[FFmpeg-user] Smooth FPS change via ffmpeg

[Carl Eugen Hoyos]

Am Mo., 23. Sept. 2019 um 23:19 Uhr schrieb Michael Koch
<astroelectronic at t-online.de>:
>
> Am 23.09.2019 um 23:07 schrieb Carl Eugen Hoyos:
> > Am Mo., 23. Sept. 2019 um 23:04 Uhr schrieb Michael Koch
> > <astroelectronic at t-online.de>:
> >
> >> ffmpeg -f lavfi -i testsrc2=size=vga:duration=10:rate=20 -lavfi
> >> "setpts='(20-sqrt(400-2*N))/TB' " -y out.mp4
> > (Does this syntax really work?)
> >
> > As said before, our mp4 muxer does not (correctly) support
> > constant frame rate.
>
> you mean it doesn't support variable framerate, right?

Correct.

> Well, the syntax gives no error message,

True.

> the resulting video has a constant framerate of 20

This is enforced for the mp4 muxer.

> and the speed changes from normal to slow
> motion. But the length is not as expected.

Carl Eugen