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AV2 video codec delivers 30% lower bitrate than AV1, final spec due in late 2025

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Re: AV2 video codec delivers 30% lower bitrate than AV1, final spec due in late 2025

#181

Earlier quoted context omitted.

1.1: Google some low-light performance reviews of cinema cameras - you'll see that ISO noise is decreasing with every generation and that some cameras (like from Sony) have that as a selling feature. 1.2.: Google "how to shoot a night scene" or something like that. You'll find most advice goes something along the lines of "don't crank the ISO up, add artificial lighting to brighten shadows instead". When given a choi…

I am reasonably confident that I know this subject area better than one could learn from three Google searches. “ISO noise” is not even a real term; you are talking about digital sensor noise, which can further be luminance noise or colour noise. Opinions about luma noise being “unaesthetic” are highly subjective, depending a lot on stylistic choices and specific sensor, and some would say luma noise on professional…

"ISO noise" is a thing I've heard on a few different film sets and it's a convenient shorthand for "the noise that becomes really apparent only when you crank up the gain". Now that I'm thinking about it, there's a good chance this is more of a thing where I'm from, since our native language doesn't have different words for grain and noise, so we have to diffentiate between them with a suffix, which we then incorrectly also use in English. I guess on a film set with mostly native English speakers, noise and grain is clear enough.

Next, no shit aesthetics are subjective, I never said this is the one objective truth. I said this is a thing that many people believe, as evidenced by the plethora of resources talking about the difference between noise and grain, why tasteful grain is better than a completely clean image and how to add it in post.

And finally, come on, it's obvious to everyone in this thread that I'm referring to digital, which is also not "just a subset" it's by far the biggest subset.

So idk what your point is. Most things are shot digitally. Most camera companies try to reduce sensor noise. Most camera departments try to stick to the optimal ISO for their sensor, both for dynamic range and for noise reasons, adjusting exposure with other means. In my experience, most people don't like the look of sensor/gain/iso/whatever noise. Many cinematographers and directors like the look of film grain and so they often ask for it to be added in post.

Besides the many/most/some qualifiers possibly not matching with how you percieve this (which is normal, we're all different, watch different content, work in different circles...), where exactly am I wrong?

Re: AV2 video codec delivers 30% lower bitrate than AV1, final spec due in late 2025

#182
post #50

Will streaming services ever stop over-compressing their content? I have a top-of-the-line 4K TV and gigabit internet, yet the compression artifacts make everything look like putty. Honestly, the best picture quality I’ve ever seen was over 20 years ago using simple digital rabbit ears. You especially notice the compression on gradients and in dark movie scenes. And yes — my TV is fully calibrated, and I’m paying for…

and this is why I don't look down on those who choose to pirate bluray/4k content

Re: AV2 video codec delivers 30% lower bitrate than AV1, final spec due in late 2025

#183

Earlier quoted context omitted.

Yes, I was not strictly correct, it is a feature of AV1, but Netflix played an active role in its development, in rolling out the first implementation, and in AV1 codec development overall.

Prior codecs all had film grain synthesis too (at least back to H264), but nobody used it. Partly because it was obviously artificial and partly because it was too expensive to render, since you had to copy each frame to apply effects to it.

AFAIK, FGS support is the exception instead of the rule.

h.264 only had FGS as an afterthought, introduced years after the spec was ratified. No wonder it wasn’t widely adopted.

VP9, h.265 and h.266 don’t have FGS.

Re: AV2 video codec delivers 30% lower bitrate than AV1, final spec due in late 2025

#184
post #85

Earlier quoted context omitted.

There's no point having reference RTL. The point of reference software is to demonstrate the correct behaviour for people implementing production grade libraries and RTL. Having an RTL version of that wouldn't add anything - it should have identical behaviour. Providing a production grade verified RTL implementation would obviously be useful but also entire companies exist to do that and they charge a lot of money fo…

Could help people on the hobby or lower budget FPGA side. H.264/5/etc never really made it

There is absolutely no way an FPGA would make sense. The requirements for AV1 and H265 far exceed the hardware resources of lower budget FPGAs. For the same process, FPGA logic density is about 40x lower than ASIC, and lower budget FPGAs use older processes.

A h265 or AV1 decoder requires millions of logic gates (and DRAM memory bandwidth.) Only high-end FPGAs provide that.

