[Live-devel] CAS encrypted stream

[Ross Finlayson]

> I am trying to use live 555 to stream an CAS encrypted stream and use trick play on VOD client. Encrypted stream has ECM,EMM and CA packets as compared to original streams. Also PCR is modified
> as per new packets inserted.
> 
> I am thinking of changing the index file created from clear stream. Change will be for PCR values and transport packet numbers.
> Will this change suffice for the trick play support on VOD client or any other change also needs to be done ?

Unfortunately I don't know anything about "CAS encryption" (which I presume is the system described here: http://en.wikipedia.org/wiki/Conditional_access ), so I probably can't give you a good answer.

However, depending on what kind of 'trick play' you want to support, I'm not convinced that you would need to change the index file format.  (If you were to change the index file format to your own proprietary format, then I wouldn't be able to help you on this mailing list.)  Instead, you might be able to keep the index file format unchanged, but just change the mechanism that you use to *create* an index file.

If the only type of 'trick play' that you want to do is 'seeking' (i.e., no 'fast forward' or 'reverse play'), then you might be able use the existing index file format, provided that the index file can point to 'clean points' within the (encrypted) TS file from which you can safely resume streaming, after seeking.  (Note our function "MPEG2TransportStreamIndexFile::rewindToCleanPoint()", in "liveMedia/MPEG2TransportStreamIndexFile.cpp".)

If, however, you also want to support 'fast forward' or 'reverse play', then I'm not sure that you could do this on an encrypted Transport Stream, even if you were to change the index file format.  The reason for this is that our 'fast forward' and 'reverse play' implementations work by picking selected 'key frames' from the original Transport Stream, and creating a whole new Transport Stream - built from these 'key frames'.  I just don't see how you could do this from an encrypted stream.

But again, I don't know anything about "CAS encryption", so I'm sorry that I can't be of more help.


Ross Finlayson
Live Networks, Inc.
http://www.live555.com/

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