x265 HEVC Encoder

[nevcairiel]

Originally Posted by Stephen R. Savage

To be fair, the AVX2 speedup is still larger than the frequency penalty, so it made sense.

It is now, because they reigned in AVX2 use in some irrelevant functions with minimal speedups to reduce the effect of downclocks. They even had a presentation about that "adventure" and their findings on some conference once

[RieGo]

no AVX512:
encoded 1780 frames in 169.38s (10.51 fps), 2541.97 kb/s, Avg QP:20.40
AVX512:
encoded 1780 frames in 161.94s (10.99 fps), 2541.97 kb/s, Avg QP:20.40

makes a ~5% speed increase
considering avx512 encode was almost 10°C cooler, so maybe i can get away with +100MHz. i like it

[Selur]

okay, so nice, but not worth buying a new cpu because of it.

[Xizer]

Is anyone else having problems with getting it to work on Skylake Xeons?

x265 crashes on my Xeon Platinum 8176 server when I start it with the --asm avx512 flag.

Error: fwrite() call failed when writing frame: 3, plane: 2, errno: 32
Output 80 frames in 13.46 fps (5.90 fps)

It'll work fine on the Xeon Platinum machine as soon as I remove the avx512 flag.

And it works on my i9 7940X with the avx512 flag.

[WhatZit]

Originally Posted by Selur

okay, so nice, but not worth buying a new cpu because of it.

Not until the i7-9700K shows up (November 2018?).

[Ma]

Originally Posted by Xizer

x265 crashes on my Xeon Platinum 8176 server when I start it with the --asm avx512 flag.

One bug that can lead to crash is fixed in version 2.7+338 so please do not use older versions. Which version do you use?

[RieGo]

i'm seeing very inconsistent results

CRF-20 preset-"medium"
--------------------
Run1:
encoded 1128 frames in 27.42s (41.14 fps), 3355.47 kb/s, Avg QP:20.21
Run2 (AVX512):
encoded 1128 frames in 30.23s (37.32 fps), 3355.47 kb/s, Avg QP:20.21
Run3:
encoded 1128 frames in 27.77s (40.62 fps), 3355.47 kb/s, Avg QP:20.21
Run4 (AVX512):
encoded 1128 frames in 27.04s (41.71 fps), 3355.47 kb/s, Avg QP:20.21

but temps are still very low on avx512. i didn't expect this. probably x265 just uses very little avx512 and that's why we don't see much improvement - if any - running on lowered frequency.
maybe we can run at default speed without getting too much heat/power, if we only use it on x265... i'll give it a try

btw: i agree that avx512 is not worth getting a new cpu

[LigH]

x265 2.7+340-aa9102400f24

remove unused asmname from x265_param; added a newline in the help
(fixed VMAF warning not applicable under Windows)

[Xizer]

Originally Posted by LigH

x265 2.7+340-aa9102400f24

remove unused asmname from x265_param (may fix some crashes on Xeons); added a newline in the help
(fixed VMAF warning not applicable under Windows)

2.7+340 is the version I'm using when it crashes.

[LigH]

Sorry to hear ... so the fix is not yet committed, only proposed?

[Ma]

Originally Posted by Xizer

2.7+340 is the version I'm using when it crashes.

Thanks for more info. It looks like more serious bug (x265 works for a while). The error message is probably from decoding app that writes graphics data via pipe to x265.

There are many possible reasons for the crash, one of them is the OS (and msvcrt.dll file in your OS). Could you test VS 2015 and VS 2017 x265 binaries? They are not based on msvcrt.dll.

[LigH]

I don't have such compilers installed; someone else may have to build them.

[foxyshadis]

x265-2.7+336-07defe235cde.7z VS 17 x64, crt is statically linked so no install needed. Debug pdbs included.

[Ma]

Bisection is one of the most common method of finding bugs.
In source file common/x86/asm-primitives.cpp it is function pointers assignment with avx512 code -- from line # 4696 to 5385.
We can turn off (comment) first half of this functions (x265-1.exe) and then second half (x265-2.exe).
You can download avx512-bisect1.7z VS 2015 binaries with diff files -- if x265.exe (from clean sources) hangs, please try x265-1.exe and then x265-2.exe -- it should be that one of them hangs and second not.
Please report back the results (which from the 3 binaries hangs and which not).

[Xizer]

Originally Posted by Ma

Bisection is one of the most common method of finding bugs.
In source file common/x86/asm-primitives.cpp it is function pointers assignment with avx512 code -- from line # 4696 to 5385.
We can turn off (comment) first half of this functions (x265-1.exe) and then second half (x265-2.exe).
You can download avx512-bisect1.7z VS 2015 binaries with diff files -- if x265.exe (from clean sources) hangs, please try x265-1.exe and then x265-2.exe -- it should be that one of them hangs and second not.
Please report back the results (which from the 3 binaries hangs and which not).

All three binaries crash with the avx512 flag I'm afraid.

Is there additional information that can be provided for debug?

[Ma]

Originally Posted by Xizer

All three binaries crash with the avx512 flag I'm afraid.

Is there additional information that can be provided for debug?

Thanks for the info.

