[mythtv-users] Virtual Machines, USB tuners and PCI passthrough

Tyler T tylernt at gmail.com
Tue Jul 20 20:59:22 UTC 2010

> I know that HD
> on a combination of these would require huge usb bandwidth...

Not so sure about that. An HD stream should take no more than 32Mb/s
and USB 2.0 should handle 480Mb/s or 15 tuners. Of course, there's
protocol overhead, latency etc so you'll hit problems way before your
15th tuner. Considering most modern computers have more than one USB
controller onboard though, 3 tuners per controller for a total of 6
seems well within the realm of possibility (though admittedly I have
no personal experience). You'll take a performance hit passing all
that USB data through virtualization though -- not sure if the impact
will be significant.

I tried to do PCI passthough in Xen a couple years ago and remember
lots of pain, perhaps it's better now but I still suspect USB is going
to be be easier than PCI. Also consider that PCI is going the way of
the dinosaur, in a few years your PCI cards might be useless when your
motherboard fails or needs upgrading.

One more thought: I believe SiliconDust sells a DVB version of the HD
HomeRun. If you go that route, a Gig-E NIC in your server should be
able to handle 6+ tuners no sweat, and no mucking about with USB

Just my .02...

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