Program Guide vs OTA digital channel mappings on Feb 17

Discussion in 'TiVo Series3 HDTV DVRs' started by markens, Jan 6, 2009.

  1. Jan 6, 2009 #1 of 69
    markens

    markens Member

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    This is mostly a "heads-up" post. I called TiVo support about the following issue, and the person I talked with confirmed this information. But I'm not confident he actually knew what he was talking about, and wonder if anyone here has authoritative info:

    Issue: Program guide info for OTA digital channels (and the underlying RF channel mappings) effective midnight Feb 17.

    We all know that OTA analog signals will cease at midnight Feb 17. At that time, the digital OTA signals of many stations will change from their current (pre-transition) RF channel to a different post-transition RF channel. This will most often be their current analog channel, but that detail is not important here.

    TiVos know where the OTA digital channels are via mappings in the Tribune Media program guide info, right? For example, channel 5.1 is located on RF channel 15, and the program guide provides that mapping. That's why we don't have to scan for published OTA channels. The TiVo rep confirmed this.

    So it follows that at midnight Feb 17, these mappings will need to change to the post-transition values (RF channel 5 for my example case of 5.1) in order for the TiVo to continue to tune correctly, and apply "To Do" and "Season Pass" tasks correctly. This will have to happen at precisely the same time as the broadcasters change their transmitters in order to not have a lapse in functionality.

    So the issue, in my mind, is this: Will the TiVo program guide really be updated in this limited window so that nothing breaks? And will recordings and season passes currently in effect continue to work after the new mappings take effect?

    The TiVo rep assured me that all of this is true. While I certainly hope it is, I'm not holding my breath.

    Anyone have confirmation about this? Am I concerned about nothing? Thanks much!
     
  2. Jan 6, 2009 #2 of 69
    rainwater

    rainwater Active Member

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    It's doubtful it will happen at exactly midnight unless TiVo creates a new way to change channel mappings remotely at a specific time. More likely, it will get the new mappings when it does its daily connection. Of course no one knows for sure since how Tribune handles these mass changes is anyone's guess. I would expect there to be issues for a few days at least.
     
  3. Jan 6, 2009 #3 of 69
    pilotbob

    pilotbob New Member

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    The EPG has 14 days worth of data on it ahead of time. There is no reason to update millions of TiVos exactally at midnight on Feb 17th. Your guide data from that time on can (will) have the new channel/frequency mappings.

    I'm sure there will be some guide error... but the guide will be in place well before Feb 17th.

    BOb
     
  4. Jan 7, 2009 #4 of 69
    markens

    markens Member

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    Do you know this for sure, or are you speculating? This seems to mean the guide format has the capability to store time-based mapping information (which would certainly make this a non-issue).

    Or are you saying that *both* mappings will be present? If this is the case, then existing recordings and season passes will likely break after the transition since the TiVo will see them as separate channels. Much like the current situation of program guide listings for an OTA analog channel and its associated DTV channel. Identical program listings, but season passes for one won't pick up shows on the other.

    I hate to cry wolf, but I'm still not convinced there won't be a problem. Hmmm, just like Y2K? (I hope!)

    I guess we'll just have to wait and see.

    [Edit: Good point about guide data 14 days in advance. That should give us a good idea of what will happen on Feb 17.]
     
  5. Jan 7, 2009 #5 of 69
    bicker

    bicker bUU

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    Ostensibly, certain channels (the analog OTAs) are going away. There technically shouldn't be any guide data for them after February 17. After that, you would need to select the digital OTA channel for your recordings. The "mapping" between the digital OTA channel and the physical frequency it is being transmitted on is not something passed along with the program guide data. Rather, it is (or at least should be) obtained from PSIP, which presumably will be changing (at the moment) when digital OTA channels are switched to their old analog OTA physical frequency.

    I do wonder how long it will take the TiVo to detect a change in the PSIP data. It should be a matter of minutes, but I don't know.
     
  6. Jan 7, 2009 #6 of 69
    pilotbob

    pilotbob New Member

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    I am somewhat speculating. But, your guide certainly knows what time shows are on and what channel. Of course it does. How else would it work..

    Your guide knows that CSI is on a certain channel at a certain time on a certain day. I am sure that if that channel changes for the show that is on after Feb 17th it can already be preset for that in the guide.

    Although, the question in my mind is what maps the channels to the frequencies. It it is the guide then you should be ok. If it is the channel line up then yes that will need to be updated. But, TiVo may have anticipated this and built in some time based mapping info.

    The bottom line is, why worry about it? It is either going to work or not. I would say on the 18th check your SPs and stuff and see if it is ok. Do you record alot between Midnight and 8PM that you are worry about missing?

    This is [one ereason] why I am waiting until after Feb 17th to switch from FiOS TV to OTA. (The fact that some freqs are changing so I will need a slightly different antenna set up, not because I am worried about TiVo missing a few shows.)

    BOb
     
  7. Jan 7, 2009 #7 of 69
    SCSIRAID

    SCSIRAID Active Member

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    As I understand it, what cross references the virtual channel to the physical channel frequency is the PSIP data discovered during a 'channel scan'. As the tuner scans the physical channels, he finds out what virtual channels are on that physical channel and can map those to guide data. Now whether this is what TiVo does... I dont know. It is what TV's do.

    On Feb 18, the guide data really doesnt have to change... the virtual channel is still the same. Its the OTA physical channel that changes.

