LinHES Forums
http://forum.linhes.org/

How I got my HD5000 Air2PC Working
http://forum.linhes.org/viewtopic.php?f=15&t=7413		 Page 1 of 1
Author:  balthisar [ Fri Dec 16, 2005 7:59 pm ]
Post subject:  How I got my HD5000 Air2PC Working
This is a followup from my topic at my other thread. I stated:
balthisar wrote:
I've autodetected the following channel connected to my Comcast basic cable line using QAM:
Code:
    WJBK-DT -- 21
    WDIV-HD -- 41
    WXYZ-HD -- 71
    WTVS-HD -- 561
    WTVS-SD -- 562

According to Comcast, these channels don't exist at these channel numbers. But I'm not using an antenna and got them with a QAM search, so I'm satisfied that Comcast is proving them -- right?

Now if I look at antennaweb.org, I get the following:
Code:
WJBK-DT 2.1  Detroit
WDIV-DT 4.1  Detroit
WXYZ-DT 7.1  Detroit
WDWB-DT 20.1 Detroit
WFUM-DT 28.1 Flint
WADL-DT 39.1 Mt. Clemens
WKBD-DT 50.1 Detroit
WTVS-DT 56.1 Detroit
WWJ-DT 62.1  Detroit


Hmmm... the subchannels are identical to channels above! Again, since these other channels weren't found, I'm still convinced I'm getting these via QAM over the cable, and that Comcast simply isn't providing all of them. I conjecture, then, that Comcast is just "being cool" and providing the QAM for people without set top boxes, and if I subscribed to digital cable WITH A BOX I'd not use the QAM channels... am I missing something here?


So... I'd still like to know what's going on, but for the sake of helping others ('cos I've been helped here a lot!), here's what happened to me.

It appears I get the five channels listed above via QAM and Comcast. The DataDirect/Zap2It don't have that in the cable lineup. But... the channels are identical to the broadcast lineup but for some slight differences. For example, on Comcast QAM channel 21 corresponds to broadcast 2_1. QAM 561 corresponds to 56_1. And so on. Here's how I got it working:
  • Create the DataDirect (zap2it) lineups with the broadcast signals for my area, selecting only the digital channels (56.1, 2.1 and so on).
  • Scan for channels before running mythfilldatabase. You'll get the QAM channels on the list.
  • Run mythfilldatabase to get the zap2it data.
  • Go back in the channel editor, you'll see the broadcast channels. For each broadcast channel (like 56_1 etc), write down the XMLTVID that it has, and make the channel invisible.
  • Then for each of the true, discovered QAM channels, UNSELECT the "use over the air data" option and fill in the XMLTVID for the corresponding channel that you had.
  • In MythTV, you'll now see the appropriate data with the appropriate channel, and no false channels in the channel guide.
  • Note: for some reason on channel discovery, mythtv-setup would occassionally find two copies of every channel. Never on a fresh install, though, so I think it's a bug when dropping all of your channel data to start over. I didn't want to do yet another fresh install, so I dropped the duplicates in mySQL. The MythTV documentation indicates how to get rid of extra channels, or if you know mySQL it's obvious and easy to find.


So, any idea what's going on with Comcast here? I've got my problem fixed for now, but it's still a hack -- or is it???
Author:  akulcsar [ Fri Dec 16, 2005 9:15 pm ]
Post subject: 
Hi, balthisar.

First...thanks for following the rules and creating a new thread. :)

Second...yes, QAM is kinda hackish right now.

You are correct in that the channel numbers assigned by the channel scan do not match the channel numbers that you would use with a Comcast HD box (e.g. WDIV [NBC] is channel 4 in our area; using an antenna, WDIV-HD is channel 4.1; but on Comcast, WDIV-HD is channel 232). If I understand correctly, the channel scan attempts to pick up the station identifiers from the signal...hence, when the channel scan comes across WDIV-HD it listens to the signal a bit and decodes that its station identifier is channel 4 subchannel 1 (i.e. channel 4.1). So, it assigns that channel number (myth can use an underscore, period, or nothing to separate the channel and subchannel; it defaults to using nothing) and moves on, not knowing that your cable provider uses a completely different channel number.

