Channel ID of QAM stations on cable

[x4mer]

How are channels labelled on a cable system?

On ATSC stations, it's embedded in the PSIP, but what about for QAM on cable?

Is it proprietary, and done different by Rogers/Shaw/Cogeco etc., or is there a standard for cable?

Maybe it's not embedded in each channel, but sent separately in a data stream that contains the names of all the channels, and their mapping data.

Anybody have any info?

[majortom]

I think in OTA /ATSC it's found in what's called the TVCT table.
Terrestrial Virtual Channel table
If no entry, or missing, shows up as
physical ch - SID#

Believe for Cable / QAM they use what's called CVCT.
cable virtual channel table

If no entry is made by the cable company, likely just shows up as
Physical Channel # - SID #

I'll save one from TsReader with and without the CVCT entry
in a few and post a link here...Think Time Warner is doing it here for the local
OTA stations, and not at all for all the rest...

BTW, I think they even move stations around physically on the fly, dynamically.
I was keeping an eye on some for a while, and noticed they tend to dance around
different physical channels. Not the local broadcast stations of course, but
some of the specialty clear QAM channels I can get, vary from time to time on different
physical channels.

edit: from TW near buffalo
TsReader Dumps where for the OTA stations, you'll see it's obvious they use a CVCT to allow your TV to identify it
properly (in the HTML Export calls it TVCT, but it's really a CVCT when viewed live in TSReader App).
Couple other examples with an empty CVCT for comparison , like CBLT & CFTO, they just display the
RF CH - SID (Program number) on the TV.

What they do at the headend, and in the terminal device, etc no idea...likely there's at least as many different
standards for headend/terminal as there are unique providers/infrastructure vendors.

[57]

Here's the FAQ on Cable QAM. Someone may have made a listing of what the channels are for the particular provider at a particular location, at a particular time, but they change all the time as the channels are moved to different QAMs and can also vary by head end and provider.

http://www.digitalhome.ca/forum/showthread.php?t=32271

[x4mer]

Thanks major. It would be great if you could post the samples.

So for the non-open QAM stations like ESPN, the cable provider boxes somehow "know" what channel they're tuned to, not just by number but also by name as they display it onscreen when you change to them.

Do you know how that is done?

I'm wondering whether the cable company data could be parsed, by coding something up, if it were used in combination with a QAM capable tuner card.

I know satellite uses data streams going out periodically on certain transponders, which carries the channel list and guide data. Does cable use a similar system for the channels with no table data, or do they use some other protocol to send to the boxes?

I suppose they could be sending it using an out of band frequency, that the cable boxes listen on, so it wouldn't be possible for any tuner card to get it anyways.

Thanks for the FAQ 57.

[majortom]

I know satellite uses data streams going out periodically on certain transponders, which carries the channel list and guide data. Does cable use a similar system for the channels with no table data, or do they use some other protocol to send to the boxes?

I'm fairly certain I've seen certain Freqs that parse in to a proprietary stream, or sumthing that TSreader wasn't able to parse, exactly what I don't recall. I'll check again sometime. Takes a while to bounce through 100's of possible freqs parsing....
I'm also fairly certain they can key on something other than what ur tv is designed to key on, for association within their own proprietary epg, etc.
Cause like I said, channels move around between rf carriers quite often, but not in their guide. Exactly how it's done, I don't know. All we can do as common lay folk is poke around in TSReader, see if any data only streams stand out that might provide a clue. Not likely we'd be able to parse that though.

[Jase88]

Originally Posted by x4mer

Is it proprietary, and done different by Rogers/Shaw/Cogeco etc., or is there a standard for cable?

It is proprietary; based on the platform of choice by the cable company (i.e. Scientific Atlanta, Motorola, etc). There is no unencrypted channel plan data. And as mentioned, it changes all of the time and from headend to headend.