📡 srtla-relay-kit

One-command SRT + SRTLA relay server for IRL streaming. Bond multiple cellular connections for rock-solid outdoor broadcasts.

What is this?

A self-hosted relay server that combines SRT Live Server (b3ck edit) and SRTLA (BELABOX) into a single installer. Send your IRL stream over multiple cellular connections (bonding), and receive a single stable stream in OBS at home.

┌──────────────────┐                          ┌─────────────────────┐
│  Moblin / Belabox │    SRTLA (bonded)        │    Your VPS         │
│  (on the street)  │ ── SIM 1 ──┐             │                     │
│                   │ ── SIM 2 ──┼──▶ :30001  │  srtla_rec ──▶ SLS  │
│                   │ ── WiFi  ──┘    (UDP)    │                     │
└──────────────────┘                          │  :30000 (SRT)       │
                                               │  :8181  (stats)     │
┌──────────────────┐    SRT play               └─────────────────────┘
│  OBS at home      │ ◀──── :30000 ────────────       │
│  (receive stream) │                                  │
└──────────────────┘                                   │
        │                                              │
        ▼                                              │
   Twitch / Kick / YouTube                             │

Key Features

• SRTLA bonding — combine multiple internet connections (cellular + WiFi) for redundancy
• Open feeds — any stream name works without config changes (feed1, mycam, anything)
• HTTP stats — JSON endpoint for NOALBS integration (auto scene switching)
• One-command install — compiles everything from source, sets up systemd, opens firewall
• Oracle Cloud Free Tier compatible — runs on VM.Standard.E2.1.Micro (1 OCPU, 1GB RAM)

---

Quick Start

Prerequisites

• Ubuntu 22.04 VPS (Oracle Cloud Free Tier, AWS, DigitalOcean, etc.)
• SSH access with root/sudo
• Ports 30000/UDP, 30001/UDP, 8181/TCP open

Install

git clone https://github.com/YOUR_USERNAME/srtla-relay-kit.git
cd srtla-relay-kit
sudo bash install.sh

That's it. The installer will:

1. Install build dependencies
2. Set up swap (for low-RAM instances)
3. Compile libSRT from Haivision/srt
4. Compile SRT Live Server from b3ck/sls-b3ck-edit
5. Compile SRTLA receiver from BELABOX/srtla
6. Write config with open feeds
7. Create systemd services (auto-start on boot)
8. Configure iptables firewall

Custom Ports

SLS_PORT=40000 SRTLA_PORT=40001 HTTP_PORT=9090 sudo bash install.sh

---

Usage

After installation, you get three endpoints (replace YOUR_IP with your server's public IP):

Purpose	Protocol	URL
Publish (single)	SRT	srt://YOUR_IP:30000?streamid=publish/live/STREAM
Publish (bonded)	SRTLA	srtla://YOUR_IP:30001?streamid=publish/live/STREAM
Play (receive)	SRT	srt://YOUR_IP:30000?streamid=play/live/STREAM
Stats	HTTP	http://YOUR_IP:8181/stats

STREAM can be any name — feed1, mycam, stream123. No config changes needed.

Publish and Play must use the same STREAM name to connect.

---

Client Setup

Moblin (iOS)

1. Settings → Streams → Add
2. URL: srtla://YOUR_IP:30001?streamid=publish/live/mystream
3. Codec: H.265/HEVC
4. Bitrate: 6000 kbps
5. Adaptive bitrate: ON

Belabox

1. Open belaUI → SRTLA Settings
2. SRTLA receiver address: YOUR_IP
3. SRTLA receiver port: 30001
4. SRT streamid: publish/live/mystream
5. SRT latency: 2000 ms

OBS Studio (receive)

1. Sources → Media Source
2. Uncheck "Local File"
3. Input: srt://YOUR_IP:30000?streamid=play/live/mystream
4. Input Format: mpegts
5. Reconnect Delay: 3
6. ✅ Use hardware decoding when available
7. ✅ Show nothing when playback ends
8. ❌ Close file when inactive (keep unchecked!)

VLC

Media → Open Network Stream:
srt://YOUR_IP:30000?streamid=play/live/mystream

---

Oracle Cloud Free Tier Setup

Step 1: Open Ports in Security List

Before installing, open ports in the Oracle Cloud Console:

1. Go to Networking → Virtual Cloud Networks → click your VCN
2. Click your subnet → click Security List
3. Click "Add Ingress Rules" and add:

Source CIDR	Protocol	Dest. Port	Description
0.0.0.0/0	UDP	30000	SRT
0.0.0.0/0	UDP	30001	SRTLA
0.0.0.0/0	TCP	8181	Stats

⚠️ This is critical — Oracle blocks ports at the network level, not just the OS firewall.

