JavaScript Audio Waveform Visualizer

Creating a Javascript Audio Waveform Visualizer allows you to represent audio data in a visually appealing and informative way. This tutorial guides you through building a basic visualizer that dynamically displays the waveform of an audio file played in the browser, enhancing user experience and providing real-time feedback.

Setting up the Basic HTML Structure

This section focuses on setting up the bare bones of your project, which includes the necessary HTML elements to upload the file, display audio controls and generate the audio waveform.

<div id="content">
  <input type="file" id="thefile" accept="audio/*" />
  <canvas id="canvas"></canvas>
  <audio id="audio" controls></audio>
</div>
    <script  src="./script.js"></script>

Applying Basic CSS Styling

Basic CSS is needed to place and style HTML element created in previous step. This CSS styling ensures your audio file input, canvas, and audio controls are properly positioned and sized on the page.

#thefile {
  position: fixed;
  top: 10px;
  left: 10px;
  z-index: 100;
}

#canvas {
  position: fixed;
  left: 0;
  top: 0;
  width: 100%;
  height: 100%;
}

audio {
  position: fixed;
  left: 10px;
  bottom: 10px;
  width: calc(100% - 20px);
}

window.onload = function() {
  
  var file = document.getElementById("thefile");
  var audio = document.getElementById("audio");
  
  file.onchange = function() {
    var files = this.files;
    audio.src = URL.createObjectURL(files[0]);
    audio.load();
    audio.play();
    var context = new AudioContext();
    var src = context.createMediaElementSource(audio);
    var analyser = context.createAnalyser();

    var canvas = document.getElementById("canvas");
    canvas.width = window.innerWidth;
    canvas.height = window.innerHeight;
    var ctx = canvas.getContext("2d");

    src.connect(analyser);
    analyser.connect(context.destination);

    analyser.fftSize = 256;

    var bufferLength = analyser.frequencyBinCount;
    console.log(bufferLength);

    var dataArray = new Uint8Array(bufferLength);

    var WIDTH = canvas.width;
    var HEIGHT = canvas.height;

    var barWidth = (WIDTH / bufferLength) * 2.5;
    var barHeight;
    var x = 0;

    function renderFrame() {
      requestAnimationFrame(renderFrame);

      x = 0;

      analyser.getByteFrequencyData(dataArray);

      ctx.fillStyle = "#000";
      ctx.fillRect(0, 0, WIDTH, HEIGHT);

      for (var i = 0; i < bufferLength; i++) {
        barHeight = dataArray[i];
        
        var r = barHeight + (25 * (i/bufferLength));
        var g = 250 * (i/bufferLength);
        var b = 50;

        ctx.fillStyle = "rgb(" + r + "," + g + "," + b + ")";
        ctx.fillRect(x, HEIGHT - barHeight, barWidth, barHeight);

        x += barWidth + 1;
      }
    }

    audio.play();
    renderFrame();
  };
};