[mythtv-users] ATSC & QAM

[Steven Adeff]

On 9/15/06, jafa <hdtv at silicondust.com> wrote:
>
> >> Shameless plug, but check out HDHomeRun (www.silicondust.com) - it has
> >> two tuners and you can use one for ATSC and one for QAM.
> >>
> >> My home system has 4 x ATSC tuners (2 x HDHomeRun) and 2 x QAM tuners (1
> >> x HDHomeRun).
> >>
> >> Nick
> >>
> >
> > so it CAN do QAM! your website isn't very clear on this. If I didn't
> > already have 3 HD tuner cards I'd be very interested in trying this.
> > I do find it hard to believe the 100bT is fast enough for the two streams...
> >
> Hi Steve,
>
> Normally you are only watching a sub-stream so the network bandwidth is
> the usual 5-15Mbps per tuner.
>
> Full unfiltered QAM256 is 40Mbps per tuner.
>
> For my own system I added a $35 gigabit switch to speed up file
> transfers between my two machines. With 2 tuners running full bandwidth
> unfiltered QAM that is still only 8% of the network bandwidth to the PC.
>
> In normal use (MythTV) with two tuners recording high-def you will be
> using 2x15Mbps - this is actually less work for your computer than using
> PCI cards.
>
> In your case, assuming 15Mbps high-def TV streams... using the 3 PCI
> cards in QAM mode requires 120Mbps bandwidth to your computer. Using 3
> HDHomeRun tuners only requires 45Mbps bandwidth. You could actually
> upgrade and run 8 HDHomeRun tuners (4 units) and your computer would be
> using the same bandwidth as you are using today with the 3 PCI cards.
>
> I am running 6 tuners (3 x HDHomeRun units) - network bandwidth isn't an
> issue... however the poor hard drive is getting hammered :-)
>
> Nick

great to know. though once they allow for recording two sub-streams on
the same tuner, I'll be glad I have PCI cards. Though the HDHomeRun is
about the price of a single pcHDTV card...

perhaps when I can justify the purchase, and have replaced my 100bT
with 1000bT switches, I'll get one to play around with =D

-- 
Steve
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