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Old 26th September 2018, 00:05   #6381  |  Link
benwaggoner
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Originally Posted by RainyDog View Post
Is someone able to explain what --hdr-opt does please?

I've started to try a couple of hdr encodes and have always used --cbqpoffs -2 and --crqpoffs -2 in my standard x265 settings. But wondered if setting --hdr-opt together with those might cause issues as they all seem to be chroma/luma QP optimizations...

Thanks.
Indeed, --hdr-opt does adjust QP in a way that probably will allow you to turn off or at least lower the c?cpoffs options. I've been surprised how much a little chroma offset can increase bitrate with HDR content, so using --hdr-opt instead improves overall quality/efficiency.
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Old 26th September 2018, 10:00   #6382  |  Link
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Originally Posted by tuanden0 View Post
Well, yes... That's why I asked what it actually does As that doesn't really explain.

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--hdr-opt, --no-hdr-opt

Add luma and chroma offsets for HDR/WCG content. Input video should be 10 bit 4:2:0. Applicable for HDR content. It is recommended that AQ-mode be enabled along with this feature. Default disabled.
By 'add' luma and chroma offsets, is it also tweaking cbqpoffs and crqpoffs and, if so, how?
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Old 26th September 2018, 10:11   #6383  |  Link
Magik Mark
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May I ask which among the switches will enable faster encoding in 2 pass (default medium) with minimal or no degradation in picture quality? So far I have identified the ff:

1. --no slow first pass
2. --multi-pass-opt-analysis
3. --multi-pass-opt-distortion

I might be missing couple more things?
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Old 26th September 2018, 15:13   #6384  |  Link
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There're two elephants in the room. Your frame-crushing machine or your expectation about the speed of x265 at medium preset or both of them.
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Old 26th September 2018, 16:36   #6385  |  Link
benwaggoner
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Originally Posted by RainyDog View Post
Well, yes... That's why I asked what it actually does As that doesn't really explain.







By 'add' luma and chroma offsets, is it also tweaking cbqpoffs and crqpoffs and, if so, how?

Yes, the -cp?offs ARE the chroma offsets.

I donít recall the exact math; it was based on an IEEE paper a couple years back. But it is adaptive based on luma, and so is going to be better than just fixed offsets.
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Old 26th September 2018, 16:44   #6386  |  Link
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Originally Posted by Magik Mark View Post
May I ask which among the switches will enable faster encoding in 2 pass (default medium) with minimal or no degradation in picture quality? So far I have identified the ff:

1. --no slow first pass
2. --multi-pass-opt-analysis
3. --multi-pass-opt-distortion

I might be missing couple more things?

Those are what I know about.

When using óno-slow-firstpass you probably want to make sure to set the number of ref and b-frames to match the second pass. The first pass is less useful as a reference without those, which will hurt quality a bit, and might slow encoding.

That said, the multi-pass options and no-slow-firstpass might be incompatible in practice, since x265 canít refine stuff that the first pass didnít do. Or at least, some parameter fine-tuning might be required to make sure the 1st pass is a good reference.
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Old 26th September 2018, 17:04   #6387  |  Link
NikosD
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Originally Posted by froggy1 View Post
I have 2 recent Smart TVs (Samsung and Panasonic) and 3 blu-ray players (2 from Samsung and 1 from LG). The Samsung BD players are UHD models

None of the devices above support 10-bit H.264 decoding
Sorry for the OT.

I just got my budget Chinese tablet with MediaTek MT6797 (Xelio X20) inside - a 2016 SoC

It supports in hardware MPEG2, VC-1/ WMV3, VP8, VP9 (8bit/10bit), H.264 (8bit/10bit), H.265 (8bit/10bit)

Also, my Sony is an ATV2 with MediaTek MT5891 SoC inside and supports H.264 10bit too.

End of OT.
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Old 26th September 2018, 18:06   #6388  |  Link
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Quote:
Originally Posted by Magik Mark View Post
May I ask which among the switches will enable faster encoding in 2 pass (default medium) with minimal or no degradation in picture quality? So far I have identified the ff:

1. --no slow first pass
2. --multi-pass-opt-analysis
3. --multi-pass-opt-distortion

I might be missing couple more things?
--no slow first pass, I think misses the point of 2 pass encoding. 2pass means to spend that much more time on encoding to get that much more quality or to hit that target size. Otherwise you would just stick to 1pass encoding for speed.

I would keep options 2 and 3, and add --no-strong-intra-smoothing --no-sao --multi-pass-opt-rps for some speedups as well.
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Old 26th September 2018, 18:47   #6389  |  Link
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Originally Posted by benwaggoner View Post
Yes, the -cp?offs ARE the chroma offsets.

