How do CableCards allow my TivoHD to get schedule information?

[Betelgeuse]

Sorry if this question has already been discussed; I couldn't find it with a search.

I'm interested in how CableCards will allow my TivoHD to get schedule information for HD programming. I've been thinking about it, and it seems to me that there are two options:

1. The CableCard(s) relay the channel mapping information back to Tivo and Tivo then tells me what shows are on when (and knows how to schedule Season passes, etc.)

2. My TivoHD uses the CableCards to get schedule information from my cable provider (Comcast, in my case) and then parses the schedule in a way that it can decide what is on at what time.

So, does the schedule info come from Comcast or Tivo? Do CableCards installed in Tivo just handle the channel mapping or do they retrieve schedule information from Comcast? Or do things work in a totally different way?

[socrplyr]

the answer is basically #1

[Betelgeuse]

the answer is basically #1

OK. So does this mean that, after Comcast installs the Cablecards, the box never needs to communicate with Comcast again (unless channel mapping information changes)? In other words, is the channel mapping info stored on the card?

[bkdtv]

OK. So does this mean that, after Comcast installs the Cablecards, the box never needs to communicate with Comcast again (unless channel mapping information changes)? In other words, is the channel mapping info stored on the card?Comcast still communicates with your TiVo to send it the latest channel maps and keys.

The communication is one-way; your TiVo can't send any data to Comcast.

[logicman1]

Cablecards take the place of a set top box but do not support the 2 way comminication required for VOD. They also do not handle Switched Digital Video (SDV) a topic covered in SDV FAQ (http://www.tivocommunity.com/tivo-vb/showthread.php?t=357703). Tivo knows your channel line up based on information you provided during guided set up. Programming information is transmitted by Tivo and arrives either through a dial or ethernet connection.

Here's a Wikipedia article on Cablecards (http://en.wikipedia.org/wiki/CableCARD)

[ah30k]

Your TiVo box gets the channel lineups with programming defined on the well known channel numbers (ie 132 = History Channel) from the central TiVo server via its nightly call-ins. The data really comes from a third party like Tribune but TiVo server sends it to the box.

Digital cable transmits those broadcasts on digital QAM channels and sub-channels (ie 62-9). Since the assignment of well-known channels to QAM channels can change for any number of reasons and could vary from headend to headend, there is no way for TiVo to keep track. It is the CableCARD that provides dynamic mapping data so TiVo box can figure out which is where. The mapping data is streamed from the local headend to the CableCARD continuously and the CableCARD sends mapping data to the TiVo box.

Hope this made some sense.

[Betelgeuse]

Your TiVo box gets the channel lineups with programming defined on the well known channel numbers (ie 132 = History Channel) from the central TiVo server via its nightly call-ins. The data really comes from a third party like Tribune but TiVo server sends it to the box.

Digital cable transmits those broadcasts on digital QAM channels and sub-channels (ie 62-9). Since the assignment of well-known channels to QAM channels can change for any number of reasons and could vary from headend to headend, there is no way for TiVo to keep track. It is the CableCARD that provides dynamic mapping data so TiVo box can figure out which is where. The mapping data is streamed from the local headend to the CableCARD continuously and the CableCARD sends mapping data to the TiVo box.

Hope this made some sense.

It does make sense; thank you.

I'm just trying to figure out how I can get schedule information for "in the clear" HD channels that I receive through cable and what I need in terms of CableCard setup from Comcast.

I think you've touched on it in your post, but I just want to ask about the details a bit more. How does the information flow? As far as I can piece together, then information flows in the following steps:

1. Comcast transmits channel mapping information to Cablecards. This is something like "Channel 122 is mapped to channel 40-1"
2. My TivoHD gets schedule info from Tivo (or, more correctly, from a third party via Tivo) that includes information along the lines of, "Lost in HD airs Thursday nights from 9pm to 10:02 pm on channel 122"
3. My Tivo unit does the decoding using the CableCard information and discovers it needs to record from 9pm to 10:02pm on Channel 40-1 and call that recording "Lost," with all the standard info that usually accompanies that show.

Is this correct? If so, why is there the extra step in there (i.e. the use of CableCards to do the channel mapping)? If the Tivo schedule information knows that there's show on "Channel 122," why can't they just amend their scheduling information to say that it's on "Channel 40-1"? Or is it always on "Channel 122" in all parts of the country and different cable companies map the channels differently? If this is the case, why can't Tivo just do location-specific guides? Of course, Tivo already DOES this; I told my box all about my location and cable provider in the Guided Setup. It just seems to me that Tivo gets all the information it needs from me in order to do this without CableCards.

