[linux-dvb] How to descramble?

Perceval Anichini perceval.anichini at streamvision.fr
Sat Oct 15 09:22:50 CEST 2005


[snip]
> Decryption at stream level (That is the appropriate term ?) fails for 
> all hardware, (since that is probably not decryption at stream level 
> itself what we are looking at, for that mentioned provider) with that 
> stream, unless handled that way. For these cards it is *not* a workaround
	Isn't the descrambling stuff handled by the CA module ? Aston modules
_do_ support descrambling at stream level ! If the DVB/CI part of the
hardware does not support CA_PMT messages greater than 256 bytes or does
not support a way to split big messages in smaller ones, then it
is limited.

	Moreover, most of CA modules have a limited number of PID that can be
descrambled at the same time. And one can (at least, we do!) need
not to descramble a whole service (for instance subtitles), to allow to
descramble more services.

> If you read EN50221 carefully, you will find that this is not a 
> workaround ! 
	If this is not a workaround, this is a simplification of the
standard :).
	Because the EN50221 never says that all CA descriptors at
stream level ought to be the same, and therefore moved to program level.

> So i need to strike a balance where it works for all cards 
> supported by the driver as expected, not just one bunch of cards. 
> Something that works with everything and something that works as 
> expected. That was what i was looking for.
	That is a good start, but transposing the hardware limitation of some
DVB cards to other ones is really sad !!!! When the card could work
correctly, the driver prevents it !

> (The driver supports a wide variety of them, Technisat Skystar I, 
> Pinnacle Sat CI, VVMER, Tomato, Twinhan, Hercules, some few that came to 
> my mind) So one cannot say which one is which, even if the vendor 
> provide card models which have that limitation.
	Well, maybe that could be a module parameter ? The user actually know
which hardware he have. And even if he dont know, he should be able to
perform a few tries ?

Regards,

Perceval.




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