Could you post results of the command
x265 -V && x265 --asm avx2 -V && x265 --asm avx512 -V
For example in my system it looks like

F:\x265p\ma\avx512>x265 -V && x265 --asm avx2 -V && x265 --asm avx512 -V
x265 [info]: HEVC encoder version 2.7+340-aa9102400f24
x265 [info]: build info [Windows][MSVC 1900][64 bit] 10bit
x265 [info]: using cpu capabilities: MMX2 SSE2Fast LZCNT SSSE3 SSE4.2 AVX FMA3 BMI2 AVX2
x265 [info]: HEVC encoder version 2.7+340-aa9102400f24
x265 [info]: build info [Windows][MSVC 1900][64 bit] 10bit
x265 [info]: using cpu capabilities: MMX2 SSE2Fast LZCNT SSSE3 SSE4.2 AVX FMA3 BMI2 AVX2
x265 [info]: HEVC encoder version 2.7+340-aa9102400f24
x265 [info]: build info [Windows][MSVC 1900][64 bit] 10bit
x265 [info]: using cpu capabilities: MMX2 SSE2Fast LZCNT SSSE3 SSE4.2 AVX FMA3 BMI2 AVX2 AVX512

This bug could be not related directly to avx512 code -- could you check if it hangs if you use '--asm avx2' instead of '--asm avx512' (it is important to use --asm avx2 option).
------------------------------------------------------
Your OS is Win 8.1 that do not support avx512. This bug in x265 is not technical but conceptual -- avx512 is not auto recognized by default so option '--asm avx512' should not turn on avx512 without any check.
You can test file avx512-patch.7z with x265 that check what is supported by CPU & OS up to avx512 if option '--asm avx512' is used.
On Win 8.1 it should work with '--asm avx512' exactly like without this option, on Win 10 it should turn on avx512 if you have CPU with avx512 and you use option '--asm avx512'.

[Bhavnahari]

Originally Posted by jlpsvk

any suggested quality wise settings recommendation for 4K HDR encoding? with CRF ie 17?

If the data that is being reused comes from encoding a downscaled video (scale-factor=2), it does not make a lot of sense to use intra/inter refinement levels 0/1 as levels 0 and 1 reuse most of the information from the previous pass with no or minimal re-evaluation of analysis information. This can have a huge impact on the quality of the encode.

We have observed that --refine-inter=3 and --refine-intra=4 gives the best quality, even better than standalone x265 encodes in some cases, with a performance gain of up to 1.8X.

For 4K HDR content, you will have to modify the display settings based on the monitor. Please refer the docs for more information - http://x265.readthedocs.io/en/defaul...mation-options

[jlpsvk]

Originally Posted by Bhavnahari

If the data that is being reused comes from encoding a downscaled video (scale-factor=2),
it does not make a lot of sense to use intra/inter refinement levels 0/1 as levels 0 and 1 reuse most of the information from
the previous pass with no or minimal re-evaluation of analysis information. This can have a huge impact on the quality of the encode.

We have observed that --refine-inter=3 and --refine-intra=4 gives the best quality, even better than standalone x265 encodes in some cases,
with a performance gain of up to 1.8X.

My settings then...

--crf 17 --profile main10 --level-idc 5.1 --output-depth 10 --ctu 32 --amp --vbv-bufsize 160000 --vbv-maxrate 160000 --me star
--max-merge 5 --rc-lookahead 40 --lookahead-slices 4 --gop-lookahead 34 --ref 5 --hdr --hdr-opt --repeat-headers --no-info --no-deblock
--no-sao --no-strong-intra-smoothing --high-tier --refine-inter 3 --refine-intra 4

Of course, display settings are entered too...

Warning:

x265 [warning]: Intra refinement requires analysis load, analysis-reuse-level 10, scale factor. Disabling intra refine.
x265 [warning]: Inter refinement requires analysis load, analysis-reuse-level 10, scale factor. Disabling inter refine.

Can it be used with CRF? Or? Some parameters missing?

[Loomes]

So far no success for me running the avx512 option on my 7820x on Windows 10 64it. I tried

ffmpeg -i source.mkv -f yuv4mpegpipe - | x265.exe --preset slow --asm avx512 --crf 21 --y4m - -o dest.h265

which crashes immediately. Using --asm avx2 works fine.

I ran

x265.exe -V && x265.exe --asm avx2 -V && x265.exe --asm avx512 -V

and it showed

x265 [info]: HEVC encoder version 2.7+340-aa9102400f24
x265 [info]: build info [Windows][MSVC 1900][64 bit] 10bit
x265 [info]: using cpu capabilities: MMX2 SSE2Fast LZCNT SSSE3 SSE4.2 AVX FMA3 BMI2 AVX2
x265 [info]: HEVC encoder version 2.7+340-aa9102400f24
x265 [info]: build info [Windows][MSVC 1900][64 bit] 10bit
x265 [info]: using cpu capabilities: MMX2 SSE2Fast LZCNT SSSE3 SSE4.2 AVX FMA3 BMI2 AVX2
x265 [info]: HEVC encoder version 2.7+340-aa9102400f24
x265 [info]: build info [Windows][MSVC 1900][64 bit] 10bit
x265 [info]: using cpu capabilities: MMX2 SSE2Fast LZCNT SSSE3 SSE4.2 AVX FMA3 BMI2 AVX2 AVX512

Originally Posted by Ma

You can test file avx512-patch.7z with x265 that check what is supported by CPU & OS up to avx512 if option '--asm avx512' is used.

I tried from that package x265.exe, x265-1.exe and x265-2.exe. All of them crashed immediately. I am using the latest nightly version of ffmpeg.
Am I missing something?

[Asmodian]

Originally Posted by Loomes

I tried from that package x265.exe, x265-1.exe and x265-2.exe. All of them crashed immediately. I am using the latest nightly version of ffmpeg.
Am I missing something?

I had crashes using the builds foxyshadis posted but I was successful using LigH's build from this post. Win10 and an i9-7900X. Have you tried them?