Automatic Clear QAM station mapping now possible

[mikesm]

Hi there. As part of Comcast and other MSO's move to all digital, they are now deploying a bunch of very simplified STB's called DTA's. The DTA's are being given away to Comcast subs who have expanded basic or better service, and allows Comcast to convert the analog channels to full digital services, reclaining the spectrum and addinga ton of digital capacity to their plant.

Due to FCC regs, the DTA's can't decrypt video without using cablecard, and that makes it too expensive to deploy a typical STB. So Comcast and others are turning off crypto for the digital versions of expanded basic (SD) channels. The DTA can then tune these channels and decode them without the need for cablecard.

However, the DTA still has to be able to map logical channels to physical QAM carriers and program numbers. This is typically done using the VCT messages that are transmitted over the OOB QPSK carrier at 75 MHz, that the hdhomerun and other QAM cards can't receive. I assumed this was being done by equipping the DTA with an OOB tuner, but apparently this is not the case.

A friend pointed me to this thread: http://www.dslreports.com/forum/r21518134-Digital-Transport-Adapter-Unboxing-Photos~start=100, where a forum member who is an employee of Pace (one of the the makers of the DTA) says the DTA has no OOB receiver. The interesting posts begin at page 5.

Apparently, Comcast and others are sending PSIP type data on a QAM carrier, that contains channel mapping information not just for for those programs on that carrier, but for all the clear QAM channels on the plant. The DTA receives this as uses it to populate the channel mapping data.

This raises the possibility for the HDHomeRun to do exactly the same thing, to tune to this special "startup" QAM carrier, listen to the channel mapping data, and then map all the logical channels on the plant (including music, FM radio stations, etc...). This would be an outstanding feature to add.

Can you guys look at this and see if it's possible for the hdhomerun to do this?

[nickk]

Sure.

Are you in an area where Comcast are doing this?

Nick

[mikesm]

[ViRGE]

After having to program my VistaMC box yet again because Comcast shuffled their channels around, I had the same thought. The city I'm in started its DTA deployment 3 months ago, and they finished Monday when they cut off all of the analog Expanded Basic channels.

My DTAs indicate there's some kind of special channel at the end of their debug channel list.

Channel number: *3900
Callsign: DTA_CDL
Frequency: 153mhz (channel 19)
Subchannel: 391

My HDHomeRun confirms there's a subchannel there, albeit there's no data the HDHomeRun recognizes.

The DTA channel guide isn't perfect, but it may be a start. The only problems I can immediately see are that the DTA guide doesn't list every ClearQAM channel (it's not fed the HD ClearQAMs since it can't decode them) and Comcast's callsigns do not match those of Zap2It (the Hallmark Channel is "HALLMRK" on Comcast's list, it's HALMRKP on Zap2It's), so you'd probably have to match stations by channel number.

If SiliconDust would take a look at this, I for one would appreciate it. I'd also be more than happy to play guinea pig to help as long as this won't make my HDHomeRun or HTPC blow up.

[mbm]

[ViRGE]

There are 6 other subchannels on that channel that are carrying actual TV programming. Is that going to be a problem?

[mbm]

[ViRGE]

391: 0.0 (no data)
1044: 0.0
6012: 0.0
6014: 0.0
6021: 0.0
6022: 0.0
6023: 0.0

[mbm]

[ViRGE]

Will this stop on its own, or do I need to stop it after a certain period of time?

[mbm]

[mbm]

Any luck?

[ViRGE]

Yeah, I have a 50MB or so file from running it for several minutes. How would you guys like it delivered?

[mbm]

See private message for ftp server.

[ViRGE]