From: phil@compnews.co.uk (Phil Male)
Newsgroups: uk.misc
Subject: Re: Video Plus
Date: 2 Jan 93 03:55:10 GMT
Reply-To: phil@compnews.co.uk
Distribution: uk
Organization: Computer Newspaper Services, Howden, UK.
NNTP-Posting-Host: sage.compnews.co.uk
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keith@unipalm.co.uk (Keith Mitchell) writes:
: ian@unipalm.co.uk (Ian Phillipps) writes:
: 
: >I'm not sure if this should be posted to sci.crypt, but does anyone
: >know (or even better, has anyone reverse-engineered) the code numbers
: >appearing in the Radio Times for the Video Plus device?

They also appear in a lot of the regional and national papers, we put them
there :-)

-rw-rw----   1 phil     iseng       27568 Jun 11 21:07 /vol/src/is/libiseng/restricted/ukgemc.c
-rw-rw----   1 phil     iseng        5957 Jun 11 21:08 /vol/src/is/libiseng/restricted/ukgemc.h

: 
: Yes, they have been published on the net. The last people to do this
: received legal threats from the manufacturers of the handsets not to
: do so. The encoding is proprietary to this company and subject to
: patent protection.  Listings publishers pay for the privilege of
: printing these numbers, so it is not surprising the Video+ people
: are touchy about it.

They pay a lot of money for to publish V+ numbers. One might say several
things about this, something about selling London Bridge, or why a 'random'
digit string is easier to key than a time, but I couldn't possibly comment.

: 
: Of course, what will happen, as with most propietary encryption
: schemes used for broadcasting, is that eventually knowledge of how
: to unpick the code will be so widespread in the public domain that
: the codes will have to be changed, and you can bet the punters who
: bought the handsets in the first place will be the ones who have to
: cough up for this...

I doubt it, for several reasons (none of which I can go into here, sorry).

: 
: I prefer Teletext Program Delivery Control myself, buried but not
: dead (see pages 300/301) by the new teletext service on Channel 4.
: 
: Keith Mitchell
: 

We are providing the new Teletext service on ITV and all the TV related pages
on Channel 4. TV information on Channel 4 should now be appearing in magazine
5 sets 50 through 57 (ms 550-557). (Hence the late night hacking :-)

PDC is transmitted in two flavours, we are currently providing Method A PDC as
defined in EBU SPB 459 Revision 2 Draft 1 (Oct 1991) and commonly known as
poor-man's PDC or "StarText". Method B tests will begin on Monday.

Method A involves the video recorder parsing the TV listings page. Hidden on
the page are two extra pieces of information, the date of the first programme
on the page, and the end time of the last programme on the page. You can see
these hidden codes by hitting the Reveal button on your Teletext Remote.  The
video looks for times formatted as "number.number" and dates as
"number.number.". A cursor can be moved about the screen when the video is in
programming mode, it appears between the time and title in the listings. To
program the video you simply hit the 'vpt' button on your remote when the
cursor is on the programme you want. All the information required for
recording the progamme can be obtained from the data in the teletext page,
including the title and description.

Method B, true PDC, involves us sending an extension packet (x/26) along
with the teletext page when we transmit it. This is essentially teletext
row 26, except there can be up to 16 row 26's.

Each x/26 contains several 3 byte packets (up to 13). Each packet has two
data fields and a mode field (which identifies the data in the packet).
There are several packets associated with each programme in the listings
information. The association is made using the first two packets of a run,
these contain the row and column index for the programme as it appears on the
page. Additional information is provided in the other packets associated with
a packet run that allows a unique code to be built up for that particular
programme, the video can also generate information such as sound encoding in
use (lingual, stereo, mono). When the video is being programmed, instead of
parsing the teletext page data to obtain start/end times and dates, the video
looks up the (row,column) pair in the x/26 data it obtained when loading the
page.  The unique number is then stored in the video's program memory.

When a television programme is being broadcast, it's unique number is being
transmitted along with the images. When the video receives a number that
it has in it's program memory, it starts recording. When it stops receiving
that number it stops recording. Simple stuff. If PDC codes are not being
transmitted then the video defaults to Method A.

Currently the only people transmitting PDC codes are Channel 4, other
channels are due to start r.s.n. From Tuesday we will be supplying PDC
information for all listings pages on Teletext. We hope to supply a video
programming page (simply times and titles of films, soaps, etc listed on
a multipage one programme type per page) r.s.n.

The best video we have found for using PDC codes is the Philips VR 323.

--

phil 
   ___/   /
   /_/)  /            Phil Male, Director, Information Systems  
  / /_ '/  Computer Newspaper Services, The Bishops Manor, Howden, DN14 7BL 
 / / ///    +44 43043 Tel: 1100 Fax: 1108/2022  email: phil@compnews.co.uk