Re: AV2 video codec delivers 30% lower bitrate than AV1, final spec due in late 2025

#185
post #169
post #85

Earlier quoted context omitted.

Could help people on the hobby or lower budget FPGA side. H.264/5/etc never really made it

Can a "lower budget" FPGA really outperform a consumer-grade CPU for this? And what hobbyist is sending off decoding chips to be fabbed? If this exists, it sounds interesting if incredibly impractical.

It’s not possible on any but the largest $$$ FPGAs… and even then we often need to partition over multiple FPGAs to make it fit. And it will only run at a fraction of the target clock speed.

Re: AV2 video codec delivers 30% lower bitrate than AV1, final spec due in late 2025

#186

It’s pretty amazing people are still finding ways to make video smaller. Is this just people being clever or is it also more processing power being thrown at the problem when decoding / encoding?

I don’t know the details of AV2, but going from h.265 to h.266, the number of angles for angular prediction doubled, they added a tool to predict chroma from luma, added the ability to do pixel block copies and a bunch of other techniques… And that’s just for intra predictions. They also added tons of new inter prediction techniques.

All of this requires a significant amount of extra logic gates/silicon area for hardware decoders, but the bit rate reduction is worth it.

For CPU decoders, the additional computational load is not so bad.

The real additional cost is for encoding because there’s more prediction tools to choose from for optimal compression. That’s why Google only does AV1 encoding for videos that are very popular: it doesn’t make sense to do it on videos that are seen by few.

Re: AV2 video codec delivers 30% lower bitrate than AV1, final spec due in late 2025

#187
post #127

Earlier quoted context omitted.

Are you sure about the black-areas-blocking? I remember a long time ago, when I was younger and had time for this kind of tomfoolery, I noticed this exact issue in my BlueRay backups. I figured I needed to up the bitrate, so I started testing, upping the bitrate over and over. Finally, I played the BlueRay and it was still there. This was an old-school, dual-layer, 100GB disc of one of the Harry Potter movies. Still…

the downside of 8 bits per channel is you really don't have enough to get a smooth gradient over dark colors.

Yup. I think that’s exactly it.

Re: AV2 video codec delivers 30% lower bitrate than AV1, final spec due in late 2025

#188

Earlier quoted context omitted.

that's 19mbps including error correction. only 10 after, and that's using mpeg2 which is probably roughly equivalent to 6-7mbps av1

"A terrestrial (over-the-air) transmission carries 19.39 megabits of data per second (a fluctuating bandwidth of about 18.3 Mbit/s left after overhead such as error correction, program guide, closed captioning, etc.)," https://en.wikipedia.org/wiki/ATSC_standards#MPEG-2

But that's the whole multiplex, right?

It could be a single channel, but usually you have many in the multiplex. I don't know how it works in the US, but for DVB-T(2) that's how it is.

Re: AV2 video codec delivers 30% lower bitrate than AV1, final spec due in late 2025

#189
post #50

Will streaming services ever stop over-compressing their content? I have a top-of-the-line 4K TV and gigabit internet, yet the compression artifacts make everything look like putty. Honestly, the best picture quality I’ve ever seen was over 20 years ago using simple digital rabbit ears. You especially notice the compression on gradients and in dark movie scenes. And yes — my TV is fully calibrated, and I’m paying for…

> You especially notice the compression on gradients and in dark movie scenes. That's not a correctly calibrated TV. The contrast is tuned WAY up. People do that to see what's going on in the dark, but you aren't meant to really be able to see those colors. That's why it's a big dark blob. It's supposed to be barely visible on a well calibrated display. A lot of video codecs will erase details in dark scenes because…

If an eye is able to distuinguish all 256 shades on a correctly calibrated display, then the content should be preserved.

Re: AV2 video codec delivers 30% lower bitrate than AV1, final spec due in late 2025

#190

It’s pretty amazing people are still finding ways to make video smaller. Is this just people being clever or is it also more processing power being thrown at the problem when decoding / encoding?

I don’t know the details of AV2, but going from h.265 to h.266, the number of angles for angular prediction doubled, they added a tool to predict chroma from luma, added the ability to do pixel block copies and a bunch of other techniques… And that’s just for intra predictions. They also added tons of new inter prediction techniques. All of this requires a significant amount of extra logic gates/silicon area for hard…

Iirc Facebook did the selective encoding too. And it would predict which videos would be popular so even the first streams would get the AV1 version.
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