[FFmpeg-trac] #8590(undetermined:closed): 'telecine=pattern' error for p24, soft telecined sources

[FFmpeg]

#8590: 'telecine=pattern' error for p24, soft telecined sources
-------------------------------------+-------------------------------------
             Reporter:  markfilipak  |                    Owner:
                 Type:  defect       |                   Status:  closed
             Priority:  normal       |                Component:
                                     |  undetermined
              Version:  unspecified  |               Resolution:  invalid
             Keywords:               |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
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Comment (by pdr0):

 Replying to [comment:27 markfilipak]:
 > what I want is deinterlace of every 5th frame, starting with frame 3
 (i.e., the 'C's in the 'P P C P P P P C P P' sequence).


 >I thought that the resulting deinterlaced frame would be a line-doubled
 version of the pixel-by-pixel mean of the 2 fields -- now that I write
 that, is that 'blended'? -- because that's what I visualized when I
 dreamed up this whole scheme. It's my rather unsophisticated opinion that
 whatever is done to remove combing will be okay because the result is
 visible for only 1/60s. Even no deinterlace looks pretty damn good in my
 test videos (based on the transcodes of the p24 video that you so
 graciously provided), and way better than what my 60Hz TV displays when
 it's fed p24. (Did I mention that I hate judder more than any other video
 flaw?) :-)
 >

 I understand what you're saying - that you want to deinterlace only combed
 frames.

 You can blend deinterlace as a general approach, but I don't think ffmpeg
 has one specifically for blend deinterlacing.

 Blend deinterlacing is generally frowned upon, because it produces blurry,
 ghosted results and does not really produce smoother motion.

 This can be visually more disturbing than the original judder. You can
 argue that it might be slightly more smooth, but not much. Some people
 would say the visual disturbance makes it worse. "strobes" would be a
 common description.

 In frames notation, where each letter is a progressive frame, and where
 (AB) or (CD) is a blended frame 50/50 mix you would get


 {{{
 AA(AB)BBCC(CD)DD
 }}}


 You decide for yourself. I uploaded the test video with blend
 deinterlacing (of combed frames only) "blenddeint_combedonly.mp4"

 And yes, there is still judder , because you don't have a blend inserted
 between BB , CC  (BC), so there is a perceptual jump in motion compared to
 AA(AB)BB , or CC(CD)DD .



 > You certainly know what you're talking about. What you describe is what
 I'm seeing. Frankly, it surprises me that deinterlace is favoring the 1st
 field.
 >


 This is expected behaviour. When single rate deinterlacing, you can decide
 which field to keep, top or bottom. Top field means you would get the 1st
 of the field pair (the A field), so you end up with 3:2 . Bottom means you
 select bottom (the b field), you'd get the 2:3 cadence. You can choose by
 selecting the field order. Top is default (and should be for HD formats by
 convention)



 >
 > If there's a filter that can blend frames 3, 8, 13, 18, etc. I expect
 that using it (instead of 'bwdif=mode=send_frame') would yield the best
 results possible (which is what I originally visualized). I'm sorry I'm
 not an ffmpeg guru; at least, not yet. Is there such a programmable
 blender? For example, maybe splitting in a '-filter_complex' and
 selectively merging via some sort of blender that operates only on frames
 3, 8, 13, 18, etc.?
 >
 I don't think ffmpeg has blend deinterlacing.

 You can't just blend the telecine output and replace specific frames,
 because you'd get combed blends, not frame blends (as if frame blends
 weren't bad enough...)

--
Ticket URL: <https://trac.ffmpeg.org/ticket/8590#comment:28>
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