Sim racing is an exercise in data management. Whether you're hitting the apex at Spa or managing fuel at Le Mans, you're constantly processing telemetry in your head. But for Gran Turismo 7 players on PS5, that data has always been locked behind a silent wall. You get the dials on your screen, but you lack the one thing every real-world driver relies on: a Race Engineer.
That’s why I built RaceVoice.
What is RaceVoice?
RaceVoice is an Electron-based application that turns raw telemetry into a living, breathing personality. It doesn’t just show you that your tyres are hot; it tells you—and depending on how you've set it up, it might not be very polite about it.
The Tech Stack: Cracking the Code
Building a real-time bridge between a PS5 and a PC isn't straightforward. The project involved several layers of technical challenge:
- UDP Telemetry Decryption: GT7 broadcasts telemetry over the network, but it’s encrypted. When Polyphony Digital released the v1.50 update, the community had to scramble to find the new encryption keys and offsets. RaceVoice uses a custom Salsa20 implementation to decrypt 368-byte packets at 60Hz.
- Live Visualization: Using Chart.js, the app renders live pedal inputs (throttle/brake), G-force radars, and tyre heatmaps. It’s the kind of data visibility usually reserved for top-tier telemetry software like MoTeC, but accessible for the console.
- The AI Brain (Groq API): This is where things get interesting. Instead of hardcoded lines, RaceVoice uses the Groq API to generate reactive, situational commentary. If you’re constantly hitting the redline or braking too late, the AI adapts its "personality" to match.
- High-Fidelity TTS (Kokoro): To avoid the robotic "sat-nav" voice of the past, I integrated the Kokoro-82M ONNX engine. Running entirely in WASM on the client side, it provides human-like, urgent audio feedback without the latency of cloud-based speech.
"Gordon Ramsay" in the Pit Lane
The most requested feature during development was character. By leveraging Large Language Models, I was able to implement a "British Motorsport Slang" profile. We lovingly call it the "Gordon Ramsay mode."
Instead of saying "Tyre temperature is high," the engineer might bark: "Your front rights are absolutely cooked! Sort it out or we're in the wall!" This adds a layer of immersion and urgency, transforming the racing experience from a game into a high-stakes simulation.
Beyond the Dashboard
RaceVoice is more than just a tool; it’s a study in how we can use AI to humanise cold data. By processing hundreds of telemetry frames a second—from suspension travel to fuel consumption—and distilling them into a single, timely voice prompt, we bridge the gap between player and machine.
John Harrison, Lead Engineer, sofi.digital