[FFmpeg-user] use q:v and maxrate

[YIRAN LI]

2016-04-06 18:12 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.
>

​Hi Carl, my target is to archieve good quality while keeping bitrate under
a certain limit. I want to achieve best quality within this limit.
​That's why I didn't specify ​target bitrate.

For this purpose, what combinations of options should I use?

Thanks


> [...]
>
> > 1. for mpeg4 encoder, what qscale value is good enough
> > to keep same quality as input?
>
> Old MEncoder documentation recommends a value of 2 but I
> don't think this is what you want.
>
> > 2. if -q:v, -maxrate -bt are used together,  no matter
> > what qscale value specified, bitrate will be guaranteed
> > to be below maxrate?
>
> I don't think so: It would mean that qscale gets ignored.
>
> Please do not cross-post, it is considered rude
> everywhere.
>
> Carl Eugen
>
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