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Old 29th March 2017, 16:50   #1  |  Link
karasu
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AV1, VP9, x265, x264 low bitrate comparison

I made some test with the new AV1 codec from aomedia and I made some captures for comparison :

https://vincenttschanz.github.io/1ko...ec-comparison/

The goal was to use a very low bitrate to see which encoder will give better result and how the picture will be degraded.

Don't hesitate to tell me if I made mistakes or if I can refine the comparison, thanks.

Last edited by karasu; 29th March 2017 at 17:44. Reason: words
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Old 29th March 2017, 17:35   #2  |  Link
sneaker_ger
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Thx.
VP9 > AV1 > x265 > x264
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Old 29th March 2017, 17:36   #3  |  Link
ChaosKing
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Nice comparison!

I think VP9 wins.
And I'm a bit disappointed by x265. Worm like artefacts in frame 226 and look at the street lamp (bottom left) in frame 399
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Old 29th March 2017, 18:29   #4  |  Link
Taurus
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Thanks!
VP9 > AV1 > x265 > x264
Really amazing VP9 @ this low bitrate.
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Old 29th March 2017, 19:48   #5  |  Link
hajj_3
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not that helpful as people won't use bitrates this low with resolutions this high. A better test would be a low bitrate 840x480 or 640x360.
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Old 29th March 2017, 19:50   #6  |  Link
bstrobl
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Most of the improvements in AV1 over VP9/HEVC are still kept as experiments that need to be enabled during compile time, might be interesting to try a couple of those out.

Still good to see VP9 beating out HEVC, would have thought the performance was slightly worse. Encoder improvements maybe?
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Old 29th March 2017, 21:03   #7  |  Link
karasu
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Quote:
Originally Posted by bstrobl View Post
Most of the improvements in AV1 over VP9/HEVC are still kept as experiments that need to be enabled during compile time, might be interesting to try a couple of those out.
I'd be glad to try, do you know where I can find informations about that?
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Old 29th March 2017, 21:11   #8  |  Link
bstrobl
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I'd be glad to try, do you know where I can find informations about that?
https://www.youtube.com/watch?v=lzPaldsmJbk talks more about this (roughly 16 minutes in). A couple of experiments are listed at 36:17, but am not sure where to get a complete list. Maybe others here can pitch in for that.

Edit: the slide at 40:20 gives a list of enabled experiments to show the progress over the default build.

Last edited by bstrobl; 29th March 2017 at 21:15.
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Old 29th March 2017, 21:29   #9  |  Link
easyfab
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here the complete list:

https://aomedia.googlesource.com/aom.../configure#246
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Old 29th March 2017, 21:33   #10  |  Link
easyfab
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and here the experiments that are adopted and now default:

https://aomedia.googlesource.com/aom.../configure#471
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Old 29th March 2017, 21:39   #11  |  Link
Atak_Snajpera
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To be honest all look terrible. Besides who on earth encodes blu-ray collection using such ridiculously low bitrate? Less than 600kbps for 1920x800? Audio E-AC3/DTS has bigger bitrate than this! Increase bitrate to some more sane levels (1.5Mbps-2Mbps) and you will see that competition is better in retention of fine details.

Last edited by Atak_Snajpera; 29th March 2017 at 21:42.
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Old 30th March 2017, 07:39   #12  |  Link
Blue_MiSfit
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Why are the bitrate targets different here?
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Old 30th March 2017, 08:12   #13  |  Link
karasu
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Quote:
Originally Posted by Atak_Snajpera View Post
To be honest all look terrible. Besides who on earth encodes blu-ray collection using such ridiculously low bitrate?
They look terrible indeed, but who talked about ripping blu-ray? In this case I wanted to see the visual degradation. Beside, there are fare worse quality in production everywhere on the Web.

