2019 great x265 4k settings?

[Boulder]

Originally Posted by benwaggoner

There isn't any psychovisual tuning involved here, so looking at PSNR and SSIM differences would probably be a lot more useful than with other settings.

My gut is a smaller range with HME is probably optimal at fixed encoding time, but it'll be somewhat content dependent. HME is probably more useful to improve perf @ quality than anything else.

Do you think that just setting --ssim would be enough or is tuning needed? I did two quick tests, and at 720p (downscaled from 1080p) --no-hme with --merange 58 was better and at 1080p --hme with --merange 26 was better what comes to SSIM. I did those without changing any other parameters so the psy tunings were there.

[redbtn]

I also did tests. And with HME results are worse. Video 2000 frames, 3840x1600, HDR. Additional tests a bit later.

no-hme
encoded 2001 frames in 1364.38s (1.47 fps), 10941.58 kb/s, Avg QP:21.73, SSIM Mean Y: 0.9838777 (17.926 dB)

--hme --hme-search umh,umh,star
encoded 2001 frames in 1953.88s (1.02 fps), 10773.71 kb/s, Avg QP:21.80, SSIM Mean Y: 0.9837793 (17.899 dB)

no-hme
encoded 2001 frames in 1373.02s (1.46 fps), 10941.58 kb/s, Avg QP:21.73, Global PSNR: 48.476 (w/o --tune psnr Global PSNR: 48.511)

--hme --hme-search umh,umh,star
encoded 2001 frames in 1886.87s (1.06 fps), 10772.40 kb/s, Avg QP:21.80, Global PSNR: 48.449 (w/o --tune psnr Global PSNR: 48.481)

[benwaggoner]

Originally Posted by Boulder

Do you think that just setting --ssim would be enough or is tuning needed? I did two quick tests, and at 720p (downscaled from 1080p) --no-hme with --merange 58 was better and at 1080p --hme with --merange 26 was better what comes to SSIM. I did those without changing any other parameters so the psy tunings were there.

After some rumination, I'm not sure that HME doesn't have psychovisual impact after all. I think there could be cases where it could improve handling of random noise that would have gotten low-pass filtered at the lower resolutions, allowing the encoder to spend more bits on signal than noise.

PSNR would be terrible for measuring this. Not sure about SSIM. Looking at divergence between PSNR and SSIM, or PSNR and VMAF, perhaps could be helpful?

[Boulder]

Originally Posted by benwaggoner

After some rumination, I'm not sure that HME doesn't have psychovisual impact after all. I think there could be cases where it could improve handling of random noise that would have gotten low-pass filtered at the lower resolutions, allowing the encoder to spend more bits on signal than noise.

PSNR would be terrible for measuring this. Not sure about SSIM. Looking at divergence between PSNR and SSIM, or PSNR and VMAF, perhaps could be helpful?

At least it seems to cause changes in frametype decision. I didn't verify them to be exactly sure, but it looked like my frame-by-frame comparison had often P-frames compared against B and vice versa.

[crystalfunky]

Originally Posted by excellentswordfight

I think the reason why no one has responded here is because this is something that comes up alot, and there are plenty of threads here for you to look at to gather the information you are asking for. Apart from that, these forums arnt really that great for these types of generic questions, cause, the answer you will get it is: it depends... Which is also the correct answer.

What exactly is your question? What CRF value you should choose or if medium or slow is the best are stuff only you can answer, we dont know your compression ratio target or speed requirements. Just try different CRF-values until you find a compression ratio that you are comfortable with. It also very source dependent, very high quality 4k sources or grainy sources might break your bitrate budget when using say 18-19, and you might need to go towards CRF 20-22 (which has been the case for me when compressing stuff from DI-sources).

I find slow to be worth the speed trade off, its imo the the preset that offers the best compression without going in too deep in the diminishing return territory. But you need to decide (and probably test) if it worth the trade off for you.

x265 is already tuned for 4k by deafault, so it doesnt need much tweeking outside the presets. The only setting that has good generic properties outside that is imo no-sao (that setting alone or with deblock -1,-1 and no-strong-intra-smoothing could be looked at something as x264 tune film), but again, if you are compressing animation, you might not wanna use these settings anyway. So... It depends.


This is what I use as "base" settings for 2160p24 "film" material, I might then do some tweaking, but as most things, source dependant

--preset slow --profile main10 --level-idc 51 --crf 20 --keyint 240 --min-keyint 24 --rc-lookahead 48 --no-sao

Together with the relevant color information:

e.g.

SDR:

--colorprim bt709 --transfer bt709 --colormatrix bt709 --range limited

HDR10:

--hdr-opt --colorprim bt2020 --transfer smpte2084 --colormatrix bt2020nc --range limited --max-cll "1000,400" --master-display "G(13250,34500)B(7500,3000)R(34000,16000)WP(15635,16450)L(10000000,1)"

Would you mind giving me/us settings for 1) normal movies (I guess those you posted already) and 2) for anime movies like Finding nemo or Ghost in the shell?