mythtv box spec

Darren Davison · External Since: Jan 12, 2006 Posts: 26

hi,

I'm seriously considering binning my Sky service and building my own
mythtv setup. My Sky dish has 3 cables on it (previous house owner must
have had 3 Sky boxes, we only have one) so I assume I can create a back
end box with 3 capture cards.

What is the minimum spec (RAM, CPU) machine I'm going to need for the
back end? Additionally, what network spec will I need to consider? At
present I have a wireless (g) router and a 10/100 wired hub. I'm
guessing that might not be enough for the myth setup though.. will I
also need to invest in a switch and gigabit ethernet for all front-end
boxes? Or could I get away with using the wireless for front-end boxes?

Cheers,

--
darren@ public key
davisononline.org 0xE855B3EA

alexd · External Since: Dec 15, 2005 Posts: 52

Darren Davison wrote:

> What is the minimum spec (RAM, CPU) machine I'm going to need for the
> back end? Additionally, what network spec will I need to consider? At
> present I have a wireless (g) router and a 10/100 wired hub. I'm
> guessing that might not be enough for the myth setup though.. will I
> also need to invest in a switch and gigabit ethernet for all front-end
> boxes? Or could I get away with using the wireless for front-end boxes?

ISTR it was about 6Mbps for watching SD DVB-T. I'll measure it properly when
I get home tonight. I don't have an HD source, so someone else will have to
answer that.

Wireless speed is highly variable. Bear in mind that actual IP throughput
when connected at 54M is about 24Mbps, and you only get a 54M connection
under ideal conditions. Add to that the fact that it's half-duplex and a
shared medium [like ethernet hub vs switch], and you could get a whole lot
less.

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Tony Houghton · External Since: Jul 22, 2006 Posts: 113

On Sun, 23 Aug 2009 21:36:54 +0000 (UTC)
Darren Davison <nntp.DeleteThis@davisononline.org> wrote:

> I'm seriously considering binning my Sky service and building my own
> mythtv setup. My Sky dish has 3 cables on it (previous house owner must
> have had 3 Sky boxes, we only have one) so I assume I can create a back
> end box with 3 capture cards.
>
> What is the minimum spec (RAM, CPU) machine I'm going to need for the
> back end? Additionally, what network spec will I need to consider? At
> present I have a wireless (g) router and a 10/100 wired hub. I'm
> guessing that might not be enough for the myth setup though.. will I
> also need to invest in a switch and gigabit ethernet for all front-end
> boxes? Or could I get away with using the wireless for front-end boxes?

Any modern CPU should do, and RAM is so cheap there isn't much reason to
get less than 2GB. The graphics card is more important if you want to
play HD. ATM only NVidia 8x00 and better adaptors have stable(ish)
drivers for decoding H264 and on the VDR mailing list they're saying you
need at least a 9500 to decode 1080i *and* perform advanced
deinterlacing on it. One with its own HDMI socket and HDMI audio
obviously makes things easier if connecting to an HDTV.

--
TH * http://www.realh.co.uk

Darren Davison · External Since: Jan 12, 2006 Posts: 26

On 2009-08-24, Tony Houghton <h DeleteThis @realh.co.uk> wrote:
> Any modern CPU should do, and RAM is so cheap there isn't much reason to
> get less than 2GB. The graphics card is more important if you want to
> play HD. ATM only NVidia 8x00 and better adaptors have stable(ish)
> drivers for decoding H264 and on the VDR mailing list they're saying you
> need at least a 9500 to decode 1080i *and* perform advanced
> deinterlacing on it. One with its own HDMI socket and HDMI audio
> obviously makes things easier if connecting to an HDTV.

I take it that's all front end spec there? Useful to know too, but
interested in what I need in a back end box to make 3 capture cards and
3 lots of streaming work.. any advice on that one?

BTW: a 9500 card comes with its own whacking great fan doesn't it? How
noisy are they (was hoping for a near silent front end experience)?

Cheers,

--
darren@ public key
davisononline.org 0xE855B3EA

Tony Houghton · External Since: Jul 22, 2006 Posts: 113

On Mon, 24 Aug 2009 18:21:54 +0000 (UTC)
Darren Davison <nntp.RemoveThis@davisononline.org> wrote:

> On 2009-08-24, Tony Houghton <h.RemoveThis@realh.co.uk> wrote:
> > Any modern CPU should do, and RAM is so cheap there isn't much reason to
> > get less than 2GB. The graphics card is more important if you want to
> > play HD. ATM only NVidia 8x00 and better adaptors have stable(ish)
> > drivers for decoding H264 and on the VDR mailing list they're saying you
> > need at least a 9500 to decode 1080i *and* perform advanced
> > deinterlacing on it. One with its own HDMI socket and HDMI audio
> > obviously makes things easier if connecting to an HDTV.
>
> I take it that's all front end spec there? Useful to know too, but
> interested in what I need in a back end box to make 3 capture cards and
> 3 lots of streaming work.. any advice on that one?

