MacCaption from CPC is pretty much the only app out there for creating and encoding captions in FCP. It’s not cheap either.
We have downloaded the trial version and it does work, it’s a little quirky to figure out, but we were able to create, encode, and output captions to BetaSP. And, eventhough the app is pretty quick to format once you have a caption file, actually transcribing the darn show is the real time-killer. Better have a fast-typing person available, or look into the various types of inexpensive voice-recognition software. Just repeat the program audio into a mic and it types into a text document automatically.
FYI-If you capture a tape that has captions on it, FCP will keep those intact, as long as you do nothing to the clip on the timeline, no renders, no nothing.
Also, getting line 21 captions in and out of FCP varies greatly depending on what vehicles you use for capture and output. (ie, a Sony DSR-45 DVCAM deck WILL NOT transfer captions through it’s DV, composite, S-Video, or component connections. Captions will only flow through the Monitor Output jack on a DSR-45. While the older DSR-30 WILL transfer captions through it’s component jacks.)
Otherwise, you’re stuck with hiring a provider.