[FFmpeg-user] ffmpeg architecture question

Carl Eugen Hoyos ceffmpeg at gmail.com
Sun Apr 19 20:11:53 EEST 2020

Am So., 19. Apr. 2020 um 18:46 Uhr schrieb Mark Filipak
<markfilipak.windows+ffmpeg at gmail.com>:
> On 04/19/2020 12:31 PM, Carl Eugen Hoyos wrote:
> > Am So., 19. Apr. 2020 um 18:11 Uhr schrieb pdr0 <pdr0 at shaw.ca>:
> >
> >> 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.

> > 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.

You did not post the command line including the complete,
uncut console output. (please don't do it now)

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

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.

I am still quite sure I posted a command line that you can test. You
don't have to report back.

Carl Eugen

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