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Knowledge & practice

Triggering QLab from an ETC Eos: OSC step by step

· · 2 min read

In many theatres the lighting runs on an ETC Eos console and the sound on QLab. If both fire from one GO, that saves a hand movement and the cues always land the same way. ETC describes the process in its own support article. Here are the steps in short.

On the Eos

Under Setup, System, Show Control, OSC you set up the sending side:

  • OSC TX: Enabled
  • OSC UDP TX Port: 53000, which is what QLab listens on
  • OSC UDP TX IP Address: the IP address of the QLab Mac
  • OSC TCP Mode: leave at Packet Length (v1.0)

Use UDP for the connection. According to ETC, QLab 5 closes TCP connections after three seconds of inactivity, which makes TCP impractical for this.

Which cue fires what

There are two ways.

One string for all cues: Enter /cue/%1/start in the OSC Cue Send String field. The Eos replaces %1 with the cue number on every cue, so Eos cue 5 starts QLab cue 5. Other placeholders are %2 for the cue list, %3 for the whole number of the cue, %4 for the decimal part and %5 for the label.

One string per cue: Leave the field empty and attach a string to individual cues. For example, Eos cue 5 starts QLab cue 17 with /cue/17/start. That’s more flexible when lighting and sound don’t share the same numbering.

Watch how the numbers are written. Cue numbers in QLab are text, so “5” and “5.0” are different cues.

In QLab

The Eos can’t send a passcode, so QLab has to allow access without one:

  1. Open Workspace Settings, Network, OSC Access tab.
  2. Turn OSC access on.
  3. Tick all three boxes in the “No Passcode” row.
  4. Leave the listening port at 53000 to match the Eos.

More on ports, permissions and troubleshooting in controlling QLab via OSC.

And who presses GO?

With this setup, the lighting operator presses GO and QLab follows. That works when lighting and sound are run from one position. If the sound operator sits elsewhere, or playback gets added at short notice, QLab still needs its own reliable GO. That can be a controller with mechanical keys sending MIDI or OSC to QLab. Without a network, MIDI Show Control also works, and QLab understands it out of the box.