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SDV FAQ

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

  1. hsfjr

    hsfjr (no subject)

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    SDV-land...
    Dang, and just yesterday I stopped into the RR office and got... "We don't have any information on that."

    Can the truck stop by the house first thing in the a.m.? :)
     
  2. Firekite

    Firekite New Member

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    San Antonio, TX
    No, the examples you offer are from the marketing departments of companies who are involved in cable network tech. And honestly, I don't have a problem using that naming convention if that's where we're going with it. I do have a problem with insisting that one has nothing to do with each other and refusing to acknowledge the technical reality.

    I'm fine with that, but that's the first time in recent memory that such an objection's been made. That wasn't your point before, remember?
     
  3. classicsat

    classicsat Astute User

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    Feb 18, 2004
    Ontario Canada.
    SDV does less, actually, it just chooses/releases an existing linear stream, VOD, in addition to that, can choose a dynamic stream from a menu, and manipulate (trick-play) it, the latter which cannot (at least yet, or the cable providers don't want) over the TA interface.
     
  4. mikeyts

    mikeyts Stream Warrior

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    Jul 10, 2004
    San Diego,...
    The marketing departments get most of what they say from the engineers (many of the marketers at such companies have undergrad engineering degrees). I'm a retired software engineer who worked for over 30 years on firmware in the computer storage, large-scale networking equipment and consumer electronics industries, and I've been engineering laison to marketing a few time (I actually worked for Moto for a while, but not on broadband). I assure you that engineers and lawyers went over every word of that whitepaper :). The choice of "Switched Digital Video" as the label for the "sharing a pool of bandwidth on a edge segment between many broadcast streams" technology was probably mostly on marketing, though. It doesn't matter--the term was coopted to mean specifically that and the industry is consistently sticking to it. When you see "Switched Digital Video" or "SDV" in the related technical press or on sites like Answer.com and Wikipedia, everybody's talking about the same thing. The FAQ at the top of this thread is specifically about that technology and we as CableCARD TiVo owners (except that you aren't one, are you?) are specifically concerned with that technology and how it's shutting us out of new cable content that we had every expectation of being able to get. Posting objections of "VOD channels are SDV channels" does nothing to aid the discussion and merely creates massive ratholes like the one that we're in now.

    Sure VOD and SDV are related--they're both based on video switching, but both are much more than that. SDV, as the term is defined by the industry, is not a component of VOD.
    I'm sorry, but I don't recall stating any other objection than to people sayng things that implied that SDV is part of VOD (confusing other people into thinking that they were saying that VOD is a kind of SDV, leading to 20-post arguments). If I stated it poorly somewhere, I apologize.
     
  5. lrhorer

    lrhorer New Member

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    Aug 31, 2003
    San...
    As anyone who reads the link you posted can see, MichaelK did not say what you claim he did, and I did not say what you claim I did. As to my knowing what MichaelK meant, in a forum such as this, I cannot assume anyone means anything other than precisely what they say, because to do so is to assume others reading the very same post have the proper background to read the same things between the lines that I might have. In this particular case, however, it seemed likely the poster was making a distinction between the equipment which carries broadcast SDV and VOD. There is none such. If you are claiming he meant Howard Stern TV might be changing from purely on-demand programming to purely or partially scheduled programming, then the fact is I didn't follow at all what you claim the OP had in mind. Either way, your assertion that I "knew exactly what MichaelK meant" and it's negative connotations were inappropriate to my post.

