I'm not sure if the old DEC CRL tech reports are still around.   At one time before the Compaq-tion, some folks at CRL and the folks at Boston Public Library and WGBH were working with video and trying to extract all sorts of text from it.   I do not remember how successful they were, but there might be some hints in their tech reports.  I'll ask around and see if I can turn anything up.  Part of the problem I have is I that don't remember who was doing that work, but some of my friends might.

Clem