[FFmpeg-user] Change fps from 50 to 25

[Cecil Westerhof]

Carl Eugen Hoyos <ceffmpeg at gmail.com> writes:

> Am Sa., 12. Nov. 2022 um 13:57 Uhr schrieb Cecil Westerhof via
> ffmpeg-user <ffmpeg-user at ffmpeg.org>:
>>
>> Michael Koch <astroelectronic at t-online.de> writes:
>>
>> > Am 12.11.2022 um 12:39 schrieb Cecil Westerhof via ffmpeg-user:
>> >> I have a few videos that have a 50 fps. But the computer I am playing
>> >> them on cannot handle that properly. Can I use ffmpeg to change the
>> >> fps to 25? While still having the same length.
>> >>
>> >
>> > sure, that's easy:
>> > ffmpeg -i in.mp4 -r 25 out.mp4
>>
>> That really is easy. :-D
>>
>> I should add a '-preset veryfast'. That makes it go about three times
>> as fast (on my system).
>>
>> But that still takes a lot of time. Maybe I ask something stupid, but
>> would it be possible to drop every other frame and copy the rest?
>
> Unfortunately not if your input is h264, that is technically not possible.

That will be the case with most of them. :'-(

But it is mostly a problem with videos I download from YouTube. To
circumvent this problem I can just use:
    bestvideo[fps<=30]

-- 
Cecil Westerhof
Senior Software Engineer
LinkedIn: http://www.linkedin.com/in/cecilwesterhof