Inspiring

Question

Mixing Frame Rates of Micro Variations (and larger ones)

Forum|Forum|3 years ago
February 16, 2023
4 replies
5767 views

Greetings video nerds!
I think I need to get clarity on mixing frame rates inside a project sequence/timeline before I continue working on my showreel type of projects. Here's a real-life use I've got right now:

Commercial Demo Reel.

Goal here is to mix footage from different commercials I worked on
Source audio has been removed from footage. Using only picture, and I will add a separate music track.
Most were shot at 24 frames per second.

ISSUE: The frame rate shown in the project window varies – I have of course 23.976, but I also have 23.93, 23.98, 24.00, and 24.04 showing in the frame rate column. These are clearly intended to be 24 frames per second so…

QUESTION: Why are they showing these fps discrepancies? Why are they not all exactly 23.976?

QUESTION: Can I safely mix these in the 23.976 timeline, even if I get a warning that the little variations don’t match the sequence settings?

QUESTION: Taking this a bit further, I also have some source footage that was shot at 30 frames per second that I want to throw in there. Most of it is 29.97, but again, some are 29.92, 29.95 30.01, 30.02, etc. How do I handle these? Same way or differently?

There seems to be a lot of misconceptions around the Interpret Footage feature. I’ve seen some people say do Interpret Footage to all source material to create a congruent frame rate to work with in a sequence, and to avoid dropped frames at all cost, but as a 2nd step make sure to also do a clip duration of a certain % to bring it back up to the actual speed it should be. I also haven’t been able to find a YouTube video that explains what to do when the frame rates have micro variance (23.976, 23.93, etc)

BONUS QUESTION: If I wanted to keep the source audio of this mixed fps footage, would that affect any of the recommendations given here? If so, how?

If someone could give me definite answers to my questions here that would be so wonderful!

This topic has been closed for replies.

A

Aaron36238192wk1x

Participant

my M1 Max MacBook just can't handle a sequence with uneven framerates mixed (e.g. 50.00 fps + 29,97 fps).

Once I drop a few effects on clips, it's done. Just freezes for a few seconds, then unfreezes, untill I scroll back to that section where mixed framerate clips meet.

Warren Heaton

Community Expert

QUESTION: Why are they showing these fps discrepancies? Why are they not all exactly 23.976?

Answer: It sounds like your source footage is a mix of delivery formats where frame rates are not locked in as they are with edit formats (or "mezzanine" formats or "intermediate" formats). Sometimes there are irregular frames that throw what should show as 23.976 or 29.97 off. If the various frame rates were showing with camera originals or a mezzanine format, I'd worry. If they're showing with delivery files (ripped DVDs, downloaded YouTube, screen-recorded playback, H264 MP4s, and the like), it is what it is.

QUESTION: Can I safely mix these in the 23.976 timeline, even if I get a warning that the little variations don’t match the sequence settings?

Answer: Maybe. For a demo reel, you're probably fine leaving the source as is. If this were a paid gig, I would transcode any footage showing an irregular frame rate to ProRes in After Effects, locking in 23.976.

QUESTION: Taking this a bit further, I also have some source footage that was shot at 30 frames per second that I want to throw in there. Most of it is 29.97, but again, some are 29.92, 29.95 30.01, 30.02, etc. How do I handle these? Same way or differently?

Answer: For a demo reel, you might be fine leaving the source as is and testing which Time Interpolation method (Frame Sampling, Frame Blending, or Optical Flow) in the Clip Speed/Duration dialog box for 29.97 sources works best in your 23.976 Timeline. Optical Flow usually works best, but it varies based on the source footage. Avoid assuming a different frame rate in the Interpreting Footage options for source clips unless the source is without sound. If this were a paid gig, I would check if the 29.97 source has 3:2 pulldown and then pull that up to 23.976 in After Effects and render it to ProRes 422 LT 23.976. For interlaced 29.97 without 3:2 pulldown, I would Separate Fields in After Effects and then use Timewarp in a 23.976 Comp to render it to ProRes 422 LT p23.976. If not totally happy with those results, I'd run them through Apple Compressor (which inherited solid Frame Rate Remastering from Shake). It also would be worth running a clip through Topaz Labs Video Enhance AI to get from i29.97 to p23.976. Its upconversion is excellent. I haven't tested its frame rate remastering.

