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Old 11th January 2019, 23:20   #6622  |  Link
Ma
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Join Date: Feb 2015
Posts: 326
--ctu 64 vs. 32 && --merange 12 vs. 26 vs. 40 vs. 57 vs. 74 vs. 92

I've made a test with --merange 12/26/40/57/74/92 for --ctu 64 --qg-size 64 vs. --ctu 32 --qg-size 32

Command line:
for %m in (12 26 40 57 74 92) do (
x265 -p7 --bitrate 500 -f3333 --psnr --ssim --qg-size 64 --merange %m ../big_buck_bunny_1080p24.y4m w64-%m.hevc
x265 -p7 --bitrate 500 -f3333 --psnr --ssim --ctu 32 --merange %m ../big_buck_bunny_1080p24.y4m w32-%m.hevc
)

Results (in ctu block: speed (fps), PSNR, SSIM (dB)):
Code:
					ctu		
merange	|		64		|		32	
12	|	6.93	39.980	12.996	|	6.44	39.565	12.742
26	|	6.69	40.303	13.599	|	6.21	39.903	13.345
40	|	6.46	40.393	13.746	|	6.07	39.999	13.499
57	|	6.13	40.404	13.757	|	5.90	40.019	13.512
74	|	5.85	40.409	13.757	|	5.67	40.024	13.515
92	|	5.58	40.413	13.760	|	5.47	40.026	13.514
When --merange grows, the quality increases regardless of the size of --ctu (it may depend on the source movie).

For CPU with only 12 logical cores (6 physical) --ctu 64 is just better in preset slower for 1080p encoding.
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