Generate an audio waveform in real time using Java - javafx

Question

I'm trying to generate an audio waveform by reading an existing .wav file that updates as the music is playing in real time. For example, if the song is played, I want the waveform to be continuously generated as the song progresses. So far I was able to read data from a .wav file and generate a STATIC waveform using javafx for roughly the first 2500 samples of the song. I compared the waveform to what it looks like in audacity and it matches it pretty well. Here's what it looks like:
However, I'm confused on how I would make the waveform generate not just statically for a particular window, but generate a constantly updated waveform through the duration of the entire song. I was looking into Realtime charts and using ScheduledExecutorService but I can't seem to make the line graph draw a new point faster than once every second without it causing issues. Is there another way I should go about doing this? I've spent a lot of time on this and don't want to give up now. I attached my code below, give it a look. Thanks.
import javafx.application.Application;
import javafx.collections.ObservableList;
import javafx.scene.Scene;
import javafx.scene.shape.*;
import javafx.scene.control.*;
import javafx.scene.layout.*;
import javafx.geometry.*;
import javafx.scene.paint.Color;
import javafx.scene.shape.Circle;
import javafx.stage.Stage;
import javafx.scene.text.Text;
import javafx.scene.chart.LineChart;
import javafx.scene.chart.NumberAxis;
import javafx.scene.chart.XYChart;
import javafx.scene.Group;
import javax.sound.sampled.AudioSystem;
import javax.sound.sampled.DataLine;
import javax.sound.sampled.LineUnavailableException;
import javax.sound.sampled.UnsupportedAudioFileException;
import javax.sound.sampled.AudioInputStream;
import javax.sound.sampled.AudioFormat;
import javax.sound.sampled.AudioFileFormat;
import javax.sound.sampled.TargetDataLine;
import java.net.*;
import java.io.*;
import java.nio.*;
public class Practice2 extends Application {
public static AudioInputStream audioInputStream;
#Override
public void start(Stage primaryStage) {
int channelCounter = 2; //used to jump between left and right channel in the loop
try {
File file = new File("testData/record.wav");
byte[] data = new byte[(int)file.length()];
BufferedInputStream in = new BufferedInputStream(new FileInputStream(file));
in.read(data);
in.close();
File leftChannelFile = new File("audioData/leftChannelAmpData.txt");
File rightChannelFile = new File("audioData/rightChannelAmpData.txt");
//Defining the x axis
NumberAxis xAxis = new NumberAxis(0, 2490, 1);
xAxis.setLabel("Samples");
//Defining the y axis
NumberAxis yAxis = new NumberAxis (-675, 675, 1);
yAxis.setLabel("Amplitude");
//Creating the line chart
LineChart linechart = new LineChart(xAxis, yAxis);
linechart.setPrefHeight(1350); //picked 1350 and 2500 because it is slightly less than the height and width of my monitor. Will definitely change these values in the future
linechart.setPrefWidth(2500);
linechart.setMaxHeight(1350);
linechart.setMaxWidth(2500);
//Prepare XYChart.Series objects by setting data
XYChart.Series series = new XYChart.Series();
series.setName("Amplitude from sample");
for (int i=44; i < data.length - 1; i+=2) { //start at the 44th byte of the .wav file. This skips the header info and reads the raw data
if (channelCounter % 2 == 0) { //This represents the loop for the left channel
channelCounter++;
short tempAmp = calculateAmpValue(data[i], data[i+1]); // Since the amplitude value for each sample is represented by 2 bytes instead of 1, this function takes the next 2 bytes and gives an integer representation for it (-32728 to 32727)
if (i < 2491)
series.getData().add(new XYChart.Data(i-43, tempAmp / 50)); //divide by 50 so the amplitude values can fit within the range of my graph.
}
else if (channelCounter % 2 == 1) { //this represents the loop for the right channel. ***I'M ONLY BUILDING A WAVEFORM FOR THE LEFT CHANNEL AT THE MOMENT. ***
channelCounter++;
short tempAmp = calculateAmpValue(data[i], data[i+1]);
}
}
//Setting the data to Line chart
linechart.getData().add(series);
Group root = new Group(linechart);
Scene scene = new Scene(root, 2500, 1350);
primaryStage.setTitle("Generated Waveform");
primaryStage.setScene(scene);
primaryStage.show();
}
catch (FileNotFoundException ex){ex.printStackTrace();}
catch (IOException ex){ex.printStackTrace();}
}
public static short calculateAmpValue(byte byte1, byte byte2) {
ByteBuffer bb = ByteBuffer.allocate(2);
bb.order(ByteOrder.LITTLE_ENDIAN);
bb.put(byte1);
bb.put(byte2);
short ampVal = bb.getShort(0);
return ampVal;
}
public static void main(String[] args) {
Application.launch(args);
}
}

Answer 1

If I were looking to draw a real-time chart with JavaFX, I'd probably assume I'd be using AnimationTimer for the drawing. It runs at 60 fps. So whatever is being drawn would reflect changes made in that time period. If the audio is 44100 fps, that's 735 audio data points per animation-cycle period. I'm not clear what you are attempting, though. Are you trying to write the equivalent of an oscilloscope?