[mythtv-users] remote viewing/UPnP question

Raymond Wagner raymond at wagnerrp.com
Sun Sep 30 23:20:49 UTC 2012

On 9/30/2012 16:20, Ross Boylan wrote:
> I've taken a couple of runs at accessing myth remotely, but have yet to
> succeed.  Some of the docs I read confused me.  In particular,
> http://www.mythtv.org/wiki/UPnP says "Make sure you have a route for
> out your lan nic BEFORE mythbackend starts (route add -net
> eth0). It seems it won't work if you add the route later."

That really depends on the system configuration. Some claim having such 
a route configured is necessary for things function. I never recall 
having to do such on my systems, on either Linux or FreeBSD. Whether 
modern versions of the Linux kernel simply assume those routes and don't 
bother displaying them, or that is controlled by some sysctl, I don't 
know for certain.

> But other material suggests that isn't the only IP range that needs
> special handling.  http://en.wikipedia.org/wiki/Universal_Plug_and_Play
> says that version 1.1 references http://tools.ietf.org/html/rfc3927
> which in turn refers to 169.254.*.*.  And the discussion of multicast at
> http://tldp.org/HOWTO/Multicast-HOWTO-2.html says 224.0.0.* is for
> management of the multicast 239.*.*.* addresses.

The whole 224/4 block is allocated for use by multicast. That includes 
everything from to The UPnP autodetection 
mechanism in particular only actually uses the address 
When you want to announce yourself or perform a search, you multicast a 
datagram out on that address to anything that is listening. Technically, 
very little consumer networking gear is actually cable of multicast, so 
it all behaves like a broadcast. Inside that datagram is an address and 
port upon which you are available for unicast access. The other machines 
listening on the UPnP address then reply back directly to that address 
and port with whatever information was requested.

In order for that to work, you must exist somewhere on the network to be 
reached. Normally, your DHCP server hands your system an address. 
Sometimes, you define a static address. If you don't get anything from 
anywhere, your system automatically comes up with its own arbitrary 
address to use in the 169.254/16 range. In a fully configured network, 
you have no use for this range. If you are trying to run a network 
without having to configure anything, such that your systems are coming 
up with their own addresses to use in this space, you need access to 
that space, meaning you need an IP address in it and a route defined for it.

> My server connects to the laptop through a wireless router.

Likely not a cause of your basic problems, but something you will likely 
end up dealing with later, wireless networks suck. For high latency 
traffic such as viewing web pages, it's fine. For low latency, high 
throughput traffic like streaming video, it really doesn't cut it. 
Wireless networks will periodically drop out, even in the best of 
environments, and MythTV is designed to operate on stable, reliable 

> I tried using Vista's Media Center (WMC) and Media Player (WMP) to
> access the recordings.  I think they do UPnP, though the information
> I've found is sketchy.  Does anyone know if they work?

I've only ever used it for occasional testing, but it's always seemed to 
work well for me.

> (there is a setup screen that asks you to pick music/video/recordings
> for UPnP--I'm not sure why it's only one, but I set if for recordings).

As I understand it, that is some workaround for screwy Microsoft UPnP 
implementations. Normally, MythTV presents a directory structure to UPnP 
clients, while Microsoft clients ignore that structure, and try to 
resort all the content into its own categorization. That selector is to 
only present one set, so everything doesn't get clumped together in one 
unusable list.

> Some material indicates I need to set up a video directory, which I
> have not done.  It would be empty anyway.  Some of that material says
> I need to configure the external machine name in the folder location,
> and I see no way to do that.

All of MythTV's recording and video library (and soon music and 
photograph) storage is managed by the backend. You define the paths in 
the "Storage Directories" section of mythtv-setup.

> WMC and WMP do not detect any media servers as far as I can tell.
> avahi-discover running on my linux box also does not report any sign of
> myth.

If you left the configured defaults in mythtv-setup for MythTV to only 
listen on, all those autodetection services will be disabled.

> The recordings are directly accessible from the laptop via samba.  Aside
> from the browsing situation being bad because there are a ton of files
> with names that do not reveal their content

If you want to access the files directly from the filesystem, and have 
human-readable names, use mythlink.pl. It will produce one or more 
secondary directories filled with symlinks back to the original 
recording, with filenames formatted using the recording metadata and a 
user-supplied formatting string.

> Finally, some of the TV's I might get say they do DLNA.  Does that mean
> they will work with UPnP, or is something more required?  I realize that
> even if they work the experience won't be great.

DLNA is a subset, and attempt at tighter standardization, of the UPnP AV 
interface. DLNA capable TVs should work with MythTV using varying 
degrees of success. MythTV records content using the original MPEG2/AC3 
compression and TS container it comes in from the broadcaster, and then 
pushes that unaltered to the UPnP client, so any sanely written TV 
client should be capable of handling it. It's exactly the same thing the 
TV should be getting from its own tuner.

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