[FFmpeg-user] libx265 a lot slower

Moritz Barsnick barsnick at gmx.net
Wed Aug 19 16:06:20 EEST 2020

On Mon, Aug 17, 2020 at 22:53:12 +0200, Cecil Westerhof wrote:
> Maybe I am just dumb and I use the wrong questions, but when I
> searched I got a lot of hits that explained I needed tot switch
> because the space needed would be halved

Well, if you're driving a compact, and someone writes "you need to
switch to a Jeep, because it can pull your trailer out of the mud", do
you buy a Jeep? ;-)

I'm trying to say: Try to understand the benefits and the
disadvantages, and check against your requirements.

Do you need less space? Are you willing to sacrifice encoding speed? Is
H.265 the right codec for your type of videos? As Mick Finn pointed
out, H.265 is more designed for higher resolutions and bit depths
(IIUC). Can your target players even decode H.265? (Does the Jeep even
fit into your parking spaces? Do your feet reach the pedals?)

There's no matter of "must", "need to" - just of considerations. I
believe whatever you read, implied some other details, or forgot to
tell about them.

BTW, if someone does magic hacking, or even more optimized GPUs emerge,
x265/H.265 *may* become "faster" than x264/H.264. It isn't right now.

> (what is not true, I did see 'only' a 2/3)

It depends on the material. I'm sure there are tons of comparisons out

> and a few explained that you could not use h265
> everywhere, so you should evaluate if it was a good idea to switch.

Absolutely! Even if I could encode my material to H.265, I probably
wouldn't, except when targetting a very specific player (modern smart
phones?). My PVR/STB, my TV, ..., cannot decode it. Possibly even my PC
doesn't have enough compute/GPU power to decode it in full HD.

> In none of the hits I saw anything about a performance hit. Especially
> not a hit up to a factor three.

They should. ;)


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