What don't I understand?

[bkdtv]

What don't I understand?No source of program information exists for QAM channels such as 40-1.

Different cable companies map their channels differently, and the cable company does not supply channel information for QAMs such as 40-1. TiVo licenses guide data from Tribune Media, which only offers the information for the channel lineups supplied by the cable company.

Without a CableCard, TiVo has no way to tell whether 100-1 is CNN, SciFi, or something else. Furthermore, these QAM channels change periodically when cable systems add new channels. SciFiHD might be 100-1 in March, 88-2 in July, and 114-3 in November.

[Betelgeuse]

No source of program information exists for QAM channels such as 40-1.

Different cable companies map their channels differently, and the cable company does not supply channel information for QAMs such as 40-1. TiVo licenses guide data from Tribune Media, which only offers the information for the channel lineups supplied by the cable company.

Without a CableCard, TiVo has no way to tell whether 100-1 is CNN, SciFi, or something else. Furthermore, these QAM channels change periodically when cable systems add new channels. SciFiHD might be 100-1 in March, 88-2 in July, and 114-3 in November.

OK. This makes sense. However, there must be some way of identifying the "channel" that is going to carry ABC-HD. It is my understanding (from what I've read here) that there is some "universal" channel number (call it "U-122," for example). Then, the CableCard handles the conversion from this "universal" name (e.g. "U-122") to the more "standard" channel name that my TivoHD can understand (e.g. "40-1").

Your point about channel mappings changing is a good one, but this happens to the non-HD channels ALL THE TIME around here. Every month or so, I'm getting a notice from Tivo that my channel lineup is changed and that now some obscure network that I never watch is now on a different obscure channel.

So, is the problem just that the cable companies provide Tivo (or, more properly, Tribune Media) with the channel mapping data for the "traditional" (i.e. non-HD) channels, but don't provide the information for the HD channels?

[bkdtv]

Then, the CableCard handles the conversion from this "universal" name (e.g. "U-122") to the more "standard" channel name that my TivoHD can understand (e.g. "40-1").To clarify, the "standard" channel name would be something like 200. The CableCard tells the TiVo that CNN-HD on channel 200 in the guide should point to QAM 40-1.

Cable companies do not have any channels with dashes in their lineup.

So, is the problem just that the cable companies provide Tivo (or, more properly, Tribune Media) with the channel mapping data for the "traditional" (i.e. non-HD) channels, but don't provide the information for the HD channels?Most QAM channels are not HD. All digital channels -- SD and HD -- use QAM.

Cable companies provide Tribune with their 'official' channel lineup for all SD and HD channels -- this is the lineup you see with their own STBs, which is the same lineup you get with a CableCard. Cable companies do not provide channel lineup information for QAM channels. Tribune Media therefore cannot provide program information for those channels.

There are a few exceptions. In one or two markets, Time Warner Cable does report QAM channel information to Tribune, so TiVo users in those areas do get guide information on the QAMs without a CableCard.

But most cable companies have no interest in doing this because they continually remap their QAMs when they add new channels. I just gave one example of a QAM change in my previous post -- your example is not quite comparable, because cable companies will rearrange dozens of QAM channel assignments at once, not just one or two.

[Betelgeuse]

To clarify, the "standard" channel name would be something like 200. The CableCard tells the TiVo that CNN-HD on channel 200 in the guide should point to QAM 40-1.

Cable companies do not have any channels with dashes in their lineup.


OK. Great. This is part of the information I was interested in.


Most QAM channels are not HD. All digital channels -- SD and HD -- use QAM.

Cable companies provide Tribune with their 'official' channel lineup for all SD and HD channels -- this is the lineup you see with their own STBs, which is the same lineup you get with a CableCard. Cable companies do not provide channel lineup information for QAM channels. Tribune Media therefore cannot provide program information for those channels.

Wait; I don't understand. You say that Cable Companies provide Tribune with their official channel lineup for all SD and HD channels. However, you then say that they don't provide the channel lineup for QAM channels. Isn't QAM just a method of transmitting HD (and digital SD) channels? How can Tribune be supplied with the "channel lineups for all SD and HD channels," but they not supplied with the channel lineup for QAM channels?

