🚀 NEXUS SFU GATEWAY

---

🌟 Overview

Nexus SFU Gateway is an ultra-low-latency Selective Forwarding Unit (SFU) audio-visual streaming gateway written in pure Go. Engineered for distributed media applications, high-concurrency video conferencing, virtual events, and interactive robotics, Nexus routes RTP/RTCP streams directly between participants without transcoding overhead.

       +-----------------------+
       |   Publisher (Alice)   |
       +-----------+-----------+
                   | Ingress RTP/RTCP (Opus, VP8, H.264)
                   v
       +-----------------------------------------------------------+
       |                   NEXUS SFU GATEWAY                       |
       |  +---------------------+        +----------------------+  |
       |  | Adaptive Jitter Buf | -----> | Fan-Out Forwarder    |  |
       |  +---------------------+        +-----------+----------+  |
       |             |                               |             |
       |             v                               v             |
       |  +---------------------+        +----------------------+  |
       |  |  GCC Congestion BWE |        | NACK / PLI Rewriter  |  |
       |  +---------------------+        +----------------------+  |
       +---------------------------------------------+-------------+
                         |                           |
         Downlink 1      |                           |  Downlink 2
                         v                           v
             +-----------------------+   +-----------------------+
             |   Subscriber (Bob)    |   |   Subscriber (Carol)  |
             +-----------------------+   +-----------------------+

---

✨ Architectural Features

• Selective Forwarding Unit Core: Zero-copy packet fan-out engine with non-blocking egress ring buffers.
• Adaptive Jitter Buffer: Automatically buffers and re-sequences out-of-order packets while mitigating playout delay.
• Real-Time RTCP Feedback Controller:
  • NACK Generator: Identifies missing sequence numbers and generates RFC 4585 loss retransmissions.
  • PLI / FIR Throttling: Coordinates keyframe refresh across subscriber track changes without publisher flood.
• Google Congestion Control (GCC) AIMD: Dynamically adjusts bandwidth allocation and downscale thresholds according to RTCP receiver reports and REMB feedback.
• RTP Payload Depacketizer: Real-time packet parsing and keyframe boundary detection for VP8, Opus, and H.264.
• Real-Time WebSocket Signaling Server: Room management and session negotiation supporting concurrent rooms and auto-reconnection.

---

📦 Repository Structure

nexus-sfu-gateway/
├── .github/
│   └── workflows/
│       └── ci.yml               # Automated CI pipeline (lint, vet, race, test, build)
├── cmd/
│   └── server/
│       └── main.go              # Production gateway binary entrypoint
├── pkg/
│   ├── rtp/
│   │   ├── depacketizer.go      # VP8, Opus, and H.264 RTP depacketizer & keyframe inspector
│   │   ├── jitter_buffer.go     # Adaptive jitter buffer with sequence gap tracking
│   │   └── rtcp_handler.go      # PLI, FIR, NACK, and REMB RTCP control loops
│   ├── sfu/
│   │   ├── bwe.go               # AIMD bandwidth estimator and congestion state machine
│   │   ├── forwarder.go         # Multi-subscriber RTP stream fan-out router
│   │   └── router.go            # WebRTC PeerConnection session manager & ingress pump
│   └── signaling/
│       └── server.go            # Gorilla WebSocket signaling server & Room manager
├── tests/
│   ├── room_lifecycle_test.go   # Integration tests for signaling, room joining, leave & offer exchange
│   └── stream_forwarding_test.go# Unit & integration tests for packet routing, jitter buffer, and BWE
├── go.mod                       # Pion WebRTC v3 & Gorilla WebSocket dependencies
├── go.sum                       # Cryptographic checksums
└── README.md                    # Project documentation & benchmarks

---

🚀 Quick Start

Prerequisites

• Go 1.22 or higher
• Git

Installation & Run

# Clone the repository
git clone https://github.com/ER-brocode/nexus-sfu-gateway.git
cd nexus-sfu-gateway

# Download dependencies
go mod download

# Run the gateway server
go run cmd/server/main.go --port 8080

Health Check

curl http://localhost:8080/healthz
# Response: {"status":"healthy","gateway":"nexus-sfu-gateway"}

---

🧪 Running Automated Tests

# Run unit & integration test suites with race detection
go test -v -race ./...

---

🛡️ License

Distributed under the MIT License. See LICENSE for more information.