vbidecode - VBI data decoder
Copyright (C) 1997,98 Ralph Metzler  (rjkm@thp.uni-koeln.de)

Vbidecode decodes some of the data structures that are transmitted in the
VBI (Vertical Blanking Interval) of television transmissions.
It can decode the following formats, with some restrictions for NTSC users.

- videotext/teletext
  text based information pages (40x25 characters)

- intercast
  WWW pages transmitted via line 31 videotext in a kind of compressed
  SLIP format

- VPS
  channel information and signals for automatic start/stop of VCRs

- Videocrypt 1 and 2

VBI data is read from /dev/vbi0 which is provided by a Video Capture
card such as those using the Bt848/Bt878 family of video capture chips.