[mythtv-users] ITX vs ATX for dual-DVB system

Nick knowledgejunkie at gmail.com
Sat Oct 8 23:05:28 UTC 2005


On 08/10/05, Jules Bean <jules at jellybean.co.uk> wrote:

> The system will be for watching DVB-T digital broadcast TV, as well as
> DVDs. This means that it presumably doesn't need to be terribly
> powerful from a CPU point of view? No encoding or transcoding to do.
> It will be in the living room, under the TV, so it has to be quiet and
> look reasonable. No HDTV; I doubt we'll have HDTV DVB in the UK for a
> few years.

For few, read "likely when hell freezes over ...!" Just wait until
they start pumping out proper 1080 video and all those people who
bought HDTV-ready plasmas and LCDs (with a native v-res of 720 pixels)
realise they've been shafted...

> One of the key branch points seems to be on the source of TV-OUT
> support. On the one hand their are the cute little VIA boards with
> built in TV-OUT, a graphics chip well supported under linux, in the
> mini-ITX form factor. The problem with these is that I really want 2
> tuners, and I don't much like the idea of USB tuners dangling off the
> back of what is supposed to be a neat little machine. It *is* possible
> to buy 2-card PCI risers, but I don't know if they are reliable, or if
> they even fit inside the
> cases. (http://www.tranquilpc-shop.co.uk/acatalog/PCI_Risers.html)
> (but only the most expensive epia, the EPIA SP has SATA, and I think I
> probably want SATA?)

SATA provides better airflow in a small case (much better cable
management if the board builders manage to orient the SATA plug the
correct way and close to the HDD cage (and supply a short cable). If
you want to keep things simple, make sure the SATA controller is
supported by the distro's kernel.

> The other approach would be a standard mini-ATX motherboard, in a case
> large enough to take at least low-profile PCI cards (the AverTV 771 is
> low-profile, I believe). This would probably mean a socket 939 setup
> with a cheap AMD64 chip and some expensive quiet fans, and an
> expensive quiet case. But the sticker is the graphics card. I gather
> that most people on this list are either using the TV-OUT abilities of
> their Haupage PVR cards, or are using GeForce cards. A Haupage is
> clearly pointless in a DVB-only setup, and I really, really, really
> don't want to have an nvidia card, and nvidia's closed drivers, on the
> box. The sensible option then seems to be a cheapo Radeon 9250 TV-OUT,
> which is supported by the gatos drivers.

Supported my the fglrx ATI drivers too I should think. I'm still
happily using my ATI 9100IGP on-board TV-Out (haven't swapped back the
PVR-350 now that the xv support is there) and have not problems at all
(aside from a very slight trapezoid distortion on the LHS)

> Does anybody have any feedback on this? It's the PCI riser I'm most
> scared about, I don't understand PCI deeply enough at the hardware
> level to know if they provide good enough performance for two DVB
> tuners running in parallel.

The obvious solution - dual tuner DVB cards - are on the horizon, so
it depends how long you are prepared to wait! My Pundit-R system has 2
PCI cards on a riser (PVR and DVB-T) with no problems. The data rates
transferred over the bus are very small compared to its capacity, so I
wouldn't expect to have any problems with just 2 cards.

Nick


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