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AV1@Scale: Film Grain Synthesis, The Awakening

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Re: AV1@Scale: Film Grain Synthesis, The Awakening

#141

Post by dperfect »

crazygringo wrote: post #96

This fails to acknowledge that synthesized noise can lack the detail and information in the original noise . When you watch a high-quality encode that includes the actual noise, there is a startling increase in resolution from seeing a still to seeing the video. The noise is effectively dancing over a signal, and at 24 fps the signal is still perfectly clear behind it. Whereas if you lossily encode a still that disca…

This is a really good point.

To illustrate the temporal aspect: consider a traditional film projector. Between every frame, we actually see complete darkness for a short time. We could call that darkness "noise", and if we were to linger on that moment, we'd see nothing of the original signal. But since our visual systems tend to temporally average things out to a degree, we barely even notice that flicker (https://en.wikipedia.org/wiki/Flicker_fusion_threshold). I suspect noise and grain are perceived in a similar way, where they become less pronounced compared to the stable parts of the signal/image.

Astrophotographers stack noisy images to obtain images with higher SNR. I think our brains do a bit of that too, and it doesn't mean we're hallucinating detail that isn't there; the recorded noise - over time - returns to the mean, and that mean represents a clearer representation of the actual signal (though not entirely, due to systematic/non-random noise, but that's often less significant).

Denoising algorithms that operate on individual frames don't have that context, so they will lose detail (or will try to compensate by guessing). AV1 doesn't specify a specific algorithm to use, so I suppose in theory, a smart algorithm could use the temporal context to preserve some additional detail.

Re: AV1@Scale: Film Grain Synthesis, The Awakening

#142

Post by kalleboo »

dylan604 wrote: post #51
fidotron wrote: post #3

There are definite philosophical questions over the merits of adding noise, but the problem with their example here is their denoising process appears to excessively blur everything, so both it and the synthesized grain image look noticeably less sharp than the source. The grain itself also looks too much like basic noise, and not really grain like.

> and not really grain like that's an understatement. it just looks like RGB noise effect was added. film grain does not look like RGB noise. to me, film grain is only one part of what gave film the film look. the way the highlights bloom rather than clip. it also was more natural/organic/some descriptive other than the ultrasharp of modern digital acquisition. using some SoftFX or Black Mist type filters help, but i…

I only have their single sample in the blog post to go by, but the original source frame also looks just like RGB noise? And the recreation looks really close if I swap between them. Looks fine to me.

So as long they're analyzing the style of grain in the source properly, which the technical part of the post mentions they do...

Re: AV1@Scale: Film Grain Synthesis, The Awakening

#143

Post by notpushkin »

rainworld wrote: post #74
dylan604 wrote: post #57

Earlier quoted context omitted.

> provide distributors with a noiseless source plus grain synthesis parameters. What parameters would that be? Make it look like Eastman Ektachrome High-Speed Daylight Film 7251 400D? For years, people have taken film negative onto telecines and created content of grain to be used as overlays. For years, colorists have come up with ways of simulating the color of specific film stocks by using reference film with test…

And yet here we are: DNR -> fancy grain -> DNR -> basic, approximated grain. Because noise doesn’t compress. And you get compression artifacts even in Blu-ray releases. What’s the point of applying fancy grain when what a lot viewers end up seeing is an ugly smudge?

I think at some point studios will give de-grained versions to Netflix directly.

