[mythtv-users] Comcast Digital HD and HDTV-5500

[Greg Woods]

On Sat, 2006-11-18 at 00:20 -0800, Brian Beaty wrote:

> After 3 firewire chipsets, I gave up on it, I couldn't get a reliable  
> setup via firewire.

I am in the same boat (Comcast in Louisville, CO (near Boulder).

>  The best I could get was about a 50% success rate 

You are doing better than I. I can't get firewire to work at all.
"plugreport" shows that it is there, but I have tried all possible
combinations of poweroffs and reboots, multiple times, to no avail. The
channel changer works fine, so I know the connection is there, but I can
never record anything but empty files, and the firewire_tester program
always fails (even in reset-bus or fix-broadcast modes). test-mpeg2 also
records empty files (and yes, I know about setting -r to match what
comes out of plugreport).

I shouldn't say "never". I might be easier to stomach this if it really
was "never", but a couple of times, I had it working for a very brief
time. The recordings I got display perfectly, including HD. Closest I've
come to getting any HD into Myth.


> So I decided to sink a bit of money into it, and got a pcHDTV 5500  
> card. 

I did the same thing, but about a year and a half ago, so with me it was
a pcHDTV 3000 card. I could never make this work either. All I got was
garbled channels. Not encrypted-style garbled, the channel was there and
I could kind of see the picture, but it would break up into little
squares with garbled sound most of the time, occasionally showing the
picture for a brief period, but long enough so I could see which channel
it was. Even some brief HD pictures were seen. But I could never solve
this problem either despite replacing the power supply (some sort of
interference was theorized) and playing with latency settings. Like you,
I tried connecting the card straight to the cable line with no splitters
or amplifiers. The channel scan also showed very high signal strength
(over 98%), with or without splitters/amplifiers, so I know it was not a
signal strength issue.

> I studied the wiki carefully (http://www.mythtv.org/wiki/ 
> index.php/Adding_Digital_Cable_Channels_%28For_ATSC/QAM_Tuner_Cards_-- 
> _USA/Canada%29) The driver installed fine, Myth picks it up fine.  
> Scanning channels, I get 210 distinct QAM256 channels (which is  
> pretty darn close to what my subscription has).

I went further than this even. I gave up on the DVB card, and got an
HDHomerun. This does a little better. I am trying one tuner OTA and the
other with QAM. I still cannot make this work reliably, but at least I
can tune some channels, and I haven't given up on this yet. It looks to
be the most promising thing I've tried so far to get access to
digital/HD (my PVR-500 card has always worked great for NTSC/analog
channels). I am probably going to have to mount a rooftop antenna to
make OTA work; I get a few channels off my living room antenna, but
again no HD even though I know some channels are available in my area
(~25 miles from Denver). But this is beyond my handyman skills and so it
will require a major investment which I am reluctant to make without
knowing for sure that it would even work.


> I understand that QAM-capable tuner cards can't decode encrypted (5c)  
> digital channels. I also was under the impression that Firewire  
> couldn't pass these channels through either. 

See below; I don't think these are the same set of channels necessarily.
There are clearly some channels that I cannot tune with a direct QAM
cable attachment that are available via firewire from the STB (if I
could only make it work).

> So ~150 channels via  
> firewire, and only 31 via the 5500, it doesn't quite add up.

I got myself a TV that can tune QAM directly. I did a channel scan. The
results are interesting but disappointing. The TV can tune close to 100
channels, including many digital channels as well as all the NTSC ones
and digital versions of those same channels. Probably I will eventually
be able to get these via the HDHomerun as well (the QAM256 code doesn't
seem stable yet; I get backend crashes and "error displaying video"
bluescreens in the frontend, even with the latest SVN). But only two HD
channels are found: the local NBC affiliate, and the local PBS. That's
it. Nothing else HD is available direct off the cable without the box.
It is quite clear to me now that the channels I really want (ESPN-HD and
so forth) are simply not available without the damned STB. So it would
appear that firewire is the only available option. Lots of these
channels would be available over firewire if I could only make it work,
based on the 5c=0 setting they have on the box powerup menu. I think the
only thing left to try is swapping out the DCT-6200 box with Comcast
(which I think they will do if I ask) and hoping for better
firmware/software on a replacement box.

The point of this (aside from venting a year of frustration )-: is that
there are some channels on my cable system (and maybe yours too) that
you won't be able to get into Myth with a QAM card no matter what you
do. Firewire is the only way for those.

--Greg