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SDV FAQ

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

  1. Oct 4, 2007 #381 of 2401
    Bierboy

    Bierboy Seasoned gas passer

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    Has anyone else mentioned this apparent resolution to the SDV issue? It looks to me like it would resolve all the bitching from naysayers claiming SDV will "kill" TiVo.
     
  2. Oct 4, 2007 #382 of 2401
    ah30k

    ah30k Active Member

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    Bierboy, I know you've been around a long while so I'm stumped as to your rookie mistake. This has been all over this forum already.
     
  3. Oct 4, 2007 #383 of 2401
    PaulS

    PaulS Member

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    SDV is quite analgous to multicast in the data networking world. In fact, it wouldn't surprise me at all to find that the CableLabs folks drafted their SDV requirements from the IGMP RFC's.

    Broadcast : all datatreams/channels are sent simultaneously to all receivers

    Unicast : a single datastream/channel is sent to a single receiver

    Multicast (simplified description) : Imagine a tree, where the source of all data/channels is at the trunk, and all of the receivers are the leaves. In between the trunk and leaves, at branching points, are filtering agents. In the data world, these are multicast (typically IGMP) enabled routers, in the SDV world they are SDV-enabled nodes.

    When a client wants to receive data/channels, it sends a message towards the trunk. All of the filtering agents between that particular leaf and the trunk now know that the leaf wants to receive that data/channel, and log that info into a table. Think of it as punching a hole in a firewall, allowing specific data to flow through that firewall.

    When data/channels arrive at a filtering agent, the agent consults its table to see who is actively listening for this data/channel. It then selectively sends the data/channels to only those leafs who want to receive that data/channel. Conversely, data is not sent to leaves who did not explicitly tell someone that they wanted that data. This is where the bandwidth savings are.

    When a client is done receiving data/channels (changes channels, turns off computer, etc), it sends a message towards the trunk. All of the filtering agents between that particular leaf and the trunk now know that the leaf does not want to receive that data/channel, and removes that info from the table. The hole in the firewall is now plugged.
     
  4. Oct 4, 2007 #384 of 2401
    jrm01

    jrm01 New Member

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    This is the SDV requirement that has always puzzled me as to how TiVo will be able to do this with a dongle. TiVo doesn't know if you are watching a channel. The TV could be turned off and it doesn't know this. If not done properly it would put an added burden on the SDV node.
     
  5. Oct 4, 2007 #385 of 2401
    HiDefGator

    HiDefGator New Member

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    I don't think the cable box knows if you are actually watching the TV or not either. I think the system assumes that every cable box will be on and tuned to a channel at all times. The hope is that many of them are tuned to the same channels.
     
  6. Oct 4, 2007 #386 of 2401
    PaulS

    PaulS Member

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    True enough. Not necessarily a TiVo-specific problem, either. It's also a problem for vanilla set top boxes as well. If the box is just sitting there, tuning/recording a channel for hours on end, how do you determine if it's safe to yank the SDV stream away from it ?

    The safe answer is to have the STB continuously tell the nodes upstream that it's still actively tuned to that channel, and that they should still allow that stream to flow.

    However, knowing how the cableco's work (read : try to scrounge every penny, and actively piss off customers in the process), they'll likely propose a time limit, or have the box try to query the user to see if it's safe to yank the stream.
     
  7. Oct 5, 2007 #387 of 2401
    cableguy763

    cableguy763 New Member

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    It could be that the box is looking for presses from the remote i.e. vol up, down or mute....
     
  8. Oct 5, 2007 #388 of 2401
    morac

    morac Cat God

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    I'm pretty sure they'll use a time limit since many people just leave their boxes on all the time. If someone tuned to a SDV channel and then went away for a weekend it would tie up a SDV stream when no one is using it, which defeats the purpose of SDV.

    What will probably happen is that near the end of the time limit there will be a popup asking if you are still watching the channel. If you don't answer, the SDV switches off and is replaced by a popup telling you to push okay or something to retune the channel.

    For DVRs, the cablebox/dongle will have to be smart enough to tell the host that it's recording (or keep refreshing the request) so that the SDV stream isn't yanked while the box is recording.
     
