30fps --> 24fps WITHOUT pulldown

[agni451]

I have an NTSC 29.97fps PROGRESSIVE clip, and I'd like to convert that to 23.976fps without losing audio sync. Basically, I want delete 1 frame out of every 5, just as you would with a pulldown. I tried using tdecimate() (without tfm()) but it resulted in slightly jerky video. Any suggestions?

[jagabo]

I have an NTSC 29.97fps PROGRESSIVE clip, and I'd like to convert that to 23.976fps without losing audio sync. Basically, I want delete 1 frame out of every 5, just as you would with a pulldown. I tried using tdecimate() (without tfm()) but it resulted in slightly jerky video.

What did you expect? That's what happens when you throw out every 5th frame.

You can try using motion interpolation but it doesn't work well with complex motions. For example:

#requires MVTools

function SmoothFPS(clip source, int num, int den) { 
super = MSuper(source, pel=2, hpad=0, vpad=0, rfilter=4)
backward_1 = MAnalyse(super, chroma=false, isb=true, blksize=16, searchparam=3, plevel=0, search=3, badrange=(-24))
forward_1 = MAnalyse(super, chroma=false, isb=false, blksize=16, searchparam=3, plevel=0, search=3, badrange=(-24))
backward_2 = MRecalculate(super, chroma=false, backward_1, blksize=8, searchparam=1, search=3)
forward_2 = MRecalculate(super, chroma=false, forward_1, blksize=8, searchparam=1, search=3)
backward_3 = MRecalculate(super, chroma=false, backward_2, blksize=4, searchparam=0, search=3)
forward_3 = MRecalculate(super, chroma=false, forward_2, blksize=4, searchparam=0, search=3)
MBlockFps(source, super, backward_3, forward_3, num, den, mode=0)
}

WhateverSource(...)
SmoothFPS(24000,1001)

An example where it works well:

30p.avi (xvid) is a 24p source I sped up to 30p using AssumeFPS(30000,1001)
decimate.avi is a simple decimation of 30p to 24p using SelectEvery(5,0,1,2,3)
smoothfps.avi is 24p using the above script

[johns0]

Any reason you want to do that?You won't get any good results doing that anyway.

[agni451]

I only want go from 30fps to 24fps so that there is more quality per frame. At 24fps, the quality/frame is 25% greater than at 30fps for the same bitrate.

[jagabo]

I only want go from 30fps to 24fps so that there is more quality per frame. At 24fps, the quality/frame is 25% greater than at 30fps for the same bitrate.

Unfortunately, the quality loss from converting frame rate (with motion interpolation, frame blending, or decimation) is probably going to outweigh the gain from having fewer frames. Why not just use 25 percent more bitrate? Stuck with DVD size?