Video Framrate vs. Timecode

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mandras
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Video Framrate vs. Timecode

Post by mandras » Sun Jun 22, 2014 4:34 pm

Hi all,
I work with Nuendo since years in music and postpro, I am located in Austria.
For the first time I have to deal with a cinematic film production from US. For now I do no postro work, I only have to do some music editing in sync to the picture.
The American partners sent over a video and I am a bit confused about the video frame rate, not corresponding to the inserted timecode.
The video framerate is 23,976 fps (which is us video standard), and the inserted TC is on 24 fps.
Importing this video into Nuendo, and selecting a project framerate of 23,98 results in a non synchronous Nuendo Timecode vs. the inserted TC in the picture.
If I set the project framerate to 24 fps, Nuendo TC and inserted TC are in sync, but I get the red alert on the video track, that the project and the video frame rate do not match. Still I prefer this setting because I can spot on the correct time code values.

Can I run into any problems working in this later state?
Do I miss something?

Thanks for your help.
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Oswald Schwander
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Re: Video Framrate vs. Timecode

Post by Oswald Schwander » Mon Jun 23, 2014 4:26 pm

Can I run into any problems working in this later state?
From all I remember working with 23,976 fps I don't thinks you will run into problems. Changing the project framerate in Nuendo doesn't change speed neiher of picture nor sound; it just changes the TC grid (same second will be split in 24 or 23,976 frames). You will start a sound a couple of samples earlier or later if you are editing to frame boundaries.... and that will not make any real difference for sound-picture relationship.



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ManChicken
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Re: Video Framrate vs. Timecode

Post by ManChicken » Tue Jun 24, 2014 6:08 am

Sounds like they somehow botched the encoding of the movie. Whichever frame rate the movie says it is should match the code in Nuendo at the same rate. Can you step through it frame by frame and see a skipped or repeated timecode number (you didn't say which direction it was off) every so often?

mandras
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Re: Video Framrate vs. Timecode

Post by mandras » Tue Jun 24, 2014 9:09 pm

Thanks for your replies. I also think that sticking to the inserted timecode is the best idea. That one will be the same here and there. I can see no glitches or repeated numbers.
I just saw that there is a quite deep chapter about film transfer in the Nuendo manual. On page 764 is a chapter called "What is 23.976 fps used for". That might be the explanation for that combination of video framerate and 24 fps timecode.
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ManChicken
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Re: Video Framrate vs. Timecode

Post by ManChicken » Wed Jun 25, 2014 9:31 am

Well, whether it's 23.98 or 24, the timecode counts as 24 whole frames.. We don't really have drop-frame code at 23.98 like we do with 29.97.

If your movie says it's 23.98, and you set your Nuendo project to 23.98, but you're saying the timecode dislpay of Nuendo at some point stops matching the window burn in the movie (at least I assume this is what you meant by the 'inserted TC'?) it has to have skipped/repeated a frame somewhere.

The important part is verifying what actual frame rate the finished product is truly at, and having a correct movie playing at the correct rate. While under normal circumstances you could consider the timecode its self to be inconsequential, the actual rate of playback isn't. If Nuendo is playing the movie back at 23.98 and you're syncing audio to picture, but in reality they screwed up when making you the Quicktime and it's really supposed to be true 24fps (or vice-versa) your audio will no longer sync when they drop your mix into the original project.

You should really double check with the production company what the actual frame rate should be, and that the file they gave you is the correct rate.

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Neil K
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Re: Video Framrate vs. Timecode

Post by Neil K » Wed Jun 25, 2014 6:29 pm

I second the suggestion to check with the production company. If it was shot on film, then you might also be dealing with pull up/down. I've had a major motion picture company screw up the video/TC the same way before, so it does happen. Better get confirmation since you will probably be delivering BWAV or AAF/OMF to them.
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mandras
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Re: Video Framrate vs. Timecode

Post by mandras » Fri Jun 27, 2014 8:46 pm

Thanks again for your contributions. Unfortunately I don't get any technical answer from the video guys.

With a project rate of 23.98 fps the burned in TC is at 1:00:03:14 at the exact Nuendo hour.
With a project rate of 24 fps I stay in sync, and nudging through the frames does not reveal any glitches, although it should, you are certainly right ManChicken. Maybe I the glitch is so small that it is hard to tell, I use a fotojpg converted mov.

As I said, I do not have to do any sync to picture work other than to align music files, around 30 - 120 seconds long. I feel safe using the burned timecode as reference, although it still scratch my head about this discrepancy in the codes. Maybe I get an explanation further on, I will let you know.

Best regards
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