Storage will be your main bottleneck. IME with VDR, I never had any
problems recording two things at once while watching another (I can't
remember whether I ever watched something off disc while recording two
more though), often with Azureus running in the background, with a P3
and an ordinary Seagate 160GB HDD, so if you were only interested in SD
I'd say a newer system with a SATA II HDD could keep up with your 3
cards. However, for recording more than one HD stream at a time you
might need to consider something like RAID0. I'd join the mythtv forums
and ask there IIWY.

> BTW: a 9500 card comes with its own whacking great fan doesn't it? How
> noisy are they (was hoping for a near silent front end experience)?

I think there are silent versions, but then you're probably going to
need a big case with decent airflow. I'd be inclined to go for a lower
power build with onboard graphics and put up with the lower quality
deinterlacing. Hopefully some developer will realise that if the
graphics card is doing the hard work of decoding the video, the CPU
should have enough capacity to run one of the more advanced
deinterlacing algorithms.

Oh, about your networking, I think 802.11g is just about adequate for SD
if reception is good, but I doubt very much it would be up to HD.

--
TH * http://www.realh.co.uk

Tony Houghton · External Since: Jul 22, 2006 Posts: 113

On Mon, 24 Aug 2009 20:22:30 +0100
Tony Houghton <h.TakeThisOut@realh.co.uk> wrote:

> On Mon, 24 Aug 2009 18:21:54 +0000 (UTC)
> Darren Davison <nntp.TakeThisOut@davisononline.org> wrote:
>
> > I take it that's all front end spec there? Useful to know too, but
> > interested in what I need in a back end box to make 3 capture cards and
> > 3 lots of streaming work.. any advice on that one?

[Snip]

> I think there are silent versions, but then you're probably going to
> need a big case with decent airflow.

Speaking of big cases, I forgot to mention you'll probably be limited to
2 PCI cards unless you use a full-size motherboard and case, and it
might still be a bit tricky getting a multi-tuner card to work with the
Linux DVB drivers.

If you've got decent terrestrial reception it might be worth getting a
DVB-T card (USB if your internal slots are maxed out) too, depending on
your viewing tastes. I don't think you can get Fiver, Five US, Dave or
Virgin1 on FTA satellite.

--
TH * http://www.realh.co.uk

alexd · External Since: Dec 15, 2005 Posts: 52

alexd wrote:

> ISTR it was about 6Mbps for watching SD DVB-T. I'll measure it properly
> when I get home tonight.

Looks like lots of short spikes of 10Mbps. Averages out to around 6.5Mbps.

--
<http://ale.cx/> (AIM:troffasky) (UnSoEsNpEaTm@ale.cx)
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"If being trapped in a tropical swamp with Anthony Worral-Thompson and
Christine Hamilton is reality then I say, pass the mind-altering drugs"
-- Humphrey Lyttleton

Darren Davison · External Since: Jan 12, 2006 Posts: 26

On 2009-08-24, alexd <troffasky.RemoveThis@hotmail.com> wrote:
> Looks like lots of short spikes of 10Mbps. Averages out to around 6.5Mbps.

thanks for that.. pretty much means a cat6 wiring exercise then if I
want multiple SD or fewer HD streams?

Cheers,

--
darren@ public key
davisononline.org 0xE855B3EA

alexd · External Since: Dec 15, 2005 Posts: 52

Darren Davison wrote:

> thanks for that.. pretty much means a cat6 wiring exercise then if I
> want multiple SD or fewer HD streams?

Probably. If each client was on it's own access point, they'd each
potentially have 20 odd Mbps of bandwidth to play with. Wireless N promises
300Mbps [with IP throughput presumably half that] but I've never used it.
Some powerline networking [HomePNA] stuff claims 200Mbps throughput, again
not something I've used. If you've got coax running to places with TVs [as
your OP sort of implies], then HomeCNA can get 128Mbps out of coax. Could be
easier than pulling new copper.

If you need to test what throughput is available between two points, I
suggest iperf.

--
<http://ale.cx/> (AIM:troffasky) (UnSoEsNpEaTm@ale.cx)
19:10:41 up 111 days, 11:48, 3 users, load average: 0.35, 0.26, 0.19
"If being trapped in a tropical swamp with Anthony Worral-Thompson and
Christine Hamilton is reality then I say, pass the mind-altering drugs"
-- Humphrey Lyttleton