Another test: this time I built ffmpeg myself according to
https://trac.ffmpeg.org/wiki/CompilationGuide/Ubuntu
And here's the benchmark -- Very bad scaling:
$ time ffmpeg -i a.mp4 -c:v libx264 -crf 23 -threads 1 -c:a libvorbis
b.mp4 -y
real 9m51.886s
$ time ffmpeg -i a.mp4 -c:v libx264 -crf 23 -threads 2 -c:a libvorbis
b.mp4 -y
real 5m14.630s
$ time ffmpeg -i a.mp4 -c:v libx264 -crf 23 -threads 3 -c:a libvorbis
b.mp4 -y
real 4m11.611s
(should be: 9m51.886s / 3 = 3,28m)
$ time ffmpeg -i a.mp4 -c:v libx264 -crf 23 -threads 4 -c:a libvorbis
b.mp4 -y
real 3m27.341s
(should be: 9m51.886s / 4 = 2,46m -- as slow as 3 threads)
Another test -- Even worse scaling:
$ time ffmpeg -i a.mp4 -c:v libx264 -crf 23 -preset ultrafast -threads 1
-c:a libvorbis b.mp4 -y
real 0m59.384s
$ time ffmpeg -i a.mp4 -c:v libx264 -crf 23 -preset ultrafast -threads 2
-c:a libvorbis b.mp4 -y
real 0m37.741s
$ time ffmpeg -i a.mp4 -c:v libx264 -crf 23 -preset ultrafast -threads 3
-c:a libvorbis b.mp4 -y
real 0m34.870s
$ time ffmpeg -i a.mp4 -c:v libx264 -crf 23 -preset ultrafast -threads 4
-c:a libvorbis b.mp4 -y
real 0m34.400s
If I'm not the only one having this issue, then the devs should fix this.
On 27.11.2015 17:04, D wrote:
Here's the normal: http://pastebin.com/wyt56q4B
And here's with debug: http://pastebin.com/WxfRDKPP
(Upgraded to Ubuntu 15.10 that's why you see "gcc 5.2.1")
It was a bit slower this time after OS Upgrade -- same command and
everything otherwise:
Ubuntu 15.04: 3m22
Ubuntu 15.10: 3m45
Anyway, this is not the priority right now.
On 27.11.2015 16:15, James Darnley wrote:
On 2015-11-27 13:29, D wrote:
Nevermind, libx264 isn't doing much better:
Have you posted the full output of ffmpeg somewhere in this thread?
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