[FFmpeg-user] use q:v and maxrate

Carl Eugen Hoyos cehoyos at ag.or.at
Thu Apr 7 03:43:41 CEST 2016

YIRAN LI <mrfun.china <at> gmail.com> writes:

> ffmpeg.exe -i big_buck_bunny.mp4 -c:v mpeg4 -profile:v 15 
> -vtag DIVX -bufsize 3080000  -maxrate 8000000 -bt 8000000 
> -minrate 0 -an   a.avi

As said, this command is missing a video bitrate.

> ffmpeg.exe -i big_buck_bunny.mp4 -c:v mpeg4 -q:v 4 -profile:v 15 
> -vtag DIVX -bufsize 3080000  -maxrate 8000000 -bt 8000000 
> -minrate 0 -an   a.avi

The bitrate-related options make no sense when used with 
constant quality.

At some of point in time you have to decide:
* Either you encode with the default bitrate that FFmpeg 
uses (and that is extremely low) and get bad quality.
* Or you set constant quality which can have the effect 
of very high bitrate (that you cannot limit).
* Or you set a constant and an identical maximum bitrate 
to get high quality with an upper bitrate limit.

Please do not report that the default bitrate is low nor 
that constant quality may produce high bitrate: 
Both are not bugs.

Carl Eugen

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