Using Timecode with QLab

Timecode is a standard developed for use in the film industry to keep cameras and sound recording equipment synchronized both on set and in post production. It has since been adopted by theme parks, cruise ships, and theaters as a mechanism for linking lighting, audio, video, and automation equipment.

QLab can be controlled by either LTC (linear or longitudinal timecode) or MTC (MIDI timecode.) LTC is also often referred to casually as “audio timecode” or “SMPTE” (pronounced “SIMP-tee”.) Neither term is wrong; LTC uses an audio signal to transmit timecode, so “audio timecode” is a perfectly fair description. SMPTE stands for the Society of Motion Picture and Television Engineers which is the organization that created and maintains the technical standards for timecode. Most accurately, though, SMPTE is the name of the organization, not the name of the timecode standard.

QLab 5 also syncs to timecode, which means that when incoming timecode stops, skips ahead, or skips back, QLab is able to respond appropriately.

A note on terminology: many different terms are used in the world of timecode, some of which have linguistic roots which are racist or otherwise violent. Since there is absolutely no reason to adhere to these terms, we do not. Abandoning archaic terms which cause hurt is a small and ridiculously easy thing that we can do to make the places that QLab is used more accessible and inclusive to all.

Controlling Individual Cues

To use timecode to start cues in QLab, you first need to enable incoming timecode for the list or cart that contains those cues. This can be done in the Timecode tab of the inspector when a list or cart is selected.

Check the box labeled Sync cues in this list from incoming timecode, and then choose the sync source, sync input channel (if applicable), and SMPTE format appropriate for your system. QLab must be set to use the same format as the device that’s sending timecode in order to operate correctly.

The On Start pop-up menu allows you to configure QLab’s behavior when incoming timecode starts; should QLab start any cues whose timecode trigger precedes the first incoming frame? This can be helpful, for example, when you want to make sure that “setup” cues are run when jumping into the middle of a sequence in rehearsal. More details can be found in the Timecode tab section of this manual.

The On Stop pop-up menu allows you to configure QLab’s behavior when incoming timecode stops; should cues started via timecode stop, pause, or keep running?

The Freewheel time box lets you enter any duration between 0 and 2 seconds which QLab will use as a window of time within which timecode drop-outs will be ignored. This can help protect against stopping or pausing cues because of a momentary drop or corruption of timecode which is common (especially with MIDI timecode.)

Once that’s set, you can visit the Triggers tab for any cue within the cue list, check the Timecode checkbox, and enter a trigger time for the cue.

You can set the pop-up menu to Timecode and enter the time in the format hour:minute:second:frame, or set the pop-up menu to Real Time and enter the time in the format hour:minute:second:millisecond. You should use whichever format makes the most sense for your situation.

The Benefits of Timecode

Timecode can be advantageous when you need to link several devices to a single timeline that is non-negotiable and deliberately rigid. Each device can receive timecode from a central source, and then each device can be individually responsible for doing the right thing at the right time. If you use LTC for your timecode distribution, it can be very simple to route it since it’s just a line-level audio signal and you can use conventional audio infrastructure.

MTC, on the other hand, uses MIDI infrastructure which is frankly pretty irritating to deal with unless you’re just connecting one thing to another.

Shows that are run “on rails,” such as themed attractions, dance-only or dance-centric shows performed to prerecorded tracks, or shows in which 100% repeatability is required for safety purposes are often organized around timecode.

The main reason why you might want to use timecode instead of another show control protocol is that lots and lots of legacy equipment supports it.

The Perils of Timecode

Timecode is a bit at odds with the fundamental design premise of QLab, which is that you don’t necessarily know the amount of time that will elapse between cues. After all, in traditional live theater that’s the whole point of having cues in the first place! Using timecode locks a series of events in place without any flexibility. Obviously, that’s sometimes quite useful, but not always.

We recommend using timecode when you’re adding QLab into a situation that’s already using timecode, or when you’re connecting QLab to equipment that does not support OSC, MIDI, or MSC.

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