On 10/29/2015 09:42 AM, Paul B Mahol wrote:
On 10/29/15, P. van Gaans <w3ird_n...@gmx.net> wrote:
You all know the CSI episodes where they read a license plate by
"enhancing" some super-grainy security footage. Nonsense, right? Well,
maybe not.. If the car was parked. And it seems what I found doesn't
exist yet. (but perhaps I overlooked it)
If you quickly want to know what I'm on about, take a look at these images:
http://members.ziggo.nl/sinaasappel/images/1_original.jpg (original)
http://members.ziggo.nl/sinaasappel/images/2_40framewind.jpg (40f WIND)
http://members.ziggo.nl/sinaasappel/images/3_wind_hqdn3d.jpg (comparison
with hqdn3d and pp=tn)
All have limited jpeg compression, but I can deliver PNG files and an
XCF to experiment for yourself if desired.
So what is WIND? It's what you see if you forget/fail to do motion
detection. (like I did in the images) Also, Wind Is Not a Denoiser. ;-)
It's a way to increase the exposure time of the camera used to shoot a
movie after it's been shot. For the images, I took a 2-second somewhat
grainy clip of a building with nearly no motion. I output the frames to
PNG and load them as layers in The GIMP. I set the opacity for the
bottom layer to 100. The layer above that 50. (100/2) Above that 33.3.
(100/3) 25, 20, 16.7 and so on. Every image with noise is "wrong", some
too dark and some too light. On average, they are spot-on. The
advantage: improved quality and better compression.
To make this into a proper useable filter, it would need to do this:
1. Deshake/stabilize the image.
2. Divide image in blocks. (e.g. 8x8 pixels)
3. Figure out it the average color of an 8x8 block is changing during
the next X frames. If not, it's probably not moving and you can average
the values. If it is or is about to, it should be averaged over fewer
frames or not at all. Any area that is about to move will gradually pick
up noise so it doesn't look too unnatural.
4. Reshake the image.
Will I do this myself? Maybe, but don't hold your breath. I'm just
sharing this in case somebody finds it interesting and to make sure
nobody can patent it. (assuming it hasn't been done already)
See atadenoise.
Best regards,
P. van Gaans
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Thanks Paul! I think I scrolled past atadenoise in the docs a while ago
but had otherwise never heard of it. While searching for it there is
little to find besides the docs and source code. (i.e. no forum threads
or mentions in guides or anything) My ffmpeg doesn't even have it so I
guess it's quite a new thing. I'll first compile a fresh one and get
testing. I hope atadenoise also performs the deshaking internally as I
described since I noticed the camera is usually not fixed, without
deshaking it won't be able to match much.
I still think WIND would have been a funnier name than atadenoise, but I
don't complain. This will be great if it works as well as my pictures. :-)
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