[mythtv-users] ATSC & QAM

jafa hdtv at silicondust.com
Fri Sep 15 04:29:00 UTC 2006

>> 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 :-)


More information about the mythtv-users mailing list