[mythtv-users] Pinnacle PCTV HD Pro Stick

Carl L. Gilbert clg-social at rigidsoftware.com
Thu May 22 16:59:44 UTC 2008

On Thu, 2008-05-22 at 10:23 -0600, Brian Phillips wrote:

> Mike Perkins wrote:
> > jedi wrote:
> >> 
> >>    ANY digital capture solution is going to be simpler because it
> >> doesn't have to digitize anything. I am not sure there is such a
> >> thing as a "digital SD card" (DVB excepted). SD capture cards aren't
> >> just capturing the incoming video, they are also digitizing it since
> >> the stream is coming in as analog.
> >> 
> >>    In the US this would even be the case for "digital SD". It's going
> >> to hit your system as an analog stream and get re-digitized.
> >> 
> >>     An HD capture card doesn't have to do much work really. The data
> >> is already in a format suitable for computer consumption.
> >> 
> > Nope. Digital is digital, SD or HD, end of story. It does not hit
> > your system as an analog stream, so does not need to get encoded. As
> > I am in the UK, I don't have precise details of the
> > encoding/multiplexing methods used by ATSC, so I can't possibly
> > comment on whether or not a digital tuner card will be able to do
> > both HD and SD, or if there are only SD cards.     
> The confusion comes because SD has the connotation of being an analog
> signal.  We sometimes forget to mention that 480i/p can be considered a
> digital SD signal.  But that is the question we're asking of Carl L.
> Gilbert.  What device is he referring to that markets itself as an SD only,
> digital capture card?

I understand HD vs. SD and analog vs. digital.  I know HD is always
digital but SD can be either or.  I have not see any digital device
marketing itself as SD only, but I have seen digital devices marketing
themselves as "HD."  And there is a section in the Myth documentation
about HD cards and they are treated seperately.  So at first glance to
me, calling a digital capture card "HD" is seeming like a marketing
thing.  I am not here to tell anyone how it is, I just don't know.  I'm
trying to learn enough to know how to formulate my question so it makes
sense to people who do know.  So forgive me if I don't make total sense.

> We should also remember that even though QAM and ATSC carry digital signals,
> they are modulated with a carrier frequecy and the symbol  signifigance
> depends on the phase and amplitude of the signal at the sampling instance.
> For all intents and purposes, they are an analog signal.  They just carry
> modulated 1's and 0's.

OK, but as far as the end user is concerned, the signal that comes out
is MPEG? which can be stored directly?

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