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The thing I'm most excited about for AV1 is film grain synthesis. I can't articulate why, but I really love the look of film grain in video. Unfortunately, on m

The thing I'm most excited about for AV1 is film grain synthesis. I can't articulate why, but I really love the look of film grain in video. Unfortunately, on most codecs, film grain is a huge hassle which takes up a lot of bandwidth. But AV1 can automatically remove the grain, encode, and add it back in.

tambourine_man 8y ago
That’s amazing. I use grain to disguise compression all the time and always this should be possible.
- paavoova 8y ago
  Why not keep the bitrate higher? Or are you re-encoding already over-compressed video? In which case re-encoding and adding noise only reduces the amount of detail and bloats the encoded size with, well, noise.
  - tambourine_man 8y ago
    >Why not keep the bitrate higher? Sure, that would be the optimal situation. However, for a variaty of reasons you sometimes have to deal with overly compressed images. Adding noise on the client during play back disguises compression, making it nicer to the eye at no bandwidth cost.
bscphil 8y ago
Curious about this. Does the grain it algorithmically adds back look the same as that it takes away? In other words, is it just a better way to compress existing film grain? Different film sources have extremely different grain profiles, and people who encode movies (both production companies and pirates) will have no interest in the aspects of a codec that remove the real grain in a film to replace it with a generic alternative. I suppose they might adopt AV1 with that feature turned off, but otherwise AV1 will mostly be adopted for web video which currently doesn't have grain due to low bitrate encoding.
- 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 ago
    I 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 ago
      Search for "film grain modeling".
      - lucb1e 8y ago
        When 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 ago
        This 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
paavoova 8y ago
Is this similar to DNR schemes? Because that's a lossy process that reduces find detail, and is notorious for having been misused in many bluray releases of analog film remasters. And adding digital grain "back in" doesn't sound very authentic to the original analog source.
- sjwright 8y ago
  Film grain is so expensive to encode that in bit-rate-constrained situations you would be forced to choose between obvious ugly compression artefacts, a reasonably good image without grain, or a reasonably good image overlaid with inauthentic grain. Besides, "authentic" is such an overhyped pile of poo anyway. Everything is a reproduction; what matters should be that the artistic intent remains unaltered.
jacobush 8y ago
I am probably kind of crazy, but I love grain and worry when movies lose it. Like the fine old "Predator" movie on Bluray. Nice colors, but the grain is kind of gone. The DVD has more of it, and it looks better. I feel a ramble coming on, but I believe movies should be available in a version close to how they were viewed on theatrical release. If you think about it, the first 100 years of this artform is always going to be special.

tambourine_man 8y ago

That’s amazing. I use grain to disguise compression all the time and always this should be possible.

paavoova 8y ago
Why not keep the bitrate higher? Or are you re-encoding already over-compressed video? In which case re-encoding and adding noise only reduces the amount of detail and bloats the encoded size with, well, noise.
- tambourine_man 8y ago
  >Why not keep the bitrate higher? Sure, that would be the optimal situation. However, for a variaty of reasons you sometimes have to deal with overly compressed images. Adding noise on the client during play back disguises compression, making it nicer to the eye at no bandwidth cost.

bscphil 8y ago

Curious about this. Does the grain it algorithmically adds back look the same as that it takes away? In other words, is it just a better way to compress existing film grain? Different film sources have extremely different grain profiles, and people who encode movies (both production companies and pirates) will have no interest in the aspects of a codec that remove the real grain in a film to replace it with a generic alternative. I suppose they might adopt AV1 with that feature turned off, but otherwise AV1 will mostly be adopted for web video which currently doesn't have grain due to low bitrate encoding.

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 ago
  I 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 ago
    Search for "film grain modeling".
    - lucb1e 8y ago
      When 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 ago
        This 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

paavoova 8y ago

Is this similar to DNR schemes? Because that's a lossy process that reduces find detail, and is notorious for having been misused in many bluray releases of analog film remasters. And adding digital grain "back in" doesn't sound very authentic to the original analog source.

sjwright 8y ago
Film grain is so expensive to encode that in bit-rate-constrained situations you would be forced to choose between obvious ugly compression artefacts, a reasonably good image without grain, or a reasonably good image overlaid with inauthentic grain. Besides, "authentic" is such an overhyped pile of poo anyway. Everything is a reproduction; what matters should be that the artistic intent remains unaltered.

jacobush 8y ago

I am probably kind of crazy, but I love grain and worry when movies lose it. Like the fine old "Predator" movie on Bluray. Nice colors, but the grain is kind of gone. The DVD has more of it, and it looks better. I feel a ramble coming on, but I believe movies should be available in a version close to how they were viewed on theatrical release. If you think about it, the first 100 years of this artform is always going to be special.