x265 HEVC Encoder

[Stephen R. Savage]

Originally Posted by NikosD

But it does make sense in the context of real-world code optimization/execution.

Do you really hear from me for the first time that most non-SIMD code can't utilize a modern CPU in the way that SIMD code can ?

The only way to reach TDP limits of a modern CPU is from optimized SIMD code.

There are other limits to reach before power limits for non-AVX code.

Non-AVX code can and does reach power limits. SKX 28-core can easily reach 165 W in p95 non-AVX. RyZen 2000 hits around 150 W in p95 non-AVX with power limits disabled (which implies throttling with 95 W power limit enforced).

[NikosD]

Originally Posted by Stephen R. Savage

Non-AVX code can and does reach power limits. SKX 28-core can easily reach 165 W in p95 non-AVX. RyZen 2000 hits around 150 W in p95 non-AVX with power limits disabled (which implies throttling with 95 W power limit enforced).

Anyway, SIMD code existed before AVX2, like MMX, SSE, SSE2, SSE3, SSSE3, SEE4.x etc.

For all those SIMD instruction sets, we never had lower clocks not even for AVX1.

AVX2 is even denser than all of those sets, but that doesn't mean that there is no architecture with no performance hit.

Zen 2 could be the first one.

[katzenjoghurt]

Oh my.
Am I the only one having such a hard time encoding scenes with red light / red backgrounds?

E.g. if a character turns on a red light, his face would turn suddenly totally blocky.
Blue light is fine, green light also seems to be a bit bad, but red light is the devil.
Looks like x265 (also x264 I think) detects the scene as super-dark and reduces
the bitrate like crazy.

I doubt that it's just a display thing as I can see the problem on my Dell display,
my Benq display and my Samsung TV.

By now I fix it by scanning every source for red scenes before encoding and setting
zones like crazy via --zones startframe,endframe,b=1.5/startframe,endfr....
Super-tedious.

I was shocked again today after I checked my encoding of Disney's Aladdin...
Red sand with black dots -> blurred to unshaded flat areas.
Red stone wall backgrounds -> bluuuurr.

Looks like I need to double or triple the bitrate manually in these scenes just to keep
the subjectively visible detail level compared to the non-reddish scenes.

AQ3 won't help all too much either. The overall bitrate would get just too high if
I want to retain the details that way. *sigh*

[benwaggoner]

Originally Posted by katzenjoghurt

AQ3 won't help all too much either. The overall bitrate would get just too high if
I want to retain the details that way. *sigh*

Raise CFR with aq-mode 3. The question is what looks best at a given bitrate.

I wish x265 gave us a way to change the SAO parameters, so we could adjust how the smoothing works in different luma ranges.

[benwaggoner]

Originally Posted by Stephen R. Savage

That is why I said that hopefully the next version will have better power management to enable higher AVX and AVX-512 frequency in low intensity workloads.

And we saw thermal throttling for AVX2 get a lot better between Haswell and Skylake SP, so there is precedent for exactly that.

I suspect a truly optimized x265 would actually have different ASM depending on processor generation due to this kind of stuff.

[katzenjoghurt]

Originally Posted by benwaggoner

Raise CFR with aq-mode 3. The question is what looks best at a given bitrate.

I wish x265 gave us a way to change the SAO parameters, so we could adjust how the smoothing works in different luma ranges.

AQ3 isn't the solution for me...
I tried again yesterday... the file size doubled and still I didn't really
reach the quality I could achieve by defining zones manually.

SAO might add to it... but the issue is also there with SAO disabled.


In fact two of my past problems eventually seemed to come just from
the lighting / red area issue.

I wondered why Star Wars III gave me so much more trouble encoding than other Star Wars movies -> Answer: As Anakin turns evil here, the movie got a more reddish color coding.
https://forum.doom9.org/showpost.php...postcount=6353

Here the problem was in fact the character's dark red hair:
https://forum.doom9.org/showpost.php...6&postcount=11


With Aladdin I have the same issue now... it's dark red all over the place and super-hard to encode due to that.
It's even a problem in bright scenes.
Everything is crisp... and than there is this character wearing a dark red Fez. And the Fez is blocky and blurry.

