[FFmpeg-user] specifing frames in a specific second

[Günter Bachelier]

Hello,

I want so save specific frames from every video second (or from
specific seconds) to jpg. For example frame 5, 10, 15 and 20 (from 25)
in movie second 00:00:10

A line like
ffmpeg -i movie.mp4 -r 1 -f image2 -qscale 1 -vcodec mjpeg image-%03d.jpg
get one frame per second but which one out of the 25 (probably the first).
How can I specify frames in a specific second?

Thank you

best regards
Guenter