Your hack works perfectly for channels that are normally available over-the-air...but what about those other channels to which you subscribe?

In myth 18, if the channel scan decodes a signal but the signal does not carry a station identifier, it ignores the signal. In myth 19 (currently in SVN stage), it adds the channel with a seemingly cryptic channel number (e.g. 16#1 and, yes, there is a reason behind the channel numbers that it uses). For those channels, you would need to figure out what channel that is (basically by watching each channel) and manually entering the appropriate XMLTVID and/or change the channel number to the correct one. Still a hack, but you can get it to work. There are scripts out there that can assist with this work, but I have not tried them; thus, I cannot comment on how well they work.

There are threads elsewhere that discuss upgrading to the current SVN version of myth (which is a dangerous thing to do on a "production" machine...do it in a test environment only) if you are interested in doing so. Compiling under KnoppMyth is a painless endeavor. You actually can follow the directions right out of the "official" myth documentation on obtaining and compiling from SVN.

Good luck!
Author:  balthisar [ Sat Dec 17, 2005 11:36 am ]
Post subject: 
Wow... so you're saying that there are more than likely other QAM channels available to me over Comcast, but that they just didn't get picked up because they don't have the embedded broadcast signal the terrestrial stations put into theirs?

Rather than going on a svn (this is like cvs?) version of Mythtv, then, are these missing channels something that the Linux TV "dvb-apps" would find, then I could enter the channels manually somehow? Or heck, all I'd really need is mythtv-setup from svn -- not the front end, right?

Thanks -- I'm getting the hang of this, and this system so far is fantastic! Timely, too -- my Series One Tivo is on its last legs...
Author:  akulcsar [ Sat Dec 17, 2005 1:52 pm ]
Post subject: 
balthisar wrote:
Wow... so you're saying that there are more than likely other QAM channels available to me over Comcast, but that they just didn't get picked up because they don't have the embedded broadcast signal the terrestrial stations put into theirs?

That's what I am saying, yes. It is an educated guess based on my personal experience, though. I am not a myth developer.

Quote:
Rather than going on a svn (this is like cvs?) version of Mythtv, then, are these missing channels something that the Linux TV "dvb-apps" would find, then I could enter the channels manually somehow? Or heck, all I'd really need is mythtv-setup from svn -- not the front end, right?

Running a newer version of mythtv-setup will upgrade your database. I definitely advise against this. Check this thread (among others) for more discussion, but
  • moving back-and-forth from one version of myth to another is difficult-to-impossible most times because the database schema upgrade that is applied when you move up a version may not be compatible with previous versions.
  • the myth 19 schema may not yet have been finalized, so an SVN checkout may not upgrade properly to the released version of myth 19 (as is generally the case with an SVN version...myth 19 is not an exception in this regard).

SVN (the standard abbreviation for SubVersion) is a "supercharged" CVS. Many developers are moving off of CVS to SubVersion because it has a lot of additional functionality.

Quote:
Thanks -- I'm getting the hang of this, and this system so far is fantastic! Timely, too -- my Series One Tivo is on its last legs...

Yeah...Isaac and the rest of the myth gang have a great thing going, and Cecil and Dale have rolled it into an awesome package in KnoppMyth. I am hoping to contribute to the latter after the new year...I'm keeping it a secret for now as to what since I finally have a vacation where I can look at it closely (three weeks in Montana...SNOW SNOW SNOW!!!)

Feel free to holler with other questions. Here to help as best I can...I am happy to contribute what I can to this great project. Cheers!
Page 1 of 1 All times are UTC - 6 hours
Powered by phpBB® Forum Software © phpBB Group
http://www.phpbb.com/