[FFmpeg-devel] Idea for a better filter that reduces noise
Paul B Mahol
onemda at gmail.com
Thu Oct 29 09:42:49 CET 2015
On 10/29/15, P. van Gaans <w3ird_n3rd at 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)
> Best regards,
> P. van Gaans
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> ffmpeg-devel at ffmpeg.org
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