Step 2: SSH and Install

ssh -i your_key.pem ubuntu@YOUR_IP
git clone https://github.com/YOUR_USERNAME/srtla-relay-kit.git
cd srtla-relay-kit
sudo bash install.sh

Resource Usage

On VM.Standard.E2.1.Micro (1 OCPU, 1GB RAM, 0.48 Gbps):

Resource	Usage
CPU	2-5% (one active stream)
RAM	30-60 MB
Network	~16 Mbps peak (8 Mbps in + 8 Mbps out)
Bandwidth cap	0.48 Gbps = plenty of headroom

---

Management

# Status
sudo systemctl status sls srtla

# Quick status check
sudo bash /opt/srtla-relay/status.sh

# Restart both services
sudo systemctl restart sls srtla

# View logs (live)
sudo journalctl -u sls -u srtla -f

# Edit config
sudo nano /etc/sls/sls.conf
sudo systemctl restart sls srtla   # after changes

# Check active streams
curl -s http://localhost:8181/stats | python3 -m json.tool

---

Configuration

Config file: /etc/sls/sls.conf

srt {
    worker_threads  1;           # Worker threads (1 is enough)
    worker_connections 300;      # Max simultaneous connections

    http_port 8181;              # Stats endpoint port
    cors_header *;               # CORS (for NOALBS etc.)

    server {
        listen 30000;            # SRT port
        latency 1000;            # Latency in ms
                                 # Increase to 2000 on unstable networks
                                 # Decrease to 500 on stable networks

        domain_player play;      # Play URL prefix
        domain_publisher publish; # Publish URL prefix

        default_sid publish/live/feed1;  # Default stream ID

        idle_streams_timeout 10; # Seconds before closing idle stream

        app {
            app_player live;     # App name: play/LIVE/name
            app_publisher live;  # App name: publish/LIVE/name
        }
    }
}

How Stream IDs Work

Stream ID format: domain/app/name

• Publish: publish/live/ANY_NAME
• Play: play/live/ANY_NAME

ANY_NAME is truly anything — feed1, mycam, stream_abc. No config changes needed. Anyone who knows your server IP and stream name can publish or play.

⚠️ There's no authentication — if you need security, use non-standard ports and treat stream names as passwords, or restrict access via iptables.

---

NOALBS Integration

NOALBS automatically switches OBS scenes based on bitrate (LIVE → LOW → BRB).

Add this to your NOALBS config.json:

{
  "streamServer": {
    "type": "SrtLiveServer",
    "statsUrl": "http://YOUR_IP:8181/stats",
    "publisher": "publish/live/mystream"
  },
  "name": "SRT Relay",
  "priority": 0,
  "overrideScenes": null,
  "dependsOn": null,
  "enabled": true
}

---

Architecture

Phone (Moblin/Belabox)
  │
  ├── SIM 1 (Carrier A) ──┐
  ├── SIM 2 (Carrier B) ──┼──▶ :30001/UDP [srtla_rec]
  ├── WiFi ────────────────┘       │
  │                                │  (reassembles packets from
  │                                │   multiple connections into
  │                                │   a single SRT stream)
  │                                ▼
  │                          :30000/UDP [SLS]
  │                                │
  │                                │  (manages publish/play,
  │                                │   routes streams, stats)
  │                                ▼
  │                          :30000/UDP [SLS play output]
  │                                │
  ▼                                ▼
OBS at home ◀── SRT play ──────────
  │
  ▼
Twitch / Kick / YouTube

1. SRTLA (srtla_rec) listens on port 30001/UDP. Receives packets from multiple connections (bonding) and reassembles them into a single SRT stream, forwarding to localhost:30000.

2. SLS (sls) listens on port 30000/UDP. Handles both direct SRT connections and those forwarded by SRTLA. Manages streams (publish/play), serves HTTP stats.

3. OBS connects to port 30000/UDP with streamid=play/live/name and receives the stream.

---

File Structure

/opt/srtla-relay/
├── bin/
│   ├── sls              # SRT Live Server binary
│   ├── slc              # SRT Live Client (testing)
│   └── srtla_rec        # SRTLA receiver binary
├── logs/
│   └── sls.log          # SLS log file
└── status.sh            # Quick status script

/etc/sls/
└── sls.conf             # SLS configuration

/etc/systemd/system/
├── sls.service          # SLS systemd unit
└── srtla.service        # SRTLA systemd unit

---

Troubleshooting

"Connection refused"

1. Check Oracle Cloud Security List (most common issue)
2. Check iptables: sudo iptables -L -n | grep 3000
3. Check services: sudo systemctl status sls srtla
4. Check logs: sudo journalctl -u sls --no-pager -n 50

SRTLA won't start

# SLS must be running first (SRTLA depends on it)
sudo systemctl status sls
sudo journalctl -u sls --no-pager -n 20

# Check if port is in use
sudo ss -ulnp | grep 30000

Stream freezes / pixelates

• Increase latency in sls.conf (e.g., 1000 → 2000)
• Lower bitrate in Moblin/Belabox (e.g., 6000 → 4000 kbps)
• Check stats: curl http://YOUR_IP:8181/stats

"publisher is NULL" in logs

This is normal — it means a player (OBS) is trying to watch a stream that nobody is publishing yet. Once you start streaming from Moblin/Belabox, the message stops and OBS picks up the stream.

---

Uninstall

sudo bash uninstall.sh

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Credits

• b3ck — SRT Live Server edit for IRL community
• BELABOX / rationalIRL — SRTLA bonding proxy
• Haivision — SRT protocol
• Edward Wu — Original SRT Live Server
• NOALBS — Auto scene switching

License

MIT — see LICENSE for details.

SRTLA is licensed under AGPL-3.0. libSRT is licensed under MPL-2.0. See each project's license for their terms.