23.98 to 29.97 sync problem

[Shane Ross]

[Greg Nosaty] “Could the problem be: the 720pn24 media being edited in a 29.97 timeline in FCP?”

Yes. Why did you do that? 720p 24PN is a 23.98 format. Why did you edit it in a 29.97 timeline?

[Greg Nosaty] “Are the FCP OMF files in 23.98 or 29.97 frame rate?”

Well, the FILES might be 23.98, and the timeline 29.97. Ask the audio mixer what he got…what does it look like on his end?

[Greg Nosaty] “What is the best workflow? Should they shot in 720p24 instead of 720pn24?”

What is your intended final output? That pretty much sets the workflow for shooting and editing. It really sounds like you shot and edited without a clear idea about what you were doing…and that isn’t a good thing. If you shot 720p 24PN, you should have editing in a 23.98 timeline, exported a 23.98 OMF, and ended up with a 23.98 mix. Given the proper hardware (Kona, Matrox, Decklink) capture card, you cn convert this to any format and frame rate upon output to tape…with some limitations on some of the hardware.

What did you want to end up with as your final delivery?

[Greg Nosaty] “Keep the workflow consistent and shoot, edit, mix in 24p then add pulldown via KONA 3 on output to tape.”

If pulldown is required. I have shot and edited 720p 23.98 and output 1080psf 23.98. I have also shot and edited 23.98 and output 1080i 29.97. All via the Kona 3.

[Greg Nosaty] “If that’s the case then when does the pulldown get added to the 5.1 mix?”

The mix needs to be done at the frame rate you shot. If you shot 23.98, you needed to mix at 23.98…right from the start.

ALWAYS plan ahead…always know what you are going to do before you dive in. Poor planning here is causing you headaches, and will be costing you money and time to fix.

Shane

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[Greg Nosaty]

Thanks Shane

I normally edit in the format and frame rate the footage shot in and let my Kona 3 do all the heavy lifting. The broadcasters usually require 1080i at 29.97 with Dolby encoded 5.1 outputs to Sony HDSR. Many productions I work on choose to shoot 24p for the “pulldown” look even though they know the final deliver is usually 1080i 29.97 or occasionally 720p 59.94. I output the OMF and send it to the mix house and let them do their magic.

In this case I didn’t edit this show I just did the picture online and I didn’t question the workflow to that point. The post house doing the layback and captioning encode to Sony HDSR noticed the sync issues. Frankly, It wasn’t until then that I even noticed the media was 23.98 in a 29.97 timeline (i know, I know, what were you thinking!). But I thought if that was the problem the sync would consistently drift further out, but that was not the case here. It went in and out of sync through the whole show. Plus the mixer told me that the OMF and the Quicktime reference movie with TC burn that he received were all 29.97. So it didn’t make sense

Besides many people tell me they use FCP to do their pulldown so I would assume that FCP would pulldown the audio as well. I know differently now.

So I understand what I have to do on the picture end of the equation. What I don’t know, and have never asked any mixers or layback techs, is how does pulldown get added to the final audio mix as it gets laid back to HDSR?

cheers,
Greg Nosaty

Cinemontage Productions Inc

[Jeremy Garchow]

[Greg Nosaty] ” What I don’t know, and have never asked any mixers or layback techs, is how does pulldown get added to the final audio mix as it gets laid back to HDSR? “

There is no pulldown added to audio when outputting 23.98 material to 29.97 or 59.94. It is still 48k 16 or 24 bit audio. The audio will remain in sync, but you have to respect the processing time to adding pulldown. On Kona cards, the adding of pulldown usually happens in about a frame. So it’s best to offset your audio back one frame so that the video remains in sync. The ioHD allows you to slew the audio to account for this processing time.

Not only that, adding 23.98 material to a 29.97 timeline in FCP will cause weird pulldown issues. I am surprised you didn’t see this in the online.

Jeremy

[Aaron Neitz]

Keep in mind many audio suites still don’t recognize 23.98 as a valid format…. they have 29.97 for video and 24.0 for film. This has happened to me when I’ve been working in 1080/23.98 and they read my OMF as 24.0. This obviously causes havoc.

23.98 and 29.97 are analogs of one another as far as audio is concerned. There isn’t “pulldown” added to the audio if you intermingle these two frame rates. Sometimes I found it easier to give the mix house a Digibeta with 3:2 pulldown and tell them the OMF is 29.97. Presto you get a perfectly in sync mix for your 1080 master.

[Greg Nosaty]

I know Kona can’t keep audio in sync. I think it’s ridiculous that I have to manually offset sound that should be in sync in the first place. I pay for the flagship video card for FCP and I have to create the offset? The competition has figured out how to delay picture to match their processing time, Why can’t AJA?

But I don’t do 23.98 output to 29.97 or 59.94. I send an OMF to a mix house. Nor do I output the final 5.1 mix from my Final Cut suite so I don’t respect the pulldown processing time. The broadcasters require Dolby encoding which I can’t do in house so I output picture to Panasonic HD and I send it to another facility. They take my tape and the Mix from the audio house and do a DVCpro HD to HDSR transfer with Dolby layback of the 5.1 mix and closed captioning.

In my output the Kona does the pulldown to 29.97 but the mix house has 48K 16bit audio that was recorded on a camera shooting at 24p. Is it just magic that I change the frame rate and the original audio is supposed to match?

cheers,
Greg Nosaty

Cinemontage Productions Inc

[Jeremy Garchow]

[Greg Nosaty] “I know Kona can’t keep audio in sync. “

I think you’re misunderstanding. The video takes 1 frame to process. At the most, if all of your audio is in sync on an HD timeline and you down convert with a Kona, video will be behind audio by one frame consistently. You can simply select all the audio in your timeline (after you get it back in sync from your audio mix), move it back one frame, then cross convert with the Kona.

