[linux-dvb] How to descramble?

Dominique Dumont domi.dumont at free.fr
Sat Oct 15 09:35:56 CEST 2005

Manu Abraham <abraham.manu at gmail.com> writes:

> The first one that i had seen was with TPS, and this was the only way it 
> could be worked. In fact stream level decryption according to TPS wasn't 
> probably stream level decryption but only program level decryption. I 
> might be wrong here though, but that was the only thing that got it to 
> descramble.

You statement related to "program level decryption" is misleading. In
all cases only the elementary streams are encrypted. Sending CA
descriptors at program level is only a mean of saying "this
descriptor is valid for *all* elementary streams of this program"

Here's the section of EN50221 that specifies this behavior:

   The CA_descriptor after the current_next_indicator is at the
   programme level and is valid for all elementary components of the
   programme. The CA_descriptor(s) at elementary_stream level is (are)
   valid for the elementary_stream only. If, for one
   elementary_stream, CA_descriptor(s) exist at programme level and at
   elementary_stream level, only the CA_descriptor(s) at
   elementary_stream level are taken into account.


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