SRT Test Source

A small, self-hosted SRT test source for macOS — built to exercise SRT ingest in mimoLive, but useful for testing any SRT receiver.

It streams a looping video file (or a synthetic test pattern) over SRT and fans the same stream out to multiple simultaneous receivers — something a bare ffmpeg/srt-live-transmit listener can't do (those are 1:1). It supports both SRT Listener mode (receivers dial in) and Caller mode (the source dials out to a receiver), and ships with a small web dashboard to watch connections and start/stop caller pushes.

ffmpeg (file loop / pattern) ──SRT/MPEG-TS publish──▶ MediaMTX ──SRT listener──▶ N receivers (callers)

Requirements

• macOS on Apple Silicon
• Homebrew
• mediamtx, and ffmpeg built with libsrt — setup.sh installs/verifies both
• python3 (Command Line Tools) for the dashboard

Quick start

git clone https://github.com/boinx/srt-test-source.git
cd srt-test-source
./setup.sh            # installs mediamtx + ffmpeg(libsrt), checks python3
./run.sh              # starts the streamer + dashboard

That's it — a fresh clone streams the bundled sample video (media/test.mp4) on teststream, plus the synthetic pattern stream. To stream your own clip instead, point SRC_VIDEO at it in config.env and re-run.

In your receiver (e.g. mimoLive), add an SRT source in Caller mode:

srt://<this-mac-ip>:8890?streamid=read:teststream     # the file / test card
srt://<this-mac-ip>:8890?streamid=read:pattern        # synthetic moving pattern

run.sh prints the URL with this Mac's LAN IP filled in. Open the same URL from as many receivers as you like. If your receiver only accepts the standard streamid syntax, use streamid=#!::m=request,r=teststream.

Configuration (config.env)

Variable	Default	Meaning
SRC_VIDEO	media/test.mp4 (bundled)	Source clip for teststream. Missing → a test card is generated.
SRT_PORT	8890	SRT listener port (receivers connect here).
API_PORT	9997	MediaMTX control API (loopback only).
DASH_PORT	8080	Web dashboard (loopback only).
PATTERN_BITRATE	3M	Bitrate of the synthetic pattern stream.

Caller mode (source dials out to a receiver)

Set your receiver to SRT Listener on a port, then push to it. Two ways:

One-shot:

./caller.sh <receiver-ip> 9000          # push teststream to that listener (Ctrl-C to stop)

Managed (dashboard + CLI) — multiple endpoints, auto-reconnect:

./callers.sh add <receiver-ip> 9000               # push teststream
./callers.sh add <receiver-ip> 9000 pattern 200   # push pattern, latency 200ms
./callers.sh list
./callers.sh rm 1
./callers.sh clear

Each push pulls a running stream from MediaMTX and forwards it (stream-copy) to the remote listener, and auto-reconnects if the receiver isn't up yet or restarts.

Dashboard

Open http://127.0.0.1:8080 (started by run.sh, or run ./dashboard.sh alone). It polls every 2s and shows:

• Incoming SRT connections — every reader/publisher with remote IP, path, and bytes.
• Outgoing caller pushes — start one from the form, watch its state, stop it.

MediaMTX has no built-in dashboard; this is a tiny stdlib-Python server (control.py) on top of its control API.

Always-on (optional)

By default the dashboard runs only while its terminal is open. To start the streamer + dashboard at login and keep them alive:

./setup.sh --service      # or: ./service.sh install
./service.sh uninstall    # to remove

How it works / notes

• Multi-receiver fan-out needs a media server. MediaMTX is the SRT listener; the ffmpeg generators publish into it over SRT/MPEG-TS, and it duplicates the stream to every reader. A lone ffmpeg listener only accepts one caller.
• IPv4 binding. MediaMTX is pinned to 0.0.0.0 on purpose: a bare :port binds IPv6-only on macOS, and IPv4 receivers then can't reach it (the SRT handshake fails silently). If a connection fails with nothing in the log, check lsof -nP -iUDP:8890 shows IPv4.
• MP4 → MPEG-TS. The source is remuxed to a .ts (in ~/.cache/srt-test-source/) and stream-copied: an .mp4/.mov paces badly under ffmpeg -re (drifts to ~0.66× real time), while a .ts copy holds 1.0× and preserves the original video and audio.
• Firewall. If macOS's firewall is on, allow mediamtx (and ffmpeg for caller mode) to accept/make connections, or other machines can't reach the streams.

Files

File	Purpose
setup.sh	Install/verify dependencies (--service also installs the launchd service).
run.sh	Start streamer + dashboard together.
start.sh	Build the .ts, render the config, run MediaMTX (streamer only).
dashboard.sh	Run the control server + web dashboard.
caller.sh	One-shot caller-mode push.
callers.sh	CLI for managed caller pushes (add/list/rm/clear).
control.py	Dashboard + caller-push manager (stdlib Python).
config.env	User settings.
mediamtx.yml.tmpl	MediaMTX config template (rendered by start.sh).
service.sh	Install/remove the always-on launchd service.
media/test.mp4	Bundled sample clip — the default teststream source.

License

MIT — see LICENSE.