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19th September 2022, 09:17 | #1 | Link |
Acid fr0g
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x265 low CPU when preset medium
I have tried to encode a bunch of files with x265 on preset medium.
It can't occupy 100% CPU, while on preset slow it goes full throttle. It isn't a decoding issue, as I am using DGDecNV (and I tried sw decoding too), it isn't a slow script issue as I tried both AVS+ with and without Prefetch (and tried VS too). Any idea about how to increase CPU usage? I have tried to increase pools too but no way.
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19th September 2022, 09:20 | #2 | Link |
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--ctu 32
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19th September 2022, 10:01 | #3 | Link |
Acid fr0g
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Maximum CU size (width and height). The larger the maximum CU size, the more efficiently x265 can encode flat areas of the picture, giving large reductions in bitrate. However this comes at a loss of parallelism with fewer rows of CUs that can be encoded in parallel, and less frame parallelism as well. Because of this the faster presets use a CU size of 32. Default: 64
How much is the bitrate impact when lowering it? I forgot to say that I have a 4 core / 8 threads CPU, not so many to have parallelism problems, perhaps.
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@turment on Telegram Last edited by tormento; 19th September 2022 at 10:20. |
19th September 2022, 10:23 | #4 | Link |
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What is resolution of your video file? What is average CPU usage during encoding?
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19th September 2022, 12:28 | #6 | Link | |
Acid fr0g
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Quote:
49-81% on medium burning sun on slow
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@turment on Telegram Last edited by tormento; 19th September 2022 at 12:44. |
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19th September 2022, 12:45 | #8 | Link |
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With 80% you already use more than 90% percent of your cpu computation power. 50% is about 80%. SMT in video encoding does not give more than 20%.
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20th September 2022, 16:27 | #14 | Link | |
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Quote:
That said, there could still be some other potential bottleneck in source read, demux, decode, preprocessing, encoding, and writing out the file. And those can be limited by i/o as easily as by compute. All it takes is some slower single-threaded process somewhere in the signal chain to slow everything down. A good way to test that is to use increasingly higher --presets. If slow and slower have ballpark the same encoding time but slower has higher CPU usage, that suggests some non-x265 bottleneck. |
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20th September 2022, 16:30 | #15 | Link | |
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Quote:
I forgot to say that I have a 4 core / 8 threads CPU, not so many to have parallelism problems, perhaps.[/QUOTE] Oh! Yeah, even 480p should be able to saturate that. |
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