AV1@Scale: Film Grain Synthesis, The Awakening • Hacker News Board

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

#201

Post by arghwhat » Fri, Jul 04, 2025, 3:22 PM UTC

account42 wrote: post #169

arghwhat wrote: post #112

Earlier quoted context omitted.

The noise does not contain a signal, does not dance over it, and is not detail. It is purely random fluctuations that are added to a signal. If you have a few static frames and average them, you improve SNR by retaining the unchanged signal and having the purely random noise cancel itself out. Retaining noise itself is not useful. I suspect the effect you might be seeing is either just an aesthetic preference for the…

> If you have a few static frames and average them, you improve SNR by retaining the unchanged signal and having the purely random noise cancel itself out. That's exactly the point of GP though. Even though each individual frame might be almost indistinguishable from random noise you can still extract patterns over time. This is also the case if you don't average the frames in software but let the viewer's brain do i…

Anything with a pattern is by definition not noise, and the comment was that noise had signal. If you remove all noise, no signal or pattern is lost by definition.

However, the issue is that lossy compression removes various types of minute detail, smoothing surfaces to reduce the amount of data that has to be stored, be it noise "grain" or skin pores, according to compression settings. Storing the original noise as it was would basically make any compression impossible.

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

#202

Post by hungmung » Fri, Jul 04, 2025, 3:27 PM UTC

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…

Some of the new 4K discs use DRR and the denoising process seems to remove the pores on people's faces occasionally, leaving actors looking like their face is made of wax.

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

#203

Post by sneak » Fri, Jul 04, 2025, 3:31 PM UTC

UltraSane wrote: post #200

sneak wrote: post #196

Earlier quoted context omitted.

No, it would take a lot longer than that. You’re fighting 100 years of tradition.

You would notice 1 fps more per year?

no i will be watching 24fps films for the remainder of my life, which may be 40 more years. if all new films went up 1fps per year i would still go out to the movies in 20 years and be like “wtf is this crap?”

it would take a generation or more to eradicate this cultural context. casablanca is never going to be in 48fps.

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

#204

Post by illiac786 » Fri, Jul 04, 2025, 3:58 PM UTC

liampulles wrote: post #191

The key point some people are missing here is that removing noise from a video before compression makes it more compressible. So if you compare a video compressed without denoising/degrading at bitrate X to a video that was filtered and then compressed at bitrate X with "fake noise" added later, then the latter will have edges and details that the former doesn't. The principle of post-processing videos to add noise o…

Exactly. Everyone is going on about grain quality but are in fact comparing wheat and spelt (if I may).

What matters to Netflix is the bandwith/quality ratio, that’s it. Removing noise before and adding it in software at playback time will produces a significantly better result, at similar bit rate. Because compressing noise produces horrible results.

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

#205

Post by Wowfunhappy » Fri, Jul 04, 2025, 4:15 PM UTC

account42 wrote: post #178

Wowfunhappy wrote: post #101

Earlier quoted context omitted.

Your Van Gogh analogy makes sense for old movies. It doesn't quite explain why we're still adding grain to new movies, except for those few which are purposefully evoking older movies.

Same reason why movies still use extremely low frame rates - because people have gotten used to that effect. It doesn't help that a lot of great movies are older thus those limitations of older technology become subconsciously associated with quality.

...what makes the frame rate thing especially weird is how many TVs ship with motion smoothing enabled by default, which looks so much worse than actual high frame rate content would.

I don't like it at all. But someone must, or the TV manufacturers wouldn't do it.

Part of me thinks that it's only the people who know what "frame rate" means who prefer low frame rates, and a majority of the general public actually prefers high frame rates but lacks the terminology or knowledge to express this desire.

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

#206

Post by sharpshadow » Fri, Jul 04, 2025, 5:30 PM UTC

ricardobeat wrote: post #91

sharpshadow wrote: post #19

Fake grain really disgusts me.

This is not fake grain - it's 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 I understood it correctly they take one sample of grain and do random smaller samples of it to fill the picture with. That’s not even the original grain from each frame, but one sample for the whole video. The technique is awesome, saves huge amount of bandwidth. Personally I just like the original grain from each frame much much more, from an artistic standpoint.

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

#207

Post by tvshtr » Fri, Jul 04, 2025, 5:41 PM UTC

derf_ wrote: post #11

The "at scale" part is the real story here. Film Grain Synthesis has been available in the usual AV1 encoders for a while, but required some amount of manual tweaking to avoid creating problems, meaning it was only used in production when you had a very limited catalog, or for particularly important titles. They do not provide a lot of details here about how they overcame those problems, but it is nice to see it bein…

There's adaptive variant nowadays which makes things much easier to automate.

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

#208

Post by BoingBoomTschak » Fri, Jul 04, 2025, 7:24 PM UTC

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…

Don't want to sound too snarky, but aren't you just saying that good denoisers must be temporal in addition to spatial? Something like an improved V-BM3D (cf https://arxiv.org/abs/2001.01802) and even traditional V-BM3D works fine even on non-Gaussian noise.

Together with external noise generation (something like https://old.reddit.com/r/AV1/comments/r86nsb/custom_photonno...) that'd support external denoising (pass the reference and denoised video to get the grain spec), the whole FGS thing would be much more interesting.

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

#209

Post by Animats » Fri, Jul 04, 2025, 8:59 PM UTC

Mashimo wrote: post #162

Animats wrote: post #110

Film grain needs to die. Its time is past. Sepia photographs and running 16 FPS silent film at 24 FPS are already dead. Next, film grain. Eastman Business Park in Rochester has been demolished. Also, please stop putting dust and scratches on YouTube videos. Thank you.

But why does filmgrain need to die?

Because it's noise.

We got rid of interlaced TV. We got rid of the low-bandwidth color changes of NTSC. (NTSC video can only go through the color gamut about ten times per scan line, which is why colored text on NTSC is truly awful.) We got rid of projector film transport jank. (Except for really bad Youtube videos which use a filter to produce fake film transport jank.) Nobody wants any of those back.

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

#210

Post by UltraSane » Fri, Jul 04, 2025, 10:34 PM UTC

sneak wrote: post #203

UltraSane wrote: post #200

Earlier quoted context omitted.

You would notice 1 fps more per year?

no i will be watching 24fps films for the remainder of my life, which may be 40 more years. if all new films went up 1fps per year i would still go out to the movies in 20 years and be like “wtf is this crap?” it would take a generation or more to eradicate this cultural context. casablanca is never going to be in 48fps.

That is a very very silly attitude.