Re: AV1@Scale: Film Grain Synthesis, The Awakening

#145

Post by kalleboo »

kelsey98765431 wrote: post #26

happier and happier about leaving behind digital media to return to physical. to me this is literally slop. i want the uncompressed file stop selling me stepped on product

Physical media is what pioneered "stepping on" the product with things like Pan & Scan

Re: AV1@Scale: Film Grain Synthesis, The Awakening

#147

Post by majormajor »

kderbe wrote: post #107
crazygringo wrote: post #96

This fails to acknowledge that synthesized noise can lack the detail and information in the original noise . When you watch a high-quality encode that includes the actual noise, there is a startling increase in resolution from seeing a still to seeing the video. The noise is effectively dancing over a signal, and at 24 fps the signal is still perfectly clear behind it. Whereas if you lossily encode a still that disca…

Grain is independent frame-to-frame. It doesn't move with the objects in the scene (unless the video's already been encoded strangely). So long as the synthesized noise doesn't have an obvious temporal pattern, comparing stills should be fine. Regarding aesthetics, I don't think AV1 synthesized grain takes into account the size of the grains in the source video, so chunky grain from an old film source, with its big s…

> So long as the synthesized noise doesn't have an obvious temporal pattern, comparing stills should be fine.

The problem is that the initial noise-removal and compression passes still removed detail (that is more visible in motion than in stills) that you aren't adding back.

If you do noise-removal well you don't have to lose detail over time.

But it's much harder to do streaming-level video compression on a noisy source without losing that detail.

The grain they're adding somewhat distracts from the compression blurriness but doesn't bring back the detail.

Re: AV1@Scale: Film Grain Synthesis, The Awakening

#148

Post by CharlesW »

m3kw9 wrote: post #144

Is film grain a nostalgia effect? If kids grew up without seeing film grain, how would they feel about it?

> Is film grain a nostalgia effect?

Film grain simulation can be an effect, but that's not the primary application being described here. As @ricardobeat succinctly put it elsewhere in this post, this process usually supports "a reproduction of the original grain pattern, compressed separately from the underlying image content. The result is closer to the original picture than the denoised/compressed version".

> If kids grew up without seeing film grain, how would they feel about it?

Film isn't quite dead yet, with ~7% of features in 2025 still being shot on film and maybe 1% more taking the digital→film→digital (a.k.a. "analog intermediate") route. Unless their media diet is all super-recent and low-quality, even today's kids will have most likely seen many movies shot on film with visible grain. Popular candidates would include the Harry Potter franchise, most episodes of the Star Wars franchise, early Marvel movies, many animated Disney and Studio Ghibli features, etc.

Re: AV1@Scale: Film Grain Synthesis, The Awakening

#149

Post by indolering »

dperfect wrote: post #50

To the comments hating on grain: everything naturally has some amount of noise or grain - even the best digital sensors. Heck, even your eyes do. It's useful beyond just aesthetics. It tends to increase perceived sharpness and hides flaws like color banding and compression artifacts. That's not to say that all noise and grain is good . It can be unavoidable, due to inferior technology, or a result of poor creative ch…

Case in point: the HBO into animation. It uses static from the old analog days. It looks like shit even at 4k because random noise is impossible to compress without the exact strategy outlined here (stripping it out and rendering it later).

Re: AV1@Scale: Film Grain Synthesis, The Awakening

#150

Post by Thorrez »

majormajor wrote: post #147
kderbe wrote: post #107

Earlier quoted context omitted.

Grain is independent frame-to-frame. It doesn't move with the objects in the scene (unless the video's already been encoded strangely). So long as the synthesized noise doesn't have an obvious temporal pattern, comparing stills should be fine. Regarding aesthetics, I don't think AV1 synthesized grain takes into account the size of the grains in the source video, so chunky grain from an old film source, with its big s…

> So long as the synthesized noise doesn't have an obvious temporal pattern, comparing stills should be fine. The problem is that the initial noise-removal and compression passes still removed detail (that is more visible in motion than in stills) that you aren't adding back. If you do noise-removal well you don't have to lose detail over time. But it's much harder to do streaming-level video compression on a noisy s…

>The grain they're adding somewhat distracts from the compression blurriness but doesn't bring back the detail.

Instead of wasting bits trying to compress noise, they can remove noise first, then compress, then add noise back. So now there aren't wasted bits compressing noise, and those bits can be used to compress detail instead of noise. So if you compare FGS compression vs non-FGS compression at the same bitrate, the FGS compression did add some detail back.

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