[mythtv-users] DVICO FusionHDTV III QAM card

Michael Hartman hartmms at yzf600.dns2go.com
Thu Aug 19 21:06:05 EDT 2004

On Wed, 2004-08-18 at 19:00, Michael T. Dean wrote:
> On 08/18/2004 06:01 PM, Jay R. Ashworth wrote:
> >On Wed, Aug 18, 2004 at 05:07:54PM -0400, Michael Hartman wrote:
> >  
> >
> >>>If a (sub-)channel's data stream *was* encrypted, how would you tell?
> >>>Cause it wasn't a valid MPEG stream?  Am I the only one on the list who
> >>>gives a crap about digital cable?  ;-)
> >>>      
> >>>
> >>If the stream were encrypted, it would not play back at all. It would
> >>confuse the MPEG decoder so bad it would display nothing. 
> >>    
> >>
> >The card won't just pass the appropriate extracted PS as a PS down to
> >the bus?  It *has* to decode it into a frame buffer?  Bummer.
> >  
> >
> My understanding is that the pcHDTV and the FusionHDTV III are both 
> "software" HD tuner cards--they have no MPEG decoder hardware on board.  
> Instead, they pass demodulated signal data through the bus to a software 
> decoder.
> I think what Michael is saying is that if the channel were, in fact, 
> encrypted, the signal received over the bus would not be an MPEG stream, 
> so when it's passed to a software MPEG decoder, the decoder would not be 
> able to decode the video.  In other words, he's agreeing with your 
> initial guess of how to tell it's encrypted.

I'm not sure about how exactly it is encrypted. I know that the
Transport stream is in the clear. MPEG data exists in packets, jut like
TCP/IP traffic. The start of a MPEG2 packet is 0x4700 (or 0x0047). Most
likely the packet headers are in the clear and the payload data is
encrypted. It is also somewhat likely that even the MPEG2 headers are
encrypted. I'll investigate further and let everyone know what I find

Michael Hartman <hartmms at yzf600.dns2go.com>

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