vbidecode - VBI data decoder

Copyright (C) 1997,98 Ralph Metzler  (rjkm@thp.uni-koeln.de)
                      according to the GNU GPL in the file COPYING.


Vbidecode decodes some of the data structures that are transmitted in the
VBI (Vertical Blanking Interval) of television transmissions.
As source it requires a TV decoder card driver which conforms to the 
video4Linux interface standard and supports VBI data. 
Not all video4linux drivers do provide this kind of data, depending on the
capability of the hardware and the current state of the driver.
Currently vbidecode also only supports the raw grabbing data as provided
by the Bt848 family of frame grabber chips by Brooktree.


Here is a list of some VBI data services:

- videotext/teletext 
  text based information pages (40x25 characters) 
  PAL/SECAM-WST supported    
  NTSC-NABTS not supported 

- intercast
  WWW pages transmitted via line 31 videotext in a kind of compressed SLIP format
  PAL-WST supported
  NTSC-NABTS not supported
 
- VPS
  channel information and signals for automatic start/stop of VCRs
  mainly (only?) used in Europe
  
- closed captioned
  mainly USA, Japan ... ?
  (in Europe subtitles are ususally part of the videotext service)
  not supported

- Videocrypt 1 and 2
  includes the cryptograms which are sent to smartcards in Videocrypt decoders
  mainly used in the UK
  not supported

Since I am living in Germany I naturally cannot do any testing with NTSC
signals. So, any help by people living in countries with NTSC TV and some
programming experience would be appreciated.

Also any documentation about data structures used in intercast transmissions
(or any other kind of VBI services) would be helpful.
Until now I had to figure out most of it myself by looking at the data stream.
The references below give some hints, but e.g. the structures of the IP packages
in the German intercast transmissions (on the channels ZDF and DSF) look 
quite different and the format of the transmitted files is given nowhere.


References:

[1] R. Panabaker, THE TRANSMISSION OF IP OVER THE VERTICAL BLANKING INTERVAL OF A
    TELEVISION SIGNAL, internet-draft

[2] N. Thorne, THE TRANSMISSION OF IP OVER THE VERTICAL BLANKING INTERVAL OF A
    PAL TELEVISION SIGNAL, internet-draft

