SDV Sucks

Discussion in 'TiVo Series3 HDTV DVRs' started by spolebitski, May 1, 2009.

  1. Adam1115

    Adam1115 Well-Known Member

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    No, VOD is classified as a 2-way service, and was known to not work with one-way cablecard devices.

    Moving popular channels or even ALL HD channels to SDV was a move to kill devices like TiVo. Especially when alternatives exist, like killing off analog channels.

    As far as giving everyone STB's? That's not true either.

    They can kill all the analog extended basic channels they want. They'd only have to give out a box if they killed analog locals.

    The FCC doesn't require them to provide me a STB to get MTV and Comedy Central...
     
  2. lrhorer

    lrhorer Active Member

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    No, of course there is a limit on the number of streams being sent to customers. First of all, there can't be more streams than receivers, and the number of receivers is finite. Lets simplify a bit and assume everything is HD - no SD at all - with exactly two HD streams per QAM. In a linear system, the total number of streams on a 600MHz spectrum is 200, period. That means across the entire city, there can only be 200 total streams. That sounds like a lot, but it isn't, since every single VOD or trick-play stream must be unique, and a city with 100,000 subscribers can easily gulp down 10,000 unique streams. If we take the city and divide it in half sending one set of streams one way and the other set the other, then suddenly we can deliver 400 unique streams instead of 200. Divide it into quadrants, and now we can deliver 800 unique streams, and so forth. A typical moderately large CATV plant may employ 100 nodes or more. Potentially each one of those nodes could hypothetically deliver 200 unique streams, for a total of 20,000 unique streams, delivering a perfectly customized signal to each and every one of 20,000 receivers.

    The thing is, that's way overkill. At any given time, more than 80% of those 20,000 tuners will be tuned to one of only 5 unique streams. More than 99.9% will be tuned to one of 20 or so channels. Thus, those 20,000 streams can serve a great deal more than just 20,000 tuners. Statistically, a node with 200 streams could ordinarily supply service to perhaps 3000 receivers with no contention. It's only when the 3001st receiver tries to come online with a stream no one else is watching that the subscriber gets denied. Multiply that by 100 nodes, and you see that city-wide there can be 300,000 receivers getting a total of 20,000 unique streams with no one at all being unable to receive what they want.

    Now these numbers are very simplistic. First of all, no CATV system of which I know has a full 600MHz of SDV channels, but then on the other hand any channel - like a national network - which is pretty much certain to be received on every node in the city gets no advantage from being placed on an SDV QAM. Secondly, most CATV companies allocate more than 450 MHz of their total 750MHz spectrum for analog channels. That leaves about 300 MHz - 50 QAMs - for digital services, split between linear streams and SDV streams. Depending on node size, the number of linear QAMs is probably going to be about half that, leaving perhaps 25 QAMs - a maximum of 50 HD or 300 SD streams to be divied up between the 200 or so receivers on a node not tuned to a high popularity scheduled program. Ordinarily, that is more than enough, but every once in a while the node may wind up completely full of unique streams, and then the next person to request a unique stream will get denied. The odds of this happening are fairly low. The odds of it happening to the same person twice in a row are pretty much astronomical, once one or more timeslots have cleared.

    You wouldn't be. That's the point. That, and the fact you got dropped are the reasons why your symptoms cannot be attributed to an artifact of SDV. You are blaming an innocent defendant.

    No. 'Not in a million years. If the stream is already present on the node, then all the headend does when the host requests the stream is to respond with the frequency and timeslot where the stream can be found. The host then moves its tuner to the specified frequency and sends the specified stream to the CableCard for decrypting, if necessary. Every single tuner on the node - or for that matter in the entire city - could be tuned to the stream and it would make no difference. In a properly operating SDV system, it is only once every QAM timeslot has been allocated that a tuning request will be denied, and then only if the stream does not already exist on the node. Across an entire city of perhaps 200,000 - 500,000 tuners or more, denials are fairly frequent, but the odds of one particular subscriber being repeatedly denied on a regular basis are minuscule. Note this applies to a denial based upon the node being full - which is an artifact of the SDV system. A denial can also be issued if all the video ports at the server farm are busy. This is not an artifact of SDV, but just of an undersized server farm. It is still true, however, that this will not happen if the requested stream is already being served.

    It's no different than making a phone call and getting a fast busy reorder response. Your Local Exchange Carrier has a class 5E phone switch in its central office, serving perhaps 50,000 houses and businesses. It does not have the capacity to serve 50,000 simultaneous phone conversations. Rather, it relies on the fact less than 1 in 5 phone customers will be on the phone at any one time. Thus, it's trunk capacity is only perhaps 10,000 lines, or less. If suddenly all 50,000 customers picked up the phone and tried to dial out, the majority would get a fast busy. We watch our 5E switch traffic very carefully to determine what the peak loads on the system are, and move to purchase additional trunks if the peak load ever exceeds our trunk capacity for any period of time day or night. We want to avoid reorder responses as much as possible, but they do occasionally occur. We do not ever provide enough trunking to serve every line in the switch. Trunking is expensive, and if we bought 50,000 trunks for a switch with 50,000 active lines, 40,000 of the trunks would be permanently idle, doing nothing but wasting money.
     
