5 ms·
Depends how good you are with an encoder. It's not compression, the grain does change, but since it's just random anyway, the human eye can't notice so long as
by tfha 8y ago
Depends how good you are with an encoder. It's not compression, the grain does change, but since it's just random anyway, the human eye can't notice so long as it's the same type of grain.
Encoders generally have a few options to tune the grain that gets added back in to get it as close as possible to the original source.
- bscphil 8y agoI would be interested in seeing a post on these options and their results if you know of one. Even though grain is "random", it's not random noise and is very distinctive. No two film stocks (and probably no two movies) will have the exact same grain. It would require incredibly precise tuning to manually add back grain that matches the original in the film.
- severine 8y agoSearch for "film grain modeling".
- lucb1e 8y agoWhen I do that, I get (1) a Wikipedia page literally titled "film grain modeling", but it's only a redirect to H.264 and the only mention of "grain" on that page is in the redirect notification; (2) a patent; (3) some scientific paper supported by a few images that only show noise (is that what we're talking about? I expected grains in the sense of particle generators); (4-5-6) paywalled scientific papers; (7) a Facebook page... A link would be nicer than an apparently very specific search term.
- theoh 8y agoThis page implies that the grain synthesis step is informed by analysis of the grain in the uncompressed video: https://bitmovin.com/cool-new-video-tools-five-encoding-advancements-coming-av1/ https://bitmovin.com/cool-new-video-tools-five-encoding-adva... That is confirmed by this article: https://jmvalin.ca/papers/AV1_tools.pdf https://jmvalin.ca/papers/AV1_tools.pdf
- bscphil 8y agoThat's interesting and matches my a priori expectations. That (effectively) makes it a way of compressing grain, rather than just masking lower bitrates. You have to store information about the analysis for the decoder to work, and so there are the usual tradeoffs that come with compression.
- theoh 8y agoI don't think it really counts as compression. It's like taking the statistics of a text and generating a new one with a Markov chain. In other words, it is complete nonsense, texture synthesis, like the way some people go for printing a digital image on a fake "canvas" for a "textured, 3D look"... or maybe one of those flickering flame light bulbs. Can anybody here imagine an audio codec that added simulated hiss and crackles to make it sound like you were listening to a vinyl record? That's what this is.
- tfha 8y agoSome artists will intentionally put scratching or crackling into their music for atmosphere. Imagine an audio codec that eliminated all scratching and crackling from music. Some people may not mind but many artists would hate it. Film is the same. Directors choose the film type and grain patterns that match the look and feel they want. A more grainy film feels darker and more serious. Splotchiness contributes to an unrefined or maybe even psychotic feel. You don't want your encode removing that. You want the atmosphere of the visuals to match the original, because the director likely had that atmosphere in mind and made other decisions around it.
- theoh 8y agoWell, the problem is that the encoding process in AV1 does remove grain, only to add fake synthetic grain back in. My objection is not to the idea of encoding grain, it's with replacing it with fake synthetic grain. It's kitschy, ersatz, whatever you want to call it. I used to spend a lot of time with artist filmmakers (many of whom are very nostalgic about celluloid) and there is no way in hell they would accept this solution. It wouldn't meet their standards of authenticity. It also "fakes" a medium-specific property in a way that is unprecedented in audio or visual coding. Their solution would be to either code at high enough bitrate to capture the grain, or insist on screening on physical celluloid. That might sound extreme and unrealistic—it's what artist's film people are like—and even a bit snobby. After all, a lot of the options out there for adding film grain effects (or scratches etc.) to video are not intended for use by professional filmmakers, depending on how you define professional. There is definitely an element of snobbery to the statement that film grain should never be faked, whether by compositing something onto your home video or in a hidden way inside AV1. I hope you can see that I respect the director's prerogative in choosing grain, I just don't think this AV1 grain synthesis methodology is sound from an aesthetic/authenticity point of view. It's digital faking of an chemical/analog effect, which IMO makes it unavoidably kitsch for reasons to do with old modernist ideas of "medium specificity".
- derf_ 8y agohttps://jmvalin.ca/papers/AV1_tools.pdf https://jmvalin.ca/papers/AV1_tools.pdf has a brief technical description, but no results. It cites a DCC paper from the authors of the tool, but I couldn't find a copy online.