Converting DVD to still images
ffmpeg -r 0.25 -i video.mpg -f image2 %05d.png


ffmpeg invoke the program

-r 0.25  force the frame rate of

-i video.mpg  your input file

-f image2 %05d.png  force the format of  the output file

From the ffmpeg site:


  FFmpeg is the leading multimedia framework, able to decode, encode,
  transcode, mux, demux, stream, filter and play pretty much anything
  that humans and machines have created. It supports the most obscure
  ancient formats up to the cutting edge. No matter if they were
  designed by some standards committee, the community or a corporation.
  It contains libavcodec, libavutil, libavformat, libavdevice,
  libswscale and libswresample which can be used by applications. As
  well as ffmpeg, ffserver, ffplay and ffprobe which can be used by end
  users for transcoding, streaming and playing