[mythtv-users] Program to read virtual channel data from Comcast clearQAM

Kirk Bocek t004 at kbocek.com
Sun May 3 20:39:46 UTC 2009

Dennis Lou wrote:
> Hi,
> I wrote a program that will read the SCTE-65 in-band SI data which contains the virtual channel tables that Comcast has started providing.  Relevant to this group, one of the output options for my program is an SQL script that will update MythTV with the mapping.
> If you're not sure what I'm talking about, here's a bit of background:
> Comcast is slowly making analog go away.  For those customers not upgrading to digital TV's, they are providing free digital to analog converters (DTA's).  Traditionally, their full featured set top boxes (STB's) received all sorts of stuff such as encryption keys, guide data, etc via an out of band (OOB) POD interface.  This is a special receiver that tunes frequencies outside of the normal TV frequencies.  One of the pieces of info that's transmitted is a table that maps station callsigns and virtual channels (the integer channels that the STB's present to the user and that zap2it, the newspaper, etc uses) to RFchannel.program number that clearQAM TV's use.  For example, zap2it, my local newspaper and Comcast say FOODTV is channel 35 but my plasma says it's 78.4 and that's also what I call it in my Myth box. Since Comcast is handing out DTA's for free, they are severely cost reduced and don't have a POD interface. In it's stead, they're transmitting
>  the virtual channel table in-band (i.e. tuneable with a conventional clearQAM tuner) to allow the DTA's to do the virtual channel mapping.
> With the virtual channel map, Comcast could change FOODTV from 78.4 to 119.3 and the DTA user won't notice a thing.  He'll still change to (virtual) channel 35 and still get it.  However, I used to have to sweep the frequency band and take guesses as to where it is.  By decoding the virtual channel map, I no longer have to.
> I have posted the program here:
>  http://www.avsforum.com/avs-vb/showthread.php?p=16387681#post16387681
> If there's sufficient interest, perhaps someone could help me find proper project hosting and perhaps take over maintenance.  I just got my wife a new toy (Internet clock radio).  I think it runs Linux. I'll be busy hacking that. :-)
> -Dennis

Dennis -
I am so all over this app. I can't help with hosting, though, sorry.

I have been manually scanning and updating the clear QAM channels in the 
channels table for a couple of years now. Any kind of tool, even a 
semi-automated one, would *really* help.

Haven't had a chance to test your tool yet. You don't mention what interface 
to the tuner your tool supports. Accessing an HD-5500 attached to a host 
through a PCI slot is a way different creature than an HD Homerun accessed 
over the LAN.

More information about the mythtv-users mailing list