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Question

Proxies out of Sync with Clip

Forum|Forum|2 years ago
April 19, 2023
3 replies
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Hi,

I'm using proxies for my project, a lot of the shots have interpreted footage, change from 23.976 FPS to 24 FPS. After changing the Frame Rate I set up proxies to be created for each clip. When they came out I noticed that when they were in use the visual would be out of sync with the clip.

I've checked the proxies and they all come out to 24 FPS matching the clip after modifying. I'm really stumped by this, are there any solutions? Any help would be greatly appriciated.

Thanks!

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Fergus H

Community Manager

Warren Heaton

Community Expert

As long as you're never introducing 3:2 pulldown, you can intermix 23.976 source and 24 source in a Timeline running at 23.976 or 24 without needing to adjust the Interpert Footage settings.

If you are introducing 3:2 pulldown later in your workflow, then confrom the 23.976 source to 24 or the 24 source to 23.976 by transcoding. If the source is not already a mezzanine format (ProRes, DNx), transcode to one during that.

Remote Index

Warren Heaton,

"you can intermix 23.976 source and 24 source in a Timeline running at 23.976 or 24 without needing to adjust the Interpert Footage settings."

Not sure what your intention was with this statement, but strictly speaking, you can intermix any frame rate footage with any framerate timeline in PPro.

If your intention was to say that you can use 24fps footage in a 23.976fps timeline (or vice versa) and PPro does a speed change on the fly, that is not true. As with all frame rate mismatches, PPro does the usual rough frame rate conversion by doubling or dropping frames as needed. In the case of 24fps footage in a 23.976 timeline, for example, PPro will drop a frame every 41 2/3 seconds (every 1000th frame) as you would expect.

In practice, you might not notice this on short clips, but if you're using long (or very long) clips and/or require frame accuracy throughout then it will be an issue and it's better to effect a frame rate conversion before use the clip in timelines.

"... confrom the 23.976 source to 24 or the 24 source to 23.976 by transcoding. "

Again, I'm not sure what you're suggesting here but a frame for frame conform would require a speed change. To my knowledge, Adobe transcoding tools do not effect speed changes when they convert from one frame rate to another (ie. the original clip and the transcoded clip will always be the same duration), and frame rate conversions during transcodes are always done with the above described "rough" method of doubling or dropping frames. Please correct me if I'm wrong on that.

R.

Warren Heaton

Community Expert

@Remote Index

Yes, "it's better to effect a frame rate conversion before use the clip in timelines" without question at the source footage level - not via Interpert Footage. I hope it's clear that tthat is what I recommend. But is it always necessary? Maybe not.

For theaterical, television, and streaming, I would not mix 23.076 and 24. While we can drop any clip of any frame rate into any timeline of any framerate, doing so can result in the edited full resolution file (formerly called "edited master") failing a quality control check and being rejected. A best practice is to know our delivery frame rate (for example, 23.976 for scripted television dramas or 29.97 for packages presented during live broadcast) with source footage settings and edit settings set to match.

The important tecnical difference between 23.976 frames per second and 24 frames per second comes into play if we introduce 3:2 pulldown. Either one can pulled down to 29.97, but only one (23.976) can be pulled back up and maintain full cadance. Both frame rates have 24 whole images per second. Anything being dropped or not dropped doesn't come in to play until after 3:2 pulldown.

An example for where I'd be okay with mixing 23.976 source and 24 source is when the delivery is to social media. Rather than worry about the difference, I'd just get the delivey file exported so it can be posted in a timleine manner. It's highly unlikely it this context that the file will ever go through 3:2 polldown. It will also probably be a few minutes at most.

Remote Index

Hello Ciaran etc.,

Unfortunately, Adobe does not support their proxy workflow with the Interpret Footage command.

I've written more about this here.

I would suggest developing a workflow where you work with transcoded proxies you make 'manually' (outside Premiere Pro) and do not attach proxies.

I have asked for an update from Adobe on these limitations to Proxy Workflow and whether they will be addresssed. Adobe has answered with silence.

R.

R Neil Haugen

Legend

I'll bring this up at the Adobe booth here at NAB2023 again. I pretty much expect the answer to be as the last four or five times I've asked the devs.

Something like what I've posted on that other thread. Which is ... "Speed/Duration is the proper tool for that and simply works."

Which it does mostly.

My guess, about the documentation, is they see the printed information differently. There are two speed change tools in the app. They directly say don't use one of them, Interpret Footage, for proxies. Ergo, that clearly indicates you should use the other.

And I think a lot of users would prefer an active writeup "Use X tool for A" rather than a passive "Don't use Y tool for A".

Maybe @Fergus H could pop in here?

Neil

Everyone's mileage always varies ...

Remote Index

Niel,

I think the issues are a bit more complex than what you've indicated, even leaving aside for the moment that proxy workflow is, according to Adobe, incompatible with colour management options, audio channelization, timecode modifications, etc.

There are two speed change tools in the app. They directly say don't use one of them, Interpret Footage, for proxies.

Part of the problem is that Adobe does not "directly say" this. Here is the full text of the passage that addresses speed in the online documentation:

Change the frame rate of clips

You can use the Interpret Footage command to change the frame rate that Premiere Pro assumes for a clip. When changing the frame rate of a clip, audio is changed, in addition to the video. Changing the frame rate changes the original duration proportionally. For example, if you set a 10-second, 24-fps clip to 48 fps, it becomes half as long, with a new duration of 5 seconds. Clip frame rate is reconciled with the sequence frame rate. For example, if you change a 24-fps clip in a 24-fps sequence to 48 fps, the sequence displays only every other frame of the clip.

You can also change clip speed and duration by choosing the Clip > Speed/Duration command for a clip selected in a Timeline panel. However, such a change affects only that clip instance in a Timeline panel. Using the Interpret Footage command changes how a file is interpreted throughout a project.

1. In the Project panel, right-click the desired clip.

2. Select Modify > Interpret Footage, and do one of the following:

Select Use Frame Rate From File,

Select Assume This Frame Rate, and type the number of frames per second.

3. Click OK.

It's important to note that nowhere in this do Adobe "directly say": "Don't use proxies". They list that directive elsewhere. (Try a search for "speed" or "interpret footage" and let me know what ranking the relevant information comes up.)

"Speed/Duration is the proper tool for that and simply works."

The above passage notes the differences in the effect of using the two options - they each work differently.

R.

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