New CPU - Intel or AMD?

[Nico8583]

Hi, happy new year all
I just have a question : I can read there is an impact on the final quality when the cores number grows up. Is it still happening ? I have a 3700X (8 cores) and I would like to know if I can go to a 3900X/3950X/5900X (12 to 16 cores) without losing quality vs my 3700X.
Thank you !

[Boulder]

I've never seen any difference whatsoever, jumped myself from 1800X to 3900X. Even setting -F 1 really did nothing visibly different compared to -F 4. The filesize differences are very small at the same CRF which tells me that the content cannot differ much either.

[Nico8583]

Thank you, so perhaps I'll replace my 3700X by 3900X

[benwaggoner]

Originally Posted by Nico8583

I just have a question : I can read there is an impact on the final quality when the cores number grows up. Is it still happening ? I have a 3700X (8 cores) and I would like to know if I can go to a 3900X/3950X/5900X (12 to 16 cores) without losing quality vs my 3700X.

The default values of --frame-threads and --lookahead-threads go up with the number of logical cores available. In the past there were significant quality regressions using higher numbers of frame-threads and a few seen with --lookahead threads. Thus, more cores COULD reduce quality, although the gap is much smaller than it used to be. But if those values were set explicitly, quality would be the same regardless of number of threads. Of course, lowering those values also decreases parallelization and thus the maximum number of additional cores that can be productively used.

When I'm doing mission-critical quality encodes at lower resolutions with lots of cores, I'll set -F 1 and use --pmode.

[blublub]

So basically just leave it at auto/default? - frame-thread I mean

[benwaggoner]

Originally Posted by blublub

So basically just leave it at auto/default? - frame-thread I mean

Sometimes I lower it to squeeze out maximum quality, but I almost never increase it.

[K.i.N.G]

Currently: AMD no doubt.

[benwaggoner]

Originally Posted by Boulder

I've never seen any difference whatsoever, jumped myself from 1800X to 3900X. Even setting -F 1 really did nothing visibly different compared to -F 4. The filesize differences are very small at the same CRF which tells me that the content cannot differ much either.

The issues with higher -F weren't really seen in ABR, since they only impacted some scene changes. To find those, I would do a --log-level 2 and look at QP spikes or SSIM drops for particular frames. Worse-cases were a lot worse with lots of frame threads.

That said, I've not really seen any reproducible issues with -F >2 for a couple of years, although I've not been testing it much either.

[Forteen88]

Originally Posted by Nico8583

Thank you, so perhaps I'll replace my 3700X by 3900X

Why not replace it with the new AMD Ryzen 5000-series? That is, if your motherboard supports that (after BIOS update).
Although if you find a used 3900X for a cheap price, it would be a good buy.

[Nico8583]

Originally Posted by Forteen88

Why not replace it with the new AMD Ryzen 5000-series? That is, if your motherboard supports that (after BIOS update).
Although if you find a used 3900X for a cheap price, it would be a good buy.

Yes, a 5800X or 5900X should be a great choice but at an expansive price now. My CM is a B450M Mortar Max, the november BIOS seems to add the 5000 series support.

[tormento]

In the urge of buying, if 5xxx would be available, I'd probably buy it.

If the choice is 3xxx perhaps much better a Intel CPU with AVX512 support.

[DJATOM]

Unfortunately avx512 is not a panacea.

[Nico8583]

I would like to find a real conditions comparison (same x265 version, same settings, 4K slow or slower if possible) between 3700X / 3900X / 5800X / 5900X. Do you know where can I find it ? I would like to know the gain on a whole movie encode (example : a 4K movie - duration 2 hours). Thank you.

[RanmaCanada]

Originally Posted by Nico8583

I would like to find a real conditions comparison (same x265 version, same settings, 4K slow or slower if possible) between 3700X / 3900X / 5800X / 5900X. Do you know where can I find it ? I would like to know the gain on a whole movie encode (example : a 4K movie - duration 2 hours). Thank you.

There was that great benchmark that Sagittaire had created which gave you real world results, it just has not been updated in 3 years.

Techpowerup does all their x265 benchmarking in their reviews at CRF20 preset slow. This is probably the best source, though it is only 1080p. Ideally if the real world x265 benchmark that Sagittaire created could be updated, we could poll the users here for more updated information.

In my opinion the benchmarks that use anything above medium do not represent real world usage. If someone could update the bench Sagittaire created, I am sure it would answer a lot of our questions.

[Nico8583]

Thank you for these informations. I'll look at Techpowerup x265 benchmarking in order to have an idea at 1080p.
And I'm agree with you about medium and above.

[Nico8583]

The video length is missing from Techpowerup bench or I don't see it ? Thank you.
Thank you w1zzard from Techpowerup, very responsive. Duration : 47 seconds

[Nico8583]

Video duration (CRF20, slow, 1080p) : 47s -> 2h
i9 9900K : 85.57s (0.55x) -> 3.6h
Ryzen 7 3700X : 77.08s (0.61x) -> 3.3h
Ryzen 9 3900X : 63.76s (0.74x) -> 2.7h
Ryzen 7 5800X : 63.32s (0.74x) -> 2.7h
Ryzen 9 5900X : 53.38s (0.88x) -> 2.3h

[quietvoid]

Keep in mind that x265 rarely saturates over 8 cores on its own, regardless of the settings or parallelism optimizations (such as --pme, --pmode, etc.)
With my 5900X, it barely uses over 60% of the CPU with preset slower.

[Nico8583]

Originally Posted by quietvoid

Keep in mind that x265 rarely saturates over 8 cores on its own, regardless of the settings or parallelism optimizations (such as --pme, --pmode, etc.)
With my 5900X, it barely uses over 60% of the CPU with preset slower.

Very interesting, it's a temporary limitation ?
So the gain between 3700X and 5900X will not be very very important ?

[quietvoid]

I doubt x265 will improve on this, so it's not temporary.
More cores is still better, you can see from your results that the 5900X is 45% faster, 15-20% might be the IPC improvement, the remaining 25% is probably the extra cores.

x265 just doesn't fully load the cores most of the time.
One way I've found that improves around 10% is to use a lower --merange and increase frame threads, but that doesn't improve the core saturation much.