High core counts and video quality

General questions or discussion about HandBrake, Video and/or audio transcoding, trends etc.
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YaBoyShredderson
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High core counts and video quality

Post by YaBoyShredderson »

Im planning on upgrading my cpu when zen 3 ryzen 4000 is released soon. I am considering either the 12 core zen 3 part or the 3900x, depending on how much the zen 2 price drops, and what the difference in performance is like. May even consider the 3950x if the price drops significantly.

I heard that as thread count increases, the worse video quality gets, but that it only matters when you have fewer than 40 vertical pixels per thread, so for 1080p, thats 27 threads. So do i need to be concerned about this? I mainly use x264, but the only real reason i dont use x265 is because of how long it takes, so if i get a faster cpu i may switch.

I can always run 2 instances, and split the cpu in half anyway, but maybe i should just grab the 4700x or whatever its called, the 8 core part, and pocket the change, though im perfectly willing to pay the extra for more cores if i will see a tangible benefit.

Thoughts?
Woodstock
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Re: High core counts and video quality

Post by Woodstock »

The encoders pretty much spread their load as needed, and not use more cores than are "best". An x265 encode of a source greater than 1080p, will typically not exceed 12 cores. x264 generally tops out around 8-10 cores.

If you can afford more cores, then that means you can run multiple encodes at the same time. Don't let tales of "it gets worse from here" deter you, because they're not really a factor unless you force bad choices on the encoders.
YaBoyShredderson
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Re: High core counts and video quality

Post by YaBoyShredderson »

Woodstock wrote: Sat Jul 04, 2020 6:42 pm The encoders pretty much spread their load as needed, and not use more cores than are "best". An x265 encode of a source greater than 1080p, will typically not exceed 12 cores. x264 generally tops out around 8-10 cores.

If you can afford more cores, then that means you can run multiple encodes at the same time. Don't let tales of "it gets worse from here" deter you, because they're not really a factor unless you force bad choices on the encoders.
Cool, more cores it is then. Even if it wouldnt benefit me in this work load, at least i could game at the same time.
musicvid
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Re: High core counts and video quality

Post by musicvid »

I heard that as thread count increases, the worse video quality gets,
Do you have a link to share?
I mainly use x264,
Which I believe is optimal around 6-8 logical processors.
rollin_eng
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Re: High core counts and video quality

Post by rollin_eng »

Basically just get as much as you can afford. You will probably end up using it in the future one way or another.
YaBoyShredderson
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Re: High core counts and video quality

Post by YaBoyShredderson »

I mainly use x264,
Which I believe is optimal around 6-8 logical processors.
[/quote]

Would turning off hyperthreading be beneficial then? If its 6-8 threads, each running on there own core, that would he better than each running off half a core right?
rollin_eng
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Re: High core counts and video quality

Post by rollin_eng »

It should, 8 physical cores is better than 8 logical ones.

Also if you are running Windows that will suck up some CPU doing the random things it does. Then your web browser will take a bit too etc. etc.

That's why I recommend getting what you can afford because eventually it will get used.
rollin_eng
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Re: High core counts and video quality

Post by rollin_eng »

musicvid wrote: Sat Jul 04, 2020 7:12 pm
I heard that as thread count increases, the worse video quality gets,
Do you have a link to share?

viewtopic.php?p=182129#p182129
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BradleyS
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Re: High core counts and video quality

Post by BradleyS »

That's not really how hyperthreading works. 8c/16t isn't processes running on half cores compared to 8c/8t. Even so, x264 uses an appropriate number of threads. 1.4x logical cores IIRC.
rollin_eng
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Re: High core counts and video quality

Post by rollin_eng »

BradleyS wrote: Sun Jul 05, 2020 10:59 pm That's not really how hyperthreading works. 8c/16t isn't processes running on half cores compared to 8c/8t. Even so, x264 uses an appropriate number of threads. 1.4x logical cores IIRC.
Yeah, but if your encode is only using 8 threads its better to have those 8 threads running on physical cores rather than logical ones.
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BradleyS
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Re: High core counts and video quality

Post by BradleyS »

If it's the only thing taxing the CPU and there are at least 8 physical cores, then no, it is not a detriment to an 8 thread workload whether the CPU is exposing 8 or 16 logical cores.
Navvie
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Re: High core counts and video quality

Post by Navvie »

While X264 and X265 might not make use more than 8/12-ish cores, more cores are certainly useful for NLMeans denoising.
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