Sending a service to a second campus

A second campus watching the main auditorium live has a harder requirement than a stream to viewers at home: it plays on a big screen in front of a room full of people, and nobody there can pause or refresh. It either works at 11:00 or the service has a problem.

SRT is the right protocol for it. The rest of this page is what the protocol does not solve.

The path

main campus                        second campus
camera -> switcher -> encoder  ->  relay  ->  decoder -> projector

Both ends dial out, so neither building needs a static IP or an open firewall port — which matters, because church buildings usually have consumer internet and no one to administer it.

What you need at each end

Main campus: whatever already produces your stream — a switcher with SRT output, or the computer running OBS or vMix. If it streams to YouTube today, it can send SRT today.

Second campus: a decoder into the projector. In order of reliability:

For a room full of people, a hardware decoder earns its price the first time nobody has to fix anything.

Settings that survive a church's internet

Church buildings tend to have asymmetric consumer connections shared with Wi-Fi for the whole congregation. Plan for the worst case, which is 11:00 on Sunday with 300 phones on the guest network.

• Bitrate: 3–4 Mbit/s at 720p25 is plenty on a projector. Resist 1080p: nobody in row 12 can tell, and the extra megabits are exactly what fails.
• Latency: 600–800 ms. The second campus is not having a conversation with the first — extra buffer costs nothing anybody notices and buys real resilience.
• Audio: AAC, 48 kHz, 128 kbit/s. Audio dropouts are far more noticeable than a soft picture; never starve it.
• Keyframe interval: 1 second, so a decoder that reconnects shows a picture almost immediately.
• Put the encoder and the decoder on wired ethernet. This single change fixes more multisite problems than any setting on this page.

If you can, put the video systems on a separate VLAN or a second connection from the guest Wi-Fi. If you cannot, at least ask for QoS on the router — most consumer routers can prioritise one device.

Make it volunteer-proof

The person running the second campus should have exactly one thing to do: turn it on.

1. Decoder starts into the stream automatically on power-up. Configure once, test by pulling the plug.
2. Write the settings on a card taped to the rack: URL, port, passphrase, latency. Not in someone's email.
3. One phone number for when it does not work, and that person knows to try the test signal first — if the bars appear, the decoder and the building's internet are fine and the problem is at the main campus.
4. Start the stream 20 minutes early. Every week. The link either works at 10:40, when there is time to fix it, or it works at 11:00 by luck.

The fallback that actually saves the service

Have a plan that does not depend on the link, and rehearse it once:

• A recorded message on a laptop, already plugged in. Last week's sermon, or a prepared video. Thirty seconds of switching beats twenty minutes of a technician crouched behind a rack.
• Audio-only path. A phone call on speaker into the sound desk keeps the sermon alive when video will not pass. It is not elegant; it is far better than nothing.
• Local worship, remote sermon. If the band plays locally, only the sermon needs the link, and a 25-minute window is much easier to protect than 90 minutes.

Rehearse it on a weekday

Run the whole path at the real time of day, for the real length of the service, with the real people. Watch for:

• freezes when the building's Wi-Fi is busy — that is bandwidth contention
• audio drifting from the picture over an hour — a sample-rate mismatch, fix it at the source
• the decoder losing the stream and not coming back — set it to reconnect, and test by unplugging its network cable for ten seconds

The pull test that costs nothing: leave the free test signal running on the second campus screen for an hour. The burned-in frame counter must never skip. If it skips on a test pattern at 2 Mbit/s, your service at 4 Mbit/s has no chance, and you have learned it on a Tuesday.

Cost

A relay session for a Sunday service costs less than the coffee served afterwards — $5 covers 24 hours, and the free tier of three 30-minute sessions a day is enough to rehearse and to test every setting on this page before you spend anything.