[magick-users] convert video.wmv to jpg

[Verakso]

I am trying to find out, if there is a feature like when you convert PDF
files, that let you control the images returned from this command:

convert video.wmv stills.jpg

the video.wmv is 30 seconds, and I end up with stills-n.jpg where n is from
0 to 752

What am I missing? There must be a way to only return some of the stills,
bust as with PDF files the file.pdf[n] does not work on video.wmv[n]

/Verakso