    Many people on this forum seem to think there is some fundamental difference between SDV and VOD as it relates to the transmission standards. There is not. Many people are advocating eliminating SDV because they think SDV and VOD are independant technologies, and eliminating SDV would not eliminate VOD. In the context of a CATV system, they are not, and it would. Specifically, there are three and only three widely deployed digital video systems: linear, SDV, and IPTV. VOD uses precisely the same transmission equipment, reception equipment, and interactive protocols as that used by switched scheduled broadcasting, whatever the underlying protocol. It does require an additional set of protocols to allow the user to initiate the stream, as well as a vastly greater bandwidth from the servers. Scheduled programs allow no such control by the user, but the modulators, receivers, and streams are all identical. Indeed, while a linear QAM can distribute nothing but linear video, an SDV QAM can readily be transmitting a mixture of scheduled programs and VOD or similar programming, and that mixture can change at any moment. Looking at a particular timeslot within an SDV QAM, one moment it can be carrying a scheduled program, and the very next moment it may suddenly rewind by 30 seconds. A minute or two later it might start transmitting one of HBO's VOD offerings.

    The video protocols are somewhat similar to data networking. Many networks switch at Layer 2, that being most often Ethernet these days, but some systems still employ Token Ring or SONET based transport streams (SONET or TDM transports still being the main choce for WAN connections). Some, however, switch at Layer 3. The Layer 2 networking is roughly analogous to CATV or FIOS, and SDV switching is more or less analogous to Layer 3 switching, while IPTV is IP based and can switch at Layer 2, Layer 3, or both.

    The most common Layer 3 protocol these days is IP, although again there are others such as IPX, ISIS, etc. Similarly, the CATV provider can choose to implement SDV or IPTV or whatever other switched transport technology they may choose. There is nothing in the transport systems which prevent CATV systems from employing something other than SDV, but no matter what system they choose, no UDCP (by itself) can effectively receive program content delivered over the system of choice. By a very wide margin, SDV is the choice for most CATV providers, so in practical terms if we are talking about a switched service on a CATV system, we're talking SDV.

    The two most common layer 4 protocols are UDP and TCP. Neither one requires IP to be the networking layer: they both can quite happily transverse an IPX or ISIS network, but speaking a bit loosely they both require there to be a Layer 3 protocol to carry them. Again, similarly, VOD doesn't necessarily require SDV for its transport. It's quite easy to implement it over IPTV. It's even hypothetically possible to implement it entirely over linear QAMs, provided the CATV company doesn't mind eating up its entire 750-1000MHz network with only 3 or 4 channels. No one, however, is that phenomenally stupid, so speaking in real world terms, VOD on a CATV system requires SDV.

    It is not a useless point. No UDCP (by itself) can receive VOD. There are two reasons this is the case. One is regulatory and not absolute. To wit, the CATV providers are not bound by law to provide VOD and other 2-way services to UDCPs, no matter how they are modified. Thus, even with the TA, most users won't get VOD, video rewind, internet browsing, online banking, interactive gaming, etc.

    The second is physical. If the unit cannot receive SDV programs, it can't receive VOD. If TiVo, the CATV companies, and the CATV equipment manufacturers chose to (agreed to), the TA could readily provide VOD and the other non-scheduled 2-way services. Why? Because it is all 100% SDV, especially as far as the STB / DVR is concerned. It only requires extra software to handle VOD, not any different hardware.

    No doubt, although I haven't seen the actual numbers. It is TWC's choice.

    Which is no big surprise. VOD requires a huge amount of processing and switching power and an unbelievable amount of server bandwidth, while plain vanilla scheduled SDV requires comparatively little. Using a different analogy, SD video requires much less horsepower than HD video, and a system capable of handling SD video won't necessarily be able to handle HD video. The fact it requires more capable transmitters and receivers doesn't mean HD isn't video. Similarly, the fact VOD can easily eat up hundreds of times the server horsepower and requires additional protocols doesn't mean it isn't SDV in the CATV environment. More to the point, if the video provider in question uses some other switching protocol (can you say FIOS or IPTV?), then for that system the VOD is not SDV. The number of fiber / aluminum based CATV providers who aren't using SDV for switching is tiny, however. To put it more simply, if a CATV system deploys VOD, then they have SDV capability in place. Deploying only basic SDV capability doesn't allow them to deploy VOD, however.

