[FFmpeg-user] use q:v and maxrate

[YIRAN LI]

2016-04-07 10:56 GMT+10:00 Carl Eugen Hoyos <cehoyos at ag.or.at>:

> YIRAN LI <mrfun.china <at> gmail.com> writes:
>
> > > > ffmpeg.exe -i a.mp4 -c:v mpeg4  -profile:v 15 -vtag DIVX
> > > > -bufsize 3080000 -maxrate 8000000 -bt 8000000 -an a.avi
> > > > (so that maxbitrate will be 8000kbps)
> > >
> > > You forgot to set the video bitrate.
> >
> > my target is to archieve good quality while keeping bitrate
> > under a certain limit. I want to achieve best quality within
> > this limit.
>
> > For this purpose, what combinations of options should I use?
>
> Set both video bitrate and maximum bitrate (or maximum and
> minimum bitrate).
>

​Hi Carl,

I'm using this in a program so input video can have any bitrate, unless I
have an algorithm to estimate
best target bitrate, I can't set a target bi​trate that works good for all
possible source videos. (if target bitrate is much higher than input, there
must be some waste I think)


​For example:​

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
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

First command generates a 262kbps one and second generates a better one
with 1380kbps.



> Carl Eugen
>
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