John Wilson <wilson(a)dbit.dbit.com> wrote about the "V Chip":
(no I don't know what the protocol is for labeling
the show but I assume
it's some between-visible-scan-lines thing like closed captioning is),
Yes. In fact, it uses line 21 just like captioning, but is coded as
"enhanced data services" as per EIA 608. I think there's a newer standard
that gives the specific V-chip details.
I've been thinking about taking my closed caption decoder project, which
was formerly used in a hack to automatically mute the audio any time
O.J. was mentioned (the O.J. Mute-o-Matic, tm), and turn it into a device
to automatically find programming with high violence or "mature audience"
ratings.