timecode refresher… LTC vs. VITC

[Michael Gissing]

“And why there are two..? ”

Historic plus the fact that non video machines needed linear timecode to be recorded on audio channels to syncronise. VITC, although meant to match the LTC sometimes doesn’t so as a general rule, I use LTC as the prefered timecode source.

In theory, VITC should be able to pass through a video edit system like FCP but I know on my Decklink card you need to set the lines to be preserved, otherwise they don’t make the journey. Also the VITC in an edit sequence will show the original source timecode which may be useful, but certainly not wanted on a final master tape where the VITC and LTC should be identical.

[Steven Gonzales]

It’s actually good to have 2 on a videotape.

LTC is recorded on a linear channel on the videotape, so it can be read easily at various speeds (the frequency just changes, but can still be decoded), even those where the video information is not being read. However, being linear, LTC cannot be read when the tape is stationary on a frame (paused).

VITC is written with the video signal in the vertical blanking interval. Thus, it can be read when the machine is paused on a frame (as this means the same frame is read over and over).

[Seawild]

Thanks so much guys!!!

[Seawild]

“Historic plus the fact that non video machines needed linear timecode to be recorded on audio channels to syncronise. ”

What does that mean? :0

[Michael Gissing]

“What does that mean? :0”

It means that when timecode is used on a machine that doesn’t have an image, you can’t use VITC, only LTC. So when you used to try to syncronise a video machine and a multitrack audio machine, you needed LTC from the video machine to chase lock the timecode on the audio machine. VITC, although useful cannot replace LTC so both are required on videotape. I still use chase lock timecode in my studios via LTC

[Mark Raudonis]

Cautionary tale;

If you work with “window dubs” or “work copies”, be sure to check that your VITC and LTC timecode MATCH! If they don’t, you can end up with logging notes that reference one number and digitized off-line code that match another. And, if you’re not careful, this problem can persist for days and days worth of dubs, totally throwing a wrench in the “off-line to on-line” workflow. (Not that this has ever happened to me!) 🙁

mark

[Seawild]

Thanks!

Which is used by FCP when re-capturing for Online? I imagine LTC..

Chris

[Bouke Vahl]

FCP would not know…
The setup of the deck will be the judge of that. PVW beta has a bug that makes you want to set it to ltc, most decent decks do it auto.
No matter how, the tc info in the 422 signal is what the deck wants it to be (or how you have set it up).

And yes, if you have your deck set up wrong you are able to insert wrong VITC or even erase it.

hth

Bouke

http://www.videoToolShed.com
smart tools for video pro’s