Yea, as Ralph says… welcome to the COW. Moooo… 😉
[Dom Armano] “a) capturing a live audio/video feed from a live Video DJ performance”
You can do this with Vegas. The video capture is done via firewire and Vegas doesn’t care if you are playing a tape or using a live camera, it will capture whatever you feed it.
[Dom Armano] “b) beat-synching videos with shifts in beat (sort of like Acid for video)”
Vegas can do this too. Every project has a tempo associated with it. You can change the tempo to match the song. You can also turn on an option that tells Vegas to import audio media at the project tempo. This allows you to drop ACID loops and other media with tempo data onto the timeline and Vegas will match their tempos just like ACID does. If you need to change the tempo, change it in the project first, then everything imported after that will use the new tempo but existing audio will be unaffected.
I believe you can do everything you want right in Vegas.
~jr
http://www.johnrofrano.com
http://www.vasst.com