[linux-dvb] How to descramble?

Manu Abraham abraham.manu at gmail.com
Fri Oct 14 16:29:36 CEST 2005


Andreas Oberritter wrote:

>Hello Henrik,
>
>On Fri, 2005-10-14 at 13:52 +0200, Henrik Sjoberg wrote:
>  
>
>>If the PMT contains no CA descriptor on programme level and common CA
>>descriptors on stream level, the stream level common CA descriptors are
>>now moved to programme level.
>>    
>>
>
>This is wrong, because different ES PIDs can use different ECM PIDs.
>Moving the CA descriptors to the program level destroys their
>association to an ES PID.
>
>  
>
So what would you suggest.. ?

The condition was that they were the same and repeated, and  such common 
descriptors can be moved to program level.
In this particular case decryption at stream level failed.

In fact it was Marc who suggested this (i think ..)

People whom i can refer to on this discussion,
Marc, Dominique, Johannes, Frederick and myself. It was a while back though.

Attached is a reference of the discussion we had on the same with Marc..

-------------------------------------------------------------

Hello Dominique,

what did u change to manage to descramble ..? what was the trick ?

if all the ca_desc at es_stream_level are identical, you can put them
on program_level. The result will be the same, but this will allow to
reduce the size of the ca_pmt. If I remember correctly, you are
limited to a size of 256 bytes...

regards
Marc
P.S: I will be again on holidays next week.... may be I will have
received some good new will I will be back..



Thursday, March 3, 2005, 9:40:52 PM, you wrote:


>> I've managed to descramble video (no audio) on TF1,LCI and TPS
>> homecinema.  8-)  (and more than once !!!)
>  
>

>> Now I have to work around the PMT problem. According to Marc's hint
>> (way back in Januray) I have to put the ca_desc at program level
>> (since all ca_desc at es stream level are identical) and send only the
>> es stream headers. I'll try that this week-end.
>  
>
>> Cheers
>  
>

--------------------
 

>I don't know whether any broadcasters use it, but the fact that stream
>level CA descriptors exist proves that is is intended to make that
>possible.
>
>  
>

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.

This was after a general discussion between a lot of others as well.

Regards,
Manu




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