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SDV FAQ

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

  1. Jul 5, 2007 #21 of 2401
    vstone

    vstone New Member

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    May 11, 2002
    Martinsville...
    From ATSC standard (which is enacted in CFR by reference):

    STT - System Time Table
    CVCT - Cable Virtual Channel Table
    TVCT - Terrestrial Virtual Channel Table
    MGT - Master Guide Table

    The rules governing the transport of PSIP tables for cable are:
    • Requirement 6: The required tables for a cable system are: the STT,either the CVCT or
    the TVCT, and the MGT. For any region that makes use of the capability to change the
    RRT, that RRT shall be included in the TS if any content_advisory_descriptor in use refers to
    that region. An RRT defining the rating system for a given region shall be included in the
    TS if any content_advisory_descriptor in use refers to that region, unless that region has
    explicit standards that define the rating system and the meaning of the values in the
    content_advisory_descriptor.
    • Requirement 7: The PSIP tables shall describe all of the digital channels multiplexed in
    the Transport Stream. For convenience, the tables may optionally include information
    about analog channels as well as other digital channels available in different Transport
    Streams.

    Comment: Its hard to decipher, but I think it also requires RRT (Rating region Table) for US & possessions. ATSC also used outside US.

    From ATSC:

    IN CVCT:
    virtual channel – A virtual channel is the designation, usually a number, that is recognized by the user ...

    Comment: I'm hard pressed to believe that cable companies expect me to remember that 116-1 is WSLS HD. That is not what their channel lineup says. However, I'm going down to the local cable company to ask them what channel is what?

    I haven't noticed that cable folk are required to populate tables, but I guess I'm naive - I think its implied.
     
  2. Jul 5, 2007 #22 of 2401
    sfhub

    sfhub Active Member

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    Jan 6, 2007
    That's not what I said. If WSLS-HD OTA had PSIP VCT (which it should), your cable company is required to propogate (and adjust the channel freq/modulation/etc for cable specific info)

    I also said I didn't believe there was any requirement for the cable company to add its own PSIP VCT/CVCT info (when it wasn't present originally) One common example where this would come into play is if your system has ADS (digital simulcast) channels.

    Basically while you can expect some of your digital channels to have PSIP VCT/CVCT it likely will not cover the range of all the digital channels you can receive.

    Maybe I misunderstood what you meant by "populate" and took it to apply to more channels than you intended.

    I looked at the transport streams on my system and the OTA digital sourced stuff does have both VCT and CVCT info for the OTA digital sourced channels I checked. The ADS channels have no VCT or CVCT. My head-end used to be misconfigured to not propagate the VCT info correctly. I say my head-end rather than my cable system because the surrounding areas did have proper VCT, just not my head-end. They finally fixed that 6 months ago.
     
  3. Jul 10, 2007 #23 of 2401
    Justin Thyme

    Justin Thyme Contra sceleris

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    Mar 29, 2005
    It is not that FIOS's IPTV approach has the bandwidth so that it doesn't need SDV. It is simply that IPTV is even more efficient than SDV. The reason why is that SDV channels that are allocated do not fully utilize the bandwidth. You have a segment of a variable encoded movie that is all or nearly black, and with SDV, you still have 6 MHZ sitting there carrying no real data. With IP, during such low data periods, you are transmitting smaller packets and so the bandwidth can be used for other stuff- like your unbox downloads. :D But seriously- it allows a channel to be "Bursty". With SDV you have to allocate enough for the peak Mbps needed during an action scene even though most of the time you are using half that much data.

    By the way- that Graphic is originally from Wikipedia's article on switched video, it isn't TivoBlog's.
     
  4. Jul 10, 2007 #24 of 2401
    jrm01

    jrm01 New Member

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    Oct 17, 2003
    Pittsburgh
    In reference to the diagram: The switching is not done at the head-end, nor the distribution hub, it is done at the Optical Node, the point where fiber ends and coax begins.
     
  5. Jul 10, 2007 #25 of 2401
    monkeydust

    monkeydust New Member

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    Dec 12, 2004
    Thanks. I saw the acronym being thrown around here recently but I didn't know what it meant.
     
  6. Jul 10, 2007 #26 of 2401
    davecramer74

    davecramer74 New Member

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    Mar 17, 2006
    fios doesnt use iptv, att does. Fios has traditional setup like comcast, etc does.
     
  7. Jul 10, 2007 #27 of 2401
    ah30k

    ah30k Active Member

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    Jan 8, 2006
    Broadcast video is traditional cable QAM while interactive (VOD etc) stuff is IP. This is where the QIP name comes from.

    AT&T uses IP for the whole thing.
     
  8. Jul 10, 2007 #28 of 2401
    aymanme

    aymanme New Member

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    May 8, 2001
    Austin, TX
    I can't believe nobody has mentioned TWC in Austin, TX yet. It was the guinea pig for SDV.

    In Austin, CMAXHD, STARZHD, all Digital channels with an analog simulcast, All pacific feeds, fox reality, speed, and probably a dozen others that I forgot are all now switched.

    On that topic, is there any hope that the S3 will show some of these? In what time frame? Here, they move channels often to SDV; As the months pass, fewer and fewer channels are available w/o their box. I like fox reality and wish I still got it.

    The Tivo interface is superior, I love using it to see what's on the channels I can't get anymore.
     
  9. Jul 10, 2007 #29 of 2401
    jrm01

    jrm01 New Member

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    Oct 17, 2003
    Pittsburgh
    aymanme:

    Just curious: It sounds like you are saying that the SDV channels still show up in the Guide. true? What happens when you try to switch to that channel?
     
