[FFmpeg-user] use q:v and maxrate

[YIRAN LI]

2016-04-07 11:43 GMT+10:00 Carl Eugen Hoyos <cehoyos at ag.or.at>:

> 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.
>
>
​Thanks Carl
​


> Carl Eugen
>
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