[mythtv-users] How does MythTV Networking work?

Bruce Markey bjm at lvcm.com
Tue Feb 10 01:12:13 EST 2004


Scott Nicholson wrote:
> 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),

Probably true. Here's some cut'n'pates info about multiple
systems:

------8<-------
The backend controls tuner cards and is used for recording.
It has no GUI and is needed on each machine that has one or
more TV cards but is not needed on any machine that does not
have a tuner.

There is exactly one master backend that runs the scheduler
and assigns recording tasks to other backends (if any) which
are called slave backends. Backend are normally running all
the time so they are ready to record and available to serve
any files they have recorded.

The frontend is the GUI that users use for playback. It can
run on a computer monitor or on a TV if the computer has a
graphics card that supports TV-out. A mythbackend may or may
not also run on the same machine depending on if the system
has a TV card. Any frontend can be stopped or started at any
time with no impact on the recording schedule.

There is no master or slave frontend but frontends are often
referred to as local or remote indicating whether or not they
are on the same machine that holds recorded files. Any frontend
can play files recorded by any of the backends.
------8<-------


> 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.

That would work but it works better if you have several machines
with one or possibly two tuners each. As you add tuners, they all
compete for the same system resources. Not jsut the CPU but PCI
bus, interupts, disk cache and disk I/O, memory, and timeslices
form the kernel scheduler. Several cheap systems with one tuner
each will be more efficient and possibly cheaper than one
mamoth server.

> 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).

You don't have t worry about any of this. The scheduler on the
master backend takes care of this for you. Two tuners on a
master or one tuner each on a master and a slave are scheduled
the same way. Also, every time a slave connects or disconnects,
the scheduler is run and does the best job of scheduling for the
number of tuners available. I have a dual tuner master in my
livingroom and a single tuner slave in my bedroom for three in
production at all times. I also have a tuner on my desktop and
a test machine. If I have two NBA games, College Hoops and some
primetime shows, I can add slaves and the scheduler just assigns
the recordings to tuners as needed.

> My question is which of these two options fits in with the way MythTV 
> networking works? (or are they both legitimate options)?

Both legitimate. I think that wherever you have a TV and a
cable drop and you need to have a computer for the frontend,
you might as well drop in a tuner card and get you money's
worth.
 
> Option 1 may also therefore be cheaper(?)

2 may actually be cheaper, You can use fairly low end cheap
systems for one tuner but may need some expensive high end
parts for a server with several tuners and you may not be
happy with the results.

--  bjm


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