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12th October 2019, 18:17 | #1 | Link |
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x265: a good compromise between "slow" and "slower" presets?
Hi.
I wanted to do some encoding using x265 (ver 3.0), but i can't quite decide on the settings. Preset "slow" has pretty good encoding speed, enough that i wouldn't mind sacrificing some to get a bit higher quality encodes, but the next available preset is like 3-4x slower, which is way too slow for me. I want to tune "slow" preset to be a bit closer to "slower", and i've looked up the parameters they use, but i'm not sure which of them would offer a good tradeoff between speed and quality. I tried reading docs, but they're too technical for me to understand and don't really offer any advice. So i was wondering if anyone could give me a rough outline of which parameters would have what effect on quality/encoding speed? Thanks. Here's the list of parameters that are different between the two presets: Code:
slow slower bframes 4 8 rc-lookahead 25 40 lookahead-slices 4 1 ref 4 5 limit-refs 3 1 subme 3 4 amp 0 1 max-merge 3 4 recursion-skip 1 0 b-intra 0 1 weightb 0 1 rdLevel 4 6 tu-intra 1 3 tu-inter 1 3 limit-tu 0 4 Last edited by iz-Moff; 12th October 2019 at 18:45. |
12th October 2019, 20:09 | #2 | Link | ||
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I'll suggest the following command line :
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13th October 2019, 02:45 | #3 | Link |
Derek Prestegard IRL
Join Date: Nov 2003
Location: Los Angeles
Posts: 5,988
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I find SAO to very much be worth it today in all cases. Maybe if you're doing high bitrate encoding you can turn it off, but it really helps in motion. It does soften a bit in single frame comparison sometimes.
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13th October 2019, 03:55 | #4 | Link |
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I also find SAO to be worth it now, even when I encode to really high bitrates. The smoothing is so minor with current versions that there really is no need to turn it off anymore.
If you think x265 smooths too much with SAO on, and SAO does not help much because the bitrate is so high, then you might want to use x264 instead.
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13th October 2019, 21:27 | #5 | Link |
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Try Slower with --limit-refs 3 --no-amp --rd 4. It will be a much faster and not affect much to quality.
FullHD 16-17mb and UHD 20-22mb is high bitrate? I always use --no-sao, but maybe I should think about it Last edited by redbtn; 13th October 2019 at 21:36. |
13th October 2019, 22:20 | #6 | Link | |
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Is "--limit-refs 1" worth it? I've run some test encodes on a sample, and among the settings that are different between the two presets, "--rd 6", "--limit-refs 1" and "-no-rskip" reduce encoding speed the most. Also, only placebo preset uses --merange above 57, and 57 doesn't sound like a number that would be selected arbitrarily...
Anyway, i guess for now i'll try using pretty much the "slower" preset without "--rd 6", "--limit-refs 1" and "-no-rskip": Quote:
Thanks, yeah, that seems like a good tradeoff. Though "--amp" doesn't seem to reduce the speed a lot, at least not with the samples i tried, so i guess i'll use it. Last edited by iz-Moff; 13th October 2019 at 22:35. |
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13th October 2019, 22:50 | #7 | Link |
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If I remember correctly --amp can slow down by 20% at least for me. So, maybe it depends of the source. What you want to encode? If you are interested, I can show all my settings based my tests for 1080p and 4k hrd.
It took a long time, but I'm happy with the result. Ps: I'm pretty sure that for now (version 3.2) --no-rskip used only preset placebo, so I don't really understand why your Slower use it. Last edited by redbtn; 13th October 2019 at 22:56. |
13th October 2019, 23:38 | #8 | Link | |
Derek Prestegard IRL
Join Date: Nov 2003
Location: Los Angeles
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Quote:
Common HEVC bitrates would be like 3-5 Mbps for 1080p and maybe 10-12 Mbps for UHD. At least, that's what's commonly seen in the premium OTT streaming case. Approx 8 for FHD and 25 for UHD are the highest used in large scale streaming services. I think this is enough for very good quality with most content with slow settings, but some challenging content really does need 30+ to look really good, especially grainy content. There's a reason UHD BluRay has the bitrates it does I guess Anyway, I guess to sum things up, maybe for UHD BluRay level bitrates SAO doesn't make sense, but for anything practical for streaming you definitely want it turned on these days. IMO. |
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14th October 2019, 23:11 | #13 | Link |
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Thank you.
I would like to encode my HD and UHD BluRay collection to x265 so I have the same question. Slower is very low, slow has a good speed but I would like to keep the best ratio between speed and quality. Could you give 2 command line exemples, one for FHD and one for UHD with slow and/or slower preset ? Thank you ! |
14th October 2019, 23:25 | #14 | Link | |
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Quote:
Last edited by redbtn; 14th October 2019 at 23:40. |
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15th October 2019, 04:36 | #15 | Link |
Pig on the wing
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I downsize my encodes all the time, and I strongly recommend using Zopti to find out the optimal parameters for Bicubic resizing to compensate the loss of sharpness and detail as much as possible.
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15th October 2019, 07:17 | #16 | Link |
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Thank you.
You downsize your encodes to reduce filesize, reduce encoding time or both ? I already tried to downsize but the result was not so good than UHD encode... Perhaps my filter was not so good. |
15th October 2019, 08:34 | #17 | Link |
Pig on the wing
Join Date: Mar 2002
Location: Finland
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I downsize just to save some space, also you can easily see that a lot of material really doesn't have any details to lose if you go from 1080p to 720p, or 2160p to 1080p (of course the relative change is bigger in the latter). Quite a lot is already an upscale from 2K to 4K.
Downsizing with Bicubic with specific tuned parameters can compensate quite a lot, especially the loss of sharpness. My viewing distance to my 65" TV is about 3.5 metres, so downsizing also has a lower impact what comes to details so your situation may be quite different.
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15th October 2019, 12:31 | #18 | Link | ||||
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Quote:
--------- Nico8583 There are my settings below. No need to set Preset or you can choose Preset Medium cuz it is use defaults. For HDR Quote:
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Last edited by redbtn; 15th October 2019 at 12:50. |
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15th October 2019, 13:02 | #19 | Link | |
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15th October 2019, 14:58 | #20 | Link | |
Registered User
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Location: Russia
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Quote:
Last edited by redbtn; 15th October 2019 at 15:00. |
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parameters, presets, settings, x265 |
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