SDV Question

Discussion in 'TiVo Series3 HDTV DVRs' started by cmonroe, Oct 6, 2007.

  1. cmonroe

    cmonroe Member

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    Sep 1, 2007
    I'm quite familair with IGMP used in an IPTV environment and I'm curious if IGMP and SDV are similar in one way. As I understand it, the CableCo typically strings fiber to the neighborhood, then from the RT to the home is a coax drop. The coax drops are one big broadcast domain which is why you can see some of your neighbors internet traffic.

    Now since SDV is a flood-on-request technology, what if my neighbor or another box from the CableCo in my house requests a channel and its flooded down the pipe from the RT, would my TiVo be able to view the channel for the time while its being flooded into my neighborhood? I assume the video traffic isn't sent directly to the STB requesting it (IPTV uses IP multicast), but is there some part of the SDV technology that would hinder this from working?
     
  2. jercra

    jercra New Member

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    Sep 1, 2007
    You have it right. It's just a frequency and program number. The issue would be that any frequency/prog num combination can be used for any channel at any time. You could never predict what would be on a particular "channel" so I don't see what value there is being able to do that. This is no different than an un-encrypted VOD stream BTW.
     
  3. cmonroe

    cmonroe Member

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    Sep 1, 2007
    Ok, thats the big difference then. With IP multicast used for IPTV the streams are always sent to the same address. Channel 3 for example could always be 224.10.0.3, but whether or not its streaming to your node is a matter of whether or not it is actively being requested.

    So with SDV each time a channel begins to flood from a node it is assigned the next available frequency and that freqency ID is delievered to the STB informing it where to tune? What happens if another STB off of the node jons? No new flooding occurs, the frequency ID to join is just delievered to the STB?

    In the IP world it makes sense to always stream to the same address but in the cable world it sounds like it makes more sense to dynamically allocate frequency bands so you get the most out of the available frequency.
     
  4. ah30k

    ah30k Well-Known Member

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    Jan 8, 2006
    Yes, but your use of "next" implies sequential or incremental frequencies. It really just gets assigned an unused slot.
    The SDV management software just keeps track of how many STBs are currently tuned to the channel. The currently used channel map is sent to all STBs so if they need to join a channel there is no delay. It is this channel map that is not sent to the TiVo so the TiVo would not be able to tune to SDV channels even if they were currently turned on.
     

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