    I expect that first thing Wed morning, we will all have to do a channel scan on TiVo to update the virtual to physical channel mapping. I dont believe that info is in the guide data.
     
  8. Jan 7, 2009 #8 of 69
    markens

    markens Member

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    But the TiVo must know which frequency (RF channel) to tune in order to get the PSIP in the first place, and the evidence points to this mapping being in the OTA lineup provided by the EPG. There is a definite difference in how a "scanned" channel is handled by the TiVo (see the channel list and program guide), vs one that is in the EPG. This is the core issue I'm curious about.

    Yup, this is my question, too.

    No, I'm not that worried about the actual programs. It's much more of the tech geek in me curious about HOW this all works. So ultimately the advice to just check it out on the 18th is the most practical.

    Indeed. I think I'll probably have to do some antenna adjustments myself after the freqs change.
     
  9. Jan 7, 2009 #9 of 69
    bicker

    bicker bUU

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    What "evidence" are you referring to?
     
  10. markens

    markens Member

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    From what I've seen, channels found by channel scan are not in the program guide. So this may or may not help.
     
  11. markens

    markens Member

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    Well, to start with this is what the TiVo CS rep told me. But I take that with a grain of salt at the moment.

    Actually, now that I think about it some more, there are actually two components here: The (OTA) channel lineup obtained by the TiVo during guided setup. And the ongoing EPG data. I've been merging the two in my mind.

    So perhaps the question is really related to the lineup data.

    From my own observations of behavior:

    Tivo will only tune digital channels that it knows about. With respect to OTA channels, it handles all channels listed in the program guide just fine without a channel scan (assuming the signal is received ok, of course). Program guide data is associated with these channels as expected.

    But, of course, there will be some correlation between the channel lineup and the EPG.

    My channel list shows many channels I do not physically receive, along with their assigned RF channel. Since there is no way I could be getting PSIP for those channels, then the RF freq must be obtained some other way. I had been claiming it comes from the EPG through some sort of mapping. But now I think it is probably from separate lineup data.

    If this is the case, the it's the lineup data which must be updated, not the EPG.
     
  12. bicker

    bicker bUU

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    I understand it may appear that way, but I suspect there is a channel scan that is part of this guided setup process, when you indicate that you're using an antenna.

    Until we have reason to believe otherwise, I think it safest to believe that the program guide data traffics in the virtual channel numbers, not the physical RF assignments. I believe on major objective of PSIP is that virtual channel numbers don't change even if a channel moves to a new frequency.

    Huh? My channel list shows channels I do not physically receive, but only shows their virtual channel numbers, not their (physical) RF assignment. Heck, my channel list doesn't show any (physical) RF assignments, even for the channels I do receive. That mapping is completely hidden from our view, as far as I can tell. What am I missing?

    The virtual channel is coming from the Tribune program guide. I believe the fact that the channel scan didn't find PSIP matching that virtual channel is why you cannot receive them.
     
  13. markens

    markens Member

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    I disagree. The channels in question do not display an asterisk ("scanned channel") in my channel list (whether I receive the signal or not), nor can they be deleted from that list like scanned channels can. But we're both speculating, so I don't think we can come to a firm conclusion based on our information alone.

    I agree with you here about program guide and PSIP. But the underlying issue remains: how does the TiVo find the correct, current RF frequency so that it can be tuned in the first place? Program guide mapping to virtual channel is the next step.

    Dunno what you're missing. But my channel list (in Settings->Channels->Channel List) definitely shows the RF channel for all OTA digital channels, whether I actually receive the signal or not. Here's an example verbatim from my list:

    2-1 - KOTIDT; digital frequency 13
    NBC Affiliate​

    I agree with you that RF frequencies for QAM channels on cable do not show up in the channel list.

    No, the reason I cannot receive them is because their transmitters are on the other side of tall mountains from me. :) There are about 12 such channels listed in my lineup, in addition to many that I can receive.

    BTW, a channel scan DOES find some additional OTA digital signals, including a nearby low power translator that has already been converted to digital. There is an asterisk next to it in the channel listing indicating it was found by scanning.

    Further data point in support of a separate channel lineup: I occasionally get a message saying that my lineup has changed, and inviting me to confirm reception in the channel list setup. Obviously not a result of a channel scan.
     
  14. bicker

    bicker bUU

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    How does a television do it?
     
  15. markens

    markens Member

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    The only data point I have about TVs is how my Samsung does it, and it is by scanning. But we're talking about TiVos. Sure, a TiVo can also find channels by scanning. But the presence of details in my channel list for channels which I cannot physically receive points to some other method the TiVo has available to it. The answer to this mystery is what I seek. :)
     
  16. pilotbob

    pilotbob New Member

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    A TV doesn't need to tie the channel to an EPG. The TV just knows that channel to display on the screen and the RF channel from which to receive it.

    BOb
     
  17. bicker

    bicker bUU

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    However, a television needs to tie the virtual channel number to the physical RF. (The EPG uses the virtual channel number, eh?)
     
  18. pilotbob

    pilotbob New Member

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    I'm pretty sure that info is in the digital signal sent by the broadcaster.

    BOb
     
  19. bicker

    bicker bUU

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    Me too.
     
  20. pilotbob

    pilotbob New Member

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    So, then maybe it is a moot point. The TiVo knows what the virtual channel number is... that info is in the guide. When the TiVo can scan the RF freq and match any channel it finds with the guide using the VCN in the carrier.

    The channel list from TiVo may include this info but I am expecting that a channel scan will override this mapping info.

    BOb
     

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