If you have sync issues that are somewhere between 1 and 4 frames and inconsistent across the project, you have different issues.

[Greg Nosaty] “The competition has figured out how to delay picture to match their processing time, Why can’t AJA? “

There’s a lot that AJA does, that others don’t (720p24 to 1080i29.97 being one of them). A one frame processing delay is no big deal when you think of all the things you can do with a Kona. Other conversion hardware has 1 or more frames processing. It’s fairly common.

[Greg Nosaty] “But I don’t do 23.98 output to 29.97 or 59.94.”

No, but if you have a 29.97 timeline with 23.98 material, there’s going to be extra frames that need to be made up somewhere due to the mismatch in frame rates (and FCP does a bad job of adding pulldown in 29.97 timelines). What happens if you simply make a new 23.98 timeline and copy and paste the 29.97 timeline to a 23.98 timeline? Also, did you have a DF or NDF 29.97 timeline? 23.98 is NDF only. That could account for some offsets.

[Greg Nosaty] “Is it just magic that I change the frame rate and the original audio is supposed to match? “

Magic? Not really. how exactly did you do the online? What did you do for it? You had p2 media, correct? Did you create new graphics? Transcode the DVCPro HD? Was the original audio sync sound or recorded on camera?

Please tell us more about the project and what you have done so far.

Is this for broadcast? Do you need to adhere to any timing guidelines?

[Greg Nosaty]

Thanks Jeremy, this is a good discussion for me…

Don’t get me wrong, I believe that Kona is a great card, I own 2 and wouldn’t buy anything else i’ve seen. My point is if they know there is a one frame delay then why don’t they write it into the drivers code and save me the hassles. anyway…

Thank you for helping me realize that there is more than one issue at work here. When I watch the show in FCP it looks and sounds in sync. it’s not until I bring the stereo mix back into the sequence that you can SEE the sync issue. When you say that “FCP does a bad job of adding pulldown in 29.97 timelines” it all starts to make sense. that is problem number 1. Problem 2 is that I believed that FCP 6 was an “open timeline” and didn’t realize that it meant about the same as “real time effects” Problem 3 is that i didn’t pay attention when the project fell onto my plate. problem 4 is the mixer did some weird voodoo as well.

Here is a bit more background:

This documentary is for the french strand of the CBC, called SRC and Tele Quebec. (I’m in Canada if you haven’t guessed;). They both have fairly stringent quality control and give written reports. One of them requires a seamless 51:37;00 the other a 01:00:00;00 with bumper and commercial blacks. So everything has to match wall clock in 29.97 DF.

They shot on Panasonic P2 and then logged and transfered native DVCPro into FCP, nothing unusual. For online I’ve done things like green screen composites over slomo backgrounds, simple 3 way color correction with broadcast safe filters, lower thirds, alpha channel titles, a credit roll and 2 dissolves. I’ve done lots of shows in 24p and never run across this kind of problem before, but then again I’ve always cut in a native timeline.

To trouble shoot this problem i’ve gone back to the original “picture locked” sequence and I’ve imported the stereo mix from audio post, matched the 2 pop, and compared the production dialogue with the mix and that’s when you hear the variation in the delay. Then I compared it to the guide track from the Quicktime movie that the mixer imported into his protools session and it match the FCP sequence perfectly. The wild card was the Protools mix because everything that came from FCP worked was in sync.

I don’t ever want to go through this again and the only way to prevent it is to understand how it happened in the first place. But I’m still not clear how the original 23.98 audio can be laid back to a picture that has been pulled down to 29.97 DF if there is no pulldown added to the audio.

cheers,
Greg Nosaty

Cinemontage Productions Inc

[Chi-ho Lee]

[Shane Ross] “Greg Nosaty] “Could the problem be: the 720pn24 media being edited in a 29.97 timeline in FCP?”

Yes. Why did you do that? 720p 24PN is a 23.98 format. Why did you edit it in a 29.97 timeline?
“

What if he had archival & stock at 29.97? He would have to edit his 23.98 sources along with 29.97 stock in a 29.97 sequence for a 29.97 master. Rendering the 23.98 clips inside the 29.97 seq should add proper pulldown to his clips.

Otherwise, he would have to convert his 29.97 stock to 23.98 which would not be so easy and more costly.

How would you deal with this situation otherwise?

CHL

[Greg Nosaty]

In Fact there was standard def stock in the show. Some was BetaSP at 29.97 and some was home video in PAL DV of refugee camps in Rwanda. These were up-converted on the cheap with Mpeg Streamclip and a Nattress stands conversion plugin. The footage didn’t look great in the first place but it is in sync. In fact the whole show was in sync in Final Cut. Something happened between OMF export and layback of final mix.

Besides FCP claims to be an “open timeline” where you can drop anything media within the same video standard into the timeline, render and play. But it isn’t that simple. When I have multiple codecs in high and standard def in a project it constantly crashes. When I convert all media to the same def and codec and re-import everything is stable again.

cheers,
Greg Nosaty

Cinemontage Productions Inc

[Jeremy Garchow]

[Chi-Ho Lee] “What if he had archival & stock at 29.97?”

Whenever I face this problem, I confrom the 29.97 sources to 23.98 via a variety of methods.

[Chi-Ho Lee] “Rendering the 23.98 clips inside the 29.97 seq should add proper pulldown to his clips. “

It should, but it doens’t. It adds 2224, instead of proper 3:2. and when working in a 720p timeline, there’s no 3:2 pulldown interlaced pulldown to be had due to the progressive timeline.