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Old 25th October 2019, 14:18   #61  |  Link
redbtn
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After all, I set aq-mode 0 and it almost solves the problem. But i don't know how it affects to encode quality in general.

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Level 5.1 has maxrate/bufsize limits of 40000, not 160000.
Level 5.1 High has 160000, --high-tier is a default value

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It appears you've not set CRF OR bitrate, which means it's being encoded at the default CRF, which is quite high. If you're aiming for excellent quality, I'd start with 18 and iterate from there.
I use CRF 20 (21-23mbps) for UHD and CRF 12-14 (17-18mbps) for FHD.

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--hdr-opt will tweak the chroma QPs better than just setting the offsets. And if you didn't set HDR, you didn't get HDR metadata, and the video is likely playing back as if it had SDR values, which would look terrible!
--hdr-opt is definitely necessary, but --cbqpoffs -3 --crqpoffs -3 fixes color issues a little. I don't know why it needed with HDR.

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And don't set --chromaloc unless you've actually changed the chroma location. If you DID change that, let me know what tool you used to do it!
I didn't change chromaloc, but UHD requires Chroma subsampling : 4:2:0 (Type 2), so i add flag --chromaloc 2

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Also, where did you get your MaxCLL and MaxFALL values? A MaxFALL of 900 suggest at least one blindingly bright frame, and no consumer TV available can actually display a MaxCLL of 3200 nits. Not that content doesn't get made that way sometimes, but I'd definitely investigate the content to make sure something didn't go horribly wrong.
There is mediainfo of my sample below (it is a general movie, nothing special):

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Color range : Limited
Color primaries : BT.2020
Transfer characteristics : PQ
Matrix coefficients : BT.2020 non-constant
Mastering display color primaries : Display P3
Mastering display luminance : min: 0.0050 cd/m2, max: 4000 cd/m2
Maximum Content Light Level : 3241 cd/m2
Maximum Frame-Average Light Level : 902 cd/m2

Last edited by redbtn; 26th October 2019 at 00:57.
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Old 26th October 2019, 04:02   #62  |  Link
Blue_MiSfit
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Turning off AQ is fine sometimes, and in fact is done in the grain preset in order to "[restrict] algorithms that vary the quantization parameter within and across frames":

https://x265.readthedocs.io/en/defau...tml#film-grain
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Old 26th October 2019, 10:12   #63  |  Link
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Turning off AQ is fine sometimes, and in fact is done in the grain preset in order to "[restrict] algorithms that vary the quantization parameter within and across frames":

https://x265.readthedocs.io/en/defau...tml#film-grain
It could well be that HDR sources are often better re-encoded without AQ. It is very flat in the eyes of the encoder anyway so the decisions it makes, are most likely very different compared to SDR sources. Needs careful testing, I'd say.
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Old 26th October 2019, 21:47   #64  |  Link
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I leave AQ on for HDR, to be honest. Most of the time that works well. Sometimes it doesn't but I don't do any per-encode tuning (for my work, anyway).
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Old 28th October 2019, 08:20   #65  |  Link
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I leave AQ on for HDR, to be honest. Most of the time that works well. Sometimes it doesn't but I don't do any per-encode tuning (for my work, anyway).
If possible, could you give a command line example for FHD and a command line example for UHD (HDR10 and/or HDR10+) ? Thank you !
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Old 28th October 2019, 11:53   #66  |  Link
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First, --selective-sao 3 only applies SAO for I and P frames, but delivers almost all the potential quality benefit of SAO with a ~4% speedup. This follows general literature that SAO isn't helpful with bi-prediction.
Wow, thanks for the info. I am getting a huge speed increase by using selective-sao 2 (you might want to edit your post and make it 2, instead of 3). In fact, a lot more than 4%.
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Old 28th October 2019, 22:31   #67  |  Link
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I've been meaning to try --aq-mode 4. Since so much of the value from HDR at high resolution comes from strong local contrast, something that preserves edges better could be quite helpful.
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Old 2nd November 2019, 06:56   #68  |  Link
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I use bframe=6. According to the docs, this could shed you 25% of the workload (Am I right?). Is it really worth to keep bframes at 8, if the movie I'm encoding doesn't have so many motion?
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Old 2nd November 2019, 11:52   #69  |  Link
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Best thing is to run a test encode with maximum possible bframes then check the log file so as to determine how many bframes are actually used.
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