[FFmpeg-user] telecine pattern 5555 - Judder-free, 60 FPS telecine (?)

[Mark Filipak]

On 04/05/2020 06:03 AM, Ted Park wrote:
> Hi,
> 
> I’m a bit lost here to be honest. Do you have a plasma panel or something else that is not progressive scanning?

I have a Sharp LCD TV.

>> If telecine is performed in advance by the user and it's a 5-5-5-5 pull-down telecine, there is no judder on playback on a 60Hz TV because there is no cadence and because the video is already 60fps.
> Like here, you mean 60 fields per second right? Or is this a 60Hz lcd panel? (Also is it just convention to use 4 film frames when denoting telecine patterns? Because as you say this is just repeating each field 5 times, maybe 5-5 is necessary for the interlaced “frame”)
> 
>> A 5-5-5-5 pull-down telecine does have combing, but the combing is 2 frames out of every 10 frames (i.e., 20%). The combing (C) versus progressive (P) frames looks like this:
>> [A/a__________][B/b__________][C/c__________][D/d__________]   ...original p24 video
>> [A/a_][A/a_][A/b_][B/b_][B/b_][C/c_][C/c_][C/d_][D/d_][D/d_]   ...5-5-5-5 telecine
>> P     P     C     P     P     P     P     C     P     P           20% combing @ 12Hz
>> A-------------AB-------------BC-------------CD-------------D      judder free
>> <----1/24s----><----1/24s----><----1/24s----><----1/24s---->
>  > This is what makes me unsure of whether you actually have non-progressive-scanning viewing 
equipment… Those “combing” frames are just the regular m.o. for how an NTSC tv scans from one 
picture to the next, isn't it? Like when you say the results of your experiment looks good, do you 
mean it resembles what the 240+Hz TV’s have playing on store demo mode?

No, I mean it's what I would see in a movie theater... "UNIVERSAL" circling the Earth, smoothly, 
without judder; credit crawls scrolling up smoothly, without tiny jumps.

> If so I think that’s largely personal preference, if you like buttery smooth movement in everything, then you may have found a telecine pattern that works for you, but some people (purists, as I am tempted to call them) insist on the cadence, if not judder, that is indicative of shutter angle and the like analog traits of the source.

Shutter angle? Huh? (See previous sentence about movie theaters.)

>> Those are the facts. I don't think 5-5-5-5 telecine to 60fps has ever been done before. Some people are opposed to it as though it is religious heresy. That's not going to stop me.
>>
>> Earlier today I posted a request for help with crafting a special minterpolate filter that operates solely on the combed frames (frames 3, 8, 13, 18, etc.). That post is titled
>> "minterpolate only frames 3, 8, 13, 18, etc.".
>> I hope that someone will respond to it. But even without decombing, I consider the 60fps video to be superior to any 2-3-2-3 pull-down telecine because I hate judder.
> You probably mean a different filter, minterpolate literally interpolates between/around frames, like drawing the middle pages of a flip comic when given the first and end scene. Maybe I am missing something but you can’t operate solely on a certain frame. You can start at a certain frame I guess, but I would think an interlaced frame is a bad candidate for this.
> 
>>> ... if asked if I knew how so take this with a grain of salt but I think the general “every encode reduces information” caveat applies, especially as you’re doing some image processing in between.
>>> You might say that technically, it is a reversible process, but multiple iterations of de/compression with an efficiency-focused codec such as H.264 will quickly show diminishing returns despite any novel techniques to enhance perceived quality that you use in between decompression and compression.
>>
>> Once transcoded to 60fps, why would I ever reverse it? If I ever get a 120Hz TV, I'll simply drag out the original disc and remux to a p24 MKV container with zero loss. In the meantime I will have a 60fps video to watch that's as good as the original and is free of telecine judder.
> 
> I meant the transcoding part. It’s already been mastered onto the dvd/bd with h.264. But if you’re going to keep the original I guess it’s no harm.

When I transcode to 60fps, I make sure that the target is 'finer grained' than the source. That way, 
though I get a larger file than otherwise, I get no loss (other than the lossy source's loss). I'm 
usually transcoding from H.264 to H.265, so even though the target resolution is over-fine, the 
resulting file is still smaller than the source. My major objective, though, is to kill telecine judder.

I'm thinking of trying 8x8 macrocells sometime in the future so as to apply Nyquist sampling to the 
process and absolutely preserve resolution.

Regards,
Mark.