ffmpeg alternative to setpts for making a survey gif
Assuming you want a 30 fps 2.5m GIF, use

ffmpeg -i source.mp4 -vf "select='not(mod(n,trunc(234/2.5)))',palettegen" palette.png


and

ffmpeg -i source.mp4 -i palette.png -filter_complex "[0]select='not(mod(n,trunc(234/2.5)))',setpts=N/30/TB[v];[v][1]paletteuse" survey.gif