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Deinterlace 50i to 25p with smooth motion - is it possible?

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Zsolt KoppányiDeinterlace 50i to 25p with smooth motion - is it possible?
by on Nov 20, 2016 at 4:35:35 pm

Hello,

My original footage (.mts) setting is 1920x1080 50i (this cam can't record progressive frames)
and I'd like to export them as 25p from the timeline of AE or PPro 2015.

In the beginning, I made a composition matching my footage settings and changed Field Order to Progressive in AME. However the quality of the output (H.264) was worse than my original AVCHD source watching on both WinMediaPlayer and VLC. Artifacts (combs) doesn't occured but "stuttering" (frame skipping) appeared in the movements.

After a lot of tests, I found a solution: rendering with double frame rate

In PPro: my sequence match the original footage settings (50i) and render to 50p.
In AE: I also have to double the Comp's frame rate (50fps) and render to 50p

The result is perfect, movements got smooth like the original.
I'm aware it's not an elegant solution, but works. However I'm looking for a method how to convert 50i to only 25p without jerkyness?
I applied Fieldskit Deinterlace tryout on the footage (interpreted to progressive) with a lot of adjustments but after rendering to 25p I didn't experienced any improvement in the stuttering. Is there anyone who can achieve perfect results using such plug-ins?

Every time I use "Mercury Playback Engine Software Only", because OpenCL often interrupt rendering.

Thank you
Zsolt


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Chris WrightRe: Deinterlace 50i to 25p with smooth motion - is it possible?
by on Nov 20, 2016 at 6:51:31 pm

some cameras that shoot interlaced actually shoot 1 frame per two fields where the motion is the same
in each field. in this case, interpreting as progressive is actually the right answer.

if not, and you still want to deinterlace, a possible stutter could be from interpreting the wrong field order
top vs bottom(upper/lower).

double frame rate is one kind of deinterlacing called (frame doubling) maintaining all quality.

if you do indeed want 25p, you should know that it has its own problems being panning speed limitations, higher shutter speeds(looking like sav‌ing private ryan) and studder, jerkyness from lack of motion information. that is why you want double shutter as frame rate, shoot 50p with 2x shutter at 1/100th so when you deinterlace it becomes 25p at 1/50th. the formula is: fps/2x fps shutter. you can fix this in post with AE's timewarp shutter only or reelsmart motion blur.

if you accept all this and understand the limitations of deinterlacing, you now must accept the deinterlacing algorithms.
teranax and alchemist OD both give almost no loss in quality. Other cheaper alternatives such as adobe's built in deinterlacer, virtualdub's qtgmc, boris, fieldskit, red giant frames, all don't post compare the frames to determine if artifacts are unwanted so they will all lose some quality.

using optical flow from 50p to 25p might be slightly smoother than a simple deinterlace if your camera's cmos doesn't record perfect
fps. i.e. 60fps would be 1/60.000th second.
https://blogs.adobe.com/creativecloud/optical-flow-time-remapping-tips-tric...


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Zsolt KoppányiRe: Deinterlace 50i to 25p with smooth motion - is it possible?
by on Nov 20, 2016 at 11:45:11 pm

Thank you Chris!

I haven't paid attention these factors during recording like shutter speeds. Optical Flow choice is not available in Time Interpolation in PPro 2015, so I'll upgrade soon. I also give up using plug-in deinterlacers. I experienced that these reduce artifacts only if I interpret fields order to progressive.

you still want to deinterlace, a possible stutter could be from interpreting the wrong field order
top vs bottom(upper/lower).


I tested field order recently on the footage panel and apparently it is upperfield as I saw on it's properties.

Zs


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