[mythtv-users] Pixelation/Bad Recordings HDHR Prime -- I am at my wits end

[Captain Hook]

On Wed, Aug 28, 2013 at 3:35 PM, Greg Woods <greg at gregandeva.net> wrote:

> On Wed, 2013-08-28 at 12:09 -0700, Gary Buhrmaster wrote:
>
> > With rare exceptions, the "management" address for all cable modems
> > is 192.168.100.1
>
> Certainly not so any more. I just got a new modem from Comcast, a DOCSIS
> 3 to replace the old DOCSIS 2. This modem is clearly designed as a "one
> size fits all" for all of their customers. It has jacks for the phone
> service. It has a wireless access point built in and four ethernet
> ports. It is hard-coded with an IP address of 10.0.0.1, and it insists
> on assigning 10.0.0/24 addresses to every machine in the house. The old
> dumb modem was really just a bridge; whatever machine you plugged in to
> the ethernet port got the public IP.
>
> For me, this change sucked, because I have IP addresses hard-coded in
> all sorts of places (including MythTV of course). So I basically had to
> reprogram my Linux system that was acting as my router to account for
> this; it is attached to the "house" network, so that all the other
> machines in the house can keep their IPs. And then it is attached to the
> 10.0.0/24 net and sets its default route to 10.0.0.1. Thus I have
> another router between me and my public IP. I had to make a number of
> other changes to make this work (IPSEC tunnels and so forth; fortunately
> the Comcast box at least supports port forwarding). I continue to use my
> Netgear router as the wireless base station (that's all the Netgear is
> now, but it can be put into place to replace the Linux router if there
> should be problems with that box). The Comcast wireless network is
> useful as a "guest" network, so that I can give guests access to the
> Internet without giving them access to the house net.
>
> Comcast is in the process of replacing all of the modems in our area
> with these new ones.
>
>
> > After the modem downloads its config from the MSO it also gets a
> > management IP address (in theory only available from the cable side)
> > which is used to configure and poll the device for management purposes
>
> There is no way to access this through the web interface. All I can see
> is the "public" IP and the 10.0.0.1 internal one. But it wouldn't
> surprise me if the external interface has an additional address. One
> more reason to have another router between the Comcast device and my
> other systems. I certainly don't trust them. Or the teenage hackers in
> the neighborhood; how long before this "management" network is used to
> break into somebody's house machines?
>
> --Greg
>
>
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The IP address of my modem is in fact 192.168.100.1. It is an Arris TM702G.
I thought for sure it was a router and wireless access point as well but I
never really looked at it because I had zero intention on using it for any
of that anyway. It turns out that it just provides cable internet and
telephony. It does support DOCSIS 3.0 (but doesn't appear to be using it).
It seems to update the firmware on it's own because it is showing a build
date of May 2013, and I had it installed in September 2012. I know I
haven't updated it manually and I don't see a section in there to do so
anyway.
I probably couldn't access it through my VPN because I may already be using
that subnet here for one of our wifi networks (development or otherwise),
but I was able to access it through my PC at home.
In any case, I rewired everything again (diagram link below). Now I have
the signal from Comcast (including the MoCA filter) coming straight into
the Motorola 2-output amplifier. One of the amplifier's output feeds to
another Comcast-installed splitter (-3.5dBmV per output loss) that goes to
my TVs (and Comcast set top boxes). The other amplifier's output feeds to
the Comcast-installed coax cable that then goes into an old splitter I had
(-3.5dBmV loss per output). One of the outputs on this splitter then goes
to my cable modem. The other output of this splitter is connected my
Monster Cable splitter (-7.5dBmV per output loss), which is a 4 output
splitter. Included were 3 F-type terminators to use if you are not using
all of the outputs. With these installed, my signal was still a bit high,
so I removed them and these outputs are just empty. With this setup, my
HDHR Prime signal was still showing approximately +5dBmV, give or take
1dBmV, depending on channel.
In my quest for "0.0dBmV", I then installed yet another old splitter I had
(-3.5dBmV/output loss) prior to the HDHR Prime. So now, I have 3 splitters
in front of my HDHR Prime to intentionally drop the signal, after
amplifying it. With this configuration, I am seeing between -1dBmV and
+1.5dBmV, depending on channel. My cable modem is reporting 4 readings,
depending on "DOCID", that vary between +4.48dBmV and +6.01dBmV. New
diagram here: http://s7.postimg.org/vep1whk6j/Coax_Wiring_Home_Rewired.jpg
I went through and checked everything to make sure it was still working;
internet speeds were good, Comcast set top box worked (as did OnDemand),
and MythTV was showing me a good picture on some of the channels I was
having issues with before (AMCHD, TNTHD). I am planning on running this for
a week or so to determine how it works. Unfortunately because the issue has
been so intermittent, I think I will need that long to determine if I was
successful. The question then becomes, do I continue to utilize this
ridiculous setup of intentionally dropping signal by using splitters or do
I reduce the number of splitters and exchange the 2 output Motorola
amplifier (+11dBmV boost) for a 4 port Motorola amplifier (+7.5dBmV boost)?

The other option would be to just locate my HDHR Prime after a single
splitter directly where the Comcast signal comes into my house and run a
network cable to it as I do have an electrical outlet over there.

I should connect it to my signal is from the source prior to any splitters
just to see what signal I am receiving.  I would have done that last night,
but I didn't have a network cable long enough.  This may be tonight's
project.
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