[mythtv-users] Hook-up question

[Michael T. Dean]

On 07/31/2007 07:45 AM, Harry Devine wrote:
> I know this is going to sound like a silly question, but I'm gonna ask
> it anyway, as I'm drawing a complete blank.  How do I have to hook up my
> hardware to begin using MythTV?  I have the latest distribution of
> MythDora 4.0 installed on a HTPC setup that I just built.  It has a
> pcHDTV tuner card in it.
>  
> I live in New Jersey and have a Motorola DCT6412 digital box from
> Comcast that provides HDTV.  I also have an Onkyo stereo receiver in the
> mix.  I currently have the main cable coming into the Motorola box, then
> another coax  cable from that box down to my pcHDTV card and I can't get
> any stations to come in.  I have an optical S/PDIF cable from my PC to
> my receiver and cannot get any audio.
>  
> Any ideas or basic wiring/setup help would be greatly appreciated.  I'm
> thinking that I'm just "over"-thinking this and confusing myself.

After reading the subject, I thought this message was meant for another
type of forum.  :)

Anyway, the pcHDTV capture cards are digital capture cards--meaning they
need to receive an already-encoded MPEG stream.  So, to get TV into it,
you need to hook the cable TV connection (the one that you currently
have connected to your DCT6412) to the pcHDTV.  Assuming you have an
HD-3000 or above, it should do QAM (the modulation used to transmit
cable TV signals) without problems.  However, the big fly in the
ointment is whether your cable company decides to encrypt any or all of
the data.  Most likely you'll be able to get at least your local
channels in digital (and, perhaps, in HDTV).  Others--like Discovery HD
or Sci Fi (even in standard def)--are more likely to be encrypted.

If the channels are encrypted, you'll need to use your STB (the
Motorola) to decrypt them.  If you subscribe to a high-definition
package, your cable company is required to make available--at your
request--a STB with firewire output.  Once you have one of these, you
can record by simply hooking the firewire output from the STB to a
firewire port on your computer (may require a firewire I/O card). 
Again, though, the cable company has the choice of encrypting some of
the channels (and, again, you're most likely to get locals and less
likely to get others).

If the STB encrypts the firewire output, the only way you can capture
those channels is using an analog capture card to record.  You'd still
need the STB to decrypt the signal, then you'd connect it to the analog
capture card using, i.e., its S-Video output.   For example, the PVR-150
costs about $40-$70 (depending on where/when you buy it) and does all
the work of encoding an MPEG-2 stream for you.  With this approach, you
won't get high definition and--because the signal is being converted
into an NTSC format--you'll get low-quality recordings.  The recordings
from an analog capture card connected to a digital STB using S-Video
will be much better than those from an analog capture card connected
directly to the cable line (and using the capture cards internal tuner),
but using the STB means having a separate STB for each program you want
to record simultaneously (i.e. capturing from an STB with four capture
cards means having 4 STB's).  So, you may choose to connect your
"highest-quality" (highest-priority) capture card to an STB and just
connect other analog capture cards directly to the cable line.

The pcHDTV cards happen to support both analog and digital capture, but
if you use the analog side of the pcHDTV card, you're using a $125 card
as if it were a $10 frame grabber (and you won't get HDTV).

So, how do you know which approach to take?  Trial and error or
anecdotal evidence.  Since you already have the digital capture card,
it's easy enough to test whether that works.  Since you already have an
STB, it shouldn't be expensive to get it swapped for one with firewire
output (assuming yours doesn't already have it).  If those approaches
don't work, then you'll need to go with the analog approach.

Mike