  9. Oct 5, 2007 #389 of 2401
    snowbunny

    snowbunny New Member

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    Has TiVo explicitly said that they will deliver a fix to the SDV problem? Or are we still hoping to pressure TWC et al to not use SDV?

    Can an S2 (which is still connected to the cable company's digital converter box) *record* in HD? If so, and MRV is becomes reality, could that recording then be transferred from the S2 to the S3 (assuming that the recording is not flagged as copyrighted)?

    I can see why there'd be no reason to transfer an HD recording from an S3 to an S2 (S2 cannot display HD) but I can see a very good reason for allowing the transfer from an S2 to an S3.
     
  10. Oct 5, 2007 #390 of 2401
    DCIFRTHS

    DCIFRTHS I dumped SDV / cable

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    The S2 boxes can not record an HD signal.
     
  11. Oct 5, 2007 #391 of 2401
    bicker

    bicker bUU

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    I thought I remember reading (with regard to the dongle) that there was a four hour (or maybe three hour?) reconfirmation component to its design.
     
  12. Oct 5, 2007 #392 of 2401
    jrm01

    jrm01 New Member

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    The have explicitly said they are working with the cabelcos on a solution which will include a dongle.
     
  13. Oct 5, 2007 #393 of 2401
    Bierboy

    Bierboy Seasoned gas passer

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    Since SDV has no impact on me (and, given our cableco, probably won't for a very long time), I've paid no attention to the threads about it in these fora. I had just stumbled on this, so, of course, ignore my addled ramblings.... :rolleyes:
     
  14. Oct 5, 2007 #394 of 2401
    morac

    morac Cat God

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    This is their official position. A fix is in the making, but is not yet available.

    The S2 is incapable of recording HD content. If you hook up a S2 to a HD cable box and using s-video or RCA jacks then the S2 will record HD channels, but they will only be in SD since the cable box will down-convert it.

    It's been said that SD content will be transferable.
     
  15. Oct 5, 2007 #395 of 2401
    HiDefGator

    HiDefGator New Member

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    I don't thnk the cable companies have agreed to actually make it and distribute it yet. I believe Tivo has said this solution would work for them. I'm not as convinced the cable companies have bought into it yet.
     
  16. Oct 5, 2007 #396 of 2401
    MichaelK

    MichaelK New Member

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    also- hate to be the wet blanket- but the cable filing specifically says something like FUTURE devices might work with it. And the Tivo statement says nothing specific about CURRENT model tivo's.

    Myself I assume tivo can upgrade the S3's and THD's in use to use the new thingie but i wouldn't bet my house on it. (maybe a paycheck- but not the house or even a car...)

    Also, I'd have to agree that I'm not convinced either that cable will universally support it unless the FCC mandates it and they dont show any leanings to do that of late....
     
  17. Oct 5, 2007 #397 of 2401
    bicker

    bicker bUU

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    Cable will support it to the extent they believe that failing to do so might result in more stringent and less friendly requirements regarding separable authentication. So that means that cable companies for whom those requirements were waived will care very little, and those for who those requirements are enforced will care more.
     
  18. Oct 5, 2007 #398 of 2401
    jrm01

    jrm01 New Member

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    Maybe the individual cablecos haven't agreed to it, but their organization has agreed to it with the FCC.

     
  19. Oct 5, 2007 #399 of 2401
    mikeyts

    mikeyts Stream Warrior

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    The NCTA filing says:
    (Emphasis added). I read this to mean that new UDCP products could be designed to work with these devices from the beginning and that some current device (like the UDCP TiVos) might be capable of using it.

    The beginning of the announcement at TiVo's site reads:
    To me, this is talking about a current problem with current products and a prospective fix for that problem with current products. Not some mythical future TiVo CableCARD models, of which there arguably will be none if they fail to fix this.

    As I see it, TiVo doesn't need for cable to manufacture and distribute this thing--they could make and sell it themselves, if they have access to the proprietary protocols being used to deploy SDV.
     
  20. Oct 6, 2007 #400 of 2401
    jercra

    jercra New Member

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    Comcast SDV spec says that this parameter must configurable though it appears that they have chosen 4 hours to start. This is for all STBs not just the dongle. There is also a sepatate flag to indicate that a show is being recorded on a DVR box so that the bandwidth is not marked as reclaimable while any DVR is recording it.
     

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