[blublub]

Hi

it has been posted a couple of times that HEVC doesn't fully utilize high core count CPUs in 1080p and even 2160p.

Today I did some testing and I was really surprised at the outcome:

x265 "defaults":
numa-pools=32
frame threads=6

CPU load: 60-75%
Encoding at FPS = 5,9


x265 settings I had used for the last months to improve quality:

numa-pools=32
frame threads=2

CPU load: 65%
Encoding at FPS = 6,2


Since the CPU load was far from utilized 100% I thought it is time to RTFM again. After reading it I set "numa pools = 1" since I have only a 1 Socket CPU.


x265 "numa 1":
numa-pools=1
frame threads=1

CPU load = 2-3%
Encoding at FPS = 0,3


x265 "numa 48":
numa-pools=48
frame threads=1

CPU load = 88%
Encoding at FPS = 7,3


x265 "numa 48 - II":
numa-pools=48
frame threads=2

CPU load = 100%
Encoding at FPS = 7,8


x265 "numa 48 - III":
numa-pools=48
frame threads=3

CPU load = 100%
Encoding at FPS = 8,2


So increasing numa-pools does help with CPU utilization and speed. With frame-thread=2 the load was 100%.
Increasing numa-pools over 48 did not increase CPU load or speed in FPS any further for me.

Also when using standard numa-pools of 32 increasing frame-threads over 1 only seems to speed up the encode until a value of 2 as it can be seen that the encode with frame-thread 6 is a tad slower than with 2.
But a frame-thread value of 2 or 3 can see a real benefit after increasing the number of numa-pool to 48 since FPS maximum was 8,2 with frame-threads=3 and numa-pools=48.
Further increasing frame-threads to 5 did not result in higher FPS.

So question is: Is there any disadvantage with using high numa-pools as there is quality degradation when using higher frame-threads?

cheers