[Libav-user] Filesize difference between using ffmpeg command line and C API

Alexandre Bizeau abizeau at 36pix.com
Wed Mar 31 19:37:35 EEST 2021

After much more investigation, and understanding of x264.

I saw in the log that using the ffmpeg command line the  AVG QP are I=16,39
/ P=19.63 / B=22.56.
Compared to using the ffmpeg API in my application the AVG QP are I=7.79
 / P=10.80 / B=13.56

Which leads to a great difference in bitrate and file size. But visually, I
can't spot the difference in both videos.

What is happening in ffmpeg.c (and below) that is not replicated by default
in other options?

While using mediainfo on both my resulting file, it seems that encoder
(x264) parameters are exactly the same. I really don't know what to do.
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