Grab image from END of either swf file or mp4 file

I have 711 files that we have in either swf or as mp4's and we need a jpg for each of them - but it has to be at the end of the file - not the beginning. The files are mostly about 10 - 20 seconds long. We have a screen image system - but it takes a long time to do this - if someone is willing to do this for cheap - we are willing to spend some money to not have to do this ourselves - but can't spend much. We would need this completed in 2 days at the most.