[mythtv-users] How does MythTV Networking work?

Tue Feb 10 02:05:02 EST 2004

If you won't be watching video on the backend machine, the video card won't 
matter, true.

> I'll probably use Hauppauge PVR-250s for the capture. I can use multiple
> cards in the same machine with no problems, right? And with two (or more)
> 250s I can have two (or more) frontends watching live TV with different
> channels at the same time?

Two or more PVR-250's is perfectly possible, assuming your motherboard 
supports enough slots. I recommend using only busmastering-capable slots.

> If I'm using the PVR-250s CPU isn't a major issue, right? So a decent
> Athlon or even a Duron 900 would probably be okay? (I'll be encoding to
> MPEG2, of course).

CPU is not a _major_ issue for a backend-only machine using PVR-250's, but 
it's not a non-issue either. I'd guess that a Duron 900 with more than two 
cards may be ok for backend-only, but I don't have any firsthand data for 
that. I run a 1.4GHz Athlon box with two cards, and it hits under 30% CPU 
when recording on both cards without playing anything in the frontend.

> I assume there aren't any problems using an external fileserver for
> storage? How many video streams will I be able to record at once using an
> external NFS mount over 100MBit Ethernet?

That's simple math. I can get 8 to 10 MB/s via NFS with no other traffic and 
minimal disk activity on my server. If you are running a full duplex switched 
network it's a lot easier. (With half-duplex, multiple streams over NFS 
collide the heck out of each other and performance goes down the tubes in my 
experience.)

So I can push about 30GB/hour across my full duplex switched 100baseTX network 
in practical experience. I'm using rather modest capture bitrates 
(3500/5000), which tends to come out to 1.7GB/hour. Even if I were to use 
higher bitrates and 3 cards I'd be well below the capacity of my network.

- -James Paul

> > -----Original Message-----
> > From: mythtv-users-bounces at mythtv.org [mailto:mythtv-users-
> > bounces at mythtv.org] On Behalf Of Andrew Dodd
> > Sent: Monday, February 09, 2004 9:10 PM
> > To: Discussion about mythtv
> > Subject: Re: [mythtv-users] How does MythTV Networking work?
> >
> > Quoting Scott Nicholson <mythtv at scottnic.com>:
> > > I'm interested in building a MythTV box or boxes. I want to be able to
> >
> > view
> >
> > > both live TV and recorded shows (as well as use MythMusic, etc.) on at
> > > least
> > > two TVs in separate rooms. I want all recorded shows to be available to
> > > both
> > > TVs. I want to be able to easily add additional TVs in the future.
> > >
> > >
> > >
> > > Without knowing a lot about MythTVs network capabilities (there isn't a
> >
> > lot
> >
> > > of info on the site -- not that I've been able to find, anyway), it
> >
> > seems
> >
> > > like there are at least a couple of ways of doing this:
> > >
> > >
> > >
> > > Option 1:
> > >
> > > High-powered multiple tuner "server" in the basement (at least two,
> > > possibly
> > > three or more tuners, lots of storage) and a couple of lightweight
> >
> > frontend
> >
> > > boxes at the TVs. The frontends would need to be able to schedule
> > > recordings, etc.
> > >
> > >
> > >
> > > Option 2:
> > >
> > > Forget the server. Just build a couple of boxes to put at the TVs that
> >
> > can
> >
> > > talk to each other. One (possibly two if I decide one isn't enough)
> >
> > tuner
> >
> > > in
> > > each box, with some sort of negotiation and conflict management (i.e.
> >
> > box1
> >
> > > is scheduled to record show "A" and I schedule a recording for show "B"
> >
> > on
> >
> > > the same box -- the box detects the conflict and tells box2 to record
> >
> > show
> >
> > > "B" instead.). The boxes share their lists of recorded shows, so it's
> >
> > easy
> >
> > > to watch show "B" on box1 (even though it's box2 that recorded it).
> > >
> > >
> > >
> > > I guess there's a hybrid of these two, as well, with the individual
> >
> > boxes
> >
> > > recording to a server that's really nothing but a fileserver.
> >
> > All three options work.
> >
> > Although I've noticed that with 0.14, remote frontends can sometimes be a
> > little
> > laggy when navigating menus.
> >
> > I'm personally heading towards option 1.  I just need a motherboard, CPU,
> > and
> > RAM to move my recording backend to a seperate machine, then I need to
> > run 100
> > Mbit drops to every point in the house that has a coax running to it.
> >
> > Once I do that, I'll be ready for $100 frontends when the Xbox drops its
> > price
> > in May.  (Well, the sources I've seen say that it's a rumored drop, but
> > someone
> > that posted earlier today seemed relatively sure of it.)
> >
> > _______________________________________________
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> >
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