How do I make my Java program stop capturing audio as soon as a certain frequency has been read?

Question

I'm creating a guitar tuner in Java on the netbeans IDE and I want my program to stop capturing live audio as soon as a certain frequency has been read. This code below starts the audio capture but stops instantly. I want it to stop as soon as it reaches the frequency of the Low E string for example. I've used this website for help so far: https://docs.oracle.com/javase/tutorial/sound/capturing.html

//libraries
import static java.awt.SystemColor.info;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import static java.lang.System.in;
import javax.sound.sampled.AudioFormat;
import javax.sound.sampled.AudioSystem;
import javax.sound.sampled.DataLine.Info;
import javax.sound.sampled.DataLine;
import javax.sound.sampled.LineUnavailableException;
import javax.sound.sampled.TargetDataLine;


public class AudioInputPractice {

/**
 * @param args the command line arguments
 * @throws javax.sound.sampled.LineUnavailableException
 */
public int read(byte[] b, int off, int len) throws IOException{
            return in.read(b, off, len);
        }

public static void main(String[] args){
    
    System.out.println("Starting sound test...");
    
   
    //audio 
    try
    {
        TargetDataLine line;
        AudioFormat format = new AudioFormat(AudioFormat.Encoding.PCM_SIGNED, 44100, 16, 2, 4, 4100, false);
      
        DataLine.Info info = new DataLine.Info(TargetDataLine.class, format);
        if (!AudioSystem.isLineSupported(info)) {System.err.println("Line not Supported");}
        line = (TargetDataLine)AudioSystem.getLine(info);
        line.open();
        
        
  
    
    ByteArrayOutputStream out= new ByteArrayOutputStream();
    int numBytesRead;
    byte[] data = new byte[line.getBufferSize() / 5];
    
    System.out.println("Starting recording...");
    
    line.start();
    
    numBytesRead = line.read(data, 0 , data.length);
    out.write(data, 0, numBytesRead);
    }
    catch (LineUnavailableException ex) 
    {
        System.out.println("Error");
    }
    
    
    
    }
}

Answer 1

The code you have only reads one buffer's worth of data!

The usual thing is to put the read command into a conditional while loop. For your condition, it can be something as simple as a boolean called isRunning . As you read the data, you will presumably be shipping it on to your pitch analyzer.

The Java Tutorials has an example of such a while loop in Using Files and Format Converters. It's the first major code quote in this article. A snippet is shown below. Reading from a TargetDataLine is similar to reading from an AudioInputStream as is done in the example.

// Set an arbitrary buffer size of 1024 frames.
int numBytes = 1024 * bytesPerFrame; 
byte[] audioBytes = new byte[numBytes];
try {
    int numBytesRead = 0;
    int numFramesRead = 0;
    // Try to read numBytes bytes from the file.
    while ((numBytesRead = 
        audioInputStream.read(audioBytes)) != -1) {
        // Calculate the number of frames actually read.
        numFramesRead = numBytesRead / bytesPerFrame;
        totalFramesRead += numFramesRead;
        // Here, do something useful with the audio data that's 
        // now in the audioBytes array...
    }
} catch (Exception ex) { 
  // Handle the error...
}

The condition in the while is handled differently here. Often a boolean is used instead, as I first suggested, especially in cases where one wishes to use loose coupling as the mechanism to open or close the spigot, so to speak.