[mythtv-users] Beginner Question

Gerald S gerald at geraldandnicole.com
Sun Dec 19 17:47:17 UTC 2004

Thanks JAC,

One more question:   Since the component video coming out of my cable box is
raw video, requiring a regular capture card, how does HD impact this?  Is
this signal HD and can it be captured as HD, though it is analog?  I know
this I a lot of converting (digital -> analog -> back to digital), but it
seems it would be the most compatible scenario.


-----Original Message-----
From: mythtv-users-bounces at mythtv.org
[mailto:mythtv-users-bounces at mythtv.org] On Behalf Of Joseph Caputo
Sent: Sunday, December 19, 2004 8:21 AM
To: Discussion about mythtv
Subject: Re: [mythtv-users] Beginner Question

Gerald S wrote:
> Hello All,
> I am doing all my research before I dive into my MythTV HD project (I 
> am new to Myth & Linux, and fairly new ot HD...so bare with me:).  I 
> am using a digital cable box from Time Warner.
> I understand that my cable stream is encrypted going into my cable 
> box, which requires me to use their box.  But why can't cards like 
> pcHDTV3000 read the component video coming out of my cable box.  I 
> know it whould need to handle QAM for HD, but once that is done there 
> is still the issue of being encrypted by the cable company.  How can 
> that be encrypted, my TV would have to know how to unencrypt it?  Why 
> can't I let the box do the unencrypting and just take the signal before it
hits the TV?
> Is this because it is HD?  Or digital?  Wouldn't this work on just 
> normal analog cable, that did not need a cable box?

If you have digital cable, your digital channels come in over your cable as
MPEG-2 in a QAM transport.  A pcHDTV3000 is supposed to be able to
tune/decode these channels once the upgraded driver/firmware is released.
However, as you're aware, most of the channels are likely to be encrypted by
your cable provider, thus negating (most of) the advantage of having that

The component video coming out of your cable box is raw video, not MPEG
data.  Your cable box has already done the work of decrypting and decoding
the signal.  Thus, it's now an analog signal and you need a regular capture
card (bttv card, PVR-x50, etc) to capture it.  Think about it... you suggest
"taking the signal before it hits the TV", but your TV can't decode MPEG, so
it's got to be raw video, neh?

What you want to do *may* be possible, as the FCC has required cable
operators to provide an enabled FireWire port that you may use to capture
the digital (MPEG) data that your cable box has decrypted (but not decoded).
The catch is the content accessed via FireWire will not be HD... any HD
content will have been transcoded down to a lower resolution (say, 480p).
In any event, Myth does not currently support capturing video over FireWire.



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