[FFmpeg-user] Smooth FPS change via ffmpeg

[Michael Koch]

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?

Well, the syntax gives no error message, the resulting video has a 
constant framerate of 20 and the speed changes from normal to slow 
motion. But the length is not as expected.

Michael