[mythtv-users] Answers about pcHDTV HD-3000 support in Myth, QAM support, and more

Cory Papenfuss papenfuss at juneau.me.vt.edu
Tue Oct 19 19:06:27 UTC 2004

On Tue, 19 Oct 2004, Preston Crow wrote:

> While the HD-3000 will hopefully have support for unencrypted QAM
> digital cable streams, am I correct that there is only one coax input,
> so you won't be able to switch between broadcast and cable in software?

 	That's an interesting thought.  It doesn't sound all that uncommon 
to want to tune in some stations via QAM cable, and some via VSB 
broadcast, but I guess it wouldn't fly.  Of course, what you really are 
referring to is either a mux'd tuner, or multiple tuners.  You might 
be able to mix the RF through a VCR's RF output to select between two 
different inputs.  It would definately be a kludge, though.

> Personally, I would have kept the two coax inputs and dropped NTSC input
> altogether.  All the reports from the forums suggests that hardly anyone
> is even trying to use the NTSC side of the card, as using a hardware
> MPEG encoder is vastly superior.
 	It's not that simple.  Although I don't know for sure, I suspect 
that the two RF inputs on the HD2k were for TV and FM-radio, not TV1 and 
TV2.  Getting the smaller form-factor and possibly cheaper tuner on the 
new card were probably a factor.

 	I emailed (Jack?) at HDTV and he said that they use they were 
using the (then hd2k) bt879 chip for the PCI bus arbitration.  The Oren 
chip talked to the PC via the BT879 chip's GPIO pins, so the BT879 could 
do the DMA, etc.  That basically means that the framegrabber part of the 
board is a "free" additional feature.

 	Also, for clarification, the HD-[23]000 is *NOT* an MPEG encoder. 
It is an HDTV bitstream demodulator.  Again... 1-way modem is the right 
way to think of it.

 	I *am* interested to know if the CX23883 chip has higher quality 
than the BT87[89].  I was underwhelmed with the analog resolution limit of 
about 352x480 with my resolution test pattern testing before.  At least 
the ivtv-based ones will do 480x480 before crapping out.


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