  3. lrhorer

    lrhorer Active Member

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    Known? Did someone have to do research to figure it out? You make it sound like some deep, dark mystery. How it is classified is completely irrelevant. The simple fact is every conversion costs money and produces issues. An SDV QAM serves two-way services, completely irrespective of how it is "defined". That means SDV, VOD, trick-play, and interactive services. Yes, throwing away the investment in several dozen analog channel modulators and purchasing several hundred QAM mdoulators to serve 5 or 6 QAMs can relieve contention for SDV QAMs to carry VOD and other services, but only an idiot would do so if it is unnecessary. Converting a single analog channel to a QAM can easily cost north of $2 million in a large CATV system. Remember, whether SDV or linear, you are going to have to have a modulator for every node in the city - which can mean 400 modulators (in the case of San Antonio) or more. If you had to spend $2 million on modulators, would you use them to serve up 2 HD channels, or 20?

    As to the FCC regs, I admit I am uncertain of their details. After all, I am no longer in the industry so I don't need to know them. The point is not major to the discussion.

    That's a cute tinfoil hat you are wearing. The furor over not being able to tune a handful of HD channels by less than 0.01% of the subscriber base was quite significant. The din from killing off favorite channels of over 95% of their subscriber base would be deafening. Add to that the fact the cost of converting to digital is significant, and why on earth would anyone in his right mind spend all that capital to produce no revenue whatsoever?

    Buy a clue. The CATV companies barely care about TiVos at all. The cost of a single analog to digital conversion easily wipes out the entire profit from all their STB and DVR rentals for several years. More to the point, with far fewer than 200,000 Series III TiVos across the nation, a large CATV system with 300,000 subscribers can expect to host at most 750 Tivos, and probably less than 500 TiVos. At $20 a pop, they could rent their own DVRs to the Tivo owners for $17 more than they charge for a CableCard. Of that, at the very most $7 is profit after allowing for the cost of ownership of the DVR. Multiply $7 by 750 and you get $5250 a month. The actual number is probably more like $2000 a month, but lets be super generous and make it $10,000 a month - an absurdly high number. The San Antonio TWC system, with 300,000 subs, hauls in more than $1 MILLION A DAY. A single engineer earns more than the the total revenues lost to TiVos. Their senior managers make that much in a day. Oooh. Yeah. Getting rid of those TiVos is absolutely top priority. 'Best $10 Billion (nationwide) investment they ever made.
     
  4. DCIFRTHS

    DCIFRTHS Active Member

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    Unfortunately, many customers are limited to only one pay-for-TV provider. The local cable company.
     
  5. rlcarr

    rlcarr Member

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    Huh? Here in the Boston area RCN, Comcast, and I believe FiOS have already all dropped their analog service and have gone 100% digital.
     
  6. morac

    morac Cat God

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    That's because the actual mandate states that as long as analog channels are provided, then the basic tier must be provided in analog as well. This was done to prevent cable companies from dumping their basic tier to digital to make room for other services.

    There is no mandate preventing cable companies from completely switching to digital.
     
  7. lrhorer

    lrhorer Active Member

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    I had some of my industrial contacts do some price checking for me. Cisco's standard wholesale price for an SA-8300HDC DVR equipped with 1 M-card is $480 in 1500 quantity lots. A very large wholesale buyer such as Comcast or Time Warner can possibly expect at most a 40% - 50% discount over this, meaning their actual purchase cost per unit is at least $240 - $290. The total cost of ownership for the unit, allowing for interest, installation, repair, maintenance, and recovery would be on the order of $500, for a unit whose expected lifespan is certainly no more than 2 years on average - probably more like 18 months. At a minimum, the unit costs them $21 a month, to a maximum of perhaps $40 a month for smaller MSOs. Very few, if any, charge that much per unit for their DVRs. They don't make money on DVR rentals. They DO make money, tons of it, on IPPV purchases and pay service VOD.
     
  8. lrhorer

    lrhorer Active Member

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    I know FIOS has, but they have a very different business plan and a very different underlying technology than classical CATV systems. Are you certain about Comcast and RCN, however? Many CATV systems (like San Antonio) have duplicated their entire analog tier on digital channels, but analog sets are still able to receive the basic tier. Duplicating 70 or so analog channels on digital streams is not terribly expensive, especially if the bulk of them are SDV. With the SD locals and the 4 - 7 other most popular analog channels on a single linear QAM, handling the other 70 or 80 analog simulcasts can easily be done on a single SDV QAM, or at the very most a total of 3 QAMs.

