[Libav-user] Faster X265 encoding, buying new hardware, advice please?

Carl Eugen Hoyos ceffmpeg at gmail.com
Wed Oct 25 16:24:12 EEST 2017

2017-10-25 12:54 GMT+02:00 Dave <ffmpeg at dgmm.net>:
> Further to my previous email regarding slow x265 encoding on an
> older but fast an AMD Phenom II X6 CPU compared to a slower but
> newer Intel Core I5, is there anything I need to watch out for when
> buying a new CPU?  Are all modern CPUs "equal" in the eyes of
> libx265 or is there anything I need to avoid?.

libx265 is starting to add AVX512 optimizations, few current
cpus support it: Xeon Platinum, Xeon Gold (two units),
Xeon Silver, Xeon Bronze, i7-78xx and i7-79xx (one unit).

> Do I just need to look for number of cores and clock speed up to
> my spending limit or do should I be looking for specific features
> to optimise x265 encoding?

Contrary to decoding, multiple cores should scale nearly linearly
for encoding, so it helps to have a multi-core cpu.
(Single-core decoding can of course be slower then multi-core
decoding but it is more economical, ie it takes less cpu cycles
to decode the same amount of frames.)

> Are there GPU optimisations to take into account?  It will be
> running FreeBSD so CUDA is not really an option (if that's
> even relevant here)  If it's significantly worthwhile I could
> install a non-GUI Linux and get CUDA libs installed.

libx265 is a software encoder, hardware encoder (with
completely different speed properties) exist.

Carl Eugen

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