[FFmpeg-user] ffmpeg architecture question

pdr0 pdr0 at shaw.ca
Sun Apr 19 20:47:22 EEST 2020

Carl Eugen Hoyos-2 wrote
> Am So., 19. Apr. 2020 um 18:46 Uhr schrieb Mark Filipak
> <

> markfilipak.windows+ffmpeg@

> >:
>> On 04/19/2020 12:31 PM, Carl Eugen Hoyos wrote:
>> > Am So., 19. Apr. 2020 um 18:11 Uhr schrieb pdr0 <

> pdr0@

> >:
>> >
>> >> In his specific situation, he has a single combed frame. What he
>> >> chooses for yadif (or any deinterlacer) results in a different result
>> >> - both wrong - for his case.
>> >
>> >> If the selects "top" he gets an "A" duplicate frame. If he selects
>> >> "bottom" he gets a "B" duplicate frame .
> To clarify: Above does not describe in a useful way how yadif
> operates and how its options can be used. I do understand
> that you can create a command line that makes it appear as if
> this would be the way yadif operates, but to assume that this
> is the normal behaviour that needs some kind of description
> for posterity is completely absurd.
> Or in other words: Induction is not a useful way of showing
> or proving technical properties.

Nobody is saying this is "normal" behaviour for general use. I EXPLICITLY
wrote this is for application in a very specific scenario. 

That's what you happens when you cut and edit out the context of a clear
message , or choose read selectively. 

>> > No.
>> No?
>> But I can see the judder. Please, clarify.
>> 55-telecine outputs frames A A A+B B B   ...no judder, 1/24th second comb
>> in 3rd frame.
>> Yadif top outputs judder and no comb     ...so I assume that the stream
>> is A A A B B.
>> Yadif bottom outputs judder and no comb  ...so I assume that the stream
>> is A A B B B.
>> My assumptions are based on what I see on the TV during playback and what
>> top &
>> bottom mean. Is any of that wrong? If so, how is it wrong?
>> I apologize for being ignorant. I endeavor to become less ignorant.
> Just a few thoughts:
> There is no "yadif top" and "yadif bottom", rtfm.

"Top" is top field first, "Bottom" is bottom field first.  I placed mine in
"quotes". But it's clear what he is trying to communication

> No (useful) de-interlacer in FFmpeg duplicates a frame in
> normal operation, the thought that it might do this is
> completely ridiculous.

It does when you use it on progressive content. This is not a "normal"
operation - I explicitly said that.  This is progressive content with a
combed frame.  It demonstrates your lack of understanding of what is going
on, or you didn't bother to read the background information before replying. 

> yadif uses simplified motion compensation, you cannot combine
> it with select the way you can combine a linear interpolation filter
> (that does no motion compensation) with the select filter. Please
> avoid reporting it as a bug that this is not documented: We cannot
> document every single theoretical use case (your use case is 100%
> theoretical), we instead want to keep the documentation readable.

Nobody is saying this is a bug. This is the expected behaviour in this
specific situation.

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