A bit late to the forum, but let me add that once upon a time I got ffmpeg working with one of the experimental builds from http://vicebuilds.bplaced.net/ .. But it still seems luck of the draw, or I'm just stupid.
At the moment I got SDLvice with 3th party capture software. It works faster than winvice, but the frame rates still drop way too much. Still looking for a better solution. looking into external stream capture devices that allow connecting all kinds of retro to hdmi. Would be awesome to dust off all the old Atari, C64 and Nintendo