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Old 02-28-2009, 07:02 PM   #1
Gh0ztt
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Any way to map channels that Tivo doesn't have guide information for?

I have cable but no cable card or cable box. My local cable company provides the local networks in HD on their regular channels (channel 3 is 3.1, etc.). On my HD Tivo I have both the cable and an OTA antenna connected. I use the OTA antenna to record the local networks because Tivo will not display guide information for those channels on the cable. For instance, I have 3.1 for Antenna and 3.1 for cable, but in the guide information is only provided for the 3.1 off the antenna. I'd like to get rid of the antenna if possible because I get occasional interference, but I can't seem to figure out how to get the guide data to map to the digital cable channel. If I had a cable box the channels would be mapped differently (in the 500 range I believe)... so I think that might have something to do with the problem. Thoughts?
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Old 02-28-2009, 07:05 PM   #2
rainwater
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Without a cablecard, you can not get guide data for unencrypted qam channels.
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Old 02-28-2009, 07:05 PM   #3
pdonoghu
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You need cable cards to properly map the digital channels, and get guide data.
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Old 02-28-2009, 07:09 PM   #4
Gh0ztt
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I guess this is just some problem that Tivo has? Why would I need a cable card to get guide data for those channels when Tivo clearly has the data for them via the Antenna input? The are the same channel number whether OTA or on cable.
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Old 02-28-2009, 08:11 PM   #5
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Originally Posted by Gh0ztt View Post
I guess this is just some problem that Tivo has? Why would I need a cable card to get guide data for those channels when Tivo clearly has the data for them via the Antenna input? The are the same channel number whether OTA or on cable.
LOL. My situation is exactly the same as yours. This subject has been discussed extensively in other threads. For detailed answers to your question many times over, see (for example) this very active thread:
http://www.tivocommunity.com/tivo-vb...d.php?t=362736
It currently has over 1700 posts in it.

The short answer is as given earlier here: TiVo does not support guide info for digital channels via cable without cable card. Period. No matter how much we'd like it to!
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Old 02-28-2009, 08:28 PM   #6
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Accurate PSIP does not solve the problem of channel mapping the way cable cards do. Virtual channels provided by PSIP are only learned by a channel scan. For example when your PSIP was added to the QAM RF channel carrying 33.1 Tivo learned 33.1 maps to (for example) RF channel 77. If your cable company decides to move 33.1 from RF channel 77 to RF channel 88 your Tivo will no longer be able to find the channel, when you enter 33.1, it will tune to RF 77 and would probably show no signal since the PSIP stream for 33.1 will be missing, to repair the missing 33.1 would require a rescan.

Cable cards on the other hand will receive an updated channel map and will know where to find the cable channel version of 33.1.

Tivo does not rely on PSIP to find Antenna channels, the RF channel information comes from Tribune.
Some are under the impression that once they can see PSIP mapped QAM channels in their guide (on 5.1, 7.1, etc), then they're all set and it doesn't matter what changes their provider makes. That is not the case. If a cable provider alters their QAM configuration, you'll still see 4.1 or 5.1 on your TiVo, but it won't work until you re-run a channel scan.

The TiVo only "knows" the corresponding off-air (antenna) assignments for 4.1, 5.1, 7.1, 9.1, etc because it is told by Tribune. Tribune does not offer that information for 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. TiVo -- which uses Tribune -- therefore cannot automatically provide program information for those channels.

Now, it would be nice if TiVo users could manually remap QAM channels on their own for the TiVo. But that is not a feature TiVo supports at this time.
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Old 02-28-2009, 10:59 PM   #7
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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. TiVo -- which uses Tribune -- therefore cannot automatically provide program information for those channels.
bkdtv, this leads into another question I've been pondering. I'm planning to soon head downtown to have another chat with the tech guy at my cable system about cable card support (which they don't have at the moment), and I'd like to understand it a bit better.

