🎛️ Latency Logger

A self-hosted web app for measuring and logging video processing latency across chained devices (e.g. testers, converters, processors, and displays).

Built with:

• Node.js + Express backend (SQLite3 storage)
• React frontend (client/build)
• Designed for small embedded hosts (Raspberry Pi / LXC)

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🧠 Overview

Latency Logger maintains a database of:

• Devices (with category, I/O carriers, notes, genlock flag)
• Measurements (signal format, rate, test samples, computed mean)
• Chains (ordered device paths for inference and validation)

It can infer per-device latency by comparing known measurements in a chain against a new Device Under Test (DUT).

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⚙️ Setup

1. Install dependencies

cd /opt/latencylogger
npm install
cd client
npm install
npm run build

2. Run locally

node /opt/latencylogger/index.js
# or via systemd
sudo systemctl start latencylogger

3. Access the UI

Open your browser at:

http://:3000

🧩 API Summary

Endpoint	Method	Description
/api/devices	GET / POST / PUT	List or manage devices
/api/measurements	GET / POST	Retrieve or insert measurements
/api/chain-validate-structured	POST	Validate chain and infer DUT latency

📁 Directory Structure

/opt/latencylogger ├── client/ # React frontend │ ├── src/ # Components │ └── build/ # Compiled output (served by Express) ├── index.js # Express API server ├── db.sqlite3 # Primary SQLite database ├── package.json └── latencylogger.service # Optional systemd unit

🧪 Example Chain

Lag Tester → BMD BiDirectional 12G → Disguise vx4 → Dell U2415

When validating: • Known devices contribute to the known total latency. • The DUT latency is inferred from the measured chain mean.

🧾 License

MIT © 2025 Dan Hall