I donít recall the exact math; it was based on an IEEE paper a couple years back. But it is adaptive based on luma, and so is going to be better than just fixed offsets.
Ok, thanks again benwaggoner.

I'll leave --c*qpoffs at default for HDR ecndoes then and set --hdr-opt instead.
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Old 27th September 2018, 16:35   #6390  |  Link
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x265 v2.8+74-fd517ae68f93 (32 & 64-bit 8/10/12bit Multilib Windows Binaries)

Code:
https://bitbucket.org/multicoreware/x265/commits/branch/default
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Old 27th September 2018, 19:14   #6391  |  Link
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Originally Posted by RainyDog View Post
Ok, thanks again benwaggoner.

I'll leave --c*qpoffs at default for HDR ecndoes then and set --hdr-opt instead.
And please report back your results!
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Old 6th October 2018, 13:50   #6392  |  Link
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Apart from the required bitrate to encode a frame, is the only real difference between --rd 4 and --rd 6 just the amount of effort required by the encoder? So I could switch to using --rd 4 if I'm ready to accept that it will probably produce a bigger file but take much less time? The presets don't seem to change the setting at all from the default 3, but 4 is the one where the other settings related to RDO kick in.
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Old 6th October 2018, 15:48   #6393  |  Link
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x265 v2.9+1-169e76b6bbcc (32 & 64-bit 8/10/12bit Multilib Windows Binaries)

Code:
https://bitbucket.org/multicoreware/x265/commits/all
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Old 6th October 2018, 16:53   #6394  |  Link
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What? v2.9? Without any announcement yet? Is the mailing list broken?
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Old 6th October 2018, 18:04   #6395  |  Link
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What? v2.9? Without any announcement yet? Is the mailing list broken?
v2.9 have been out since yesterday.
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Old 7th October 2018, 19:47   #6396  |  Link
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x265 2.9+1-169e76b6bbcc (MSYS2; MinGW32: GCC 7.3.0 / MinGW64: GCC 8.2.0)

surprise
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Old 8th October 2018, 17:17   #6397  |  Link
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Originally Posted by Boulder View Post
Apart from the required bitrate to encode a frame, is the only real difference between --rd 4 and --rd 6 just the amount of effort required by the encoder? So I could switch to using --rd 4 if I'm ready to accept that it will probably produce a bigger file but take much less time? The presets don't seem to change the setting at all from the default 3, but 4 is the one where the other settings related to RDO kick in.
That seems a reasonable premise to me, for CRF encoding where VBV limits arenít a quality constraint.

I donít know if itíd be THAT much less time, but itíll help.
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Old 10th October 2018, 15:12   #6398  |  Link
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Thanks for providing builds for v2.9, guys!

I just always wonder - how to tell which cpu capabilities a build is using (AVX? AVX2? None?).
As far as I can tell x265.exe -V is misleadingly saying "using CPU capabilities X Y Z" but in fact it is actually just listing MY CPU's capabilities.
Is that right?
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Old 10th October 2018, 15:22   #6399  |  Link
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Originally Posted by katzenjoghurt View Post
Thanks for providing builds for v2.9, guys!

I just always wonder - how to tell which CPU capabilities a build is using (AVX? AVX2? None?).
As far as I can tell x265.exe -V is misleadingly saying "using CPU capabilities X Y Z" but in fact it is actually just listing MY CPU's capabilities.
Is that right?
This page got links to different builds of x265, some explicitly supports AVX2,
Quote:
All binaries do the same, so it is only about encoding speed. My recommendations are: for AVX2-CPU the fastest should be VS 2017 AVX2 version, for AVX-CPU – VS 2017 AVX version, for SSE4-CPU – VS 2017 none or GCC none version, for SSSE3-CPU – GCC SSSE3 version, for CPU without even SSSE3 – GCC none version. You can determine fastest version by comparing encoding time on the same short sample.
http://www.msystem.waw.pl/x265/
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Old 10th October 2018, 15:25   #6400  |  Link
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Originally Posted by katzenjoghurt View Post
I just always wonder - how to tell which cpu capabilities a build is using (AVX? AVX2? None?).
As far as I can tell x265.exe -V is misleadingly saying "using CPU capabilities X Y Z" but in fact it is actually just listing MY CPU's capabilities.
Is that right?
x265 uses all those instruction sets by default using runtime selection. If you CPU support it, and x265 has code for it, it'll get used.

Some people try to get a tiny bit of extra performance by allowing the C/C++ compiler to use those instructions sets to optimize the code, however one should know that compilers are limited in what they can do, and the majority of the "hot" (ie. important) code is manually optimized and unaffected by the compilers choices.

In my experience, the differences between a generic build with just the ASM enabled that the x265 developers wrote, and a build that allows the compiler to additionally use AVX/AVX2 to optimize the remaining code is relatively small, probably low single digits percentages.
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