Also, current encoding speed is also a problem IMO.
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Old 30th March 2017, 08:14   #14  |  Link
karasu
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Originally Posted by Blue_MiSfit View Post
Why are the bitrate targets different here?
My goal was to aim for the same resulting file size for fair comparison. AV1 gave me the first size and I had to adapt settings for the other encoders to match as closely as possible.
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Old 30th March 2017, 12:01   #15  |  Link
ChaosKing
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If think it would be also nice to see all 4 encodes with a 1000kb/s and 1500kb/s bitrate. I wonder if vp9 will still be the winner...
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Old 30th March 2017, 17:24   #16  |  Link
Tommy Carrot
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VP9 and AV1 use golden frames, which means every Nth frame has much higher quality than the rest of them. So looking at individual frames can be misleading, because if you're looking at golden frames, or a few frames after them, the quality is much higher than the average quality of the video. x264 and x265 doesn't cheat like that, not to mention golden frames introduce a rather annoying effect during normal playback, i wish codec developers would abandon this technique (but they won't, because it improves the metrics...).
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Old 30th March 2017, 18:50   #17  |  Link
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Originally Posted by Tommy Carrot View Post
VP9 and AV1 use golden frames
Isn't that the same as I-frames? Do you know a way to check the type of frame when decoding ?
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Old 30th March 2017, 18:56   #18  |  Link
ChaosKing
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Try this:

http://stackoverflow.com/questions/3...e-using-ffmpeg
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Old 30th March 2017, 19:44   #19  |  Link
Quikee
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Originally Posted by Tommy Carrot View Post
VP9 and AV1 use golden frames, which means every Nth frame has much higher quality than the rest of them. So looking at individual frames can be misleading, because if you're looking at golden frames, or a few frames after them, the quality is much higher than the average quality of the video. x264 and x265 doesn't cheat like that, not to mention golden frames introduce a rather annoying effect during normal playback, i wish codec developers would abandon this technique (but they won't, because it improves the metrics...).
AFAIK golden frame is just a VP9 terminology for a reference frame from the past (a P frame would have a golden frame) so from that VP9 and AV1 don't have anything special than other codecs have. Boosting the quality of a golden frame makes sense if it serves as a reference frame for more other frames and boosting its quality improves the prediction. I would be surprised that x264 and x265 doesn't do something similar. What you describe is when the frame quality is boosted too much and this is just a fail of the rate control. Many would agree that the rate control in libvpx (the reference VP9 implementation) is not good. In libaom there is a rather new experiment available - "xiphrc", which is the theora / daala rate control adapted for AV1 and it shows promising results already, but it needs a lot more work and tuning.

Generally, I don't think it makes sense to test AV1 without enabling many of the experiments (I expect most of them will be part of AV1). Which one to enable is also not known and won't until they'll evaluate them and either drop or accept them as default. So that would be at the time near bitstream freeze.
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Old 30th March 2017, 21:27   #20  |  Link
Tommy Carrot
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Quote:
Originally Posted by karasu View Post
Isn't that the same as I-frames? Do you know a way to check the type of frame when decoding ?
No, they are regular p-frames, just with boosted quality.
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Originally Posted by Quikee View Post
AFAIK golden frame is just a VP9 terminology for a reference frame from the past (a P frame would have a golden frame) so from that VP9 and AV1 don't have anything special than other codecs have. Boosting the quality of a golden frame makes sense if it serves as a reference frame for more other frames and boosting its quality improves the prediction. I would be surprised that x264 and x265 doesn't do something similar. What you describe is when the frame quality is boosted too much and this is just a fail of the rate control. Many would agree that the rate control in libvpx (the reference VP9 implementation) is not good.
You're probably right, it could be improved with some tuning, they are boosted way too much in vp9, and in AV1 last time i checked a few months ago. In some cases the periodic sharpening effect is very noticeable and annoying. X264 and x265 don't have anything like that, they have very consistent quality. You could get similar effect with them if you set I-frame distance to 1 second or so, but generally you don't do that.

Last edited by Tommy Carrot; 30th March 2017 at 21:31.
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