    As I said, it's a minor point, however, as converting the analog tier to digital is not too terribly expensive. Delivering several hundred digital channels all on linear QAMs rather than SDV is hideously expensive though. For a very tiny fraction of the cost, they can deliver more than 100 times as many channels by employing SDV. They would be utter fools not to.
     
  9. morac

    morac Cat God

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    I'm not sure if Comcast is going all digital every where, but they are heavily pushing DTA and cable boxes now. In my local office there are pamphlets stating that DTAs or cable boxes will eventually be needed for all channels above 20 (basically anything other than limited basic). They are also giving out 3 free DTAs per address.

    So at this point Comcast is pushing analog to digital conversion over SDV. With Comcast's current compression for each analog channel they drop they can add 3 HD channels. Dropping from 70 analogs down to 20 would free up 150 HD channels worth of space.

    About a year ago, I asked a few local techs about SDV since many of them also work in Cherry Hill, NJ (one of Comcast's SDV test areas) and they pretty much universally despise it. They say it's a nightmare to support. That might be why Comcast moved away from SDV deployment.
     
  10. MichaelK

    MichaelK Active Member

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    18 months?

    wouldn't that be a HUGE amount of churn - the average cable cusomer is leaving after 18 months? Actually wouldn't a DVR customer even be likely to churn less even?

    Churn aside they reuse all the boxes. So people break them that often or dont return them?

    you KNOW way more than I do for sure but 18 months seems way way way low.
     
  11. MichaelK

    MichaelK Active Member

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    some "older" cable cities were 100% cablebox already becasue of piracty converting that to all digital isn't so bad. I know some of the 5 boro's of NYC were like that. Much of NY is all digital becasue of it (not sure if they keep locals duplicated in analog)

    too my knowledge (limited as I'm an hour outside NY)- they only use SDV significantly for foreign langauge stuff. And NYC has at least TW and Cablevision, maybe comcast also. I guess they just havn't needed SDV much yet since they got rid of analog early on since they were all box already.
     
  12. spolebitski

    spolebitski Member

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    So I have been having problems with the SDV channels on my TWC. Next week a tech is going to change my cards, change tuning adapters (resolver) in my TiVo and provide a TWC DVR (Digital Box) to check if the TWC box has problems tuning to SDV channels like the TiVo Box.

    I assume the tech is going to try to prove that the TiVo box is faulty and it is not a TWC issue. This is often the response with many at TWC, it must be your box ... we suggest you use our equipment.

    My question is this, can it be the TiVo? Could the TiVo be faulty? This only happens with SDV channels. My HD locals that are not SDV come in great, never a problem, it only happens to SDV channels.

    The tech who is working on this has been great. He doesn't care that I have TiVo he just wants to make sure the cable service works.
     
  13. realityboy

    realityboy Well-Known Member

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    I'd think it would be more likely that it was the tuning adapter than the Tivo, but I'm certainly not as knowledgeable as some in this thread.
     
  14. Chris Fox

    Chris Fox New Member

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    Here's my take on the issues thus far:

    spolebitski's problem is unfortunate, as tracking down the culprit for SDV issues is more complicated than in a tradional cable network. And I think we can all agree that your average cable CSR experience is not pleasant, making things more frustrating. But that doesn't mean that SDV sucks...

    lhorer's assessments of SDV is right-on-the-money. A well built network has tremendous upside. I like to think of it as IPTV for cable. When someone wants to watch a channel that no one else is on, the system has to allocate bandwidth to show it. If ANYONE else is watching the channel on the node, then you just have to tune to the already playing stream. This is a similar mechanism to IGMP Joins and Leaves for IPTV streams. If someone on your node is watching a channel (as in spolebitski's case), you are GUARANTEED to be able to watch it, barring some hardware issue.

    There is only so much cable can do with 600 MHz.

    From what I understand, Verizon deploys B-PON ONTs which can transmit data downstream at 622 Mbps. That is enough bandwidth to support the 32 users per PON for data and voice, but not IPTV. They are using RF video instead for non-VOD/PPV, which adds a seperate wavelength to the fiber for sending TV via a coax connection.

    Once costs come down, Verizon will move to G-PON which has ~ 2.4 Gbps downstream which serves 64 ONTs. This will finally give them the bandwidth needed for HD IPTV.

    So Verizon has a pretty good advantage over cable with the current B-PON + RF video, as far as bandwidth goes. Once they move to G-PON, they leave cable in the dust. Cable must use something like SDV to more efficiently use the network bandwidth.