Is it just that the Cable Companies supply Tribune with the *universal* channel numbers and not the QAM channel numbers? If so, does this seem really stupid to anyone else? Presumably, at the time the cable companies provide the channel lineup info, they know how the channels are mapped. This information is (apparently) updated often since the schedule information always seems fairly up-to-date.

Is it just a case of cable companies choosing to not give Tribune the channel mapping data or is there some technical hurdle that I'm not getting?


But most cable companies have no interest in doing this because they continually remap their QAMs when they add new channels. I just gave one example of a QAM change in my previous post -- your example is not quite comparable, because cable companies will rearrange dozens of QAM channel assignments at once, not just one or two.
I don't know; it seems like it's a similar amount of work to tell Tivo about 100 new channel mappings as it is to tell it about 1 new channel mapping. And, honestly, how often are channels re-mapped? In the 6 months that I've had my TivoHD, there have literally been zero changes in how my QAM channels are mapped.

[morac]

Wait; I don't understand. You say that Cable Companies provide Tribune with their official channel lineup for all SD and HD channels. However, you then say that they don't provide the channel lineup for QAM channels. Isn't QAM just a method of transmitting HD (and digital SD) channels? How can Tribune be supplied with the "channel lineups for all SD and HD channels," but they not supplied with the channel lineup for QAM channels?

You're over thinking this. He's saying that companies don't provide Tribune with the QAM mapping.

Using bkdtv's original example:
SciFiHD might be 100-1 in March, 88-2 in July, and 114-3 in November.

Say SciFiHD is channel 210 on your cable system. As far as Tribute knows it is 210. It doesn't matter if the actual QAM mapping is on 100-1, 88-2 or 114-3, Tribune will always report it as being channel 210. Therefore the TiVo will always show it as being on channel 210. All the QAM mapping goes on behind the scenes (handled by the CableCARD) so there aren't any channel lineup changes as far as the TiVo is concerned.


Think of it this way. Say you have a friend with a Verizon land line phone. Now say the person ports his number over to an AT&T cell phone service. He still has the same number so the phone book doesn't need to be updated and calling that number will still reach him. Only what happens behind the scenes has changed.

This is analogous to how cableCARDs work. In this example the phone number would be like the channel number and where it ends up is the QAM channel.

[Dancar]

Now here's a related question: How do cablecards control what channels you get? If I decide I want HBO, does Comcast send a HBO decryption key to the CC in my tivo? When I cancel HBO, do they send a command to my CC only to erase the key so I can't see HBO anymore?

[ah30k]

Now here's a related question: How do cablecards control what channels you get? If I decide I want HBO, does Comcast send a HBO decryption key to the CC in my tivo? When I cancel HBO, do they send a command to my CC only to erase the key so I can't see HBO anymore?The answer depends somewhat on whether you are on an SA system or a Mot system since they use different encryption methods but in general you are correct. Also their are tier keys (ie the digital sports package) and specific channel keys (ie HBO).

[Betelgeuse]

You're over thinking this. He's saying that companies don't provide Tribune with the QAM mapping.


I'm only quoting this part because I think this is exactly the answer to my question: the companies don't provide Tribune with information about the QAM stations. But this just appears to be a "choice" of the cable company rather than some technological limitation. Is this because they want to sell/rent me their DVR (or cable box) instead of using my Tivo?

[bkdtv]

Is this because they want to sell/rent me their DVR (or cable box) instead of using my Tivo?Cable engineering departments are the ones who deal with the QAMs, and they don't want to concern themselves with channel lineups. Engineering departments want the ability to alter QAMs at any time without external concerns. QAM assignments are viewed as the internal workings of a private cable network; QAM assignments are not designed or setup with customers in mind.

Your particular Comcast may not change or rearrange their QAMs often, but many do whenever they add new channels or replace / update equipment.

[jkovach]

In addition, different head-ends of the same cable system may have their channels mapped differently. Now to the customer using a cable box or device with cablecard(s), the channel may always appear to be on channel 142 no matter where you are in the cable system. But in neighborhood A, it's coming in on QAM 40-2, and in neighborhood B it's coming in on QAM 63-4. And at the same time, channel assignments are changing very FREQUENTLY, but to the customer the are TRANSPARENT because the cable box or cablecard device handles the mapping.

So, the cable co sends the lineup to the cablecard, the cablecard tells the Tivo that QAM 63-4 is channel 142. Tivo has the lineup from Tribune that says that for your cable system, 142 = CNN. And Tivo has the listings for CNN, which it then ties to whatever is on channel 142.

