DMX, Art-Net and OSC: The Languages That Run a Show

Why a Media Server Needs a Language

A media server on its own is just a powerful computer with video outputs. What turns it into a show tool is the ability to be controlled. Somebody, or something, has to tell it what to play, when, how bright, and with which effects. And in the world of live events, that instruction comes in a handful of protocols that almost nobody outside the industry has heard of.

If you want to do anything fun with the Hippos, from a projection on a barn at Game Fair to a window display in the byalag lokal, these protocols are how you'll do it. The good news is that they're simpler than they sound, much of the software is free, and the hardware has become cheap. This episode walks through them, from the oldest to the newest, and ends with a practical recipe for running a whole village-scale show from one laptop.

DMX, the Cable That Refuses to Die

The oldest and most important is DMX512, almost always just called DMX. It was standardised in the mid 1980s by the American theatre technology organisation USITT, as a way to stop every lighting manufacturer using its own incompatible control system. Before DMX, a dimmer from one brand might not talk to a desk from another. After DMX, everything spoke one language.

DMX is beautifully simple. A controller, usually a lighting desk, sends a continuous stream of numbers down a cable. The stream has 512 slots, called channels. Each channel carries a value from 0 to 255. That is all. One set of 512 channels is called a universe.

What those numbers mean is up to each device. A simple dimmer might use one channel, its brightness. A colour LED light might use three, red, green and blue. A moving head light might use twenty, for pan, tilt, colour, gobo pattern, focus, zoom and so on. Each device is set to a starting address, and it listens to that many channels from there. Set one light to address 1 and the next to address 21, and they don't step on each other.

The magic of DMX is how dumb it is. It just shouts numbers, forty-odd times a second, forever. If a cable is unplugged and plugged back in, the light picks up the next frame and carries on. No handshake, no drama.

The cable is a chain. The desk connects to the first light, the first light to the second, and so on down the line. At the end of the chain, you're supposed to plug in a terminator, a small plug with a resistor in it, which stops the signal reflecting back and causing flicker. Countless amateur shows have had mysterious flickering lights that were fixed by a two kronor terminator.

Officially DMX uses five-pin XLR connectors. In practice, lots of cheaper equipment uses three-pin, the same as microphone cables, which leads to a long and loud debate in the industry about whether it's acceptable to use microphone cable for DMX. Short answer, it often works over short runs and fails mysteriously over long ones, because the cable is designed for a different kind of signal.

Art-Net, DMX Moves Onto Ethernet

By the late 1990s, shows were getting bigger. A large rig could need dozens of universes, which means dozens of separate DMX cables running from the desk. At the same time, ordinary computer networking had become cheap and everywhere.

A small British company called Artistic Licence had the obvious idea. Wrap DMX data into network packets and send it over Ethernet. They called it Art-Net, and made it free to use, which is the main reason it took over. Any manufacturer could implement it without paying anything, and almost all of them did.

With Art-Net, one network cable can carry many universes. Later versions of the protocol can address tens of thousands of them. A lighting desk, a media server, a laptop and a box called a node, which converts network data back into plain DMX for older lights, can all sit on the same switch.

That's why there were reels of Ethernet cable in the haul, and why the back of the V3 Hippo has those chunky locking network connectors called etherCON. They're ordinary RJ45 network plugs inside a rugged metal shell, designed to survive being stepped on, rained on and yanked during a festival changeover. Art-Net is very likely what those ports were used for. The lighting desk talked to the Hippo over Art-Net, and the Hippo responded like a very complicated light.

There's a second network version of DMX called sACN, short for streaming ACN, an official standard from the entertainment technology association ESTA. It does the same basic job as Art-Net, with some technical improvements in how data is routed on bigger networks. Most modern gear speaks both. For a home or village project, the choice doesn't matter much. Whichever your software prefers is fine.

OSC, the Musician's Protocol

DMX and Art-Net come from lighting. The third protocol comes from music.

OSC, Open Sound Control, was developed at a research centre for music and audio technology at the University of California, Berkeley, around the turn of the millennium. It was designed as a more flexible replacement for MIDI, the protocol that synthesisers and drum machines have used since the 1980s.

Where DMX is a fixed list of 512 numbers, OSC sends named messages. Instead of channel 47 is 200, an OSC message says something like slash layer one slash opacity, 0.8. The names are readable, you can make them up, and the values can be numbers, text, or several things at once. It travels over the network just like Art-Net.

That flexibility makes OSC the favourite of artists, coders and interactive installations. A phone app can send OSC. A Python script can send OSC. A sensor connected to a little microcontroller can send OSC. And many media servers, including Green Hippo's, can be controlled by it.

For someone who builds things by directing AI to write code, this is the important bit. OSC is the bridge between your world and the show world. A script that reads the weather, or a database, or a live dashboard, can fire OSC messages at a Hippo and make it change what's on screen. No lighting desk required.

Timecode, Keeping Everything in Step

One more language is worth knowing, because it's how big shows synchronise everything to music. It's called timecode, specifically SMPTE timecode, from the same Society of Motion Picture and Television Engineers that standardised SDI.

Timecode is a running clock, hours, minutes, seconds and frames, embedded in a signal. In its oldest form, called LTC, it is literally an audio signal, a rough buzzing sound that can be recorded onto a spare audio track. When a backing track plays, its timecode plays alongside it, and every device that can read timecode knows exactly where in the song you are. The lighting desk fires its cues, the media server jumps to the right frame, the pyrotechnics go off on the beat, all locked to that one clock.

For a village show, this opens a lovely possibility. Put a music track and its timecode together, program lights and video against it once, and then the whole show plays itself, identically, every time you press play.

Running a Whole Show From One Laptop

So here's a practical recipe, scaled for Kall rather than a stadium.

Software first. There's a free, open-source lighting control program called QLC Plus. It runs on Mac, Windows and Linux, it speaks DMX, Art-Net, sACN and OSC, and it's more than capable of running a village show. There are others, including free versions of commercial consoles that are limited in number of universes but still generous for small setups.

Hardware next. To control ordinary DMX lights from a laptop, you need a small USB to DMX interface, a box the size of a deck of cards. These have become cheap. Or an Art-Net node, which does the same thing over a network cable. Plug the lights into the box, and the laptop can control them.

Then the media server. The Hippo connects to the same network switch, and QLC Plus sends it Art-Net, just as a professional lighting desk would. Channel by channel, you choose which clip plays, how bright, what colour, which effect. Or you skip the lighting desk approach entirely and drive the Hippo with OSC from a script.

Start with one light and one clip. Make the light go red when the video goes red. Once that works, everything else is just more of the same.

And if you want hands-on control, any cheap MIDI controller, the kind with faders and pads sold for music production, can be mapped to the software. A row of physical faders is much more satisfying than clicking on a screen, and a lot more impressive to the person standing next to you at Game Fair.

Why This Matters for the Haul

Here's the bigger point. The Hippos in the haul were built to sit in exactly this kind of network, talking DMX over Art-Net to a lighting desk, maybe locked to timecode, maybe triggered by OSC. They were never meant to be standalone computers. They're instruments, waiting for someone to play them.

And the instruments to play them with are cheap and free now. A laptop, a free program, a small interface box and the Ethernet reels already in your car. With those, a pile of auction hardware turns into a proper show rig. A projection that changes colour with the lights. A video wall that reacts to data. A Game Fair arena where the announcer's voice, the lights and the screen all move together.

That's the language lesson. DMX for the lights, Art-Net to carry it over the network, OSC for everything clever, and timecode to keep it in time. Learn those four words, and the Hippos stop being museum pieces and start being toys.