    Which wouldn't be possible if they didn't use the same switching protocol. It's called SDV. I never said the two terms were anything like synonyms. I also never said they were fundamentally inseparable. What I did say is that if it's VOD on a CATV system, it's SDV (with an insignificantly small number of exceptions for those using some switched protocol other than SDV).

    Which is PRECISELY what VOD is... and video rewind... and video internet browsing... and On Demand PPV... and interactive gaming... and video conferencing... and of course scheduled SDV broadcasts.

    ... and it applies perfectly to VOD. Nothing in that definition limits the bandwidth of the service, requires any of the services to be authorized for multiple viewers, requires any of the services to be limited to a particular schedule, or requires any of the services to be restricted from initiation by one of the edge segments. Logically, the only difference between VOD and "ordinary" SDV is the video stream at the server is initiated by a user if it is VOD and by an automated system (often a network feed) if it is scheduled programming. Physicaly the difference is that a single scheduled feed only requires one continuous data stream coming from the server, while a VOD service can require hundreds or perhaps even thousands of intermitytent streams.

    I'll let all my friends and former colleagues who are still video engineers in the CATV industry know they are wrong according to themselves. As far as "unproductive" is concerned, the number of posts above which suggest some of the readers think VOD could be deployed in a CATV system without deploying SDV (or some other switched system which would be just as incompatible with the TiVo) is quite significant, and I do not consider any post which seeks to correct such misaprehensions to be unproductive. If you find them so, the skip them. No one is forcing you to read my posts. Indeed, I consider any attempt to fundamentally differentiate the issues with VOD and SDV in the context of the TiVo or understanding how either works to be counterproductive.
     
  6. lrhorer

    lrhorer New Member

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    Aug 31, 2003
    San...
    Well, not just VOD, but all on-demand and interactive services other than regularly scheduled SDV programming. In terms of the number of streams and amount of bandwidth used, many CATV systems employ a great deal more in services other than VOD and scheduled programming (both linear and switched) put together.
     
  7. lrhorer

    lrhorer New Member

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    Aug 31, 2003
    San...
    You are claiming I cannot say I have a dog because she is an Irish Wolfhound. Well, almost. Where this analogy breaks down is that not all VOD is SDV, but in all but a very tiny number of CATV systems, it is. I can't think of any Irish Wolfhounds anywhere who aren't dogs, my dog's belief she is human notwithstanding.

    Let's put it this way. If some of the people in this forum and elsewhere had their way and the FCC forced every CATV system to rip out their SDV equipment, what would happen to VOD on those systems?

    Answer: it would stop dead cold, because the equipment and protocols which deliver SDV are the same ones which deliver VOD. VOD requires additional equipment at the TOC, to be sure, and the switches must have much greater throughput. You can insist that "VOD isn't SDV" all you want, but it uses the same streams as SDV, the same modulators as SDV, the same receivers SDV, has precisely the same engineering problems with UDCPs that SDV does, requires the same upgrades SDV does (yes, plus some additional ones), and produces an output which is completely indistinguishable from SDV. Oh, and by the way, what does a CATV company have to purchase, install, and maintain after implementing a VOD system - including STBs and DVRs - in order to deliver SDV? Nothing whatsoever. But VOD and SDV are completely separate and must be considered to be unrelated? OoohhhKaaaayyyy.....

    No, it doesn't. It does imply any CATV system which offers VOD has SDV, which is accurate although not quite 100% true. There are a small handful of exceptions.

    I never said that was the case. SDV is what is used by virtually all CATV systems to deliver VOD. FIOS uses IPTV. In the early days when we were working on the Pegasus project (and I was working for Time Warner Cable) we tried a number of switching systems to deploy VOD in the lab. I have no doubt there are still some small CATV systems out there using proprietary switching protocols to deliver VOD. I know for a fact some have tried IPTV, but I don't know if any fiber and aluminum providers are still toying with IPTV or not.

    No, you don't, which is the point you seem to be missing completely. Scheduled video only requires an input stream to the server, which can be almost pathetically puny. VOD requires the server to originate the streams and requires them to originate potentially thousands of streams. All the scheduled video sever really needs to do is encrypt the incoming stream and pass it on, assuming it's encrypted. If it's a local broadcast stream, it doesn't even do that.

