New lineups for new qam-addressable Comcast channels?

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New lineups for new qam-addressable Comcast channels?

Post by StefanJ »

Comcast is starting to drop its Standard Cable plan in many areas. The conversion entails replacing the upper-range analog channels with digital equivalents. Subscribers will get an STB and a couple of simple "DTAs" so their analog TVs won't be useless.

I've learned that these new channels will be clear QAM channels. Actually, they're already there in my area, Portland OR. I can tune them in with my HDTV (no cable card or STB, just a straight QAM tuner). This means that digital PC card tuners like my pcHDTV3000 should be able to pick them up without a STB, DTA, or the complexity of an IR blaster.

Now, SD currently provides two Comcast lineups for my area:

97124 Beaverton, US Comcast Tualatin Valley Regional Cable
97124 Beaverton, US Comcast Tualatin Valley Regional - Digital CableDigital

The former only includes analog channels, 2-77.

The latter includes the digital channels, 1-722. These are the "presentation" numbers that Comcast assigns; they don't have a mapping to QAM addresses. This is handy for those with STBs and IR blasters.

The problem is, neither is ideal for the situation that I find myself in. My digital tuner is able to receive the QAM channels, but the channel details (name, callsign, XMLid) have to be added manually. I've already done with this with the "broadcast" clear QAM digital channels (e.g., OBPTV-DT, 10_1) available on standard cable by editing the detected channels and putting in the XMLid from the broadcast channel lineup.

More and more SD users are going to find themselves in this situation. I believe a third Comcast lineup is called for. It would list the channels in QAM channel format, rather than the digital channel number format. If I understand things correctly, the mythtv channel scanner would then be able to automatically fill the database tables with the appropriate information, making these channels available immediately, with no further editing.

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Re: New lineups for new qam-addressable Comcast channels?

Post by rmeden »

I've asked Tribune about QAM tuning info many times, and the answer is basically the cable companies don't want them distributing it.

MythTV does allow for manual channel configuration. I recommend you use the Digital lineup as it will have all the channels, and manually map the XMLID of the station to the QAM tuning info.

If there is interest and some development help, SD could probably host a generic XMLID -> QAM API. Another problem is I have heard QAM tuning info changes frequently (daily), but I'm not sure.


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Re: New lineups for new qam-addressable Comcast channels?

Post by killabee44 »


I am setting up my HTPC and am running into this exact same problem. I am in South Florida with Comcast and here the clear QAM channels are in this format:

103-30, 130-34, etc.

This HTPC is a Mythbuntu machine. This is all new to me so if no channel lists for QAM is available I might get a refund on my SD subscription. If anyone has figured a fix please advise. Thanks.

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Re: New lineups for new qam-addressable Comcast channels?

Post by StefanJ »


The QAM channel format is "hidden" in normal use. The cable company configures their STBs -- the official way to view their offerings -- so that the channel selection is a simple numeric list, with no dashes or what-not.

The classic channels retain their old number. For example, in Portland SyFy has been "59" for years and years. The STB knows it is on 64-6, and displays what is on that channel when the user tunes to channel 59.

New channels, such as the HD versions of channels and new channels that broadcasters added to take advantage of digital, are added as high-numbered channels. So, while ABC's HD channel is 2-1, the STB translates it to something way up there. 702 or something.

SD's guide data uses the cable company's channel numbers.

What does this mean to you?

Use MythTV's mythtvsetup app's video sources page to scan for channels. Then use the Channel Editor page to assign the "channel guide" number -- the one you see in the newspaper TV listings -- to the digital channels.

Here's the rosetta stone:

Plug in your zip code, then select your cable system. It shows how the clear QAM channels in your area map to the Comcast channel listings.

In my Myth setup, I actually have a mix of number types. My channel list looks like:

2 = Analog channel 2, still available on basic cable.
2D = Standard def Digital version of channel 2, which is 91_40 but I renamed for conveinience sake.
2_1 = High-def digital version of channel 2, which is 91_2 and 702 on the Comcast channel guide, but which I again renamed.
6 And . .
6D So . . .
6_1 On . .

Which channel I choose for a particular recording depends on which tuner is available, and whether I care about HD or not. So, might record CSI on 6_1 with one tuner, and The Office on 8 on the other analog tuner (who cares about hi-def for a sit com).

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Re: New lineups for new qam-addressable Comcast channels?

Post by markbean »

I had the same problem. The good news is that there is a tool to help you out. More details are available

I am an extreme newbie but I've made some progress. I can't speak to if this is the most efficient way to do it. I downloaded and compiled the tool. You need to find something called a VCT_ID which I believe is what the STBs use to map channels to virtual channels. The wiki link give directions on how to find your VCT_ID but I don't have a STB so I couldn't do it. I ran scte65s with no arguments and it showed a few different mappings (My understanding is that these are currently being broadcast in the clear by Comcast). I picked the mapping that looked like what my mapping should be. I ran the scte65s with the ID and it generated a text file to insert into MySQL. I followed the wiki's instructions on how to import the file into MySQL but I needed to specify the user was root (sudo does not work, it's a mysql switch -u or something). I then made sure the the source had the proper lineup and ran mythfilldatabase. It worked! Unfortunately all of my HD local broadcast channels were gone. I then scanned for channels and added them back. Now I could only see listing information for the SD channels and not the HD channels. I'm now going through the process of manually changing the XMLTV IDs for the HD channels to match their SD equivalents. Since they broadcast the same info it seems like it should work. Thoughts?

If someone knows of a better or more efficient way to do this please let me know. Also, since this is such a time drain, I will want to backup the channels settings after I'm satisfied with them. Any suggestions on how to do that? Could I just output to a text file and then import them to mysql (as per the wiki instructions) if I need to restore them?

I hope that this helps. I'm a newbie who has been helped by many so I would love to be able to pay it forward.

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Re: New lineups for new qam-addressable Comcast channels?

Post by StefanJ »


You might have more luck asking that question on the MythTV user email list. There's a better chance of finding someone with the specific answers you seek.


I believe that Myth doesn't like it when channels share the same xmlid.

The HD versions of network channels have their own xmlid. You can find them in the Broadcast lineup for your area. There aren't that many, so I just added them manually.

FWIW: The HD version of the PBS station in my area has a slightly different lineup than the SD station. The differences aren't much, but they're there!

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