#93 HydraEye: camera-based presence detection for kiosks

Overview

Camera-based presence detection service for kiosk Mac Minis. Auto-launches experiences when someone approaches, returns to attract screen when they leave.

Architecture

Qt app (HydraExperienceNet) is the hardware broker for camera and microphone, avoiding macOS TCC permission issues for CLI tools.

Qt app captures webcam frames (320x240, 0.5 FPS), serves on localhost:9742
hydraeye is a hydranode role, polls Qt for frames, runs frame differencing detection, serves presence on localhost:9741
hydraheadflatscreen polls hydraeye for auto-launch decisions
Config comes from HydraCluster (EyeConfig on Node)

Qt app as hardware broker

The Qt app also handles mic relay for native Heads:

Captures mic audio, encodes Opus, sends RTP to Body:47995
Same protocol as browser WebRTC path, hydravoice on Body needs no changes
One TCC permission grant covers both camera and microphone

Detection algorithm

Frame differencing against reference frame (empty room)
15% pixel threshold + 3-frame debounce for presence
5% threshold + configurable idle timeout for absence
CPU: <0.5% of one core (76,800 pixels at 320x240)

HydraCluster config

EyeConfig on Node:

eye_config:
  threshold: 0.15
  idle_timeout_seconds: 30
  debounce_frames: 3

Prerequisites

Issue #92: hydraheadflatscreen queries Experience Library (deployed upstream)
Qt app mic relay to Body via Opus RTP
These give native Head feature parity with browser streaming before adding presence detection

Scope

New hydraeye Go binary (hydranode role)
Qt app camera + mic broker endpoints on localhost:9742
HydraCluster EyeConfig on Node store
hydraheadflatscreen integration (poll hydraeye for auto-launch)

HydraIssues