I pressed the mute button, when I got one signal.
I also get the same problem if I use a Player, rather than a Processor.
I am running on Win95, JDK1.3.
Any thoughts?

Answer 1

i'm having the same problem. but i tried with teh audio property settings. and get resolved. wat solution u found? i would like to know how u solved your problem, plz let me know very soon.
Thanks,
Parth Pandya
Hello.
I have just downloaded JMF 2.1.1 and have cribbed one
of the examples to produce an application that will
capture audio input, process it and pass it straight
to the speakers. However, I am getting echo, i.e. the
input signal appears twice at the speakers, shifted by
about half a second.
Now, before you tell me that it is due to feedback
from the speakers to the microphone, I must tell you
that my audio signal is from a radio plugged into the
mike socket of my PC, so there is no chance of any
external feedback.
Below is the code:
import javax.media.*;
import javax.media.protocol.*;
import javax.media.control.*;
import javax.media.format.*;
public class ExampleClass2 implements
ControllerListener {
     private Object waitSync = new Object();
private boolean stateTransitionOK =
ansitionOK = true;
     private Processor proc;
     public ExampleClass2 () {
MediaLocator locator = getLocatorByName ("JavaSound
d audio capture");
          try {
               proc = Manager.createProcessor(locator);
               proc.addControllerListener(this);
               proc.configure();
               waitForState (Processor.Configured);
               proc.setContentDescriptor(null);
               proc.start();
//               waitForState(Processor.Started);
//          proc.getGainControl().setMute(true);
          } catch (Exception ex) {
               ex.printStackTrace();
               System.exit(1);
* Block until the processor has transitioned to
d to the given state.
* Return false if the transition failed.
boolean waitForState(int state) {
     synchronized (waitSync) {
     try {
while (proc.getState() != state &&
& stateTransitionOK)
          waitSync.wait();
     } catch (Exception e) {}
     return stateTransitionOK;
* Controller Listener.
public void controllerUpdate(ControllerEvent evt)
vt) {
     if (evt instanceof ConfigureCompleteEvent ||
     evt instanceof RealizeCompleteEvent ||
     evt instanceof PrefetchCompleteEvent) {
     synchronized (waitSync) {
          stateTransitionOK = true;
          waitSync.notifyAll();
} else if (evt instanceof ResourceUnavailableEvent)
     synchronized (waitSync) {
          stateTransitionOK = false;
          waitSync.notifyAll();
     } else if (evt instanceof EndOfMediaEvent) {
     proc.close();
     System.exit(0);
     public static void main (String [] args) {
          ExampleClass2 two = new ExampleClass2();
Now, the really interesting thing is that if I
uncomment the lines that mute the processor, I get
only a single signal out of the speakers. It appears
as if there is some connection between the mike input
and speaker output.
Just to make sure, I tried this with JMStudio and got
the same result. When I captured input, I got two
signals output until I pressed the mute button, when I
got one signal.
I also get the same problem if I use a Player, rather
than a Processor.
I am running on Win95, JDK1.3.
Any thoughts?