Understanding denoising (NLMeans) paramters

General questions or discussion about HandBrake, Video and/or audio transcoding, trends etc.
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anderstn
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Joined: Wed Jan 08, 2020 8:45 pm

Understanding denoising (NLMeans) paramters

Post by anderstn »

Hi

I have a lot of stuff on blu-ray and having successfully ripped all my music I figured I would do the same with my movies and shows. Now I have come across a show where there is a lot of film grain. I guess this is either a result of the early days of shooting straight to rather low resolution digital cameras mixed with [Censored] up-scaling or some really weird aesthetic choice to make the whole thing appear more movie like. I doubt it's a bad film transfer given how recent the show is. Either way it looks awful.

I tried reading the guide to NLMeans here on the forum:
viewtopic.php?f=4&t=30135&p=139077

I think I understand most of the basics and can probably trial and error my way to the a better result based off the presets. However given that all the presets use the same settings for all three channels if only one set of parameters are specified there is a seventh parameter in the presets that I don't quite understand. For instance the light preset tuned for film originally looked like: 3.0:0.8:7:3:2:0:4.0. When I try to map this to the new method of specifying custom parameters I end up with one more parameter than I should have. At least if I have understood the guide. So what does the last parameter correspond to in the new way of specifying custom parameters?

If somebody want's to cut straight to the chase and make recommendations for changes the goal here is to get something akin to the pure grain reduction of the light preset tuned for film without as much smoothing of fine detail. Time is not really an issue here as there is no real rush to get this archived and I can chip away the process over time.
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BradleyS
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Re: Understanding denoising (NLMeans) paramters

Post by BradleyS »

4.0 is the chroma strength, cb-strength=4.0

Cb will inherit all other parameters from Y, and Cr from Cb.
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BradleyS
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Re: Understanding denoising (NLMeans) paramters

Post by BradleyS »

As far as preserving more detail, you're probably at or close to the algorithm's limit. You could try changing the patch size and search radius to 5 and 5 instead of 7 and 3; it might be better and it might be worse for your source. Encoding time should be about the same, maybe slightly faster.
anderstn
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Joined: Wed Jan 08, 2020 8:45 pm

Re: Understanding denoising (NLMeans) paramters

Post by anderstn »

Thanks for the feedback. I'll try the different patch size and radius if nothing else i'll just try and ease off a bit and go for something between ultralight and light in terms of the overall effect.
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