    Chris

    P.S. If you think SDV has some nasty problems to deal with, just wait for IPTV. Having data, voice, and TV all running through the same ethernet switches is very difficult to maintain properly (QoS, STP to break switch loops, DoS protection, etc)...
     
  15. kevinivey

    kevinivey New Member

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    I had more luck tuning sdv channels with the TiVo tuner adapter than with a TWC supplied HD box. We have 139 sdv channels on my system. I have a nick name for sdv,

    S witched D igital V oodoo.
     
  16. lrhorer

    lrhorer Active Member

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    Yeah, that's what it was running when I was in the industry. It's possible it's higher now, but I expect not.

    That's not the average length of time the customer stays active. That number was closer to 4 years when I was in the industry.

    Ordinary breakage from careless handling, vandalism, theft, unit failure, obsolescence, fire, lightning, power surges, accidental trauma, and finally people simply taking off without paying their final bill or returning the unit.

    'Not really. Rental units of any type have much lower lifespans in general than the very same unit owned by a single individual. Not only that, but it's not unusual for a new model to come out every 2 - 3 years, so even with careful handling, a unit is likely to have to be replaced within 36 months - and the leased CATV boxes are anything but carefully handled. I never worked in converter repair, but I did frequently saunter through their area, and I had a number of friends who did work in converter repair. I also know how much we spent monthly for converter repair. It was appalling. It was also almost unbelievable how badly some of the converters were treated. Many of the STBs would go swimming, and not all of them in swimming pools. The repair staff had to be careful, because it was not uncommon for them to be exposed to hazardous materials of a wide variety, including bodily fluids and waste solids - human or otherwise.
     
  17. lrhorer

    lrhorer Active Member

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    Yeah, but they are receiving a lot of flak about that. Most MSOs rate shape to 2 HD + 1 SD video per QAM. I've seen a number of complaints concerning poor video quality at 3 HD per QAM.

    Yes, or at least 100 HD channels, at a cost of $100 Million or so in a large metropolitan area. For $20 Million or so, they could leave 60 analog channels and add perhaps 1000 HD SDV channels including a number of VOD and IPPV channels, plus add features like "do over", interactive banking, voting, etc.

    Well, it's not quite a nightmare, but it is certainly much more difficult. Despite some other forum member's objections, SDV is obligately a 2-way protocol, and if the upstream communications are not working, then neither does SDV. Upstream communications present a number of challenges. Believe me, I know. Getting the upstream user band working and keeping it working were big issues when we first started deploying 2-way services. With the much shortened cascades using fiber nodes, some, but by no means all, of the issues have been greatly mitigated.
     
  18. lrhorer

    lrhorer Active Member

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    Yes, of course. A failure of the USB communications between the TiVo and the TA will most certainly cause a failure of all SDV channels, and it could always be a hardware failure of the TiVo which is causing the USB issues. It could also be the USB cable, or the TA. The USB port in general is not the most reliable thing on Earth, which was one reason I strenuously objected when the suggestion was first made to go with a USB implementation, and my personal experience at least bears out my objections. Not only have I occasionally had a loss of communications between one or more of my TiVos and their respective TAs, but I own or manage no fewer than six different PCs (all different models) tied to six different peripherals running four different operating systems, all of which have intermittent USB problems.
     
  19. morac

    morac Cat God

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    It does degrade quality and yes people are complaining about it, but not enough to make Comcast really care from what I can tell. Many people can't really tell the difference (hell, 18% of HDTV owners can't tell the difference between HD and SD). Cox and Cablevision jumped on the 3-in-1 bandwagon last year.

    That may be one of the problems then. Comcast is basically a hodge-podge of cable systems purchased over the last few decades. Many of the cable lines are quite old and weren't very well maintained.

    Even in areas like mine, where they offer CDV and other 2-way dependent services, the upstream signals tends to become highly erratic several times a year (for reasons only Comcast knows). Sometimes it can take weeks to fix. I'm told there's systems a lot worse than mine.
     
  20. lrhorer

    lrhorer Active Member

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    Which equals serious quality problems, especially upstream.

    If you've ever taken a look at a spectrum analyzer on a live CATV system, you would know why. Think about it for a second. Any issue causing noise, interference or distortion in the downstream plant will only affect customers downstream from the problem, and only in that one area. A different problem in a different area will only affect the folks in that area, and the effect is not cumulative, so even though there is a problem, it may not be very severe, perhaps not even noticeable. Upstream feeds are completely different, though. Any interference problem on any line anywhere in the system winds up back at the headend, so in general even a fairly good plant can suffer multiple issues. If two or more of the issues happen to affect a particular frequency - a very common occurrence - then the effect is cumulative as it would never be in the downstream environment. Sometimes it would amaze me upstream communications worked at all on some trunk lines. Sometimes they wouldn't work, and indeed even now sometimes they don't. Tracing such issues is a very tedious, and usually service affecting task.
     

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