On 04/19/2020 02:56 AM, pdr0 wrote:
Mark Filipak wrote
I would love to use motion compensation but I can't, at least not with
ffmpeg. Now, if there was
such a thing as smart telecine...
A A A+B B B -- input
A A B B -- pass 4 frames directly to output
A A+B B -- pass 3 frames to filter
X -- motion compensated filter to output
Unfortunately, ffmpeg can't do that because ffmpeg does not recurse the
filter complex. That is,
ffmpeg can pass the 2nd & 4th frames to the output, or to the filter, but
not both.
What kind of motion compensation did you have in mind?
Hahahaha... ANY motion compensation. ...Is there more than one?
"recurse" works if your timestamps are correct.
Carl Eugen said that, too. How could the timestamps be wrong? I was using the test video ("MOVE"
"TEXT") that you gave me. I proved that, for that video (which I assumed was perfect), ffmpeg
traversal of the filter complex does not occur.
Interleave works with
timestamps. If "X" has the timestamp of position 3 (A+B or the original
combed frame)
Interleave may work with time stamps (PTC), but is interleave going to prevent recursion to the
input of a 2nd select?
Double rate deinterlacing keeps all the temporal information. Recall what
"interlace content" really means. It's 59.94 distinct moments in time
captured per second . In motion you have 59.94 different images.
That may be true in general, but the result of 55-telecine is
A A A+B B B ... repeat to end-of-stream
So there aren't 59.94 distinct moments. There're only 24 distinct moments
(the same as the input).
Exactly !
That refers to interlaced content. This does not refer to your specific
case. You don't have interlaced content. Do you see the distinction ?
Well, of course, but why are we (you) discussing interlaced content?
You
have 23.976 distinct moments/sec, just "packaged" differently with repeat
fields . That's progressive content. Interlaced content means 59.94 distinct
moments/sec
Single rate deinterlacing drops 1/2 the temporal information (either
even,
or odd fields are retained)
single rate deinterlace: 29.97i interlaced content => 29.97p output
double rate deinterlace: 29.97i interlaced content => 59.94p output
There is no 29.97i interlaced content. There's p24 content (the source)
and p60 content that combs
frames 2 7 12 17 etc. (the transcode).
I thought it was obvious but those comments do not refer to your specific
side case. You don't have 29.97i interlaced content .
Okay, it's academic. I'd like to stick to 55-telecine. Okay? I was getting
confused.
You apply deinterlacing to interlaced content. You don't deinterlace
progressive content (in general)
I agree wholeheartedly. So why are we discussing deinterlace? I'll tell you why (I think). It's
because the only ffmpeg filters that will decomb are called deinterlacers.
29.97i interlaced content are things like soap operas, sports, some types of
home video, documentaries
Agreed.
Once again, this is a terminology problem. You are one person who
acknowledges that terminology
problems exist, and that I find heartening. Here's how I have resolved it:
I call a 30fps stream that's 23-telecined from p24, "t30" -- "t" for
"telecine".
I call a 30fps stream that's 1/fieldrate interlaced, "s30" -- "s" for
"scan" (see Note).
I call a 60fps stream that's 23-telecined, then frame doubled, "t30x2".
I call a 60fps stream that's 55-telecined from p24, "t60".
Note: I would have called this "i30", but "i30" is already taken.
Now, the reason I write "p24" instead of "24p" -- I'm not the only person
who does this -- is so it
fits an overall scheme that's compact, but that an ordinary human being
can pretty much understand:
16:9-480p24 -- this is soft telecine
4:3-480t30 -- this is hard telecine
16:9-1080p24
I'm not listing all the possible combinations of aspect ratio & line count
& frame rate, but you
probably get the idea.
It's descriptive, but the problem is not very many people use this
terminology. NLE's , professional programs, broadcast stations, post
production houses do not use this notation. e.g "480p24" anywhere else
would be native progressive such as web video. Some places use pN to denote
native progressive . So you're going to have problems with communication...I
would write out the full sentence
In my guide, I do explain what "16:9-480t30" means, for example. I do it one time, in one chapter
that's dedicated to terminology. Then I use it throughout. That saves having to write a paragraph
(and readers having to read a paragraph) every time I refer to 30fps hard telecine, for example.
Erm... I'm not analyzing a mystery video. I'm transcoding from a known
source. I know what the
content actually is.
I thought it was obvious, those comments refers to "in general" , not your
specific case. More communication issues..
There are dozens of processing algorithms (not just talking about
ffmpeg).
There are many ways to "decomb" something . The one you ended up using
is
categorized as a blend deinterlacer because the top and bottom field are
blended with each other. If you examine the separated fields , the fields
are co-mingled, no longer distinct. You needed to retain both fields for
your purpose
No, I don't. I don't want to retain both fields. I want to blend them.
That's what
'pp=linblenddeint' does, and that's why I'm happy with it.
Yes, that should have said retain both fields blended. The alternative is
dropping a field like a standard deinterlacer
Thank you. I think my sanity is returning now.
There is no distinction in terms of distribution of application for this
type of filter. You put the distinction on filtering specific frames by
using select. You could apply blend deinterlace to every frame too (for
interlaced content) - how is that any different visually in terms of any
single frame there vs. your every 5th frame ?
I honestly don't know. What I do know is if I pass
select='not(eq(n+1\,5)\,3))' to the output
unaltered but I filter select='eq(n+1\,5)\,3)',pp=linblenddeint before the
output, the video looks
better on a 60Hz TV. I don't want to pass the progressive frames through
'pp=linblenddeint'.
It was meant as a rhetorical question.., failed...
Your combed frame looks exactly like every frame for an interlaced video. If
I took a 59.94p video and converted it to 29.97i .Every frame would look
like your combed frame.
That's not so. For your hypothetical video, the line-to-line "combing" would be 1/60th second. For a
telecined video, the line-to-line "combing" is 1/24th second -- much worse.
The point is, visually, when looking at individual
frames, combing looks the same, the mechanism is the same.
(see above).
The underlying
video can be different in terms of content (it might be interlaced, it might
be progressive) , but you can't determine that on a single frame
Sure I can. If I put 1/60th second of comb next to 1/24th second of comb, I think anyone would see
that the 1/24th second frame looks worse.
You could have used a different filter, maybe a box blur , applied on the
same frame selection . Would you still call that "decomb" ?
Yes, but only because I call the original frame "combed".
Same here - anything that works to reduce the "combing" can be categorized
as a decomb filter, including deinterlacing. Including blurring. Including
whatever x,y,z filter . It's non specific
You know, I think we agree on everything.
Regarding inverse telecine (aka INVT), I've never seen INVT that didn't
yield back uncombed, purely
progressive pictures (as "picture" is defined in the MPEG spec). Can
you/will you enlighten me
because it's simply outside my experience.
It happens all the time. This is simply reversing the process. Inverse
telecine is the same thing as "removing pulldown". You get back the
original
progressive frames you started with.
Okay, that's what I thought. Since INVT produces the original p24, it's
not combed. I thought you
said that inverse telecine can produce combing. My bad. :)
Yes.
But there is something else called "residual combing" . It's not the same
thing, it's when fields are slightly misaligned, such as with some old low
quality DVD's . It's not as distinct as combing, the lines are very fine.
Shall we stick to 55-telecine, please? This academic ride you are putting me on
is making me dizzy.
Also, sometimes there are things like cadence breaks - such as when edits
were made before IVTCing . Again, with lower quality productions. So IVTC
process in software often includes adaptive field matching and additonal
post processing and comb detection. It's not just a fixed pattern.
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