[FFmpeg-user] Confusion about quality parameters

[Carl Eugen Hoyos]

Am Di., 25. Juni 2019 um 20:32 Uhr schrieb Ulf Zibis <Ulf.Zibis at gmx.de>:
>
> Am 25.06.19 um 20:16 schrieb Carl Eugen Hoyos:
> > Am Di., 25. Juni 2019 um 20:11 Uhr schrieb Ulf Zibis <Ulf.Zibis at gmx.de>:
> >> Am 25.06.19 um 15:04 schrieb Carl Eugen Hoyos:
> >>> Am Di., 25. Juni 2019 um 14:15 Uhr schrieb Ulf Zibis <Ulf.Zibis at gmx.de>:
> >>>
> >>>> my input is a 1.5 minute mp4 video with 19.5 MB
> >>>>
> >>>> When I use (with build from dev):
> >>>>     ./ffmpeg in.mp4 -c:a copy out.mp4
> >>> You do not specify an encoder here, mp4 defaults to x264.
> >> If I understand Moritz and my output correct, it's quite contrary:
> >> the dev build defaults to mpeg4.
> > In this case (your forgot to provide the complete, uncut console
> > output, so I had to guess) you have to provide either a constant
> > quantiser or a bitrate for the command line to produce useful
> > output (assuming state-of-the-art input as opposed to very low-res
> > video).
>
> Do you want to say, that ffmpeg by default always markably decreases the
> bit rate and with that the quality, so a high res video is transcoded to
> a low res video and a low res to a very very low res one?

Definitely not.

The default bitrate may be too low for your requirements though.
(Please avoid sending a patch.)

> Btw, sorry that I assumed you know what I meant with "build from dev".
> But anyway I had post-posted the *complete* console output some minutes
> later,

Separating the command line from the console output is a safe
way to ensure its content is missed (qed).

Carl Eugen