BONUS QUESTION: If I wanted to keep the source audio of this mixed fps footage, would that affect any of the recommendations given here? If so, how?

Answer: For a demo reel, add it to the timeline and see what happens. If taking the route of transcoding to ProRes to conform to 23.976, leave the source audio with the file to hold sync. If a change in pitch is noticed, adjust for that during the audio mix.

O

OrlandoJetsetAuthor

Inspiring

Hi Warren - picking up from a few months ago! Thanks for taking the time to really go into details with this. I'll admit it was a little bit over my head because I'm not a video "expert" and I mostly just make demo reels for my own showcase,, to post on YouTube/Vimeo in 1080p. I'm not hired by any company to produce award-winning reels... at least not yet lol. But I do obviously want my reels to look as best as possible, and more importantly, I just want to make sure I avoid any pitfalls I may not be aware of. Most tutorials I've watched just drop in their footage and let Premiere do its magic. And their exports look fine enough for me!

I would like to ask though... you mention conforming (or transcoding).... not sure if those terms are interechangeable and mean the same thing... but you described a specific process using After Effects. Could I achieve the same simply using ShutterEncoder or Handbrake? Not sure if what Neil had suggested is the same thing you're suggesting - just using a more simple software to achieve it.

R Neil Haugen

Legend

"Transcoding" is inputting one format/codec, and exporting a different format/codec.

For media with the truly odd framerates of say 27.82 ... anything not a "normal" 23.976, 29.97, or 59.94, it's probably "variable framerate" ... screen capture apps and many phones and some GoPro/drone media are of this ilk. Audio is constant, but the framerates constantly shift as the device only records the bare number of frames it needs to keep detail fairly ok.

None of the Adobe apps fully correct that to constant framerate that I know of. So that's where using Handbrake or ShutterEncoder is useful, as, if you set the controls to do so, they can correct this and output straight media. I tend to like S-E, but ... they recently moved the "set to constant framerate" option to deep in their preferences, so you have to hunt for it.

"Conforming" is the process of taking say the clips of a sequence from one app and getting them into another, with any scaling changes, speed changes or ramps, and audio files correctly reproduced.

This is done of course if you send your project to someone to color/grade it in say Resolve or Baselight. You send the media, an "XML" and/or "EDL" file, and a low-bitrate H.264 of the sequence. They use the XML and EDL files to get most of the clips laid out on the timeline, put the H.264 file on V2, and go through and check that all clips are correct in to out, cuts, scale & speed changes.

Conforming is also sometimes used to refer to cadence corrections ... that 3:2 "pulldown" that Warren mentioned. You should look that up, it's interesting if you don't need it but absolutely necessary to know for when you do!

And no, S-E and Handbrake can't do pull-downs, but Ae has one of the best utility functions for that around.

Pull-down is needed especially for some interlaced to progressive, and progressive to interlace, with certain framerate differnces. If you are prepping for the web, probably not much of an issue. Premiere seems to handle cadence changes pretty decently for most usage. You might notice a repeated frame, or one might appear to be skipped, on occasion. But in general, interlaced to progressive works ok.

You cannot give that to any broadcast facility though! Many broadcast facilities still require interlaced, and in the US in 29.97, and ... that must be perfectly retimed and interlaced. Ergo, using Ae after you learn what it is you're doing.

So ... S-E and Handbrake do great for converting VFR to CFR. For transcoding in general, Premiere and MediaEncoder can do say H.264/mp4 that is already CFR to say ProRes quite handily. And can convert progressive to interlaced.