I know that digital streams (with correct PSIP, hopefully) are sent via QAM on RF channels of the cableco's choosing. And that the cable card takes care of dynamically mapping the virtual channel to the RF channel so it can be tuned (much like the Tribune lineup static mapping does for OTA channels).

But further details are murky to me. How does it really work? In particular, how does the proper guide data get hooked in? That is, what is the relationship between station (say a local such as KTVLDT), "published" cable channel (something like 802?), current QAM channel carrying the digital stream (802 or something else?), virtual channel (from PSIP?), and its published guide id/info?

What mapping is going on in the TiVo via the cable card to glue everything together so that when I select channel "10.1" it knows what to do? And how does adding additional subchannels in a stream impact the situation (since they ultimately get mapped to the same QAM channel for tuning)?

I'd really like to understand how these pieces fit together so I can have a more intelligent chat with the cable dude. Thanks for any insight and/or pointers to other resources.
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Old 03-01-2009, 12:24 AM   #8
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But further details are murky to me. How does it really work? In particular, how does the proper guide data get hooked in? That is, what is the relationship between station (say a local such as KTVLDT), "published" cable channel (something like 802?), current QAM channel carrying the digital stream (802 or something else?), virtual channel (from PSIP?), and its published guide id/info?

What mapping is going on in the TiVo via the cable card to glue everything together so that when I select channel "10.1" it knows what to do? And how does adding additional subchannels in a stream impact the situation (since they ultimately get mapped to the same QAM channel for tuning)?
Suppose QAM 107-4 has PSIP which tells it to display on 10.1.

When you do a channel scan on the TiVo, it gets to 107-4 and the PSIP tells it to remap that channel to 10-1. So that's what it does. If the cable company moves channel to 118-2 in two weeks, your 10.1 would still point to the old 107-4. You would have to re-run channel scan to correctly remap 118-2 to 10-1. [Same cable companies move channels around more often than others. When I had Comcast, they did it every few months when they added new channels.]

Cable companies do not report this 10-1 or 107-4 information to guide data providers. They view it as internal to their system. They only report the information for the channel in official lineup, which might be something like channel 510. Tribune and TVGuide receive the information for 510 and then pass it on to their customers (like TiVo).

One of the main functions of a CableCard is to retrieve a channel map. This channel map tells the device that channel 510 (displayed for the user) is really 107-4. If the cable company moves that channel from QAM 107-4 to QAM 118-2 in two weeks, the CableCard channel map is updated dynamically to reflect that. No channels scans or reboots are necessary.
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Old 03-01-2009, 03:21 PM   #9
markens
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Cable companies do not report this 10-1 or 107-4 information to guide data providers. They view it as internal to their system. They only report the information for the channel in official lineup, which might be something like channel 510. Tribune and TVGuide receive the information for 510 and then pass it on to their customers (like TiVo).
Thanks, this was the part that I wasn't sure about. So each distinct channel of programming has a static, distinct channel in the published lineup (510 in your example) which gets mapped as necessary by STB/cable card. Got it.
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Old 03-01-2009, 04:29 PM   #10
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bkdtv, this leads into another question I've been pondering. I'm planning to soon head downtown to have another chat with the tech guy at my cable system about cable card support (which they don't have at the moment), and I'd like to understand it a bit better.
Unless they have a waiver every cable system with digital channels is required to support cable cards.
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Old 03-01-2009, 05:13 PM   #11
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Unless they have a waiver every cable system with digital channels is required to support cable cards.
My earlier statement wasn't quite complete: This system does not have any digital channels other than clear-QAM rebroadcasts of locals. They don't supply or support of any kind of STB; customer equipment is required to receive the clear-QAM channels. Is the presence of just these clear-QAM channels enough to trigger the requirement to support cable cards? I didn't think so, but I don't really know.
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Old 03-01-2009, 05:40 PM   #12
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Is the presence of just these clear-QAM channels enough to trigger the requirement to support cable cards? I didn't think so, but I don't really know.
No. FCC requires it for all major cable companies, but exempts smaller one (I think if system is smaller than 750 MHz).
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