mrtc — Minimal WebRTC in C (vibe-coded)

A minimal, working WebRTC implementation in C, entirely vibe-coded with AI. Built to learn how WebRTC works under the hood and to evaluate AI-assisted development for complex systems programming projects.

Implements the full protocol stack (ICE, DTLS, SRTP, RTP, SDP) from scratch, with VP8/Opus media codecs and a multi-party video conference application.

Follows the Pion model: the rtc core is codec-agnostic and operates at the RTP payload level. The media library provides optional codecs and pipeline orchestration on top. All public API functions use the rtc_ prefix.

Features

• STUN/ICE/TURN — NAT traversal, candidate gathering, connectivity checks, relay
• DTLS 1.2 + SRTP — encrypted media (AES-128-CM, HMAC-SHA1-80)
• RTP/RTCP — media packets, sender/receiver reports, jitter/loss stats
• SDP — multi-media session description (audio + video + data channels)
• Data Channels — message framing over DTLS
• Peer Connection — high-level WebRTC API
• VP8 (libvpx) + Opus (libopus) — video/audio codecs with RTP packetization
• Media pipeline — encode-once fan-out, jitter buffer, rate control
• Conference library — multi-peer orchestration
• Signaling — WebSocket client + server for meeting management
• Applications — chat (terminal) and conf_sdl (SDL3 video conference)

See ARCHITECTURE.md for design details and project structure. See ROADMAP.md for planned improvements.

Dependencies

Library	Purpose	Required by
OpenSSL 3.0+	DTLS, SRTP, HMAC, random	common, rtc
libwebsockets	WebSocket protocol	signaling
cJSON	JSON parsing	signaling
libvpx	VP8 codec	media
libopus	Opus codec	media
SDL3	Camera, audio, graphics	app/conf_sdl
CMake >= 3.10	Build system	all

Building

# Linux
sudo apt install build-essential cmake libssl-dev
mkdir build && cd build && cmake .. && make

# Windows (MSYS2 UCRT64)
pacman -S mingw-w64-ucrt-x86_64-{gcc,cmake,openssl,ninja,libwebsockets,cjson}
mkdir build && cd build && cmake -G Ninja .. && ninja

Running

# Start signaling server
./signaling/signaling_server 8080

# Chat (text over data channels)
./app/chat/chat --meeting test          # run in 2+ terminals

# Video conference (SDL3)
./app/conf_sdl/conf_sdl --meeting test  # M=mute, V=camera, Q=quit

Tests

20 executables, 119 tests. No external framework.

# Run all tests (from build/)
for t in rtc/test_*.exe media/test_*.exe signaling/test_*.exe; do ./$t; done

# Or individually
./rtc/test_stun
./rtc/test_peer
./media/test_media_pipeline
./signaling/test_signaling

License

Public domain / educational use. Not intended for production.