Linear Timecode (LTC)
Many musicals use Linear Timecode (LTC) to sync production departments such as lighting, sound, and projection to the music.
What is LTC?
LTC (Linear Timecode) is an audio signal that encodes a timecode (hours, minutes, seconds, frames) that connected devices decode to determine exactly where in a song they are.
LTC is audio
Because it travels as audio, a standard audio output carries LTC to any device with a timecode input.
Why theater uses it
LTC synchronizes music playback with the technical departments. It runs alongside the click playback like a stopwatch, translating measures and beats into time so other departments can tie its cues to a specific point in the score
How it works in practice
If the downbeat of a measure sits at timecode 00:02:04:10 and a lighting cue is set to that address, it fires exactly on that measure, regardless of what anyone is doing at the lighting console.
How KTPlayer outputs LTC
In a show file that uses LTC, a dedicated LTC channel appears in the mixer (typically channel 2). It behaves like any other channel:
- It has a fader, meter, and output assignment.
- You route it to a physical output on your audio device, usually a mono line out that runs to the lighting console.
- The operators of the other systems receive that LTC signal and patch it into their own equipment.
Pull the LTC fader during testing
LTC sounds harsh: it's designed for machines, not human ears. Before testing audio, pull the LTC channel's fader all the way down (to -inf ). Bring it back up only once LTC is given its own output in the theater.
LTC and tempo changes
Warping a cue, by any tempo or pitch change, breaks its LTC: the timecode stops being valid and downstream systems lose sync. If you must change the tempo of an LTC cue, see Warping for your options.
Implementing LTC in your production
- Confirm your show file contains LTC (often channel 2).
- Confirm which departments require it.
- Route the LTC channel to the agreed physical output.
- Keep the LTC fader down during rehearsals and testing.
- Bring it back up for tech and performances.