Our little company does quick turnarounds of shows for broadcast and currently handle our CC needs via live captioning. We end with a DVCAM master with the line 21 info encoded on it, dupe to BetaSp for shipping out, and away it goes. Several years now and it's a workflow that works for us.
Our next goal is going to be to take that master tape and "preserve" the CC info all the way through DVD. It is my understanding that things are not going to work out like I had hoped (read - easy).
We have both AVID and FCP and will most likely be doing our DVD products in DVDSP. Using either the Mojo or Multibridge we have no problems capturing 720x486 and creating QT's with the CC info.
From there - does anyone have experience creating .SCC files from already existing line 21 info? Most of what I have dug up is regarding going the other way. Does CPC or anyone else make a product that can "extract" the info (for lack of a better term). Can it be done in house (see same day turnarounds) or must we send away to have done?
Alternately - Does anyone have experience creating DVD's using a set-top type burner from a DVCAM (or similar) master and having the CC info still present on the final product?
As you correctly deduced, when a 720x486 video file is compressed to MPEG-2 for DVD (720x480), the captions will not be preserved unless special steps are taken.
Fortunately, CPC software can extract the line 21 captions from a 720x486 movie file and then export a .SCC file for DVD. MacCaption even supports batch conversion and scripting for high volume workflows, so it is definitely possible for same day turnarounds as long as you have the software. (We can do it as a service as well but not same day.)
To answer your other question, most of the consumer DVD set-top recorders do in fact record closed captioning. They decode the line 21 and mux the caption data into the recorded stream. But in my experience, some of the more "professional" models do not (go figure).