I’m currently playing with footage that has 25 fps and the entire project is going to be playing at “half-speed”, slow motion ( 2 duplicate frames).
PROBLEM: I set the speed to 0.500000 and every eighth frame is a triple (instead of double) and the 2 frames following this are singles.
GOAL: I need to achieve an even 12.5 fps, which would equal an even 25 frames per “2” seconds made up entirely of 2 consecutive duplicate frames (no triples, no singles).
The closest I got to a uniform frame rollout was setting the speed to 0.480000 - this gives me a triple every 12th duplicate frame (which gives me perfect 24 frame clips).
I’m no stranger to tedious editing and cutting out a single frame from every single second at .480000 speed, however, I wanted to pose the question here in case anyone had better ideas or solutions on how to achieve the goal: 25 fps, half-time - uniform 2 duplicate frame rollout.
Any thoughts, tips, ideas, or suggestions is greatly welcome and sincerely appreciated!
Maybe there is a problem with your Video Mode, accurate seeking on your file, or your methodology to check it. I made a 40 second clip at 25 fps in Shotcut using a color clip with a Text: Simple filter with keyword #frame#. I exported this using preset intermediate/DNxHR to get GOP=1 and fast, reliable seeking. Next, I open it (Video Mode is 25 fps), and change Properties > Speed to 0.5. Starting from the beginning, I press Shift+Page Down. The counter in the video always increments by 25 until the end. I went back to the beginning, and except for the first frame, which does not repeat, I always see it step by 2 frames and not “every eighth frame is a triple (instead of double) and the 2 frames following this are singles.” I stepped through the first 200 frames.
Maybe you should ensure the video mode is 25 fps and maybe convert the clip to edit-friendly.
The clip is Frame Rate: 25.000000
The Timeline Output is Frame Rate : 25.000000 fps
I converted the clip to “Edit-friendly” - best/biggest, Lossless: Ut Video/PCM MKV. It created a 775 MB MKV file (from a 15 MB source file), pretty large file, did it in 16 seconds.
It is still doing the ‘triple frame, single frames’ roughly ~ every eighth frame. I closed the clip, re-opened it using the converted clip - still the same issue.
Unless I’m missing something, the only other thing you mentioned it could be, “accurate seeking on your file”. I’m not sure how to check this or what else I can try to remedy this?
I can see the same issue (but at different frequency) with a random 25fps video from a sony camera (original .m2ts, converted to edit friendly). Here’s my test file. The same seems to happen in an older version 22.12.21.
For me, at 0.5x speed the frames are duplicated ok until frames 27-28-29 (timecode 1:02, 1:03, 1:04) which all 3 are identical, then the next frame 30 is unique, then 31 also unique, then correct 2 frame duplicated until
The same 3 - 1 - 1 duplication at frames 55-56-57 (timecode: 2:05, 2:06, 2:07) with 58, 59 unique.
The next one seems to be at 111-112-113 (4:11, 4:12, 4:13), but the next 2 frames are not unique, they are 2-duplicated then the other next 2 are unique.
The original video has unique frames when going 1 by 1 at 1x.
I tried the “shift by 2 frames + invert + blend mode add” method to see frame differences and put a marker where I could see identical 3 frames and these are the times (not sure what the pattern is or if I missed some):
(frames and timecode, these are timeline times from the 0.5x video)
For what this is worth - I started changing the speed to various speeds between 0.480000 and 0.500000 (was curious to see if it would kick the one triple frame somewhere between).
I eventually landed on “0.499500” and it is now a perfect uniform half-speed, 2 duplicate frame rollout, I checked every single frame (both the converted edit-friendly and original source had the same result).
I expanded the clip as far as 10 seconds, copy/pasted the clip to above track, cropped half of it, mirrored it, have been applying filters, and the 10 second clips are perfect synchronized half-speed rollouts through entire clip.
