On 04/19/2020 02:08 AM, pdr0 wrote:
Mark Filipak wrote
My experience is that regarding "decombing" frames 2 7 12 17 ...,
'pp=linblenddeint' (whatever it is) does a better job than 'yadif'.
"lb/linblenddeint
"Linear blend deinterlacing filter that deinterlaces the given block by
filtering all lines with a
(1 2 1) filter."
I don't know what a "(1 2 1) filter" is -- I don't know to what "1 2 1"
refers. pdr0 recommended it
and I found that it works better than any of the other deinterlace
filters. Without pdr0's help, I
would never have tried it.
[1,2,1] refers to a vertical convolution kernel in image processing. It
refers to a "block" of 1 horizontal, 3 vertical pixels. The numbers are the
weights. The center "2" refers to the current pixel. Pixel values are
multipled by the numbers , and the sum is taken, that's the output value.
Sometimes a normalization calculation is applied with some implementations,
you'd have to look at the actual code to check. But the net effect is each
line is blended with it's neighbor above and below .
Thank you, pdr0. That makes perfect sense.
In general, it's frowned upon, because you get "ghosting" or double image .
Yes, that's what I see. But I don't care. Why don't I care? 1, ghosting is plainly evident for
planes such as building sides during panning shots, not for patterned surfaces such as landscape
shots or people's faces, and 2, it greatly reduces the (apparent, but not real) judder that would
otherwise show up for the original, "combed" frame. When you also consider that the ghost is there
for only 1/60th second, it becomes nearly invisible. Of course, that's not true for 23-telecine. In
23-telecine (i.e., 30fps), there are 2 combed frames, they abut each other, and each of them is
1/30th second. That means that the ghosting is 1/15th second -- clearly awful.
1 frame now is a mix of 2
different times, instead of distinct frames. But you need this property in
this specific case to retain the pattern in terms of reducing the judder .
Other types of typical single rate deinterlacing (such as yadif) will force
you to choose the top or bottom field, and you will get a duplicate frame of
before or after ruining your pattern . Double rate deinterlacing will
introduce 2 frames in that spot, ruining your pattern . Those work against
your reasons for doing this - anti-judder
BINGO! You are a pro, pdr0. You have really taken the time to understand what
I'm doing. Thank you!
By the way, my first successful movie, 55-telecine transcode has finished. (The one I did earlier
today has PTS errors.) Hold on while I watch it ("Patton" Blu-ray).
Oh, dear. There were no errors, yet the video freezes at about 3:20. If I back up 5 seconds and
resume, the video plays again, through where it froze, but the audio is gone (silence). If I
continue letting it play, the audio eventually resumes, but at the wrong place (i.e., audio from a
scene several minutes further along in the stream). If I continue letting it play, the video freezes
again. The total running time (which should be a constant), is not constant. It stays just ahead of
the actual running time by, about 2x seconds, until the video freezes, at which time the total
running time also freezes at the value it had prior to the freeze.
I think that this 55-telecine is stressing ffmpeg in ways it's not been stressed before and is
exposing flaws that I fear the ffmpeg principals will not accept because they think what I'm doing
is a load of crap.
To me, deinterlace just means weaving the odd & even lines. To me, a frame
that is already woven
doesn't need deinterlacing. I know that the deinterlace filters do
additional processing, but none
of them go into sufficient detail for me to know, in advance, what they
do.
Weave means both intact fields are combined into a frame . Basically do
nothing. That's how video is commonly stored.
Yes, I know. I thought I invented the word "weave" -- I wanted to avoid the word "interlace" -- for
lines that have been combined in a frame: "Woven lines" instead of "interlaced lines". I would have
used "interleave", but someone fairly significant in the video world is already using "interleave"
to replace "interlace" when referring to fields: "Interleaved fields" instead of "interlaced fields".
If it's progressive video, yes it doesn't need deinterlacing. By definition,
progressive means both fields are from the same time, belong to the same
frame
There ya go. You have read the MPEG spec.
Deinterlace means separating the fields and resizing them to full dimension
frames by whatever algorithm +/- additional processing
Single rate deinterlace means half the fields are discarded (29.97i =>
29.97p) . Either odd or even fields are kept .
Oh, now I understand you. You see, I don't want to do that. What I want is to not throw away either
odd or even. I want to blend them. If you throw away the combed frame's odd field, then 55-telecine
(A A A+B B B) becomes the same as 46-telecine (A A B B B). If you throw away the combed frame's even
field, then 55-telecine becomes the same as 64-telecine (A A A B B). I've done those by direct
configuration and by employing yadif, and I don't like the judder. 46-telecine and 64-telecine both
have judder. I hate judder. I will accept a 1/60th second of blended frame (nearly impossible to
notice) in lieu of judder. I've taken strongly planar objects with extremely strong edges in panning
shots that produce a lot of telecine judder when p24 is fed to my 60Hz TV, and by 55-telecine, made
the judder a non-issue and the 1/60th second blended frame noticeable only if you watch the edges
intentently (and even then the fleeting edge fuzzing is not at all objectionable).
_______________________________________________
ffmpeg-user mailing list
ffmpeg-user@ffmpeg.org
https://ffmpeg.org/mailman/listinfo/ffmpeg-user
To unsubscribe, visit link above, or email
ffmpeg-user-requ...@ffmpeg.org with subject "unsubscribe".