  10. Jul 10, 2007 #30 of 2401
    aymanme

    aymanme New Member

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    May 8, 2001
    Austin, TX
    It will give you a gray screen for a while and then tell you "not available". I do not believe the Tivo service knows which channels are unavailable to the current generation of cable cards / hosts. So all the channels still show up in the guide unless you manually take them out.
     
  11. Jul 13, 2007 #31 of 2401
    vstone

    vstone New Member

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    Martinsville...
    Interesting visit to TWC in Myrtle Beach, SC yesterday. I was asking for a channel lineup for clear QAM tuners. The CSR said they don't have one and when SDV was activated, these tuners wouldn't get ANY stations anyway. I was happy to hear a CSR admit that she had even heard of SDV, but not too happy with her message (assuming it's true). I would have thought that the basic tier, often called the Broadcast Tier, would remain available. CFR says the basic tier must be unscrambled/unencrypted. I suppose that SDV technically doesn't violate this, which must make the cable folk happy that they can get one past the FCC.
     
  12. Jul 13, 2007 #32 of 2401
    MichaelK

    MichaelK New Member

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    NJ

    I'm voting that's a line cable isn't stupid enough to cross.

    doing that surely will get the FCC off it's butt about SDV and force an open standard.

    I suspect cable may do everything but the rebroadcast locals in SDV though.

    in the scheme of things it does them little harm to leave the big 4 on all the time anyway- on any given primetime a large fraction of the tv's are tuned to those 4 so it would be virtually impossible for a node not to have the big 4 on at any given time. So they only really would be thowing a bone to the second tier broadcasters and besides PBS how many of them are HD? In most markets you could use a couple QAM 256 fot the big 4 and then one QAM256 slot for eveything else.

    3 Qam slots for locals and 122 for switched video, vod, ppv, internet and voip on a 750mhz system. Why wake the giant over 3 qam slots? So far the fcc isn't doing a darn thing about it so leave the status quo and throw them the locals in the clear on qam.
     
  13. Jul 13, 2007 #33 of 2401
    moyekj

    moyekj Well-Known Member

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    Jan 23, 2006
    Mission...
    If my cable co. ever goes as far as including all the locals & HD locals in SDV then it will be time to dump them completely and go OTA only since my S3s would be useless with cable anyway. I suspect SDV is coming to my headend sometime this year but don't know the scope yet...
     
  14. Jul 14, 2007 #34 of 2401
    TiVoMonkey

    TiVoMonkey New Member

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    The Jungle
    There is absolutely no reason that cable companies will put locals onto SDV.

    SDV is about bandwidth savings. When you have channels that are watched by the majority of all users in a cable system, there is no bandwidth savings for those channels, if the SDV servers are ALWAYS switched to the locals.

    The channels will remain unswitched, just as any other popular channel would be. If you watch We and Discovery Science a lot, expect those to be switched. But ABC, NBC, CBS, main HBO? No way.
     
  15. Jul 14, 2007 #35 of 2401
    cwoody222

    cwoody222 Active Member

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    Buffalo, NY
    Do you have any info about TWC Buffalo?
     
  16. Jul 15, 2007 #36 of 2401
    sfhub

    sfhub Active Member

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    Jan 6, 2007
    I wouldn't say there is absolutely no reason. Instead I would say there are reasons why they wouldn't place locals on SDV.
     
  17. Jul 15, 2007 #37 of 2401
    vstone

    vstone New Member

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    Martinsville...
    I think MHD & A&EHD are SDV on TWC in Myrtle Beach, SC (which probably means all of TWC in SC) , but I can't confirm that.
     
  18. Jul 15, 2007 #38 of 2401
    TiVoMonkey

    TiVoMonkey New Member

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    The Jungle
    And again, I would say absolutely no reason.

    It's a waste of resources to switch channels that most of their subscribers watch. If someone out of a particular node is always watching a local channel, then there is no reason to switch that channel.
     
  19. Jul 15, 2007 #39 of 2401
    moyekj

    moyekj Well-Known Member

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    Jan 23, 2006
    Mission...
    That thinking is the conventional wisdom (and what is led me to my 1st S3 purchase in the 1st place even though I knew all about SDV), however just because something makes sense doesn't necessarily mean that's the way it will be implemented. The SDV motto is go big or don't go at all. Sure if a cable company is just experimenting with SDV it won't happen, but if there is all out deployment of SDV once testing phase is over I wouldn't be too surprised to find a cable headend implementing ALL digital channels on SDV. I say be ready to deal with the worst case scenario when it comes to this issue which leaves a lot of upside if it doesn't materialize into much.
     
  20. Jul 15, 2007 #40 of 2401
    sfhub

    sfhub Active Member

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    Jan 6, 2007
    Umm, keeping in mind bandwidth is the most important resource, what bandwidth are you wasting? At worst, you are break even minus a small amount of overhead.

    How do you know a local channel is really always being watched? There are scenarios where a local channel could be static for certain events, but switched otherwise.

    Conventional wisdom has it that foreign language tier should be switched. In some areas that might be reversed. In heavily hispanic areas, telemundo, HBO-spanish, etc. could be way more popular than some of the locals. I don't pretend to know what every mix of population in the US tends to watch. Switching everything lets the system sort everything out on its own.

    I'm not arguing for switching locals. As I mentioned earlier there are many reasons why it should *not* be switched. I just don't agree there are no reasons why it should be switched.
     

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