Broadcasting with BELABOX

By the end, your BELABOX will be broadcasting over SRTLA to your stream key, adding up every modem you’ve plugged into it.

You need: any plan with a stream key · BELABOX with belaUI at hand · two connections or more · 10 minutes

Before you start

BELABOX only makes sense with SRTLA: that’s what splits your broadcast across several connections and puts it back together on arrival. If you’re going live on a single SIM, you gain nothing over SRT; see Choosing a protocol.

Steps

1. In the dashboard, open Stream Keys and set the Protocol selector to SRTLA.

2. Hit Publish to copy the URL. It looks like this: srtla://<server>:<port>?streamid=publish:<your-key>.

3. Open belaUI in your browser (phone, tablet or laptop, doesn’t matter).

4. belaUI won’t take the URL in one piece: split it into the fields it asks for.

   belaUI field	What you put in	Where it comes from
   SRTLA server	<server>	What sits between srtla:// and the colon
   SRTLA port	<port>	The number after the colon
   Stream id (SRT)	publish:<your-key>	Everything after streamid=
   SRT latency	Leave it as it is if you don’t know what to put	—

5. Pick resolution, fps and a maximum bitrate below your plan’s cap (table below).

6. Plug in and switch on every modem and connection you’re going to use, and wait for belaUI to list them.

7. Hit go live. In the dashboard, the key goes from No signal to Streaming.

Note

The SRTLA server and port aren’t the same as an SRT key’s. If you copy the URL from another key or from an old note, it won’t connect. Always copy it from the Publish button of the key you’re going to use.

Checking that bonding is adding up

Two checks, one on each side:

1. In belaUI: look at the connection list while you’re live. Each one has to be contributing something. If one is stuck at zero, it isn’t taking part in the split — usually because it has no data left, because the modem dropped or because the carrier left it with no coverage.
2. In the dashboard: the Live signal card shows the Current bitrate. That number has to look like the sum of what you see in belaUI, not like what a single connection contributes.

Acid test: unplug a modem in the middle of a test run. The bitrate drops a step, but the stream doesn’t cut. If it cuts, there was no bonding.

Bitrate caps

Plan	Key cap
Stream Key Lite	9,000 kbps
Stream Key	9,000 kbps
OBS Basic	6,000 kbps
OBS Standard	6,000 kbps
OBS Pro	10,000 kbps

Not working?

belaUI keeps trying to connect in a loop and the dashboard won’t move off No signal. Check the port: it’s easy to leave the SRT one (the playback one) in the SRTLA field. Copy again with Publish and split server, port and stream id one more time.

It connects, but the bitrate is that of a single modem. The key isn’t on SRTLA in the dashboard, or belaUI is pointing at a plain SRT server. With SRT there’s no split: one connection and that’s that.

It stopped connecting out of nowhere, without touching anything. You Rotated the key or changed the Region: the previous URL stops working instantly. Copy it again. More detail in Rotating the key and security.

Next step

• Broadcasting with Moblin — the bonding alternative from your phone.
• Choosing a protocol — when SRTLA is worth it.
• Unstable bitrate — if it adds up but sinks now and then.