Well u cannot make screencaps from packed files but u can eg. unpack them all and then as source use *.avi or path of folder with movies.
Avek Reviewed by Avek on . [How to] Create screencaps on linux We're going to use here mtn instead of mplayer which could not work on ur vps or server coz of something. What's the advantage of using it? No gui required, quite simple usage, very fast time of getting caps 0,5-5 seconds (on standard settings) So here we go: Rating: 5