[dvblast-devel] [PATCH] software descrambling

[Christophe Massiot]

Hello,

Le 29 juin 2010 à 13:27, Sergiy a écrit :

> Here is glue patch, that implements software CSA descrambling through libdvbcsa.
> Only BISS & constcw supported.

I am not completely convinced about including DVB-CSA in DVBlast for several reasons :
 - it adds one more dependency (libdvbcsa), while I'm trying to eradicate libdvbpsi to make packaging easier
 - distributions which already refuse to bundle libdvdcss or some parts of libavcodec will definitely refuse to take libdvbcsa and maybe DVBlast at the same time
 - in the old UNIX way of doing things I'd prefer to keep the principle one-task = one program.

Typically in the command-line language it would give :
dvblast | dvbcsaenc | vlc | whatever

In that case what I would suggest is to use DVBlast to output the encrypted stream to a specific multicast address (or to localhost if multicast is not available), and write a new program which would read such a stream and descramble it with libdvbcsa. This approach is much more modular and could be extended to BISS-E or traditional CA with ECMs. I would expect such a program to be merely an implementation example of libdvbcsa, and it could even be into the same package (like we have examples for libdvbpsi). The only drawback would be extra system calls for writing and reading scrambled packets, but on today's machines it is perfectly negligible (and if you're telling me "how about embedded systems ?" I'd just say that libdvbcsa won't run on them anyway).

However if a consensus emerges to link DVBlast with libdvbcsa, I would suggest rewriting the patch to take into account what I've just checked in (timestamps for every packet and jitter buffer). You would only need to start a thread to do the descrambling.