    No, it wouldn't, because all one would be left with is a bunch of hyper-powerful servers and switches with no way to get the signal to the user. I don't know where you got the notion VOD uses a separate set of video equioment from SDV, but it doesn't. Remove SDV from the CATV system and VOD is gone... kaput... blasted... it no worky. Now do you understand?

    Which includes VOD and other on-demand services. Scheduled video services (linear and switched) may utilize in aggregate a few Gbps at the TOC. On demand sevices (including VOD) can easily require 100Gbps or more. There is more than one switching protocol which can be used to deliver on-demand services, but almost universally the one chosen by CATV providers is SDV. Now if you want to differentiate the service provided by scheduled SDV from the underlying protocol, then OK, but it is the exact same protocol used by SDV and requires all the same equipment and software used by SDV. We also need a name for it. What do you suggest? The only way to remove SDV capabilities from the system is to remove those protocols, in which case pffft! goes VOD, your assertion notwithstanding.

    It's not a generic term. It refers specifically to the switching protocols used by almost every CATV system which deploys switching, so it's almost universal in CATV circles. There isn't a separate one for VOD and other interactive and on-demand services.

    Capiche?
     
  8. lrhorer

    lrhorer New Member

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    Aug 31, 2003
    San...
    Obviously. From an engineering standpoint it is a mostly superfluous distinction, especially from the standpoint of the customer's receiver (in this forum, a TiVo). It can be a significant distinction, however, in light of the FCC regulations on what must and must not be supported on UDCPs. If the distinction is made, however, then it also must be made between the services implied by the term "SDV" and the underlying protocols, since those same protocols are used by on-demand services, including VOD. This is not being done (or apparently understood) in this thread. Certainly, it's not unheard of for a single term to refer to both a service and it's underlying protocols.

    True. It also, however, relies on an underlying switching protocol set, or rather it must in all practicality do so. It generates far too much bandwidth to be practical on a linear system. For almost all CATV systems that underlying protocol is SDV, or if you insist the same protocol set used by SDV.

    Indeed it has. I never suggested it hadn't. Since my personal familiarity with VOD extends back into the early 1990s, it would be singularly odd should I do so.

    I have never done so, or at least not intentionally. The fact I expounded the deduction that (virtually) any CATV system which offers VOD is employing SDV in no way confuses the two. When I say "VOD" I mean the service which allows consumers to select a program from a menu and start playing it on their TV from the headend. When I say "VOD and similar services" I mean anything which employs the VOD protocols to deliver a user controlled video from the headend. When I say "SDV" I mean the protocols used by the vast majority of CATV systems who deploy switching at all which allow a different set of digital streams to be delivered to each independent edge network. Unless I specifically limit the use of those protocols to scheduled programs, the term is intended to include on-demand services.

    I don't, but I do use it to include VOD and other on-demand and interactive services. What term would you prefer I use to include all services which employ the digital video switching protocol set also used by scheduled SDV? I suggest you make it a good one, because I rarely have any reason to limit the discussion to scheduled programs, especially since they are a tiny minority.
     
  9. lrhorer

    lrhorer New Member

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    Aug 31, 2003
    San...
    Oink. <flap flap>

    :D
     
  10. dig_duggler

    dig_duggler losing enthusiasm

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    Sep 18, 2002
    Birmingham, AL
    Not that it really matters, but when does Q2 actually end? Just curious as to when the reported timeframe is officially missed....
     
  11. classicsat

    classicsat Astute User

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    Feb 18, 2004
    Ontario Canada.
    End of June, in my mind, of the calender year.
     
  12. bicker

    bicker bUU

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    Georgia
    Indeed: Q2 ends June 30.

    That doesn't mean anything will happen by then. That metric was just put forward as a goal, not a promise.
     
