Buy a Raspberry Pi 5 for each screen.
That is genuinely the whole answer for playback. Add an Apple Silicon Mac in the control room if you want to send live video, and nothing else. Herald does not sell you an appliance, and it does not charge per screen for hardware you already own.
The rest of this page is the detail that matters six months in: which card to buy, what power actually needs to be, which Macs the Relay runs on, and what to tell whoever looks after your network.
- Raspberry Pi 5, 4 GB
8 GB is fine too, but 4 GB is plenty for signage
- Official active cooler
Not optional. A hot Pi slows itself down and stutters
- Official 27 W USB-C power supply
Underpowering a Pi causes faults that look like software bugs
- 32 GB high-endurance microSD card
Buy the endurance-rated one. This is the part that dies
- Micro HDMI to HDMI cable
Both Pi 4 and Pi 5 use the smaller micro HDMI socket
- Case
Keeps the board from collecting dust behind the TV
Get a CanaKit Raspberry Pi 5 starter kit. It is the whole list in one box, with good parts: the board, a case with a fan and heatsinks, the right power supply, an SD card, and the HDMI cable. Pick the 4 GB one. The card it comes with works fine; swapping in a high-endurance card is optional and buys a longer life behind the TV.
A preloaded kit turns up ready to plug into the TV, with everything on this list already in the box.
If you would rather assemble it yourself, all of it is ordinary, off-the-shelf kit from any electronics supplier. We have left the prices off on purpose: they move around far too much for anything printed here to stay honest.
One small computer per screen.
One player runs one screen. It goes from cold to picture in about a minute, keeps everything it needs on board, and never wants a keyboard, a mouse or someone to log into it.
| Board | Status | Notes |
|---|---|---|
| Raspberry Pi 5 (4 GB or 8 GB) | Recommended | Validated on every release. This is what to buy |
| Raspberry Pi 4 (4 GB or more) | Legacy | Deprecated August 2026. Existing players keep running, new features are not tested on it |
| Raspberry Pi 3, Pi Zero | Not supported | Not enough power to hold a picture reliably |
| Smart TV apps, streaming sticks | Not supported | Herald runs the screen itself. There is no app to install on a TV |
| Content | How it plays | Notes |
|---|---|---|
| Video | Full HD | Smooth, full screen, with sound if the TV wants it |
| Photos and slides | Any format | Herald converts whatever you upload, iPhone photos included |
| Live video | Full HD | The feed from your control room, under a second behind |
| Web pages | Yes | Dashboards, countdowns, scrolling messages |
| Sideways or upside down | Yes | For screens mounted portrait, or hung from a ceiling |
| Oversized files | Handled for you | Herald resizes anything too big before it reaches a screen |
Cheap SD cards are the number one failure
Signage writes continuously, day after day, and a bargain card gives out in months. Buy an endurance-rated card, or a USB SSD if the deployment is large enough to be worth the extra cost.
Underpowering a Pi looks like a software bug
A phone charger will boot a Pi 5 and then fail strangely under video load. Use a supply rated for the board, or a PoE hat you trust, and fit the active cooler while you are at it.
Herald Relay runs on a Mac.
It is a native menu-bar app for Apple Silicon. Install it on the Mac already sitting in the booth, point it at your Cloud, and adopt it with the code it shows you. There is no Dock icon and nothing to babysit.
A small Linux machine works too if the room suits it better. One Relay covers a building, and you only need one per location that sends video.
| Host | Status | Notes |
|---|---|---|
| Apple Silicon Mac (M1 and later) | Recommended | A small app in the menu bar. Most booths already have a Mac that will do |
| Intel Mac | Not supported | Herald Relay needs one of the newer Apple chips |
| Small Windows or Linux mini PC | Compatible | Works, and is a fine choice if there is no Mac in the room |
| Source | Type | Notes |
|---|---|---|
| Your video switcher | By cable | A capture card in the Mac takes the program feed straight off the switcher |
| Elsewhere on your network | By network | From a switcher, OBS, or another computer. No extra card needed |
| The computer running the service | Its own screen | Herald sends what that machine is already showing |
| Host | Workload | Notes |
|---|---|---|
| Mac mini M2 | 4 feeds at once | Four different live feeds, full HD, at the same time |
| Mid-range mini PC | 4 to 6 feeds | Four to six different live feeds, full HD |
| Entry-level mini PC | 2 feeds | Enough for an overflow room and a lobby |
How many you get depends on picture quality and where the feeds come from. These are numbers we have actually run, not estimates off a spec sheet.
Nothing has to be opened up.
The short version for whoever looks after your network: screens call out to Herald, nothing calls in, and the live video never leaves the building. If they want the exact detail before signing it off, ask us and we will send it.
| Question | Answer | Notes |
|---|---|---|
| Opening the firewall | Not needed | Screens reach out to Herald. Nothing reaches in from the internet |
| Live video | Stays inside | It travels between your own machines and never leaves the building |
| Wired or Wi-Fi | Either | Wired is better for live video. Wi-Fi is fine for everything else |
| Their own network | Encouraged | Screens are happy on a separate network if you prefer |
Run a cable where you can, especially to screens showing live video. Wi-Fi works everywhere else, and you can put a screen onto your Wi-Fi from the dashboard without going near it. A screen that loses its cable moves over to Wi-Fi and back again on its own, without ever dropping off.
Plenty of buildings put their screens on a network of their own, away from the office machines. Herald is happy that way. The screens and the Mac sending live video just need to be able to see each other.
Any TV with an HDMI socket.
Consumer TVs are fine. Commercial panels last longer if the screen runs all day, but Herald does not care which you hang.
Mount it any way up
Landscape, portrait either way round, or upside down for a ceiling mount. Tell Herald how the screen is hung and it turns the picture to match. For a portrait screen, design your slides tall and they will fill it exactly.
TVs that turn themselves on
Herald wakes your screens before the doors open and puts them to sleep at night, so nothing is lit at two in the morning. It also keeps the TV's input labelled Herald instead of something like HDMI 2, and puts the label back if the TV forgets it.
A knocked cable is survivable
Pull the cable out and the player carries on regardless. Plug it back in and the picture comes straight back, correctly sized, without anyone touching anything. Herald tells you when a screen loses its cable, so a dark TV in a back hallway does not go unnoticed for a fortnight.
Nothing to install, nothing to keep running.
The part you actually work in is a website. There is no server to buy for it, and no software for your IT person to look after.
Your own web address, updates applied for you, backups taken every night. Sign up and you are setting up your first screen ten minutes later.
Your media can live in your own Google Drive, and the nightly backups land there too. If you ever walk away, you already have everything.
Start with one screen and a Pi you already have.
Plug the player into the TV, type the six digit code it puts on screen, and pick what to play. If it does not suit you, you are out an evening and nothing else.