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Getting started

Install RoomCast on your Mac, learn the main window, and test the whole path at home before people arrive.

Download RoomCast for MacShare with your venueStuck on a step? Tell me

What to bring

• A Mac with macOS 13 Ventura or later (Apple silicon or Intel).
• RoomCast, installed in the Applications folder.
• The sound source: a USB or Thunderbolt audio interface from the sound desk, the Mac’s built-in microphone for a small room, a headset or earbuds, or — for music from an app or DJ software — the free BlackHole 2ch driver (see Broadcast music from an app).
• Your own small Wi-Fi network for the phones and the Mac. A portable or travel router is the reliable choice. The venue’s Wi-Fi often blocks phones from seeing each other. More detail is in Your network and the QR poster.
• Power for the Mac and that router. Closing the laptop lid puts the Mac to sleep.

Install and first open

1. Download RoomCast from roomcast.channel. The current file is the disk image RoomCast.dmg.
2. Open the disk image and drag RoomCast to Applications. Running it from the disk image or from Downloads makes macOS treat it as untrusted, and it then behaves oddly.
3. Open RoomCast from the Applications folder.
4. Allow the microphone when asked. That permission is how the app hears the sound desk.
5. When you first press Start Broadcasting, macOS may ask whether to allow incoming connections so phones on the Wi-Fi can reach this Mac. Click Allow.

The current download is signed with Apple Developer ID and notarized. Most Macs open it after you drag it to Applications and double-click it. The first open may show that the app was downloaded from the internet; choose Open.

The first time you open RoomCast you may see Welcome to RoomCast and Getting Started. Those screens explain that there is no sign-in or account, that the Wi-Fi does not need internet, and that sound can come from the Mac’s microphone, an application, a headset or earbuds, or a mixing desk.

On the main window, Help includes Getting Started, FAQ, and Troubleshooting.

If macOS blocks the app

If a dialog says “RoomCast” Not Opened – Apple could not verify…:

1. Click Done. Do not click Move to Trash.
2. Open System Settings → Privacy & Security.
3. Scroll to Security, find “RoomCast was blocked…”, and click Open Anyway.
4. Confirm with your password or Touch ID, then click Open.

On macOS 13 and 14, Control-click (right-click) RoomCast in Applications → Open → Open can also work, as can Open Anyway in System Settings → Privacy & Security. If macOS says the app is damaged, the download or the signature is broken. Download it again.

After an update

A new download is quarantined again, so macOS may ask you to open it once more. It may also ask for the microphone again. If you previously clicked Don’t Allow, go to System Settings → Privacy & Security → Microphone.

The main window

The main window is built around two cards, then support and help.

Broadcast

• Start Broadcasting starts the stream. Stop Broadcasting ends it.
• Change Sound Source opens the input picker.
• Input level shows whether sound is reaching RoomCast.
• Volume adjusts the broadcast level. 0 dB leaves the volume unchanged.

Listen

• A QR code for the listen link.
• The listen address, with a .local fallback shown as well.
• Open PDF QR Poster saves a PDF of the poster and opens it so you can print it yourself.
• Listening now shows how many people are connected.

Support RoomCast has links to Ko-fi, Patreon, and Buy Me a Coffee.

Help has Getting Started, FAQ, and Troubleshooting.

Set it up at home, then test it

Do this once, on the Wi-Fi you will take to the venue.

1. 1

   Turn on your router

   Turn on your router. It does not need the internet.

2. 2

   Join the Mac and reserve its address

   Join the Mac to the router, with the Mac’s address reserved so it stays the same.

3. 3

   Install and allow access

   Install RoomCast and open it. Allow the microphone. If the firewall asks whether to allow incoming connections (it may name RoomCast or mediamtx), allow them. mediamtx is the helper program the phones connect to.

4. 4

   Choose the sound source

   Plug in the audio interface, or use the built-in microphone for this test. For music from an app, set up BlackHole first. In Settings, choose the input. For speech, leave quality on Speech 32k.

5. 5

   Watch Input level

   Watch Input level on the Broadcast card. Talk, or play the desk. The meter moves before you go live. If it stays empty, the Mac is listening to the wrong input.

6. 6

   Start Broadcasting

   Press Start Broadcasting. The Listen card should show the listen address, for example http://192.168.1.20:8889/. An older poster or QR code that still ends in /live opens the same page.

7. 7

   Join the same Wi-Fi on your phone

   On your phone, join that same Wi-Fi. A phone still on the house network will not open the link.

8. 8

   Scan and listen

   Scan the QR code, or type the link. Tap play. If you hear nothing, unmute using the listener steps on Your network and the QR poster.

9. 9

   Make the poster

   In Settings → Poster, type the Wi-Fi name, the password, and the security type. Then, on the Listen card, press Open PDF QR Poster. The PDF opens so you can check it. Print that PDF from Preview, or any PDF app.

10. 10

    Confirm the address stays put

    Stop the broadcast. Power the router off and on, start the Mac again, and confirm the listener link is unchanged.

Take the same router, the same Mac, and that PDF to the event.

Up and running? If RoomCast helped, you can buy me a coffee.

On the day

1. Turn on your own Wi-Fi. It does not need the internet.
2. Join the Mac to it and open RoomCast. Confirm the listen address matches the poster.
3. Connect the sound desk to the interface, or confirm the music-app path. Check Input level.
4. Press Start Broadcasting. Listening now shows how many people are connected.
5. Listen on your own phone once, on that Wi-Fi, before people arrive. The page title is the broadcast title from Settings → Stream.
6. Put the poster where people can scan it. Remind them about the Wi-Fi name and the unmute step.

Stop with Stop Broadcasting when the session ends. Quitting the app also stops the stream.

How many people, and the delay

About 50 phones on a modern Wi-Fi router can listen at once. The real number depends on the router, other traffic on the network, distance and walls, and the quality setting.

The delay is usually around half a second, even on busy Wi-Fi. That suits talks, live translation, teaching and music. It is not meant for lip-sync to live video.

Bandwidth

Every listener is their own copy of the audio. Multiply the preset’s kilobits per second by the number of phones, then divide by 1000 to get megabits per second. The worked example below is for 50 phones:

So 50 phones at Music 96k use about 4.8 Mbps of audio (96 × 50 ÷ 1000). Speech at the same 50 phones is about 1.6 Mbps. The network also carries a little protocol overhead, so leave some spare room.

A phone’s personal hotspot, at about 5 to 10 devices, is still only for a rehearsal or a handful of listeners.

Limits worth knowing

• The stream is local. People off your Wi-Fi cannot listen, including people at home.
• There is no recording in the app.
• About 50 phones on a modern Wi-Fi router can listen at once. The real number depends on the router, other traffic on the network, distance and walls, and the quality setting.
• The delay is usually around half a second. That is fine for talks and music, not for lip-sync to live video.
• Phone operating systems may pause the audio when the screen locks or the browser is in the background.