[mythtv-users] Strange Issue with Myth and HDHomeRun

[John Welch]

I've had MythTV up and running for closing in on a year now.  For the last
month I have been trying to integrate a HDHomeRun into my system.
Unfortunately I've run into a string of problems, the latest of which is a
strange one that has me stumped.  I've been posting on the HDHR forums (
silicondust.com), but so far no one over there has come up with any ideas.

First, some background on my systems.  I have a split back-end/front-end
setup.  The B/E has an AMD Athlon XP 2200+ processor, with 1 GB of memory,
and a NVidia FX-5200 graphics card.  The system has two tuner cards; a
PVR-150 for analog channels, and a pcHDTV HD-3000 card for SD/HD channels.
I have a Comcast cable feed coming into a four-way splitter, with two
outputs going to the tuner cards, and the other two going to the HDHR.  With
both the HD-3000 and the HDHR I'm getting around 45 QAM256 channels.  The
F/E system has an AMD Sempron 3100+ processor, also with 1 GB of memory and
a NVidia FX-5200 graphics card.  Both systems are running Fedora Core 6,
with all updates applied.  Both systems are running Myth SVN packages from
ATrpms bleeding repo (revision 12674, from on or around January 30th).  I
noticed this issue prior to upgrading to the SVN version, which was
necessary to fix another issue with the HDHR and the tuning of QAM256
channels.  So, I don't want the fact that I'm running SVN to be a red
herring here.  For my network setup I am using IPCop as a firewall, and have
the Myth B/E system and the HDHR in my DMZ network (orange network in IPCop
terms).  The F/E system is on my internal (green) network.  This network
setup has never caused me any issues with MythTV or anything else.

Now on to the problem.  I can record content from the HDHR as long as I
don't do anything with Myth on my F/E system while the recording is taking
place.  However, as soon as I bring up MythTV on my F/E the HDHR recording
becomes "corrupt", for a lack of a better term.  By corrupt I mean there are
severe video and audio breakups and dropouts to the point where the
recording is unwatchable.  This is not just a playback issue; the corruption
is actually in the file.  For testing purposes I have run some of the F/E
functions on the B/E system and this does not cause the corruption to
occur.  This is leading me to believe that there is some type of network
issue, but I can't figure out what the problem is and why it is happening.
Over on the HDHR forums it was suggested that I look at UDP stats using
'netstat -su', but this did not reveal any problems.  I've also looked at
the interface itself using 'ifconfig', but here too I'm not seeing any
collisions, or dropped packets, or anything like that.

My next troubleshooting step is to try to setup a test Myth box in my
internal network, and to also temporarily move the HDHR to the internal
network.  Even if this proves to be the solution I'd like to understand why
my current live setup is not working.

Any thoughts or ideas on the cause of, or a solution to the problem would be
greatly appreciated.

John
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