title: ffmpeg in opencv 2.4
body: <p>I am using opencv, but it is very pick with video types that it will open. I have version 2.4 of opencv and it apparently has ffmpeg support built in, though it does not open any movie files correctly, obj.grab() returns false and retrieve(frame,0) return NULL. So it seems to me that FFmpeg is not working correctly, is there something I need to do to turn it on, from internet searches people seem to suggest that from 2.4 onward it is a non-issue(though apparently not). Any help, all the other threads seem to just aout stop short of the answer for me. </p>
  
  <p>(windows 7, Visual studio 2010, opencv 2.4) </p>