[FFmpeg-user] timelapse framerates

[Michael Koch]

Hi all,

I have a few questions about making timelapse videos from many pictures. 
The following command makes a video with framerate 25 and works as expected:
ffmpeg -framerate 25 -start_number 123 -i IMG_%4d.jpg -codec:v mpeg4 
output.mp4

My questions:
1. Is it possible to make a video with different input and output 
framerates? For example, using each input picture twice? I mean without 
duplicating and renaming the the input pictures.
2. Is that also possible for arbitrary input and output framerates? 
(i.e. output framerate is not an even multiple of input framerate) ?
3. Is it also possible to make the output framerate bigger than the 
input framerate, which means some of the input pictures are skipped?

Thanks,
Michael