[FFmpeg-user] Wanted: Fields-to-frames filter that does not add cosmetics

[Paul B Mahol]

On Sat, Mar 6, 2021 at 7:11 AM Mark Filipak (ffmpeg) <markfilipak at bog.us>
wrote:

> On 2021-03-05 21:31, pdr0 wrote:
> > Mark Filipak (ffmpeg) wrote
> >> On 2021-03-05 11:13, James Darnley wrote:
> >>> On 05/03/2021, Mark Filipak (ffmpeg) wrote:
> >>>> I seek a fields-to-frames filter that does not add cosmetics. In my
> >>>> pursuit,
> >>>> I look for such a
> >>>> filter every time I peruse the filter docs for anything. I've yet to
> >>>> find
> >>>> such a filter.
> >>>>
> >>>> Do you know of a fields-to-frames filter that does not add cosmetics?
> >>>
> >>> separatefields - "splits each frame into its components fields,
> >>> producing a new half height clip with twice the frame rate and twice
> >>> the frame count"
> >>
> >> Yes, I could do (and have done) that, followed by 'shuffleframes=00',
> >> followed by 'tinterlace' [1].
> >> But that seems like a lengthy (slow) way to do what should be a simple
> >> (faster) thing [2].
> >>
> >> [1] [A+b] ==> [A][b] ==> [A][A] ==> [A+A]
> >> [2] [A+b] ==> [A+A]
> >>
> >>
> >> If you're curious about what I'm doing, look:
> >> [A+a][B+c][C+d][D+d][D+d]   ...SOURCE is a (consistent) mess [3]
> >> [A+A][a+a][B+B][c+c][C+C][d+d][D+D][d+d][D+D][d+d]
> >> ...yadif=mode=send_field
> >> [A+A][a+a][B+B][B+B][C+C][c+c][D+D][d+d]   ...shuffleframes=0 1 2 2 4 3
> 6
> >> 7 -1 -1
> >> [A+a][B+B][C+c][D+d]   ...tinterlace=mode=interleave_bottom to make
> TARGET
> >> [4]
> >>
> >> [3] Telecined (=30fps) ==> frame 1 discard (=24fps) ==> frame 3 repeat
> >> (=30fps).
> >> [4] The TARGET is beautiful. No cosmetic filtering needed (or possible).
> >>
> >>
> >> [A+a][B+c][C+d][D+d][D+d]   ...SOURCE
> >> [A][a][B][c][C][d][D][d][D][d]   ...separatefields
> >> [A][a][B][B][C][c][D][d]   ...shuffleframes=0 1 2 2 4 3 6 7 -1 -1
> >> [A+a][B+B][C+c][D+d]   ...weave=first_field=top to make TARGET
> >>
> >> Hmmm... That appears to work. I'll try it.
> >>
> >> I guess I got stuck on using tinterlace as the last step and couldn't
> see
> >> that separatefields &
> >> weave would be simpler (and faster) than yadif and without yadif's
> >> cosmetics.
> >>
> >> Thanks!
> >
> >
> > Yes, yadif is not the right filter for what you're doing, because of the
> > spatial interpolation. Yadif is a deinterlacer, and as a general rule you
> > don't deinterlace progressive content (that has matching field pairs), or
> > you'll degrade it
>
> I think it would be helpful if I clarified. I've got 2 balls in the air.
> 1, go with what I outline
> above (specifically [B+B]), or 2, allow [c] to mate with [B] (in addition
> to mating with [C]) and
> apply yadif to just the [B+c] frame, thusly:
>
> [A+a][B+c][C+d][D+d][D+d]   ...SOURCE
> [A][a][B][c][C][d][D][d][D][d]   ...separatefields
> [A][a][B][c][C][c][D][d]   ...shuffleframes=0 1 2 3 4 3 6 7 -1 -1
> [A+a][B+c][C+c][D+d]   ...yadif(frame n%4==1 only),weave=first_field=top
>
> The video is an actor making a comment. Her name fades in-out, below and
> to the right.
>
> The more I look at the bob of that text in the [B+B] frame (otherwise the
> bob is not noticeable),
> the more I'm leaning towards some sort of cosmetics even if it introduces
> a very, very slight judder
> (i.e. c][C+c] is effectively 1+1/2 frames).
>
> In my first tries (a couple of days ago), I applied yadif to all frames
> and didn't like the results.
> I hate fuzzy and I hate judder even more, but now I'm considering both for
> what is effectively +1/2
> frame.
>
> > Mark Filipak (ffmpeg) wrote
> >> [4] The TARGET is beautiful. No cosmetic filtering needed (or possible).
> >
> > Cosmetic filter is wanted and possible on B+B.
> >
> > B is an orphaned field, missing it's partner "b" . B+B is going to be
> full
> > of aliasing/stairstepping...
>
> Since it's for only 1/24th second, aliasing & bob really are not
> noticeable (except for the
> aforementioned text). (BTW, the ffmpeg docs have only 3 references to the
> word 'alias'. All 3 are in
> '8.6 acrusher'. Are the devs avoiding the word 'alias' for a reason?)
>
> >... The field interpolation algorithm used to
> > generate the pseudo "b" makes a difference. For example, -vf
> nnedi=field=t
> > applied selectively on that B+B frame will look substantially better,
> almost
> > like a fake B+b . Or temporally filtered B+b (from A+a and C+c data),
> such
> > as with QTGMC in vapoursynth or avisynth will look better than either. If
> > you want demos or more info let me know
>
> Thanks for the offer. You're very generous. I'll try hard to not burden
> you.
>
> I experimented with 'nnedi' a couple of months ago and will retrieve my
> notes. And I do pipe to/from


All your notes are invalid.


>
> VapourSynth for other tasks (mostly to use InterFrame) so I'm somewhat
> familiar with it. I'll try
> both your suggestions (and I'll try to not be too stupid).
>

estdif filter can act as smart bobber, and is faster then nnedi.


>
> You've given me a good push. Thanks so much for the guidance!
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