  13. mikeyts

    mikeyts Stream Warrior

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    Jul 10, 2004
    San Diego,...
    Under the best of circumstances, engineering estimates made as far ahead as that one was are of limited accuracy. Being an estimate of a cooperative effort by CableLabs, Motorola, Scientific Atlanta, TiVo and all of the major cable providers, this one had almost no chance of being precise. Still, I don't think that it will be more than 2 or 3 months late, which is pretty good, considering.
     
  14. MichaelK

    MichaelK New Member

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    NJ
  15. Jun 1, 2008 #1616 of 2401
    moyekj

    moyekj Well-Known Member

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    Jan 23, 2006
    Mission...
  16. Jun 1, 2008 #1617 of 2401
    mikeyts

    mikeyts Stream Warrior

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    Jul 10, 2004
    San Diego,...
    I feel fairly certain that TiVo's going to have to work that out themselves. Not being able to get a potential boatload of new conditional access channels is one thing (and in some places, like Hawaii, a bunch of old ones); not being able to figure out where the non-conditional access ones are is another and most definitely not the cable industry's problem. I have to think that only people attaching them to certain certified pieces of equipment in which one or more leased CableCARDs is installed will ever get one of these things.
     
  17. Jun 1, 2008 #1618 of 2401
    jkovach

    jkovach TiVoing since 1999!

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    Gilbert, AZ USA
    For Cox subscribers in the Phoenix market, here's a list of the channels that are being moved to SDV on 7/1/08, per the letter I received in the mail yesterday:

    109 Cox Real Estate 2
    110 Daystar
    112 INSP
    113 EWTN
    114 BYU-TV
    125 C-SPAN 2
    126 C-SPAN 3
    133 DIY
    144 Fox Reality Channel
    155 BET Jazz
    156 Great American Country
    157 Fuse
    158 G4
    159 Logo
    163 Fit TV
    170 Fox College Sports Atlantic
    172 Fox College Sports Pacific
    173 Fuel
    405 TV Chile
    410 De Pelicula
    411 De Pelicula Clasico
    412 CineLatino
    413 VeneMovies
    417 History en Espanol
    418 Discovery en Espanol
    422 Discovery Familia
    423 TOON Disney en Espanol
    424 Boomerang en Espanol
    425 Sorpresa
    430 MTV Tres
    432 Bandamax
    433 VideoRola
    434 mun2
    438 ESPN Deportes
    439 Fox Sports en Espanol
    440 GoITV
    444 CNN en Espanol
    445 Canal Sur
    449 EWTN Espanol
    500 iNDEMAND Previews
    601-606 ESPN Game Plan / ESPN Full Court
    650 NBA League Pass Preview
    651-659 NBA League Pass / MLS Direct Kick
    671-684 MLB Extra Innings / NHL Center Ice
    840 Public Safety
    850 Public Safety
    851 Public Safety
    853 Public Safety
    854 Public Safety
    856 Public Safety
    857 Public Safety

    So far, I have to applaud Cox for selecting channels with limited appeal, and none that are HD. Of course, I know that's the whole idea behind SDV (moving limited appeal channels to it, and leaving the rest alone), but there were rumours that in the Phoenix market the plan was to put everything digital on SDV.

    In my case so far, I see no need to get a tuning adapter, even if it is free. I either don't subscribe to most of these channels, or in the exceptionally rare case I need to record something from one I can use my S2 that is still hooked up to a cable box.

    Jeff
     
  18. Jun 1, 2008 #1619 of 2401
    bicker

    bicker bUU

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    Georgia
    Yes, Jeff, I'm encouraged by that selection of channels. It shows a very good sense of perspective. Hopefully Comcast will follow the same general model.
     
  19. Jun 2, 2008 #1620 of 2401
    Enforcer

    Enforcer New Member

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    Apr 21, 2008
    San Antonio, TX
    You guys in phoenix are lucky. In San Antonio all the good stuff is SDV. Give them time, they'll screw you eventually. I can't wait for the adapter. Tired of having to go into my office to see all the channels.
     

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