Because it's a single HTML file using standard browser technologies, it requires no installation or server. You just open the file in a modern web browser.

How it Works: The Core Technologies

The application is built on three key browser-based technologies:

1. Web Audio API (For the Voice Changer)

This is a powerful JavaScript API built into modern browsers for processing and synthesizing audio.

• Audio Capture: The app uses navigator.mediaDevices.getUserMedia to request access to your microphone and capture your voice as an audio stream.
• Audio Graph: The Web Audio API works by creating a "graph" or "chain" of AudioNode objects. The audio stream flows from a source, through one or more processing nodes (the effects), to a destination (your speakers).
• Applying Effects: Each voice effect is created using a different combination of nodes:
• Robot/Radio: A BiquadFilterNode is used to isolate or remove certain frequencies, making the voice sound tinny or filtered.
• Distortion: A WaveShaperNode is used to apply a mathematical curve to the audio signal, creating a distorted, crunchy sound.
• Cave Reverb: A ConvolverNode is used to simulate the acoustics of a physical space. In our case, we create a synthetic "impulse response" to mimic a large, reverberant room.
• Switching Effects: When you select a new effect from the dropdown, the JavaScript code disconnects the old chain of audio nodes and connects a new one, changing the sound instantly.

2. TensorFlow.js (For the Face Tracking)

This is Google's open-source library for running machine learning models directly in the browser. We use a pre-trained model to avoid the complexity of training our own.

• Video Capture: The same getUserMedia call that gets microphone access also gets access to your webcam, streaming the video to a hidden <video> element.
• Face Landmarks Model: The application loads the face-landmarks-detection model, which is highly optimized to run efficiently in the browser. It's trained to identify 476 keypoints (or landmarks) on a human face in real-time.
• Detecting Mouth Movement: In a continuous loop (requestAnimationFrame), the app performs these steps:

1. It passes the current frame from the hidden video to the TensorFlow.js model.
2. The model returns the coordinates of all 476 keypoints on your face.
3. We are only interested in the mouth. The code specifically gets the coordinates of keypoint 13 (on the upper lip) and keypoint 14 (on the lower lip).
4. It calculates the distance between these two points. The greater the distance, the more open your mouth is.
5. This distance is "normalized" into a simple value between 0.0 (mouth closed) and 1.0 (mouth fully open). This value is stored in the mouthOpening variable.

3. HTML Canvas (For the Animated Face)

The <canvas> element provides a "drawing board" in the browser where we can render 2D graphics using JavaScript.

• Drawing the Face: A simple cartoon face is drawn using basic shapes: a large circle for the head, two smaller circles for the eyes, and so on.
• Animating the Mouth: The mouth is drawn as an ellipse. The key to the animation is that its height is directly controlled by the mouthOpening variable we got from TensorFlow.js.
• The Animation Loop: When requestAnimationFrame runs, it gets the latest mouthOpening value and immediately calls the drawFace() function to redraw the entire face with the newly calculated mouth height. This happens so quickly (up to 60 times per second) that it creates the illusion of smooth animation.

How to Use the Application

1. Save the Code: Save the entire code block into a single file named voice_changer_face.html.
2. Open in Browser: Open the file in a modern web browser like Google Chrome or Mozilla Firefox.
3. Click Start: Press the "Start Application" button.
4. Allow Permissions: Your browser will prompt you for permission to access your camera and microphone. You must click "Allow" for the application to work.
5. Choose an Effect & Speak: Once the status says "Ready!", select a voice effect from the dropdown menu and start speaking. Your modified voice will play through your speakers, and the animated face's mouth will move in sync with yours.