You don't need Video-SL (though you do need the demo version installed if you need to import new videos into your Scratch Live library). The Rane TTM 56 mixer cannot control the crossfader of MixEmergency, so you would need a MIDI controller to fade the videos (there are also other options, such as assigning a keyboard shortcut, or a special mode that allows you to use the vinyl to fade the video). The best thing to do is to download and try the demo version. The demo is the full version of MixEmergency, but is time-limited to 30 minutes of use each time you run it, and will display a demo overlay over the output screen.
