I am going to finish such a project soon myself, including some old Video8 tapes! Sounds like you're on macOS, Any reason you didn't use iMovie for the capture itself?

The Video8 tapes have already been digitalized via a Digital8 camcorder, but apparently you can get even better quality out of old analog tapes with the vhsdecode project. Let's see if I ever get around to that, but at least it bypass Firewire entirely: https://github.com/oyvindln/vhs-decode https://www.reddit.com/r/vhsdecode/

Mostly wanted to fully automate the pipeline (auto-rewind tape, scan tape head position, etc) and iMovie is just using the same AVFoundation APIs under the scene that you can call manually. Took some notes here if helpful: https://pierce.dev/notes/automating-our-home-video-imports

Wish vhsdecode was easier to use in practice! Such a cool idea but a bit too inconvenient to hack your own hardware like this...