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Mixing 24fps and 25fps on the timeline

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Graham Trott
Mixing 24fps and 25fps on the timeline
on Jun 21, 2012 at 9:47:08 am

Briefly, I'm editing a live music video, where one camera was operating at 24fps PAL (covering the drummer) while the rest were at 25fps PAL. Reason was, the rogue camera did not have the option for 25fps - video shot in US, but for UK market here. Shot on DSLRs, when converting to Pro Res, I did not change the frame rate of the drum footage, as I felt the sync might drift. I've edited with this footage mixed in and all looks fine.

However, my question is - when I output, will there be a problem - either in how it outputs with a mix of fps, or in the way the film looks?

By conforming from 24 to 25 fps in Cinema Tools, or initially during conversion with Magic Bullet Grinder, I was concerned that messing with the frame rate might put me in a world of pain with regard to sync - drums have to be on the spot with every beat. I'd value m' learned friends opinions here, and apologies if this is an obvious query - I'm a bit of a newbie on the technical side, so be gentle with me!

Regards
Graham


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Jessica Muth
Re: Mixing 24fps and 25fps on the timeline
on Jun 21, 2012 at 3:40:10 pm

Graham,

Anytime you mix frame rates, it's going to be a pain. It's better to remove frames than to add them. I would, if possible, export as 24 fps PAL instead. That way, any of your raw footage that is 24 fps won't become interlaced when making it 25 fps.

Jessica Muth
Production Operations Manager
Video Labs
Rockville, MD
301-217-0000
jmuth@videolabs.net


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Graham Trott
Re: Mixing 24fps and 25fps on the timeline
on Jun 21, 2012 at 4:22:17 pm

Thanks Jessica - interesting. Would there be a shift in the running time overall, or will my sound remain synched after output to 24fps?

I'm getting a thin green line at the bottom of the screen on playback where some of the drum footage is used - but not all of it! I think I've seen a thread on this issue, so didn't flag it up on this post, but mention it in passing....


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Neil Patience
Re: Mixing 24fps and 25fps on the timeline
on Jun 23, 2012 at 11:51:24 am

Have to say I partially disagree with Jessica. She is totally correct that mixed frame rates are a huge pain and ideally should be avoided. However if your video is going anywhere near TV as opposed the the net then 24 fps is a pain as you will need to get it all 25 again. All UK TV is 25fps. 24 is a film standard not a TV standard.
Since you shot on DSLR then all your footage will be progressive so you basically have some 25P and some 24P. Its not going to become interlaced if you use 25.

If you reconform the 24 footage to 25 in Cinema Tools then it will be speeded up slightly. So you will get some sync issues but if your shots are short you may not notice. However the same will be true if you conform the 25 to 24, other than it will be slightly slowed down.

If you have a 25 frame sequence and it all looks good then I would stick with that. ideally you need to see it on a proper TV monitor rather than a computer monitor to make totally sure its all OK.

24 is fine for the net or if you need a direct correlation with film shot at 24. If TV is involved stick to 25 or it will come back to bite you somewhere down the line.

best wishes
Neil
http://www.patience.tv


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Graham Trott
Re: Mixing 24fps and 25fps on the timeline
on Jun 23, 2012 at 12:56:33 pm

Thanks Neil - that makes a lot of sense.

Here's the thing - the 24fps footage is of the drummer in the band I have filmed. I've layered video tracks in FCP, synched up with the live audio that was recorded separately. I've chopped down through the video layers to reveal the drums wherever I need to see them. So, once I've conformed the footage to 25fps in Cinema Tools, and then reconnected the media, I will have footage that over a clip length of five minutes, will have increased by some 10 seconds or so. Which will obviously knock everything out of wack.

I guess I know the answer to the question, but I guess that means re-editing/positioning the drum track on the whole programme? Ouch!

It has been suggested that in Compressor, you can change the frame rate but keep the length of the clip the same. However, when I tried that, the new clip would not play - settings problem maybe?

The simplest way is obviously Cinema Tools, as it's more or less instant, but the clip length is changed.

What to do?

Yes - I know - I'm a muppet for not doing it in the first place before starting the edit, but surely, the drum clip would not have synched anyway with the soundtrack, having been stretched to 25fps?

Graham


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Neil Patience
Re: Mixing 24fps and 25fps on the timeline
on Jun 23, 2012 at 2:22:32 pm

You are correct, if you conform the 24P drum shots to 25 they will no longer sync throughout the 5 mins or so. So yes it will mean a certain amount of repositioning shot by shot. As long as they are not too long you should be able to reasonably get them to look in sync but obviously they will be a frame out every second.

Changing 24 to 25 in Cinema tools will be perfect in terms of not giving any motion artifacts but the length will change. You could try speeding up the clip by 4% but this may introduce some slight "jerkiness" to the shot.

The problem with changing the framerate but keeping the duration is that something has to give in terms of a frame of 24 needing to be .96 of a frame of 25. So you often end up with some kind of repeat/interpolation/frame rate artifact that makes the motion slightly un-smooth.
Hardware standards conversion would do a good job but not going to be easy/cheap.
In terms of quality overall you are probably going to get the best result by biting the bullet and re syncing/retiming the drum shots.
You are right, sadly you were always going to hit this issue given that one camera was 24 and one 25.

best wishes
Neil
http://www.patience.tv


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Graham Trott
Re: Mixing 24fps and 25fps on the timeline
on Jun 23, 2012 at 3:04:25 pm

Neil

Thanks again - yes, at least the drum clips are short in duration - in most cases, a few frames, or less than a second, so I'm sure it won't look too bad at all. It will become more of a pain to find the right bit as I move along the timeline where the shift is greater. Oh well, live and learn.....


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Thanos Papadopoulos
Re: Mixing 24fps and 25fps on the timeline
on Dec 19, 2012 at 9:37:27 am

Hi to all, I have a similar problem. My material there is no need to be synchronized. I have two dslr cameras one with 25fps and another one with 23.98 fps. its a documentary with two characters. One of them was shot with 25fps and the other one with 23.98 fps and I want to cut in parallel action. but I have something like drop frames even when I convert my material from 23.98fps to 25fps. Although, I did the convert with fcp quicktime conversion.
Can you help?

P.s I'm in Europe so, I dont know if it matters but, I'm with pal system.

Fix it in Pre.


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