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

[Brian Beaty]

I'm a Comcast Digital/HD subscriber in the Fresno, CA area. I got  
myth 0.20 up and running via Firewire to the DCT6200 that Comcast  
gives out as their HD STB. It tuned 85% of my channels (pretty much  
all but in-demand, PPV, and HD versions of subscription channels).  
Probably ~150 digital channels, and nearly 100 analog channels total.

After 3 firewire chipsets, I gave up on it, I couldn't get a reliable  
setup via firewire. The best I could get was about a 50% success rate  
with recording, the rest of the time the Firewire port would just  
fail to get any data or fail to change the channel. From all the  
research I could find, this was "common" with firewire setups (of  
course, most of the people that write to the mailing list, or post on  
net are doing so trying to answer problems they have), and I suspect  
it's more a failing of the DCT6200 than linux firewire support. The  
firewire issues are not the subject of this letter, however...

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

Some other research on pcHDTV's forums revealed that Comcast strips  
out all channel/program info, so all 210 channels show up as  
"Unknown". No big deal. I sat down for 3 hours, going through them in  
Live TV mode, and editing the channel information.

Out of the 210 channels, only 31 had any signal, and of those 31,  
only 22 of them actually matched up to anything on my subscription  
list (9 mystery or bonus channels, depending on how you look at it).  
The other 177 channels were black background with a small blue square  
in the lower right hand corner.

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. So ~150 channels via  
firewire, and only 31 via the 5500, it doesn't quite add up. I also  
can't get NTSC signals via Myth at all (they work fine via tvtime on / 
dev/video). Supposedly the DVB driver supports this, but scanning / 
dev/video with myth, and it doesn't even attempt to scan, it just  
skips right to an empty scan list.

Also interesting to note, is that mythtv's scanner finds 210 QAM  
channels, linuxtv's dvb apps scan detects 243 QAM channels, and the  
dtvscan util from pcHDTV finds 252. None of them list any signal  
strength or channel info, but from what I can tell, this is a bug  
with DVB support in the 2.6.18 kernel, and Comcast stripping all  
program information.

I  could get all channels if I use the CATV or S-Video output on the  
DCT6200 (assuming I can stumble upon getting NTSC working in myth),  
set the 5500 up to just record NTSC Ch3, and use 6200ch (or an IR  
blaster, but that would be even more money...) to change the  
channels; I get all my subscribed channels (even encrypted ones), but  
I lose HD, still have to go via the STB, and I could have just gotten  
a $30 capture card rather than a full-blown QAM-compatible HD tuner  
card - so I'd rather not do this.

For the purposes of troubleshooting, I've connected the tuner card  
straight to my cable outlet, with no other devices or splitters on my  
cable line. I'm running Fedora Core 5, Kernel 2.6.18.2239, with the  
latest 5500 drivers compiled and installed from pcHDTV's site. Myth  
0.20-144 from the atrpms distro.

Any advice on getting this 5500 working, or should I ebay it and head  
back via either the firewire/STB output route?


-bb