CALYPSO MediaPipe Face Mesh Demo

Important Finding: Android GPU Zooming Bug

During testing across different Android devices, we discovered a critical bug related to MediaPipe's WebGL execution (delegate: "GPU") on Android smartphones.

The Issue

On many Android smartphones (unlike tablets which often have desktop-class browsers or better GPU floating-point precision), initializing the MediaPipe FaceLandmarker with delegate: "GPU" does not throw an error.

However, it fails silently by causing compounding floating-point math errors across frames. This manifests as a "zooming" or "drifting" effect where the tracked face mesh grows infinitely in size and quickly disappears off-screen.

Because no exception is thrown by the WebGL context upon initialization, a standard try...catch block cannot detect or recover from this failure during runtime.

The Solution: Auto-Detection

We implemented an automatic device detection script in www/index.html using the navigator.userAgent to apply the correct hardware delegate based on the device:

// Android tablets typically omit "Mobile" in their user agent string, whereas smartphones include it.
const isSmartphone = /Mobile/i.test(navigator.userAgent);
const chosenDelegate = isSmartphone ? "CPU" : "GPU";

• Smartphones: Are forced to use delegate: "CPU". This bypasses the WebGL precision issues entirely, keeping the tracking perfectly stable (with slightly higher battery usage).
• Tablets: Are allowed to use delegate: "GPU". High-end tablets handle the high-precision WebGL calculations smoothly, providing faster processing and lower power consumption.

This allows us to deploy a single FaceMeshDemo.apk that performs optimally and reliably across both tablets and smartphones.