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AV1@Scale: Film Grain Synthesis, The Awakening

(netflixtechblog.com)
252 points CharlesW | 2 comments | 03 Jul 25 16:34 UTC | HN request time: 0.599s | source
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smusamashah ◴[03 Jul 25 18:37 UTC] No.44457975[source]▶
The original grain that is captured is actually a detail and not total random noise. I believe you can make up the vague sense of original scene if you could somehow extract that grain/noise alone.

It's like reducing an image to tiny dots with dithering (reminds of Atinkson dithering). Those grains are not a noise, they are a detail, actual data. That's why real grain looks good IMO.

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1. mmastrac ◴[03 Jul 25 19:51 UTC] No.44458595[source]▶
If you extract the grain (e.g. by subtracting a blurred version of the image), the result contains mostly noise, not meaningful scene information outside of some variation according to image brightness. Film grain is random, so the extracted "grain layer" doesn’t encode original image detail but film grain itself encodes relative lightness in its _density_.
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2. account42 ◴[04 Jul 25 10:46 UTC] No.44463320[source]▶
Mostly noise but not just noise. There is a reason why quality de-noising is a hard problem and the lost information becomes more apparent for videos where our brain is better able to extract it from the original noise.