🏎️ Telemetry Lab

A high-performance, low-latency telemetry capture and analysis suite for sim racing games (Assetto Corsa, Assetto Corsa Competizione, iRacing, Le Mans Ultimate, etc.).

This project is built using a hybrid C/Rust architecture:

• telemetry-fetcher (C11): A lightweight, low-level capture agent that maps game shared memory regions (Windows MMIO) at high frequencies (up to 360Hz) and writes them to disk in a highly packed, proprietary binary stream format (.rts).
• telemetry-analyzer (Rust): A robust GUI-driven analysis application built using egui and eframe to parse .rts files in microseconds and plot driver inputs, speeds, GPS track maps, and suspension/tire behaviors for lap optimization.

---

📁 Repository Structure

telemetry-lab/
├── telemetry-fetcher/ # C capture utility
│ ├── include/
│ │ ├── adapters/ # Windows MMIO mappings for AC & iRacing
│ │ └── rts/ # Custom file writer & binary structures
│ ├── src/
│ │ ├── adapters/ # Game shared memory readers
│ │ ├── storage/ # File storage logic (.rts format)
│ │ └── main.c # Capture lifecycle and mock generation
│ ├── CMakeLists.txt
│ └── mingw-toolchain.cmake # Cross-compilation setup for Windows target
│
├── telemetry-analyzer/ # Rust GUI analysis application
│ ├── src/
│ │ ├── parser.rs # Zero-allocation .rts file parser
│ │ └── main.rs # egui desktop GUI & plotting pipeline
│ └── Cargo.toml
│
└── README.md # Main documentation

---

📑 RTS (Racing Telemetry Stream) Binary Specification

The .rts file extension represents a high-speed, zero-boilerplate telemetry stream. To achieve maximum throughput and minimal write latency, it writes packed binary representation directly from the CPU register states to disk, conforming to little-endian alignment.

Both the C writer (rts_writer.c) and Rust parser (parser.rs) align structures strictly to 1-byte boundary alignment:

• C:#pragma pack(push, 1) / #pragma pack(pop)
• Rust:#[repr(C, packed)] with bytemuck safe casts

Byte-Level File Layout

+------------------------------------------------------------+
| RTS HEADER |
| - Magic Signature (4 bytes) "RTS\0" |
| - Version (1 byte) |
| - Game ID (1 byte) |
| - Metadata Length N (2 bytes, uint16_t) |
+------------------------------------------------------------+
| METADATA PAYLOAD |
| - UTF-8 JSON String (N bytes) |
+------------------------------------------------------------+
| TELEMETRY FRAMES STREAM |
| - Frame 1 (77 bytes, packed telemetry struct) |
| - Frame 2 (77 bytes, packed telemetry struct) |
| - ... |
| - Frame M (77 bytes, packed telemetry struct) |
+------------------------------------------------------------+

---

1. RTS File Header Layout (Variable Length)

The header starts with an 8-byte fixed block, followed immediately by a variable-length metadata string payload.

Offset (Bytes)	Type	Field Name	Description
0x00 - 0x03	char[4]	magic	Magic signature bytes: 'R', 'T', 'S', '\0'
0x04	uint8_t	version	File structure version (currently 1)
0x05	uint8_t	game_id	Game enum code (0=Unknown, 1=Assetto Corsa, 2=ACC, 3=iRacing, 4=LMU)
0x06 - 0x07	uint16_t	metadata_length	Length N of the following metadata payload string (Max 65,535 bytes)
0x08 - (8+N-1)	char[N]	metadata	UTF-8 encoded JSON metadata string (e.g., track name, car, driver)

---

2. Standardized Telemetry Frame Layout (77 Bytes Fixed)

Every telemetry sample is recorded as a single contiguous, packed block of exactly 77 bytes. To avoid alignment paddings, 1-byte packing is strictly enforced.

Offset (Bytes)	Field Offset	Type	Field Name	Units / Scale	Description
0	0x00	uint32_t	session_time_ms	ms	Time elapsed since session start
4	0x04	float	throttle	[0.0, 1.0]	Driver throttle position (0% to 100%)
8	0x08	float	brake	[0.0, 1.0]	Driver brake pressure/position (0% to 100%)
12	0x0C	float	clutch	[0.0, 1.0]	Driver clutch position (0% to 100%)
16	0x10	float	steering	[-1.0, 1.0]	Steering angle: negative=left, positive=right
20	0x14	float	speed_ms	m/s	Absolute vehicle speed in meters per second
24	0x18	float	engine_rpm	rpm	Current engine RPM
28	0x1C	int8_t	gear	integer	-1=Reverse, 0=Neutral, 1+=Forward Gears
29	0x1D	float	pos_x	meters	3D World X coordinates (GPS translation)
33	0x21	float	pos_y	meters	3D World Y coordinates (Altitude)
37	0x25	float	pos_z	meters	3D World Z coordinates (GPS translation)
41	0x29	float	lap_distance	meters	Distance traveled from the starting line
45	0x2D	float[4]	suspension_travel	meters	Susp. travel array: [FL, FR, RL, RR]
61	0x3D	float[4]	tire_temp_c	°C	Core tire temperatures: [FL, FR, RL, RR]
77	0x4D	float[4]	tire_pressure_kpa	kPa	Tires inflation pressures: [FL, FR, RL, RR]

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🛠️ Build and Compilation Instructions

1. Compiling the C Telemetry Fetcher

Since sim racing games are predominantly Windows-only, the telemetry-fetcher uses Windows shared memory APIs. However, it can be built/cross-compiled on Linux using the MinGW compiler toolchain.

To Cross-Compile for Windows on Linux: Ensure you have mingw-w64 packages installed on your system.

cd telemetry-fetcher
mkdir build &&cd build
cmake -DCMAKE_TOOLCHAIN_FILE=../mingw-toolchain.cmake ..
make

This produces fetcher.exe in the build directory, ready to run on any sim racing rig.

---

2. Compiling and Running the Rust Analyzer

The analyzer can run natively on both Linux and Windows systems.

Prerequisites: You will need Rust installed on your computer.

cd telemetry-analyzer
cargo run --release

• Click "Open File..." in the GUI to load any .rts binary file (e.g. the standard dummy_telemetry.rts generated by the fetcher).
• Interact with the speed graphs, throttle/brake maps, tires thermal state plots, and top-down visual GPS track maps.