Larix Broadcaster to OBS: Free SRT & RTMP Setup Guide

Larix Broadcaster is a free phone app (works on iPhone and Android) that turns your phone into a live camera. It speaks both SRT and RTMP — these are just the two common “languages” used to send live video over the internet. This guide sets Larix up to send your camera to a StreamRelay endpoint (your personal drop-off point on our servers), so the video shows up inside OBS on your PC.

Before you start

• Larix Broadcaster installed (iOS or Android).
• A StreamRelay endpoint — the dashboard gives you a ready-made publish URL (the web address your phone sends video to, with your secret publish key baked in). From €9.99/month.
• OBS on your PC, ready to pull the feed — OBS is the free broadcasting software that grabs your video and sends it on to Twitch, YouTube, etc.

Step 1: Create a new connection

Open Larix → Settings (gear) → Connections → New connection. A “connection” here just means one saved set of where-to-send-the-video details.

Step 2: Enter the StreamRelay URL

This URL is the address your phone delivers the video to. Pick one:

• SRT (recommended for cellular):

  srt://<id>.ingest.stream-relay.eu:4000?streamid=publish:live/<slug>:_:<publishKey>

• RTMP:

  rtmp://<id>.ingest.stream-relay.eu:1935/live/<slug>?pass=<publishKey>

  (Use the publish URL from your dashboard — it carries your secret publish key in the ?pass= part. Some apps split RTMP into a server box and a stream-key box; if so, put everything up to the slug — rtmp://<id>.ingest.stream-relay.eu:1935/live/<slug> — in the server box and pass=<publishKey> as the stream key, or just paste the whole URL into the server box and leave the key box empty.)

Larix figures out whether you mean SRT or RTMP from the start of the URL (the srt:// or rtmp:// part), so you don’t have to pick a protocol separately. Save the connection and make sure it’s switched on (ticked).

Step 3: Set video and bitrate

In Settings → Video, choose your resolution and frame rate, then set the bitrate — how much data per second your video uses. Higher looks sharper but needs a stronger, steadier connection. StreamRelay carries one single connection (no bonding), so leave headroom rather than maxing it out:

Setup	Resolution	Bitrate
Stable WiFi / strong 5G	1080p30	4000–6000 kbps
Average mobile signal	1080p30	2500–4000 kbps
Weak or crowded signal	720p30–60	1500–2500 kbps

If the stream stutters or the connection drops mid-broadcast, that’s usually the bitrate outrunning the signal — drop one tier and try again.

Step 4: Go live and add it in OBS

Tap the record/broadcast button to start sending. Now tell OBS where to pick the video up: add your endpoint as a Media Source (OBS’s term for an incoming feed) — see the OBS setup guide.

SRT or RTMP in Larix?

Larix handles both well. On a mobile (cellular) connection, use SRT — it recovers better when the signal wobbles and feels snappier (lower latency, meaning less delay). Use RTMP when you just want the simplest, most-compatible option. See SRT vs RTMP.

Frequently asked questions

Does Larix Broadcaster support SRT? Yes — create a connection with an srt:// URL. Larix also supports RTMP.

Why won’t Larix connect? Verify the URL scheme, port, and stream-id/key, confirm the connection is enabled, and that your StreamRelay endpoint is active.

What bitrate should I use in Larix? For 1080p30 over SRT on a stable connection, 4000-6000 kbps. On weaker mobile signal, drop to 2500-3500 kbps at 720p30-60 so the stream holds instead of buffering.

Larix shows “Connection failed” — what’s wrong? Almost always a mismatched URL. Check the port (4000 for SRT, 1935 for RTMP), that the streamid or pass parameter matches your dashboard exactly, and that you copied the full publish URL without extra spaces or line breaks.

The stream connects but OBS shows nothing — why? The Larix-to-relay leg and the relay-to-OBS leg are separate. Confirm the connection is enabled and actually broadcasting in Larix, then check the Media Source URL in OBS matches your endpoint’s read/pull address, not the publish address.

Keep reading

New to this? Start with the phone-to-OBS guide. Curious how Larix compares to Moblin and IRLPro? See mobile streaming apps compared.