AV1 (AOMedia Video 1) [main thread]

[spoRv]

This comparison used old encoder versions, but you can see how they look with VERY LOW bitrate - less than 600kbps for an HD source!

You have AV1, VP9, HEVC and AVC.

http://video.1ko.ch/codec-comparison/

[spoRv]

I merged all my AV1 threads into this one; hope everything is clearer now...

[spoRv]

Updated first post

[nat]

thank you very much spoRv for your effort

[spoRv]

Here I try to summarise the reasons why I think AV1 could be the best codec for restorations:

• free and open to anyone - content, software, hardware producers
  
• encoding now is faster than h265, with better quality at same bitrate
  
• at same quality, AV1 file is usually at least 30% smaller than x265, the reference HEVC encoder
  (depending on the encoder chosen, settings, resolution etc.)
  
• it could be easily decoded via software by average computers
  (and some smartphones too)
  
• it could be hardware decoded by some last generation CPUs and GPUs
  
• it could be hardware decoded by few cheap TV BOX/media players
  (like the ones with SoC based on AMLogic s905x4 or Rockchip RK3588)
  
• hardware decoding is mandatory for Android TV 10 devices
  
• Netflix switched to AV1 recently
  
• Google mainly uses AV1 along with VP9
  
• it has an unique feature: grain synthesis
  

Those are all good reasons to embark in a (quite relatively) new codec right now, but the last one is the most interesting for us.

Even if VVC is more efficient than AV1 in UHD - according to some sources up to 20% more - the problem is, when encoding a grainy source, an higher bitrate is needed to encode it perfectly; the fact that AV1 could use the grain synthesis where VVC can't - at least for now - would make the AV1 the real winner.

Example (with rough bitrate requirement and saving estimations based onto several late comparisons):

non-grainy source, 3840x2160 resolution, full frame 16:9, 24fps progressive, 4:2:0 10 bit, high motion rank, would require a CBR bitrate of about

• 68mbps in AVC
  
• 36.2mbps in HEVC
  
• 24mbps in AV1
  
• 21.7mpps in VVC - using the best subjective quality bitrate saving of 40% in comparison to HEVC
  

now, the same source but with grain should need about 1.5x bitrate (if not more) to encode the grain perfectly, so our figures would be:

• 102mbps in AVC
  
• 54.3mbps in HEVC
  
• 36mbps in AV1
  
• 32.6mpps in VVC
  

Those are in lines with UltraHD Blu-ray bitrates - actually they are, on average, even higher - and with what I tested some years ago encoding HD grainy sources - that required about 12/16mbps depending on content = 48/64mbps for UHD.

But AV1 could encode the grainy source using the same bitrate used for non-grainy one, obtaining a quite good result, so in that case would be:

• 24mbps in AV1 (using grain synthesis)
  
• 32.6mpps in VVC
  

Even if actual bitrate requirement to optimally encode a grainy source could be different from the previous figures, the advantage of AV1 using grain synthesis Vs VVC without it remains - even if grain reconstuction would never be perfect, I bet that a grainy source, encoded in AV1 with grain synthesis would beat a VVC encoded at the same bitrate.

[deleted user]

The film grain synthesis feature is really cool and potentially game changing. Happy to read it because I often thought about how cool it would be if a codec could do exactly this - remove the grain and encode it separately. Although of course this is technically a different approach of sorts, since the grain isn't encoded but parametrized.

I was never happy with how grain ended up looking in encodes, even in high bitrate encodes. There's always just something ... missing. And the motion estimation blurs and warps the grain, it's really ugly and takes away the film feel.

The results seem to look really good, my only critique is that while the grain will *look* the same, it will not actually be the same grain, so it's arguably not a preservation in the truest sense. But then, it's superior to what we have right now, where grain will be affected by the motion estimation and look unsharp and warpy and unnaturally static, ruining the feeling of a nice fluid crystalline grain field like when actually projecting a film. I presume that with this you will actually have a unique grain field on each frame that's not motion compensated, which sounds great!

I suppose, at the very least, this feature could make for a nice low-bitrate option for projects, if nothing else.

You really got me interested in this AV1 stuff, I have to check it out at some point. Is the film grain synthesis already implemented?

[spoRv]

Yes, it's already implemented - I've written about it in another thread, just follow the second link on top of first post.

TL;DR: https://screenshotcomparison.com/comparison/19863
as you can see, the synthesized grain does mask compression problems found in the source - which is an AVC encode of the JPEG2000 DCP trailer.

Sure, it is NOT the exact grain, but it is simulated very closely - I mean, a fine grain would be a fine grain, a coarse grain would be coarse, and the pattern would be very similar.

It's all about the source, and the encoding bitrate:

• if the grain is in the lossless/uncompressed source, a very high bitrate is needed to preserve it perfectly
  
• if the grain is in the lossy source, it is already not the one present in the original source
  
• if we want to add a grain plate, this is not the grain present in the original source
  

so, unless we have a lossless/uncompressed grainy source - I'm thinking about film scan, for example - and we don't want, or can't, encode it at a very high bitrate, for all the other cases the grain synthesis is a great solution!

[spoRv]

Just a side note: I read almost everywhere that Youtube uses VP9 for pretty much everything (with AVC as fallback), while AV1 is used for videos with more than 1 million views.
Well, on my small TV Box that happens to be able to hardware decode both VP9 and AVC, I've seen quite many videos encoded with AV1 much below the 1 million views - some even below 1 thousand! It seems that newer ones are AV1, while older ones - even with 15m views - still use VP9.

So, my educated guess is that some newer videos use AV1 even with low view count; but did not understand following which criteria, though!

[dwalkerdon]

Just a side note: I read almost everywhere that Youtube uses VP9 for pretty much everything (with AVC as fallback), while AV1 is used for videos with more than 1 million views.
Well, on my small TV Box that happens to be able to hardware decode both VP9 and AVC, I've seen quite many videos encoded with AV1 much below the 1 million views - some even below 1 thousand! It seems that newer ones are AV1, while older ones - even with 15m views - still use VP9.

So, my educated guess is that some newer videos use AV1 even with low view count; but did not understand following which criteria, though!

what was the resolution of the AV1 files with below 1,000 views? I find that the lower res vids tend to be uploaded in AV1

[spoRv]

what was the resolution of the AV1 files with below 1,000 views? I find that the lower res vids tend to be uploaded in AV1

It could be indeed... IIRC 854x480 - but I noticed only one or two videos with less than 1000 views AND encoded in AV1.

I'll check the next times!

I'm curious... what if someone upload an already encoded video in AV1 or VP9? (with proper resolution and bitrate)
Would Youtube leave it untouched? Convert it anyway?