Slowing Down Video but with the same No of Frames Per Sec

[Alwyn]

I want to slow down a video but keep the frames per second up.

My understanding of AssumeFPS is that it basically stretches the video, slowing it down, but keeps the same total number of frames. This results in movement that is more jerky.

What I'd like to achieve is this: say if I slowed down the video by 2 ie double the play time, I'd have double the number of frames in the slowed-down video so that, in effect, the frames per second remained the same and smoothness was retained.

What I've tried is to increase the frames per second in a clip with RIFE (say, 25fps to 50fps) then used AssumeFPS to lower the film play speed. The results weren't too bad, but I'm curious how others would achieve this?

[poisondeathray]

What I've tried is to increase the frames per second in a clip with RIFE (say, 25fps to 50fps) then used AssumeFPS to lower the film play speed. The results weren't too bad, but I'm curious how others would achieve this?

That's how I'd do it

What about it made the "results weren't too bad"- what was wrong with it, or how could it be improved in general terms ? e.g were there artifacts, did you try other models ?

[dellsam34]

I don't see any other way of doing it, Basically you duplicate the frames for 1/2 speed, triple the frames for 1/3 speed, quadriple for 1/4 speed and so on and so forth assuming these are progressive frames. There may be some scripts or software out there to do frame temporal interpolation to smooth out motion, PDM may have a better idea about those.

[Alwyn]

Thanks both.

@PDR, my first attempt was with a screen capture which was a bit jerky anyway. I then tried with a HD H264 phone video (after I CFRed it ) and it worked nicely.

One thing, when I attempt RIFE and then AssumeFPS in the same script, VDub2 has a hissy fit and crashes, so I had to convert to 60fps first, then run AssumeFPS as a separate script.

This is my original script (I'll be the first to admit I know little about the RIFE part; this is just a modified Jagabo RIFE script) which VDub2 didn't like:

ffms2("Ski CFR 30fps.mp4")

converttoyv12

z_ConvertFormat(pixel_type="RGBPS", colorspace_op="709:709:709:l=>rgb:709:709:f")
Rife(gpu_thread=1, model=11, fps_num=60000, fps_den=1000, sc=true, sc_threshold=0.12)
z_ConvertFormat(pixel_type="YUV420P8", colorspace_op="rgb:709:709:f=>709:709:709:l")

AssumeFPS(7.5)


Prefetch(24)

[poisondeathray]

A jerky screen capture will probably be VFR, have dropped frames etc.. In order to get smooth motion, you'd need to address the original jerkiness first before the interpolation step

If the script in vdub2 is a hard crash without any error message, then I can only guess. AssumeFPS shouldn't induce a crash. Perhaps try removing the prefetch line - your bottleneck will be RIFE anyways and prefetch won't help much, and can actually make it process slower

[Alwyn]

Perhaps try removing the prefetch line - your bottleneck will be RIFE anyways and prefetch won't help much, and can actually make it process slower

That was it; removing the Prefetch stopped the crashing. There also was no pre-opening screen flashing and blinking (which almost always happens when I open a script with RIFE in it with Prefetch) and the AVS, without the Prefetch, opened almost instantly.