[FFmpeg-user] Truncated file with ffmpeg but resulting output is x2 bigger!?

[Philip Rhoades]

People,

I truncated a 14s file with:

   ffmpeg -i 20201016_055828.mp4 -t 00:00:09 -async 1 cut.mp4

and although about 35% of the frames were removed, the resulting mp4 was 
double the size - why is this?  I did a before and after mediainfo 
comparison - see here:

   http://pricom.com.au/Diff.html

and the only things that jump out at me are:

   Format settings                          : CABAC / 4 Ref Frames
   Format settings, Reference frames        : 4 frame

ie changed from 1 to 4 . . but is that the explanation?

I am using:

   ffmpeg-4.2.4-1.fc31.x86_64

Thanks,

Phil.
-- 
Philip Rhoades

PO Box 896
Cowra  NSW  2794
Australia
E-mail:  phil at pricom.com.au