[FFmpeg-user] crf vs preset in x264 and x265

[Nicolas George]

Hi.

For a long time, I have been using x264, now I am trying to see if x265
is mature enough for my tastes and needs.

I always a crf setting and presets.

With x264, if I change the preset for a slower one while keeping the
crf, I get a smaller size, with the quality stays roughly the same. That
is good, that is exactly what I expect and want.

With x265, on the other hand, the tests I just ran show that a slower
preset gives a larger file and better quality. That means the crf is not
really constant across different presets.

Is there something I am missing?

For reference, the command line I am using for my tests is:

time ffmpeg -y -nostdin -i input.mkv -an -vf scale=1280:720 \
  -c:v libx265 -preset medium -crf 24 -f rawvideo x265_24_medium.bin

Regards,

-- 
  Nicolas George
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