package greenfoot.sound;

import javax.sound.sampled.AudioFormat;
import javax.sound.sampled.AudioSystem;
import javax.sound.sampled.DataLine;
import javax.sound.sampled.LineUnavailableException;
import javax.sound.sampled.TargetDataLine;




| Gets the overall level of the default microphone plugged into the system.
| @author Michael
|
public class MicLevelGrabber
{       
private static final MicLevelGrabber INSTANCE = new MicLevelGrabber();
   
   private final AudioFormat format;
   
   private int level;
   
   private final Runnable updator;
   
   private volatile boolean running;
   
   private boolean reportedFailure;

   
   


| Create a new mic level grabber and initialise the updator.
|
private MicLevelGrabber()
   {        
      format = new AudioFormat(22050, 8, 1, true, true);
      updator = () -> {
           
      try {
               
      TargetDataLine line = (TargetDataLine) AudioSystem.getLine(new DataLine.Info(TargetDataLine.class, format));
      line.open();
      line.start();
      int bufferSize = (int) (format.getSampleRate() / 20) * format.getFrameSize();
               
      byte buffer[] = new byte[bufferSize];
      int bytesRead = line.read(buffer, 0, bufferSize);
      line.stop();
      line.close();
      level = (int) ((getRMS(buffer, bytesRead) / 127) * 100);
               
      reportedFailure = false;             
      }
           
   catch (LineUnavailableException ex) {
      if (! reportedFailure) {
         System.err.println("Couldn't get mic level: line unavailable");
                   
         reportedFailure = true;                 
         }             
      }
           
   catch (IllegalArgumentException iae) {
      if (! reportedFailure) {
         System.err.println("Couldn't get mic level: can't match 22050,8,1 audio format");
                   
         reportedFailure = true;                 
         }             
      }
           
   finally {
               
   running = false;             
   }         
};
}

   



| Get the singleton instance of this class.
| @return the instance.
|
public static MicLevelGrabber getInstance()
   {        
   return INSTANCE;     
   }

   



| Update the microphone level (spawns off a new thread) and return the
| level. It will most likely be the previous result that's returned,
| however for things like meters where the level is being constantly
| monitored this shouldn't be a problem.
|
| @return  a microphone input level, between 0 and 100
|
public int getLevel()
   {
   updateLevel();
       
   return level;     
   }

   



| Spawn off the thread to update the mic level value, if it isn't already
| running.
|
private synchronized void updateLevel()
   {
   if (!running) {            
      running = true;
           
      new Thread(updator).start();         
      }     
   }

   



| Get the root mean square average of an array of bytes.
| @param arr the array of bytes.
| @param lim the index to read up to in the array.
| @return the root mean square of the values.
|
private static double getRMS(byte[] arr, int lim)
   {        
   double average = 0;
       
   for (int i = 0; i < arr.length && i < lim; i++) {            
      average += arr[i] * arr[i];         
      }
       
   average /= arr.length;
   return Math.sqrt(average);     
   } 
}