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Going from 23,98 to 25 fps


Olle Sjostrom

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Story is that me and my company shot a short on RED in 23,98 mode. Based on that it will be easier to convert to NTSC and it's compatible with PAL as well.

Now we're sending the film to a festival in Sweden that only accepts HDCAM and not HDCAM SR which would be preferable.

And HDCAM doesn't take 23,98.

So we decided to speed up to 25 fps.

Enter: Problems

I used the waves plugin to pull the audio up with a ratio of 1.0416, which syncs up perfectly in Pro Tools. So far so good.

Now we imported the video and audio into FCP. No sync. Wtf?

Okay so it turned out the audio had a TC metadata stamp which was empty.

In a 25 fps project, with a 25 fps video file on a 25 fps 48khz sequence, the audio doesn't sync even if the audio is the exact same length as the video file and the exact same timecode values.

I changed the audio TC stamp to be 25 fps. Still no sync.

If I stamped the pulled up version of the audio to be 23,98, there's sync!

The duration of the file is wrong, It ends earlier than the video file.

I used Wave Agent to change the timoecode stamp.

So now there's really no problem, there's sync and the video is on tape and all is well. But how the hell can this be? Is it an FCP issue? Does anyone have an explanation?

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HDCam will absolutely do 23.98 -- it may come up as 23.976 in the display, but it's the same thing. Take the 23.98 HDCam master, play it back at 25fps, and dub it straight across to another HDCam recorder set for 25fps. Let the VTR do the 4.1% speed up. I think this will be less trouble, faster, and cheaper than trying to do the speed-up in Final Cut Pro or any other editing program. There are more sophisticated ways to do it, but this is pretty straightforward.

Stuff gets converted all the time, every day, by post houses. Standards are granular -- this is not a major headache. Note that there will be a pitch shift in the audio, and the film will play faster, but that's the price of being in a 25-frame country. If the pitch-shift bothers you, then you could always bring the audio into Pro Tools, use a pitch shifter to leave the sound alone but bring the pitch down a notch, and then lay this audio back to the HDCam for final delivery. I have done this in cases where either I felt or the client felt that the actors were talking like Donald Duck. (This was a big problem on Magnum, P.I., which I worked on for a couple of years in the 1980s.)

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Marc, the post house we used pcouldn't do a hdcam at 23,98. Not sure why it couldn't. It all worked out in the end, we did a good pull up with a software for the video, and the pull up of the audio with PT, a waves plug..

Everything matched in pt, when we imported the exact same files in Fcp they just didn't sync.

It wasn't until I changed the metadata of the audio file to 23,98 TC rate, that it was in sync in Fcp, even though it looked like it wouldn't be in sync.

I also thought an hdcam tape would do 23,98 no probs...could it be an older model tape recorder that's the issue? Btw hdcam (not hdcam sr) sure looks like it's a dying format. The only post house we found that could do it weren't sure it worked cus they hadn't used it in a while... :S

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Ah, it's possible they can't handle the 23.98 tape because they have no 23.98 sync reference. That's very possible. Here in LA at a place I used to work for, we had 10 color-correction rooms... and only four of them could do 25fps PAL! So we have the same problem in reverse in America.

Excellent that you came up with a solution. I'm waiting for confirmation from a tape op friend of mine to double-check that HDCam can internally change standards. I'm positive that it can, but what I'm not sure of is how bad the artifacts are. Strange things can happen when you suddenly speed up the picture by a few percent.

HDCam is an older format (started in 1999), but all newer HDCam-SR VTRs can play and record on those tapes with no problem. I have heard rumors that all videotape formats are dying; I would be curious to ask Sony at NAB in April how much longer they intend to support HDCam-SR and their other cassette-based systems. I think they'd like to bail on all of them.

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Just to check your workflow...

What type plug-in was the Waves plug? Audiosuite plug that you used to process the audio? RTAS that you used in real-time to re-record?

We're you using BWF? Did you check the timestamp using a different software than WA?

It was probably FCP voodoo, but it's worth asking the questions.

-Brian

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Just to check your workflow...

What type plug-in was the Waves plug? Audiosuite plug that you used to process the audio? RTAS that you used in real-time to re-record?

We're you using BWF? Did you check the timestamp using a different software than WA?

It was probably FCP voodoo, but it's worth asking the questions.

-Brian

The waves plug was the soundshifter stereo parametric one

I audiosuited it

I used wav and I did not check in any other software except also Fcp and wave agent...

And the weird part is that it didn't sync when the duration matched on both video and audio, but when the audio was in 23,98 and video 25, there was sync.

Just voodoo I hope, cus else I hope the post studio would have a better explanation than "ehm I dunno wuts goin' on dewd"

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I did just confirm with my old tape op that yes, just taking a 23.98 HDCam tape and setting the playback VTR to 25fps will play it back correctly. That's a real-time standards conversion, speeding up the picture and track by about 4%. Very cheap, fast, and easy to do.

BTW, he tells me that many data-centric post houses in LA are still using HD VTRs around the clock... because producers are nervous about data files, and they want to make sure all their shows are backed up to tape! (We're talking a primarily TV post house.)

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I did just confirm with my old tape op that yes, just taking a 23.98 HDCam tape and setting the playback VTR to 25fps will play it back correctly. That's a real-time standards conversion, speeding up the picture and track by about 4%. Very cheap, fast, and easy to do.

BTW, he tells me that many data-centric post houses in LA are still using HD VTRs around the clock... because producers are nervous about data files, and they want to make sure all their shows are backed up to tape! (We're talking a primarily TV post house.)

Hmmm. Could be this post house's make of the tape recorder just can't handle 23,98 recording I guess.. :/ Great tip! I'll tell them about it and see what they can do..

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It's possible they just never tried it. My friend told me, since the tape is playing back at 25.00fps, it doesn't care that the data was recorded at 23.98 -- it just makes it fit the available data rate. It's all in the menu settings (and there are literally hundreds of them in the HDCams, like 400-500 layers of software menu settings). You practically need a degree to dive deep into these machines.

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