SRT IN - OUT OBS / vMix

[markusnygard]

A Strom/GStreamer newbie question
How do I get SRT IN to Strom as a caller
lets say the the IP of Strom is 172.232.340.494:30024
I want to use a streamid obs_1
then in OBS that makes the obs streamurl srt://172.232.340.494:30024?streamid=obs_1
but what block or element do I use in Strom, activated beta so my alternatives is "srtsrc" and "MPEG-TS/SRT Input"
MPEG-TS/SRT Input is the easier since there is no alternative to fill in
But if I want to send it back?
So in Strom I want it to be al listener so I want my vMix to be a caller and I dont care if the streamid is obs_1 or obs_x as long as I can define it. This is due to the fact that then I can output more than one stream from the same IP:PORT which is need for example for a videomixer solution with PGM1, PGM2, CLEAN etc
So in block "MPEG-TS/SRT Output" you can just add the SRT URi so how but that be? and what would the obs stream url be srt://172.232.340.494:30024?streamid=publish:obs_x
br markus

[markusnygard-priva]

add some screenshoots of my setup
the only thing I can verify is working is that SRT from vMix is recived by Strom and the stream is not recived FROM strom to vMix
here is also now my real IP
vMix output settings

Strom flowboard

properties of srtsrc

properties of MPEG-TS/SRT Output

SRT recevier in vMix

[markusnygard-priva]

a small update change output to srtsink

but at some point srtsrc did loose streamID

[srperens]

Here's a revised answer:

---

Hi Markus!

SRT IN – receiving from OBS/vMix

Use the srtsrc block. The key thing to understand is that mode=caller is the default in SRT URIs, so if you want Strom to act as a listener you need to set mode=listener explicitly – this applies to both input and output blocks. To bind on all interfaces you can omit the IP part entirely:

srt://:30024?mode=listener&streamid=obs_1

OBS then connects as caller with:

srt://[your-strom-ip]:30024?streamid=obs_1

SRT OUT – sending to vMix

Same principle with srtsink. If you want Strom to be the listener and vMix the caller:

srt://:30024?mode=listener&streamid=obs_1

vMix connects as caller to srt://[strom-ip]:30024?streamid=obs_1.

One port = one stream

It's worth noting that the srtsrc and srtsink elements in GStreamer do not support stream-ID multiplexing – each element handles exactly one connection on one port. If you need PGM1, PGM2, CLEAN etc. you'll need separate ports per stream. True stream-ID multiplexing (multiple streams on a single port routed by stream-ID) requires a dedicated SRT relay/multiplexer in front. If we see enough demand for that kind of functionality we may look at building it natively into Strom, but for now separate ports is the way to go.

Stream-ID disappearing from the UI

This is likely not a bug – the properties panel doesn't do live updates on save. You need to save the flow and then restart it for values to take effect. If the stream-ID field appears empty after a restart, try saving and restarting the flow again and it should persist correctly.

Hope that helps!

[markusnygard-priva]

Thanks for the answer so which ports are open in OSC strom inbound UDP? since it just says 30024 I thought that that was the only one open and there fore you would need to use streamID:s. On a selfhosted computer it is a totally different thing. Even if I thing something like srt://IP:PORT?streamid=read:obs_1 should work. At least it is supported like that in mediaMTX

[srperens]

Good question! You're right that on a self-hosted machine you can open as many ports as you like, so using one port per stream is straightforward. In OSC-hosted Strom the situation is different – only a single port (30024) is exposed per instance, which is exactly why stream-ID multiplexing becomes relevant there.

However, as mentioned, srtsrc and srtsink in GStreamer don't support stream-ID-based multiplexing – each element handles one connection, full stop. The streamid parameter in the URI is passed along in the SRT handshake, but GStreamer won't route multiple callers to different pipelines based on it. So even on port 30024, you can only have one active SRT connection per element.

The streamid=read:obs_1 / streamid=publish:obs_1 convention you see in mediaMTX is a mediaMTX-specific routing feature – mediaMTX is essentially an SRT multiplexer that understands those prefixes and routes streams accordingly. GStreamer's SRT elements have no equivalent logic.

So to summarize:

• Self-hosted, multiple ports: one srtsrc/srtsink per port, works fine
• OSC (single port 30024): you're limited to one SRT stream in and one out with the current GStreamer-based blocks
• True stream-ID multiplexing on a single port: would require something like mediaMTX in front, or a native multiplexer built into Strom – which is something we'd consider if there's enough demand

[markusnygard-priva]

how about the srtserversrc? could it do the trick?

[srperens]

srtserversrc is just an older deprecated version of srtsrc.. so nope, sorry