[mythtvnz] Extracting EPG from sky

[David Zanetti]

--=-Rm0pzkRm8Br7VVcPvg3B
Content-Type: text/plain
Content-Transfer-Encoding: quoted-printable

On Fri, 2006-02-03 at 14:17 +1300, Steve Hodge wrote:
> On 2/3/06, David Zanetti <david.zanetti@catalyst.net.nz> wrote:
> > FWIW, the DVB spec _does_ allow EPG data to be encrypted. Yes, it'll be
> > a last step, but one they can probably do with little fanfare.
>=20
> Video and audio decryption is offloaded, but what are the chances data
> decryption can be handled the same way? I guess if the spec allows
> encrypted EPG data there is a reasonable chance.

They're all just PIDs, so there's no technical difference.

Big bit of DVB coming, if you don't care for the details, please skip :)

Everything in the TS you get from the transponder (or a broadcast tower
doing DVB-T, it's all the same) is broken down into seperate streams
identified by PIDs. There's special PIDs like 0x0, containing the
Programme Association Table (tells you where to find the PIDs describing
end-user services), and 0x1 for the Conditional Access Table (what CAs
are in use, and their PIDs for private data), and so forth. Video and
audio are also PIDs, as is the guide data (0x12 for Event Information
Table).

So the standard DVB CA interface is based around telling the decryption
engine to decrypt several PIDs, and arranging the flow of those streams
over the engine. It's possible the engine has a low limit for the number
of PIDs it will decrypt at once, but it should certainly be greater than
2.

In the spec, everything except the system PIDs and tables can be
encrypted. EIT is technically a system PID, but it's explicitly allowed.

IIRC. :)

--=20
David Zanetti <david.zanetti@catalyst.net.nz>
Team Leader, Systems Administration
Catalyst IT Limited
+64-4-8032233 +64-21-402260

--=-Rm0pzkRm8Br7VVcPvg3B
Content-Type: application/pgp-signature; name=signature.asc
Content-Description: This is a digitally signed message part

-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.1 (GNU/Linux)

iD8DBQBD4rXRei0cZZ0ajFMRArUSAKCpsReu7Qms73MmYu3EtAxmkgrkSQCggSni
3AgWnPGEp/hcGdxQEzkr1us=
=Dl8m
-----END PGP SIGNATURE-----

--=-Rm0pzkRm8Br7VVcPvg3B--