Video to Audio Transformation on the client side with JavaScript

It is possible to execute a Video to Audio Transformation on the client side (in the user’s browser) using JavaScript. Here are some approaches you can use:

Using Web Audio API

The Web Audio API provides a way to manipulate audio data in real-time within the browser. You can use it to extract the audio from a video element and save it as an audio file.

// Create a new audio context
const audioContext = new (window.AudioContext || window.webkitAudioContext)();

// Get the video element
const videoElement = document.getElementById('video');

// Create a MediaStreamSource object from the video element
const mediaStreamSource = audioContext.createMediaStreamSource(videoElement.captureStream());

// Create an Analyser node to analyze the audio data
const analyserNode = audioContext.createAnalyser();

// Connect the MediaStreamSource to the Analyser node
mediaStreamSource.connect(analyserNode);

// Get the audio data from the Analyser node
const audioData = analyserNode.getByteFrequencyData();

// Save the audio data as an array buffer
const arrayBuffer = new Uint8Array(audioData.length * 2);
for (let i = 0; i < audioData.length; i++) {
    arrayBuffer[i * 2] = audioData[i];
}

// Create a new Blob object from the array buffer
const blob = new Blob([arrayBuffer], { type: 'audio/wav' });

// Save the blob as an audio file
const link = document.createElement('a');
link.href = URL.createObjectURL(blob);
link.download = 'output.wav';
link.click();

Using getUserMedia and Web Audio API

You can use the getUserMedia method to request access to the user’s media, and then use the Web Audio API to extract the audio from the video element.

// Request access to the user's media
navigator.mediaDevices.getUserMedia({ video: true })
  .then(mediaStream => {
    // Create a new video element
    const videoElement = document.createElement('video');
    videoElement.srcObject = mediaStream;
    videoElement.play();

    // Get the audio data from the video element
    const audioData = getAudioDataFromVideo(videoElement);

    // Save the audio data as an array buffer
    const arrayBuffer = new Uint8Array(audioData.length * 2);
    for (let i = 0; i < audioData.length; i++) {
      arrayBuffer[i * 2] = audioData[i];
    }

    // Create a new Blob object from the array buffer
    const blob = new Blob([arrayBuffer], { type: 'audio/wav' });

    // Save the blob as an audio file
    const link = document.createElement('a');
    link.href = URL.createObjectURL(blob);
    link.download = 'output.wav';
    link.click();
  })
  .catch(error => console.error(error));

Using MediaRecorder to wrap the Audio to Video Transformation

You can use the MediaRecorder API to record the video and audio data from a video element, and then save it as an audio file.

// Get the video element
const videoElement = document.getElementById('video');

// Create a new MediaRecorder object
const mediaRecorder = new MediaRecorder(videoElement.captureStream());

// Add an event listener to the recordeddata event
mediaRecorder.addEventListener('dataavailable', event => {
  // Get the audio data from the event
  const audioData = event.data;

  // Save the audio data as an array buffer
  const arrayBuffer = new Uint8Array(audioData.length * 2);
  for (let i = 0; i < audioData.length; i++) {
    arrayBuffer[i * 2] = audioData[i];
  }

  // Create a new Blob object from the array buffer
  const blob = new Blob([arrayBuffer], { type: 'audio/wav' });

  // Save the blob as an audio file
  const link = document.createElement('a');
  link.href = URL.createObjectURL(blob);
  link.download = 'output.wav';
  link.click();
});

// Start recording
mediaRecorder.start();

// Stop recording after 10 seconds
setTimeout(() => mediaRecorder.stop(), 10000);

Note that these examples are for illustrative purposes only and may require modifications to work with your specific use case. Additionally, you will need to ensure that the user has given permission to access their media and that the browser supports the necessary APIs.

Basically – nowadays – the browser is very powerful. It could also handle a lot of logic – even without javascript: https://programtom.com/dev/2023/08/26/how-to-accomplish-good-user-experience-with-no-javascript/