But ... if you need to get proper broadcast spec 29.97 interlaced, you may need Ae and setting pulldown or up corretly.

Have I stirred the mud adequately? lol

Everyone's mileage always varies ...

Warren Heaton

Community Expert

You want to treat your demo reel workflow like a documentary workflow.

What will the settings be when you have a full-resolution, stand-alone edited file? The answer to that informs how you conform source footage settings and configure your Timeline settings.

Assuming that your demo reel will be uploaded to YouTube, Vimeo, or FrameIO (in case you haven't looked into it yet, a FrameIO Presentation Link is a great way to share a demo reel with prospective clients via email, text message, Slack message, Discord, etc. and an Adobe level FrameIO plan is included with our Creative Cloud subscription), then ProRes 422 LT 2160p24 or 1080p24 (true 24 or 23.976) is a good option unless the majority of the source footage is i29,97.

R Neil Haugen

Legend

First, any clip showing a non-standard time ... those odd .04 like things? Are clearly VFR ... variable framerate ... meaning the capture device was set to a certain FR but continuously changed actual recorded FR during the clip depending on motion/detail 'need'.

I would recommend using the free ShutterEncoder utility app to convert those to CFR ... constant framerate. Then use the files created by SE to replace those in your project. And at the same time, you can make the FR more consistent as a bonus.

For standard video media, Pr tends to work pretty well with mixed FR sequences. So ... make a test sequence, either by creating a new sequence from settings you set or by selecting a clip with the right framesize/rate for your project.

Then drop several clips of different FR on it. Does it work correctly?

Neil

Everyone's mileage always varies ...

O

OrlandoJetsetAuthor

Inspiring

Hi Neil, thanks so much for taking the time to answer this post and for introducing me to ShutterEncoder. If I understand correctly this conforming of VFR clips to CFR is something that cannot be achieved using Adobe's included Media Encoder? This is something that absolutely requires a 3rd party solution?

Also, such "conforming" from VFR to CFR - will that change any of these source clips' duration, even when dealing with such small variations in frame rate? If so, how long before it starts to show an "out of sync" problem? For example, I have another project - a music video - where I shot a few angles using my phone while also capturing clean audio of the musical performance separately. Will I run into sync issues if I try to sync the audio track I captured to source VFR footage that has been conformed to CFR? Since the variations of frame rates are so small, will it eventually lag (or get ahead) of the audio track? I would think that the duration of the video would have to match the duration of the audio but ...You're the expert. 😉

Finally, what did you mean by "For standard video media"?

O

OrlandoJetsetAuthor

Inspiring

Interpret Footage has a couple functions. You're talking about only clip speed here.

The devs have told me the the Interpret Footage "apply X framerate" is meant primarily for changes either involving cadence changes (a rabbit hole of its own) or when you want Premiere to treat it as a particular speed, different than say when simply dropping it on a timeline.

It has nothing to do with variable framerate changes. Nor general speedramps either.

Neil

When I look at my list of footage in Premiere, is it safe to assume that everything showing 23.976, 24.00, 29.97, 30.00 and 59.94 are all constant frame rates? (If it is, then I won't have to open the properties box of every clip I imported.)

Alternately, I was going to ask if any footage that is NOT these exact values means it must be variable frame rate and should be conformed into a constant frame rate first? As per the logic of your first reply "any clip showing a non-standard time ... those odd .04 like things? Are clearly VFR .."

However, I just looked at the properties of a few clips that are 23.98 (which by my logic and according to your answer should have been VFR) but when I looked at its properties inside Premiere, they did NOT indicate "Variable frame rate detected".

So I'm a bit confused now, because I thought odd numbers like that meant they were variable frame rate, and an easy way to tell if something needs to be conformed to something standard but this breaks that logic. And because of that, I don't know if I should still conform this one to 23.976 in ShutterEncoder or just drop it in the timeline since it is NOT variable frame rate.

Any advice? I'm sorry if it's taking me a bit to understand.

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