[mythtv-users] New Build

Robert Johnston anaerin at gmail.com
Thu Mar 11 10:26:18 UTC 2010


On 11/03/2010 1:57 AM, Eric Yanush wrote:
> First I would like to say thanks for the guide, it was awesome. I used
> it to set up my initial mythtv box using Max.
> I originally had a p4 2.8ghz set up with an fx5200, but it just couldn't
> handle the HD content.
>
> I am going to use HD content, and that was part of the reason I thought
> the atom wouldn't be fast enough to deal with 2 let alone 4 simultaneous
> streams.
> I do plan on adding atleast 2 more frontends to the mix, (and for those
> I love the idea of the ION, and I also have an appleTV outfitted with a
> crystal hd card)
> and the concern was that the atom would not have enough power to be able
> to commflagg more than 1 stream and run a frontend possibly watching
> live tv at the same time, let alone 2 more streams,
> as I was under the impression that myth could not utilize VDPAU to
> commflag, although that would be awesome:)

Looking through the archives, it seems that while VDPAU *could* be used, 
it currently isn't.

> As far as HD space, how far will the 1tb drive get me, is there a sort
> of average per hour size?

Well, with SD I get a rate of around 1Gb/hour. I believe HD is more like 
5Gb/Hour, so 1000/5 = 200 hours. Given that you'll probably also want to 
load your movie collection on there, you will find, however, that HDD 
space will disappear very quickly! :)

> The only other reason that I was leaning towards the I3 based setup, was
> expandability. In the future I could get a faster lga1156 processor and
> possible expand the life of the machine.
>
> The idea of mounting the Revo to the back of the tv. is an awesome idea,
> I am just not sure about the idea of having to run a seperate machine
> for storage. I am trying to design this system with energy efficiency in
> mind, and have found a few articles that show that the clarkdale series
> chips can have a system idle draw under 25W!! Plus I seem to be seeing
> that the core I3-530 is quite a cool running chip, hence the scythe
> ninja mini, as in the nsk2480 the two 120mm case fans are right beside
> the processor socket, and the processor could then be passively cooled.
> However I do imagine an atom chip could be passively cooled without the
> fans in the case.

Correct. In fact, a decent Atom system is entirely fanless (Or has a 
single, tiny fan).

> So essentially my only holdbacks from an atom based frontend is the
> expandability factor, being able to add more fronends in the future, and
> having it handle the full workload, and being able to future-proof this
> system somewhat, by being able to replace the processor, and having the
> extra expansion slots, as most micro ATX LGA1156 boards have atleast one
> pci express slot and one legacy pci slot, (most having two pci-e and one
> pci) vs. the atom platform having only the one pci-e slot.

Having an Atom-based frontend (or a combo FE/BE) won't change whether or 
not you can add extra frontends. The CPU load to stream the data around 
from BE to FE is negligible (It's almost entirely DMA).

> The only other issue I see with either a micro ATX atom board or a Revo
> is the fact that to expand to four streams, I need atleast TWO ethernet
> interfaces, and either a third or a wireless card for internet access....

You need at least 2 interfaces to stream anything, as the "Multicast 
receiving" interface is non-routable on your local network, and I have 
not managed to work out a way to get a "Virtual" network card to work 
properly. The other issue is that Myth (currently) doesn't have a way to 
designate which interface it uses for IPTV "Tuner"s. It currently tries 
to bind the multicast stream on every tuner, which is fine when you only 
have "Local net" and "IPTV net", but when you have "Local net", "IPTV 
Net 1" and "IPTV Net 2", it won't work (As it will tune net1 and net2 to 
the same channels, using up both allocations, and potentially causing 
corruption with doubled packets). I've put in a request to enable 
interface filtering for multicast sockets 
(http://svn.mythtv.org/trac/ticket/6447), but it's been closed as I 
don't have the wherewithal or coding knowledge to actually code up a patch.

> Is there anyone out there that has an I3 or I5 based system that could
> provide me with feedback??
>
> And Since you seem to be the foremost expert on the Max/Mythtv setup,
> have you found a way to get the channels like Spike and Peachtree to
> playback correctly?

No. There is some form of "Content Protection" going on, that appears to 
have blank patches in the data stream. I can only assume that the STB is 
getting and merging these blank patches from some other source, but it 
doesn't appear to be a multicast or unicast source that I can tell. And 
further discussion of circumventing these kinds of measures needs to be 
taken off this particular list, as our US-bound hosts may be slapped 
with a DMCA suit of some description.
-- 
Robert "Anaerin" Johnston


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