Participating Frequently

Question

Interpret Footage vs Speed/Duration

Forum|Forum|2 years ago
May 4, 2023
5 replies
5903 views

Ok I know this question has come up multiple times. I use a lot of mixed frame rates, mostly 60fps, some 30fps & 24fps. I always interpret footage for every clip to 23.976. The footage looks smooth and crisp in slow motion like it's intentionally supposed to. I understand many people think this is not the correct way, especially when using proxies. I have intentionally not used proxies for this exact reason. However whenever I hire an editor they are use the speed/duration and it NEVER looks as good as using interpret footage. I'm very aware that 60fps on a 24fps timeline should be slowed to 40% using the speed/duration, however it does not look as good as interpret footage, ever. It looks choppy and terrible looking to my eye. I do not see the benefit in using speed/duration with the exception of using proxies and that's it. While I know this would significantly speed up my workflow the footage just does not look as good. Can anyone help me understand why you would use the speed/duration to slow footage when it doesn't look as good, just to use proxies?

Thank you!

Editing

A

Alexander Birthday Cake

Participant

Thank you for this awesome post. I have a question about this. Are you leaving your sequence settings at what the footage was shot at, i.e 60fps (or 59.94)? Or are you making your sequence settings 23.976 to match what the footage is now interpreted as? I guess changing it to match the new interpretation would affect all the other stuff in your sequence that is not meant to be slowed through "interpreting footage". Perhaps I just answered my own question. Would still like to hear from you. Thanks

EditorPete

Known Participant

This is a bit off topic, but I've been using this for slowing down footage recently. It also is a great scaler.

I do not work for this company, just wanting to share.

https://www.topazlabs.com/topaz-video-ai

Remote Index

Hello Rettig Co.,

I’ve written about this elsewhere, collecting notes here for your reference.

This is part of the larger problems with limitations on proxy workflow that I’ve written about here.

"If your workflow relies on modifying the source clips using any of the following commands [Modify Audio Channels, Interpret Footage, Modify Timecode, Modify Captions], do not use proxies in Premiere Pro. Doing so will result in unexpected behavior."

CHANGING CLIP SPEED - THE MANUAL

“The speed of a clip is the rate at which it plays back compared to the rate at which it was recorded.”

The manual lists 4 ways of effecting speed changes.

The manual gives two ways to change the speed of a clip here: (under 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. ... Changing the frame rate changes the original duration proportionally. ... You can also change clip speed and duration by choosing the Clip > Speed/Duration

The manual also gives three ways to change the speed of a clip here.

In total, the 4 means of effecting speed changes are:
Interpret Footage
Speed/Duration command
Rate Stretch tool
Time Remapping feature

SOME NOTES

The manual is typically sparse on details and bereft of informative comparisons but a couple of things are worth pointing out.

1. Using the Interpret Footage command changes how a file is interpreted throughout a project.
2. You can apply Speed/Duration changes at the Project clip level or at the Sequence clip level. Changes made at the project level are respected when adding new instances into a sequence.
3. You also make the good point that if a user wishes to apply speed changes to a conformed clip, this might be easier if the first conform is done via Interpret Footage (ie. original 60fps; interpret footage to 23.98; then speed effect to 200% for double).

4. It also should be noted that any optical flow or equivalent process is not representing the orignal frames and potentially (almost certainly) introduces artefacting.

PERSONAL PREFERENCE / POSSIBLE TEST

Personally I prefer using the "Interpret Footage" version as you do (unless built-in proxy workflow is necessary) because I trust it more for frame for frame interpretation (ie. not duplicating or dropping any frames). But I believe with precise percentages the speed effect should in theory yield the same quality results. This will be difficult if fractional frame rates and non-fractional frame rates are involved (ie 60fps speed change to 23.98fps requires 39.996etc. %... does Premiere round this number?). In any case, it would be easy enough to set up an objective test of this. (I never have.)

OTHER TOOLS

I have asked about other tools to conform media from one frame rate to another frame rate at the Finder / File Explorer level. Currently I know only of Shutter Encoder.

R.

Rettig Co.Author

Participating Frequently

R.

This is all great information that you provided. Thank you kindly for the information. The issue regarding the worklow relies heavily on the fact that when I send off work to editors they all use proxies for obvious reasons. But I want to maintain the same video quality whether it is contracted out or completed myself. You brought up a very good point about fractional frame rates and whether Premiere would round this number. This might explain why it looks different than when I've interpretted the footage. I have never done an extensive test for this, only through watching in Premiere. I still stand with the point of speeding up a conformed clip. For example if I film in 60fps and interpret the footage to 23.976 on the sequence this will slow my footage down to 40%, but the speed/duration will be listed at 100% (because this is the baseline on the timeline.) Then I decide that the footage is "too slow", e.g., my clip is going to be 3 seconds in length on my timeline but in slow motion it doesn't get the full pan of say a flower. I can use the speed/duration to speed up the clip from 100% to 200%. This allows the footage to go through more of the footage but since it's conformed to be slow motion, the footage is more stabilized. The only downfall as I have previously noted is that because it's sped up, it looks a little unatural to a good eye because the motion blur is not what 24fps would look like. I am definitely going to test this when I can to see if the difference is visibly noticeable outside of Premiere.

Thank you,

Grant

Remote Index

Grant,

The issue regarding the worklow relies heavily on the fact that when I send off work to editors they all use proxies for obvious reasons.

One way of working with proxies in consideration of this issue is to simply work with proxies as source media (not attached).

What I mean is this - create the proxies as you normally would, but import (or link) these proxies as source media (ie. do not "attach" them as proxies to camera original). Working this way, Premiere will simply treat the clips as it would any other media (ie. you can use "Interpret Footage"). To be clear: it's only the built-in proxy workflow (ie. attaching proxies) that is limited in this way.

Working this way (a more traditional offline / online workflow) means you relink to camera originals later - and that can produce its own set of issues (particularly if the cam origs and proxies are different resolutions) but it is a workflow worth considering.

R.

Kevin-Monahan

Community Manager

Hi Reggig Co.

Are you engaging the Optical Flow option in Speed/Duration? Try it and report back.

Thanks,
Kevin

Kevin Monahan - Sr. Community and Engagement Strategist – Adobe Pro Video and Audio

Rettig Co.Author

Participating Frequently

Hello Kevin,

Yes the time interpolation was already changed to optical flow. I've tried this several times now on different timelines each. Interpreting footage 60fps to 23.976 looks smoother than just slowing down the footage to 40% and engaging optical flow. It just looks choppy and stuttery to my eye. It also brings up another issue that I've run across. Typically if I interpret my footage to 23.976 and then decide I want to speed the clip up, I can change the speed/duration to say 200%. This allows me to keep the smoothness but gives more action such as if I'm panning in. The only issue here is because it's not actually 24fps, my eye can tell there's not the typical motion blur that there would be at 24fps. So I'm wondering why Adobe wouldn't just fix the proxies to account for the interpret footage. I've read there are ways to start the proxies and stop the media encoder to trick the encoder to create the proxies to mimic the interpret footage. I know this is long and I'm sure I'm not using the correct terminology, but I'm trying to find a seamless solution when sending off films for editing. Thank you!