Hey soft,
best thing is use the alesis HD24. If your video source has LTC out, just leave 1 track for LTC on the alesis.
If not, try to get a deck to record the video simultanesouly during performance. Something like BetaCAM or Mini DV (using a Professional / semi pro deck). Use a MOTU MIDI time piece to sync them up. You can do this by converting the Alesis MTC to LTC to feed the deck. This way, you will have the video deck time TC chasing your Alesis TC. In post should be a lot easier.
Just make sure your Alesis is the master as it only has MTC out and nothing in.
Hope this helps
Regards
Robin