[mythtv-users] cablecard

[Brad Templeton]

On Thu, Apr 07, 2005 at 04:17:51PM -0400, Jay R. Ashworth wrote:
> Yes, let's please clarify what we're discussing.
> 
> What *I* am discussing, and want to see either Hauppauge or Plextor
> build, is a tuner card similar to the ones we see now, but which can
> tune QAM digital cable, and using a CableCard plugged into it, decrpyt
> the incoming video, and pass it on digitally to the PC, the way the
> AirPC cards and the like do.
> 
> It wouldn't by any means be a "MythTV" product, or an open source
> product, or anything else.  It would merely be a product which *we*
> *could* make use of, without having to be Microsoft, and sell
> closed-source software which would enforce all kinds of
> fair-use-denying garbage we're not interested in.
> 
> But make no mistake: it would be a normal commercial product, just like
> current-day tuners are: it would will pretty much exactly the same role.
> 

The problem is the specs require content protection.   To be an OCAP
compliant DVR, you must not store the video unencrypted on hard disk,
for example.   You must protect it.   And, there are "robustness"
requirements which mean it must be hard for users to change the
system so that they can get at the data.


This is not possible in a traditional open source system.   If the
DVR has access to the unencrypted video at any time (which you want it
to of course) then any user can, due to the GPL, modify the program
to get access to the video.   Thus it can't meet this requirement on
traditional hardware.

It would be possible, though very much not in philosophical agreement
with the open source way, to run a "secure" MythTV on TCPA style
hardware, like possibly Microsoft's palladium.  In this case, the
system would be signed and could not be modified by the user on that
machine.  (They could still modify it and run it on another machine
but that machine would not be the one with the cable card in it...)

Such a system could do what MCE will probably do.  Encrypt all video
on disk, take steps to keep the keys secure in a hardware box that
only allows the signed software to use it and so on.

Again, this is not a likely path for MythTV.  A company could
take MythTV and modify it to work this way, and still be compliant
with the GPL, but users could not modify the system on their secured
box, they could only modify it to run on other boxes lacking
cablecards, which is not very useful.