[fauxreaper]

Originally Posted by katzenjoghurt

Oh my.
Am I the only one having such a hard time encoding scenes with red light / red backgrounds?

Use --cbqpoffs and --crqpoffs with negative values.

[katzenjoghurt]

Woah! These parameters sound interesting! I need to get home and try them out!
Thank you, fauxreaper!

[benwaggoner]

Originally Posted by katzenjoghurt

AQ3 isn't the solution for me...
I tried again yesterday... the file size doubled and still I didn't really
reach the quality I could achieve by defining zones manually.

You need to compare at the same bitrate. So try 2-pass VBR or a higher CRF. SDR content can often get away with a higher CRF with aq-mode 3.

Trying the chroma offsets is also a great idea, at least for those scenes. So glad to have —zones!

[katzenjoghurt]

I'm giving up... crqpoffs and its brother also didn't work wonders. The bitrate went up... but even at the maximum of -12 it still didn't reach a detail retention level I liked.

And aq-mode 3 didn't work out for me as well... I went as far as setting aq-strength from 1 to 5, ultimately with a crf of 33 (~6000kbps) but... no.


If someone is out for a challenge... grab Aladdin and try to bring it down to a 5000kbps encoding without totally smeared red backgrounds.
You'll start to hate the ladies at the window at 0:07:19 - 00:07:24.

Personally I'll go on with zones... It'll take hours but it will work in the end.

[Stereodude]

Originally Posted by katzenjoghurt

I'm giving up... crqpoffs and its brother also didn't work wonders. The bitrate went up... but even at the maximum of -12 it still didn't reach a detail retention level I liked.

And aq-mode 3 didn't work out for me as well... I went as far as setting aq-strength from 1 to 5, ultimately with a crf of 33 (~6000kbps) but... no.


If someone is out for a challenge... grab Aladdin and try to bring it down to a 5000kbps encoding without totally smeared red backgrounds.
You'll start to hate the ladies at the window at 0:07:19 - 00:07:24.

Personally I'll go on with zones... It'll take hours but it will work in the end.

What speed preset are you using? Ultrafast?

[katzenjoghurt]

Medium

[benwaggoner]

Originally Posted by katzenjoghurt

Medium

Ah. I suggest slower as the fastest preset that really starts exercising HEVC’s more unique features. I might throw in --tskip to see if that might help this weird case. It can sometimes help with sharp and weird edges.

Also, if you have a target file size and are comparing different encoder settings, you really should be using 2-pass VBR. It’s really hard to compare features when both output AND file size is changing.

Lastly, Are we sure that negative values reduce chroma QP? I had it in my head it was the other way around. But I rarely use that feature.

[katzenjoghurt]

http://forum.doom9.net/showpost.php?...postcount=2269

[benwaggoner]

Originally Posted by katzenjoghurt

http://forum.doom9.net/showpost.php?...postcount=2269

Thanks! Yes, negative numbers reduce chroma QP and thus enhance chroma quality.

[jlpsvk]

Ok... give up on Dolby Vision encoding now. Question is. How to encode my first HDR10+ bluray with x265 to preserve HDR10+? Can HDR10+ be played from MKV? Or must be m2ts?

[Selur]

@jlpsvk: What do you use for playback on a pc? (For reencoding HDR-10+ data: 1. extract meta data using hdr10plus_parser 2. reencode with x265 while specifying the extracted data 3. multiplex to the container of your choice)

[jlpsvk]

Originally Posted by Selur

@jlpsvk: What do you use for playback on a pc? (For reencoding HDR-10+ data: 1. extract meta data using hdr10plus_parser 2. reencode with x265 while specifying the extracted data 3. multiplex to the container of your choice)

Thanks for that. I am playing on OPPO, not PC.

[SeeMoreDigital]

Originally Posted by jlpsvk

Thanks for that. I am playing on OPPO, not PC.

Do you have an HDR10+ compatible TV too?

[jlpsvk]

Originally Posted by SeeMoreDigital

Do you have an HDR10+ compatible TV too?

yes i have. Samsung UE65NU7442

Should I use --dhdr10-opt too??? can i crop?