[FFmpeg-user] libx264 very bad scaling with 4 real CPU cores (no HT)

Lou lou at lrcd.com
Tue Dec 1 19:29:30 CET 2015

On Tue, 1 Dec 2015 19:17:14 +0100
D <dcmhoybdpzkh at web.de> wrote:

> 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

This means little without the complete console output. For example, how
do you know you didn't compile with --disable-yasm?

Why are you encoding audio if you want to benchmark video?

You don't need to output an actual file if you want to benchmark

  $ time ffmpeg -i input -c:v libx264 -f null -

What kind of performance does the default threads setting give? You can
just omit -threads and the default will be used.

In the console output when using the defaults, what value appears for
"threads=" in the x264 info? (You may have to output to a file instead
of null for it to appear).

Now for the important question: did you also test the x264 cli tool?
Of course you will need to use the same input for both ffmpeg and x264.

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