Cablecards do the following:
a) Map the channels to fixed #s, so that even if a channel moves to a different QAM channel, the customer will still find it on channel X. If the cable company does decide to move it to channel Y, then you will receive a lineup change msg on the Tivo, assuming your cable co lets Tribune (the Tivo listings data provider) know.
b) Provide authorization for the channels you are paying for, including an expiration date/time that needs to be refreshed, otherwise you will lose non-basic channels at that date & time.
c) Receive the decryption keys for authorized channels that are encrypted, so the Tivo can decrypt them.

[joec00l]

Cable companies do not provide channel lineup information for QAM channels. Tribune Media therefore cannot provide program information for those channels.

There are a few exceptions. In one or two markets, Time Warner Cable does report QAM channel information to Tribune, so TiVo users in those areas do get guide information on the QAMs without a CableCard.


I use Clearview Cable, which is a small company serving an area around Harford County Maryland. They started sending free unencrypted HD channels for all the major networks about a year ago. They have been consistently the same QAM channel for quite some time now. They claim they do not have cableCards and may be small enough to get away with it.

Then something interesting happened: I have a Tivo Series2 and about a month ago I noticed that the guide data included channel information for the digital channels, just without the subchannel listed. For example if I look for upcoming Lost episodes, I see identical listings for "10 - WMAR" and "85 - WMARDT". On my TV (which has a built-in QAM tuner) I tune to 85-3 to watch the network. Do you think the listing actually contains enough information for the Tivo HD to tune into the network without a cableCard since it seems to know the appropriate digital channel? Does anyone have any experience with a situation where they have a digital channel listed in their TiVo guide without a cableCard?

Thanks!

[joec00l]

Another thought: If channel listings are available to TiVo but they just aren't mapped to the proper QAM with full subchannel etc, why couldn't Tivo provide the ability for a person to manually enter the full QAM channel information for each channel in the listing that required such a mapping? It wouldn't be as elegant as a CableCard but it would sure be better for those of us who may not be able to get properly set up with one.

[ah30k]

Another thought: If channel listings are available to TiVo but they just aren't mapped to the proper QAM with full subchannel etc, why couldn't Tivo provide the ability for a person to manually enter the full QAM channel information for each channel in the listing that required such a mapping? It wouldn't be as elegant as a CableCard but it would sure be better for those of us who may not be able to get properly set up with one.There are whole threads dedicated to this question.

[joec00l]

There are whole threads dedicated to this question.

Thanks, I'll try to find them. It just popped into my head and I spit it out. :)

[ah30k]

Thanks, I'll try to find them. It just popped into my head and I spit it out. :)I wasn't trying to be nasty. Try this http://www.tivocommunity.com/tivo-vb/showthread.php?t=362736&highlight=manual+map

[joec00l]

Just to follow up on my question a few posts back about getting HD channels without a cable card:

I got my Tivo HD from woot.com Friday and set it up. Using the Tivo Guide data that was available for the unencrypted network stations on digital frequencies, I was able to tune into - and schedule - HD content without using a Cable Card (like channel 85-3 for example). It seems the cable card solution is necessary if you have a digital cable subscription which I do not have. I just have regular cable with no cable box, and get a few free digital channels that I can pick up with a plain QAM tuner. In that case it is more important that the channels be listed in the Tivo Guide data.

I also get Discovery HD now, but unfortunately that hasn't made it into the Tivo guide data yet. Tivo knows there's a channel there now, but not what's on it. Now is when it would be great if I could manually associate that new channel with the guide data for my existing Discovery SD channel. Come on Tivo, get to work on that!

[bamachick19]

Sorry if this question has already been discussed; I couldn't find it with a search.

I'm interested in how CableCards will allow my TivoHD to get schedule information for HD programming. I've been thinking about it, and it seems to me that there are two options:

1. The CableCard(s) relay the channel mapping information back to Tivo and Tivo then tells me what shows are on when (and knows how to schedule Season passes, etc.)

2. My TivoHD uses the CableCards to get schedule information from my cable provider (Comcast, in my case) and then parses the schedule in a way that it can decide what is on at what time.

So, does the schedule info come from Comcast or Tivo? Do CableCards installed in Tivo just handle the channel mapping or do they retrieve schedule information from Comcast? Or do things work in a totally different way?

TiVo has a 3rd-party company that gathers all that info from your cable provider. The cablecards actually do provide the tivo with a channel map which allows the tivo to know what channels to receive info for.