SRT vs. RTMP: Which Is Better for IRL Streaming?

When you stream live from out and about, your phone (or an encoder — an app or small device that turns your camera into a stream, e.g. Moblin, IRLPro or Larix) sends video to OBS on your home PC through a relay (a middleman server that catches your stream and hands it on). The “protocol” you pick is simply the language your phone and the relay use to talk to each other — and it changes how your stream behaves when the network gets shaky. Here are the two main choices, SRT vs RTMP, compared for exactly this job, plus which one to use with your StreamRelay endpoint.

SRT vs RTMP at a glance

	RTMP	SRT
Latency	Low	Lower (tunable)
Recovery on packet loss	Stalls / reconnects	ARQ retransmit on the link
Encryption	No (RTMPS adds TLS)	Built-in AES
Setup	Paste-and-go	A few params (latency, stream id)
App support	Universal	Wide and growing
Best for	Stable connections	Variable / cellular connections

What is RTMP?

RTMP (Real-Time Messaging Protocol) is the old, reliable workhorse of streaming — it’s been around for years and almost everything speaks it. It’s simple: you paste in a server address and a key, hit go, and you’re live.

Strengths of RTMP

• Supported by virtually every encoder and app — it just works everywhere.
• Zero tuning needed — paste it in and go.
• Fast and predictable when your connection is stable, like wired internet or strong Wi-Fi.

Limitations of RTMP

• It insists on receiving every piece of video in order, so if a piece goes missing your stream pauses while that piece is re-sent — you see a freeze.
• No built-in encryption (a version called RTMPS adds it, but not every app or platform supports RTMPS).
• It struggles on mobile data, where little drop-outs are normal.

What is SRT?

SRT (Secure Reliable Transport) is the newer protocol, built specifically for pushing live video over the unpredictable public internet — exactly the conditions you face streaming from a phone on the move.

Strengths of SRT

• ARQ is its trick for dealing with a flaky network: when a bit of video goes missing on the way, SRT quietly asks for it again and slots it back in, so brief drop-outs don’t freeze your picture.
• Built-in AES encryption — your stream is scrambled so others can’t snoop on it, no extra setup required.
• Tunable latency: you can tell it to wait a little longer before playing, which gives it more time to fix problems. More delay, but a smoother stream.

Limitations of SRT

• A little more setup than RTMP — you set a latency value (how long it’s allowed to buffer) and a stream id (a label that tells the relay which stream is which).
• Platforms like Twitch and YouTube can’t receive SRT directly — they only take RTMP. So you need a relay or OBS in the middle to translate, which is exactly the setup you’re building here.

Head-to-head comparison

Latency

Latency just means delay — how long between something happening in front of your camera and viewers seeing it. Both protocols are fast. The difference is that SRT lets you choose how much delay you’ll accept in exchange for smoothness. For IRL streaming over mobile data, a small SRT latency value gives you a smooth picture without a noticeable lag.

Reliability on unstable mobile networks

This is where SRT shines. Thanks to ARQ, when a packet (a small chunk of your video) gets lost on your mobile connection, SRT re-requests it over that same connection and patches the gap — so a quick signal hiccup doesn’t freeze your scene the way RTMP would. One important honesty note: this is recovery over a single connection only. It is not connection bonding — it does not combine several internet connections (like two SIM cards) into one.

Encryption and security

SRT encrypts your stream out of the box with AES (a strong, standard way of scrambling data). RTMP doesn’t — you’d need the RTMPS variant for that, and RTMPS isn’t supported everywhere.

Encoder app support

RTMP works in every app. SRT is supported by Moblin, Larix, IRLPro and OBS — in other words, all the apps you’d actually use for IRL streaming.

Which should you use?

Pick SRT if…

You stream over mobile data or any connection that comes and goes, you want low delay, or you want your stream encrypted. This is the best default for IRL.

Pick RTMP if…

Your connection is rock-solid (strong Wi-Fi or wired), or your app or workflow only supports RTMP, or you simply want the easiest paste-it-in-and-go path with nothing to configure.

Both work with a single-connection EU relay

StreamRelay accepts either protocol — but one connection at a time. To be clear: it does not bond multiple connections together (no SRTLA, no multi-SIM). Whichever protocol you pick, the relay carries that one stream from your device into OBS.

Latency, DE-CIX Frankfurt and why location matters

Whichever protocol you choose, the biggest factor in delay is plain geography — how far your video physically has to travel and how directly it gets there. You choose your relay location in the dashboard. Today that’s DE-CIX Frankfurt, one of the world’s largest internet exchange points (a major hub where networks meet and hand traffic over) — with more EU locations on the way. That means EU traffic takes a short, well-connected route. It’s also GDPR-compliant (built to the EU’s data-protection rules) and EU-hosted, and your stream keys stay yours.

Keep reading

Ready to set it up? Follow the phone-to-OBS guide or the OBS setup guide. New to IRL? Start with the complete IRL streaming guide.