Dart

Point a camera at something. Get an RTSP stream out the other end.

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The Problem

Hardware encoders are expensive. A dedicated box that takes HDMI in and spits RTSP out will set you back £800+. They work fine, but when you've got a pile of cheap capture dongles and a spare Pi lying around, it feels like overkill.

Enter Dart.

What is Dart?

Dart is a tiny, focused utility that takes video in and streams it out as RTSP. That's it. No frills, no bloat, no £800 price tag.

It's part of the SlingShot family of tools, but it stands on its own.

Inputs

• HDMI capture cards — Any V4L2 device. Cheap USB capture dongles work fine.
• Webcams — Same deal. If Linux sees it, Dart can use it.
• RTSP streams — Transcode and re-stream existing IP cameras.

Outputs

• RTSP — Connect your VMS, your NVR, your SlingShot instance, whatever.

Quick Start

The easiest way to get going is the config wizard:

dart --config-new

It'll scan for cameras, probe capabilities, and write a config file for you. No manual TOML wrangling required.

Or if you prefer to do things by hand:

# HDMI capture card on /dev/video0
dart --config config.hdmi.toml

# Webcam
dart --config config.webcam.toml

# Re-stream an existing RTSP source
dart --config config.rtsp.toml

Config Wizard

The --config-new flag walks you through setup interactively:

For V4L2 sources (webcams, capture cards):

• Scans and lists all connected video devices
• Probes supported formats and resolutions via v4l2-ctl
• Lets you pick resolution and framerate from what the hardware actually supports
• Writes a working config

For RTSP sources (IP cameras):

• Takes the RTSP URL
• Probes the stream with ffprobe to detect codec, resolution, framerate
• Asks if you want passthrough or transcode
• Writes a working config

Dependencies: v4l-utils for V4L2 probing, ffmpeg for RTSP probing.

Configuration

Dart uses TOML config files. Here's an example for an HDMI capture card:

[server]
rtsp_port = 8554
bind_address = "0.0.0.0"

[[sources]]
name = "hdmi"
type = "v4l2"
device = "/dev/video0"
format = "UYVY"           # For HDMI capture cards (TC358743, etc.)
width = 1280
height = 720
framerate = 30

[sources.encode]
bitrate = 2000            # kbps
keyframe_interval = 30
preset = "ultrafast"
tune = "zerolatency"

For a standard webcam, you can omit the format field:

[[sources]]
name = "webcam"
type = "v4l2"
device = "/dev/video0"
width = 1920
height = 1080
framerate = 30

[sources.encode]
bitrate = 4000

For relaying an existing RTSP stream:

[[sources]]
name = "camera"
type = "rtsp"
url = "rtsp://192.168.1.100:554/stream1"
latency = 200
fallback = "/path/to/fallback.jpg"

Why GStreamer?

Because it works. Because it's battle-tested. I know how to make RTSP servers from SlingShot, so this is a no brainer.

Dart wraps GStreamer and handles all the pipeline nonsense so you don't have to.

Hardware Requirements

If it can run Linux and has a USB port, it can probably run Dart.

Tested on:

• Raspberry Pi 4 (1080p/25fps, no sweat)
• Random x86 mini PCs
• Actual servers (overkill, but sure)

Part of the Family

Dart is a focused breakout from SlingShot. If you need:

• Ultra-low bandwidth streaming over QUIC → SlingShot
• Simple HDMI/V4L2 to RTSP → You're in the right place

Contributing

This is early days. It works for my use case, but your mileage may vary.

Found a bug? Open an issue. Got a fix? PR welcome.

Licence

AGPL-3.0. See LICENSE.