Interpret Footage from 60fps to 24fps results in choppy, weird playback

[lehestro]

What am I missing? I feel like I've done this countless times, but it's been a minute. Has premiere changed?

I have a bunch of footage shot at 60 fps (59.94 to be precise), and in order for them to play in slow motion I go to Modify>Interpret Footage>Assume this frame rate and set it to 23.976 (my timeline's frame rate).

Instead of getting smooth, slow-motion playback, Premiere duplicates each frame, resulting in choppy playback. Basically it's showing every frame, but for 2 frames each, exactly the same behavior as if the footage was shot at 30 fps and then speed changed to 60 fps with frame duplication as the interpolation. 

The footage is from a Canon R5, in case that matters.

Confused that I'm even having this issue. Grateful to the hive mind.

Premiere 24.4.1, macOS Sonoma 14.5 m1 Max, plenty of RAM n all those things.

[R Neil Haugen]

A couple things.

First ... according to the devs, "interpret footage" is designed for cadence changes primarily. Needing broadcast-level 3:2 pulldowns. Especially involving interlaced media. Which does not seem like the case for you.

For all "regular" speed changes, the appropriate tool is the "Speed/Duration" one. Unfortunately, there you do need to do some beginning math to figure out the percentage change to match one frame rate to another, but it's pretty easy. Many tape the sheet by the keyboard for reference. (Yea, we shouldn't have to do that but oh well.)

Second, that may be long-GOP media ... meaning that there are only actual, complete image frames (iframes) maybe 9-100 frames apart. In between are partial data-sets of 1) the pixels that have changed since the last iframe, or 2) pixels that will change before the next iframe, or 3) BOTH.

This requires the app to decode up to 100 frames at times for especially drone media simply to display the next single frame of the clip.

This imposes enough of a load for general playback, but when speed-changing, it can overwhelm the system. So doing a full render & replace of such clips on a timeline, to say ProRes422, can then get everything running smoothly again.

[lehestro]

Thanks Neil. This is a cadence change, though,  (at least as I understand it). Normally the method I describe above works (and is a safer method than speed/duration changes, because that invokes different frame interpolation computations on Premiere's part. I just needed to tell the "tape machine," as it were, how fast to spin my footage). Turns out, the issue isn't with premiere at all, but with the way the camera captured 60fps (in this case, the Canon R5). 

[R Neil Haugen]

Ahh ... there's so many possibilites, it's fun to keep up with ... not.

For anyone reading this thread, typically, if media is 59.94 progressive, to be slowed on a 24 fps (normally in reality 23.976) ... the Speed/Duration tool is the one to use, as that work does not involve any cadence change or frame creation ... you just "apply" the frames of the high-speed capture at the sequence frame rate. 

So to drop 59.94 as slo-mo on a 23.976/24fps sequence, you use Duration/Speed set to about 40% I think. 

But if you're dealing with 59.94 interlaced, to a 23.976 or 24fps sequence, then you need a "cadence change" also. Looking up "3:2 pull-down" can be useful.

[lehestro · Accepted solution]

Ok, so in case this happens to anyone else, the issue is NOT Premiere. The issue is with the footage from the R5 camera itself. (I don't know if this extends to other cameras in the R series, or if this has since been fixed in a firmware update or something, but it's happening with the camera my client used). It seems that if you shoot 60fps, but the shutter speed is less than 1/60, it will duplicate every other frame instead of capturing distinct frames. Basically it shoots a frame twice.