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SDV FAQ

Discussion in 'TiVo Series3 HDTV DVRs' started by bdraw, Jul 3, 2007.

  1. Apr 5, 2008 #1321 of 2401
    DCIFRTHS

    DCIFRTHS I dumped SDV / cable

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    If there is a recording in progress, the dialog does not appear, and the channel does not change, correct?
     
  2. Apr 5, 2008 #1322 of 2401
    bicker

    bicker bUU

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    As long as it is a user-initiated recording. It was quite a controversial issue before the spec came out, but I do remember the end-result being that it seems that TiVo suggestions can be interrupted if the channel is needed for another customer's deliberate purpose.
     
  3. Apr 5, 2008 #1323 of 2401
    JohnnyO

    JohnnyO Crimper

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    I'm glad to see they thought of some examples. FYI - in Adobe Reader it is the 42nd page, but it appears to be page 36 of the Document (Reader gives "page numbers" to the index, etc.).
     
  4. Apr 5, 2008 #1324 of 2401
    mikeyts

    mikeyts Stream Warrior

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    Yes. There is a field in the resolve_tuner_req() APDU called "tuner_use_status" with the following set of values:
    0x0 – Live full screen video (no HDD recording)
    0x1 – Live full screen video (HDD recording)
    0x2 – Live PIP or POP video (no HDD recording)
    0x3 – Live PIP or POP video (HDD recording)
    0x4 – Recording only
    0x5 – Inactive
    0x6 – Speculative Recording
    0x7 – Reserved​
    So, when TiVo (or some other UDCP) requests a channel from the Tuning Resolver it has to say why it wants that channel; one reason is "Speculative Recording", like TiVo's "record suggestions" feature. If the system knows that a channel is solely in use on a segment by one or more DVRs which are recording things that they just think that their owners might be interested in then the bandwidth used for that channel will be reclaimed first in a crunch, regardless of whether those recordings are complete or not.

    Also note the "Inactive" status:
    In other words, if the UDCP requested a channel for purposes of recording, it's required to tell the Tuning Resolver when it has finished recording. I suppose that a UDCP might also send this if its user placed it in a "Standby" mode when the channel he or she was watching wasn't being recorded.

    The "tuner_use_status" field is also present in the udcp_status_rsp() message, a response from the UDCP to the Tuning Resolver sending a udcp_status_req() packet, which is basically the TR asking for an update on what the UDCP is doing.
    Yeah, sorry--I usually say "PDF page 42" to distinguish from "page labelled 42".

    Not only did they specify Tuning Resolver related message examples, they give an appendix of use cases (Appendix I, starting on PDF page 45). Listing all intended usage scenarios is part of modern formal software design technique and such a list is particularly useful for development of regression testing.
     
  5. Apr 5, 2008 #1325 of 2401
    HDTiVo

    HDTiVo Not so Senior Member

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    Do future TiVo suggestions appear in the ToDo List? If so, then an interrupted Suggestion would be a change in behavior that might affect users negatively.
     
  6. Apr 5, 2008 #1326 of 2401
    SCSIRAID

    SCSIRAID Active Member

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    No. Suggestions are not in the TODO list.
     
  7. Apr 5, 2008 #1327 of 2401
    HDTiVo

    HDTiVo Not so Senior Member

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    That´s good, but also since Suggestions are a key differentiating TiVo feature (in TiVo´s opinion and business plan) the disruption of them would disadvantage TiVo.

    A person who likes their TiVo to record Suggestions would not get all they hoped for out of TiVo.
     
  8. Apr 5, 2008 #1328 of 2401
    mikeyts

    mikeyts Stream Warrior

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    You can ask TiVo specifically about what it would suggest (TiVo Central->Find Programs->TiVo Suggestions) and if you have automatic recording of suggestions turned on and check that list frequently you might be surprised when something doesn't show up, but there might be any number of reasons for that (if, for instance, there's no space it won't record it either). I doubt that many people bother to check that list; most probably enjoy the surprise of finding recorded Suggestions that they really want to watch.

    Ultimately, unless TiVos become much more popular than they are (or cable providers should add speculative recording to their DVRs), if this ever happens, something is wrong; bandwidth in the SDV pool should never get that scarce. However, if it did happen it'd be a shame if a huge bunch of TiVo Suggestions being recorded on unpopular channels should stop someone from getting to watch or record something that they really, really wanted to see.
     
  9. Apr 5, 2008 #1329 of 2401
    Eccles

    Eccles Mostly harmless

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    The intent of this design is that speculative channel requests will be denied or preempted if there are insufficient resources for non-speculative requests from other devices, i.e. if other subscribers' non-speculative requests would otherwise be denied.

    This is in effect no different from the way that TiVo operates already - it will record suggestions if and only if there is no conflicting non-speculative request. This new standard simply expands that paradigm to take in the entire neighborhood, not just your one machine.
     
