New feature: QAM Maps

New feature: QAM Maps

Postby rkulagow » Tue Dec 27, 2011 10:29 am

As part of our commitment to you, our subscribers, we have started offering QAM maps.

What's QAM?
QAM is a method of digitally encoding television programs in a format suitable for transmission over coax cable. When you connect a digital tuner to a cable system and run a “channel scan”, the device is searching for unencrypted television signals.

Most cable providers will make your local over-the-air stations available - some providers may give you your entire basic digital package. Some give you nothing.

What's a QAM map?
A QAM map is a text file in channels.conf format containing the call sign, the QAM frequency, the XMLID, the channel number and the program ID for that call sign. For example:
Code: Select all

Call sign WBBM is on frequency "567000000", it's channel "2" on this particular head end's digital lineup, the XMLID is 11299 and it's program "1" on that QAM frequency.

Why do I need a map?
Because running a scan in your application or a tool like "azap" may result in a scan that gives you:
Code: Select all

and that's much more difficult to work with.

Where do QAM maps come from?
They come from you, and the other Schedules Direct subscribers that are in your head end.

QAM maps are generated by users?
Yes. Tribune's systems (the source of the data for Schedules Direct) are not programmed to support QAM because the cable companies don't want to distribute QAM data, so Tribune isn't going to do the R&D to support QAM if there's no "market" for it. Since the cable companies are the ones that would need to request the requirement, (and they're not), Tribune isn’t going to implement something which won’t be used, and which the cable companies won’t supply data for in the first place. We've asked Tribune, and for whatever reason, the cable companies seem to consider QAM tuning information as proprietary. Smaller cable providers, such as Universities may make their QAM information available, but there is still a lot of work on the backend that would need to be done to allow that to get distributed.

I don't see a QAM map!
That's because we don't have information for your head end.

There are two programs that have been developed to allow you to run a scan and share that with Schedules Direct, and thereby with others.

This program extracts a QAM map from an already-configured MythTV system:

This one performs a scan using a Silicon Dust HDHomeRun Prime:

Once we receive a QAM map, our staff will check the mapping for accuracy and make the appropriate edits.

OK, I see that there’s a QAM map for my headend. What do I do with it?
Because Schedules Direct provides support for multiple operating systems, we will provide you with the QAM map. It is up to your application to perform whatever import function is required.

How can I learn more?
Send email to

For discussion regarding this feature, please see the General Discussion forum.
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