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

Dave ffmpeg at dgmm.net
Wed Oct 25 23:09:47 EEST 2017

On Wednesday 25 October 2017 15:24:12 Carl Eugen Hoyos wrote:
> 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.

Thanks Carl.  There seems to be very sparse information around in
terms of comparison benchmarks and system recommendations but
what you say more or less keeps it simple.  I doubt I'll be forking out
for the latest bleeding edge CPU so it pretty much boils down to as
many cores and MHz as I can afford, carefully matched to a decent
motherboard and RAM with plenty of onboard data transfer bandwidth.

Should I  be wary of AMD though or do the more modern CPUs support
the same extensions as Intel, or at least are supported by the encoder
such that I'm not going to end up with a pig in a poke if I choose AMD?

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