Possible to add line 21 captions to composite output?

Hello all,

I don't know the particulars but would it be possible to somehow inject custom closed-caption text strings into the line 21 VBI of the composite output signal? I'm not sure if the PI would give me access to do such a thing but any help would be appreciated!

There was some discussion, but no concrete conclusion, at viewtopic.php?p=44113#p44113 and subsequent posts. Although the details were about European teletext the same principles would be applicable to North American Closed Caption.

Thanks for the link, that did indeed have some good information. Another question, would the Pi allow me access to the VBI, or is that cut off?

Also since this is a Broadcom chip, do any of the devs know if there is an API for accessing the VBI encoder? Thanks