I don't think we did much testing, but the rev 4 was designed to do TV out.
You will need to set the C&T video timing for TV (I have vague memories of
an XFConfig file that had these, maybe one of the old ones in the DEC code
release?), but as far as I can remember there was no programmable interface
to the encoder. I see there is a comment on hardware changes for PAL
(untested). As always, check for the datasheets and notes on the web page

http://www.research.digital.com/SRC/iag/info/dnaext/hardrev4.html

Other people (or maybe you!) have commented on rev 4 problems with the
latest firmware, maybe you could send the OFW startup script that works for
you! I suspect by the last firmware revision nobody was testing rev 4s.

Mark