Gordon Dexter on 9 May 2009 09:55:21 -0700

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Re: [PLUG] -- Mostly-OT -- Mythbuntu & Comcast channels?

Isaac Bennetch wrote:
> By the way, I have no idea how your setup would be affected by the
> digital copyright flags that are sometimes set in digital
> transmissions. There are flags that are supposed to prevent recording,
> etc, but whether they are set, transmitted to you, understood by your
> tuner, or adhered to by your software are beyond my working knowledge;
> but worth a bit of homework if you think about going all-digital. For
> that matter, Comcast may encrypt some of the digital channels (IIRC,
> which is a stretch, they are required to pass the local broadcast
> channels in the clear, but are able to encrypt the rest. Determining
> whether that's still true and whether they actually do that on your
> specific system is left as an exercise for the reader).
> ~isaac
Basically you have two options.  You will eventually have to choose one, 
because cable companies are phasing out analog signals completely, for 
the simple reason that those signals take up more bandwidth than the 
digital ones.

Assuming you choose to upgrade to the cable box+IR blaster setup that 
Isaac mentioned, you won't need to purchase a new tuner.  You'll just 
program MythTV to change the channel on the cable box, using a little IR 
LED that sends the same signals as the remote.  If you go this way 
you'll be strictly limited to low definition.  Cable companies have been 
known to forcibly downscale the HD outputs for unprotected outputs, such 
as non-HDCP-HDMI, composite, and s-video.  Since your tuner would only 
work for low definition anyways I doubt you'll care.

If you want to actually record in high definition, you can get an ATSC 
tuner that supports QAM.  Cable providers broadcast some of their 
channels in a form that you can decrypt without using their cable box, 
using an ATSC tuner with QAM.  Since that doesn't let them enforce DRM 
on it, they only broadcast the major networks unscrambled, because 
they're required to by the FCC. See 
http://en.wikipedia.org/wiki/QAM_tuner and 
http://www.linuxis.us/linux/media/howto/linux-htpc/tuner_cards.html for 

Right now there is a broadcast flag in ATSC signals.  It's part of the 
spec, and companies occasionally enable it for shows they don't want you 
copying.  However!  Hardware is not legally required to respect it in 
any way at all, however, due to a court ruling that the FCC overstepped 
it's bounds in mandating it.  So ATSC tuners are available that 
completely disregard the broadcast flag, and happily work with MythTV.  
The pcHDTV HD-5500 is a good example, available at http://www.pchdtv.com/.

Getting premium content requires a more sophisticated setup.  
Unfortunately cablecard tuners that work with PCI are tied to all sorts 
of DRM cruft that pervades the entire computer, probably using TPM, and 
Linux drivers are presumably nonexistent.  See this thread: 
http://www.avsforum.com/avs-vb/showthread.php?t=934453 for conversation 
on that subject.  Since you don't seem to want much premium content I'm 
assuming this is more than you need, but it just goes to show the 
extreme lengths media companies will go to in order to keep their 
content locked down.

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