  10. Apr 6, 2008 #1330 of 2401
    lrhorer

    lrhorer Active Member

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    You missed one of the important steps in communication (added in bold):
    Unless, of course, the channel is presented in the clear, which sometimes may be the case, even with SDV.
     
  11. Apr 6, 2008 #1331 of 2401
    lrhorer

    lrhorer Active Member

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    (Emphasis mine.) As time goes by, eventually almost every channel will become "unpopular". With thousands or even tens of thousands of channels from which to select, and VOD being the norm rather than the exception, eventually there may not be any channels with a lion's share of the market. When that day comes, for the most part the only marginally "popular" channels will be those which are being recorded by DVRs, including TiVo Suggestions. It will be incumbent upon the CATV provider to maintain their plant so that the number of receivers on each node is small enough that the available bandwidth can service the needs of every sub on the node. As you said:
    Which means the CATV provider will need to keep ahead of viewing stats. As long as they are diligent about this, there won't be a massive problem with this issue.
     
  12. Apr 6, 2008 #1332 of 2401
    sfhub

    sfhub Active Member

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    Depends what level of abstraction your are looking at. The host device (TiVo) that is handling the SDV interface calls is never handed the decryption key. TiVo tunes to the channel given by the SDV request, realizes it is encrypted, and hands off the stream to the CableCARD, which then does its black box conditional access and decryption, and eventually hands back the decrypted stream (re-encrypted if CCI=non-zero) to TiVo. In the process of decrypting the stream, the CableCARD does recover the decryption key, but that key is not exposed to the TiVo code that is handling the SDV. TiVo has no idea whether a decryption key was retrieved or not, just that it has been handed back a stream it can use.
     
  13. Apr 6, 2008 #1333 of 2401
    lrhorer

    lrhorer Active Member

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    True. The point is, another user won't be able to "piggyback" off the newly established stream unless his unit also handles SDV. Various schemes have been proposed via which a user would like to use a secondary STB to do the requesting and then let the TiVo gulp down the stream. I was treating the TiVo and CableCard as a single system.
     
  14. Apr 6, 2008 #1334 of 2401
    mikeyts

    mikeyts Stream Warrior

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    We've been sampling the cable providers' special spiked Kool-Aid, haven't we? I don't see this scenario ever happening without some kind of automated channel composition mechanism. You can't sell advertising in a pool of "thousands of channels" when you can't expect for more than a few people to ever be watching such a channel in any given market. I'd bet real money that we'll never see more than 500 linear programming channels.

    If VOD becomes the norm (a possibility), then DVRs (and Tuning Resolvers) become useless. The cable providers will be allowed to treat all VOD programming with "Copy Never" protection because you lose the timeshifting excuse for allowing copying. In any case, the Tuning Resolver isn't going to give subs access to VOD.
     
  15. Apr 6, 2008 #1335 of 2401
    MichaelK

    MichaelK New Member

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    thanks for pointing that out- I didn't realize fresh keys got exchanged all the time like that.
     
  16. Apr 6, 2008 #1336 of 2401
    mikeyts

    mikeyts Stream Warrior

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    Actually, I don't believe that they do. There's nothing in the Tuning Resolver specification to allow a key to be delivered. Messages sent to the CableCARD will establish decryption keys; the TR's resolve_tuning_response() will identify the tuning information with the source-ID given to the CableCARD for the channel--the CableCARD's maps will tell it whether its authorized to decrypt the channel or not. (So far as I can understand it).
     
  17. Apr 6, 2008 #1337 of 2401
    MichaelK

    MichaelK New Member

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    yep

    sfhub pretty much explained that earlier but i didn't htink it was worth adding another post to say so.

    maybe I should have...
     
  18. Apr 7, 2008 #1338 of 2401
    HDTiVo

    HDTiVo Not so Senior Member

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    The difference is the former is of TiVo´s own design and the latter introduces the possibility of a third party intruding and disadvantaging the TiVo operation.


    Also, now that it has been mentioned that a list of future suggestion recordings can be viewed by the user, there is even more possibility for disappointment.
     
  19. Apr 7, 2008 #1339 of 2401
    MichaelK

    MichaelK New Member

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    The ability to look at suggestions has been there from VERY early on. Like in 2.x variants if I recall. And for all the years it's been there- just being on the list has NEVER been a guarantee that a suggestion would record. Way back with 2.x some of the boxes had 14 hrs of recording ability- for many people shows they explicitly wanted didn't get recorded or were deleted early- never mind suggestions.

    If people use that feature they quickly learn that suggestions might show up and might not so if something looks interesting they should ask it to record. I’ve looked at the list at times and for the life of me I can’t figure out how it translates into what actually winds up on the box later.

    so while there is certainly more possibility for disappoinment- I dont think it's huge numbers of people that will be bent.
     
  20. Apr 7, 2008 #1340 of 2401
    HDTiVo

    HDTiVo Not so Senior Member

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    That is probably right.
     

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