TiVo Community Forum banner
  • TiVoCommunity.com Ambassador Program Now Open! >>> Click Here

SDV FAQ

854K views 2K replies 303 participants last post by  dlfl 
#1 ·

What is SDV?


SDV stands for Switched Digital Video, a scheme where not all TV channels are broadcast out from the cable headend to the homes that it serves all of the time. This is attractive to cable companies, because they can offer more TV channels than their cable plant has the bandwidth to broadcast. For example, your cable company may have 10 different channels in your lineup, but only 5 physical channels to send them from the headend to the houses they service. This requires a cable box that can communicate back upstream to the headend and say "I would like to watch ESPN2HD now" and then headend would take that request, assign it to a frequency and then tell the cable box "ESPN2HD is available on xxx,xxx kHz"




What does this mean for the Series 3, Tivo HD and TiVo Premiere?


With out an additional Tuning Adapter supplied from the provider, the Series 3, Tivo HD and TiVo Premiere is not able to communicate upstream to the cable headend, so it cannot send the request for channels that are assigned to SDV. Users of the S3 and THD will not be able to watch or record any of these channels.

Which channels will be converted to SDV?

Traditional methods send every channel to everyone, and if no one on your head-end is watching that channel, the bandwidth is effectively wasted. SDV allows them to turn off that channel when it's not being watched so that another channel can occupy that bandwidth. If a channel is always being watched it will probably never be converted to SDV. So the less popular a channel is, the more likely it will be converted to an SDV channel. See this Multi-Channel news article. That being said, there are some providers who use SDV to deploy a very large number of channels, though.


The solution

The NCTA and TiVo worked together for over a year and finally the first working solution has reached TiVo owners in NJ on Comcast. The device from both Cisco and Motorola are called Tuning Adapters (formerly known as Tuning Resolvers) and connect via USB to the TiVo (9.4 or higher) and feature pass-through coax connections, so a splitter is not needed. So when you attempt to tune a channel delivered using SDV, the TiVo sends a signal via USB to the Tuning Adapter which sends the signal via coax upstream to the providers head-end. This turns the channel on and returns the tuning information back to the TiVo.

In a demo at the Cable Show a few years ago I had a chance to play and was not able to notice any difference in speed when changing channels that were deployed with traditional QAM or SDV.

Depending on the head-end there are two solutions, Motorola and Cisco (formerly Scientific Atlanta). If your operator hands out Cisco set-top boxes, then odds are they'll use a Cisco TA.

The Cisco STA1520


The Motorola MTR700


Some providers are offering these for free, but some charge at first or after a few months.

Here is TiVo's FAQ that address the Tuning Adapter.

Here is Time Warner's FAQ about the Tuning Adapter.

San Antonio TWC customers can pre-order their Tuning Adapter from here.

Here is some of the history of the Tuning Adapter, formerly known as the tuning resolver:
http://www.tivolovers.com/2007/05/10/mr-tivo-goes-to-washington
Here is TiVo's official info on the adapter.
http://tivosupport2.instancy.com/LaunchContent.aspx?CID=CBECF1B9-88DE-4B74-82C1-754C3260112A
CableLabs press release about USB dongle
http://cablelabs.com/news/pr/2007/07_pr_dcr_devices_112607.html
NCTA and TiVo press release
http://www.prnewswire.com/cgi-bin/s...11-26-2007/0004711019&EDATE=#linktopagebottom
Of if you want to do something about it, report your missing channels to the FCC.
http://www.fcc.gov/cgb/complaints_general.html


What about FIOS?


Right now, because of the fact that FIOS uses fiber optic cable to your house, FIOS has no plans to deploy SDV - they have instead chosen to invest in expanding their QAM RF overlay infrastructure and use IPTV for PPV and VOD.

Where is SDV located right now?

SDV deployments are changing very rapidly and impossible to track, in fact even most of the CSRs don't know if their company uses SDV and even if they do, not which channels.

Tuning adapters are here to stay
TiVo has asked the FCC to modify the rules pertaining to 3rd party CableCARD devices and eliminate Tuning Adapters. The proposed solution was to allow the TiVo to communicate via IP to the operators servers to perform the requests that are currently handled by the TA. This would've require that you have internet service from the same provider, but would eliminate a set-top box from the equation.

TiVo claimed it was necessary to increase reliability and would reduce costs for the operators. The NCTA and its members claimed that the TAs are well accepted and supported and it is not necessary to make any changes.

The FCC determined that it would rather not mandate a specific solution, but instead mandated the SDV channels work for CableCARD users and will be making it easier to report issues so that consumers could help enforce the mandate.
 
See less See more
3
#28 ·
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.
 
#29 ·
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?
 
#30 ·
jrm01 said:
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?
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.
 
#31 ·
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.
 
#32 ·
vstone said:
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.
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.
 
#33 ·
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...
 
#34 ·
moyekj said:
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...
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.
 
#36 ·
TiVoMonkey said:
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.
I wouldn't say there is absolutely no reason. Instead I would say there are reasons why they wouldn't place locals on SDV.
 
#38 ·
sfhub said:
I wouldn't say there is absolutely no reason. Instead I would say there are reasons why they wouldn't place locals on SDV.
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.
 
#39 ·
TiVoMonkey said:
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.
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.
 
#40 ·
TiVoMonkey said:
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.
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.
 
#42 ·
Good question Jim.

I have wondered this myself. I heard from a friend of mine here in Charlotte that one time he tried to watch an OnDemand channel, but couldn't because there wasn't any bandwidth available.

I think that the cable companies will start with small SDV implementations so that if there are any bandwidth issues that very few people are affected, but after that initial implementation I think that SDV will be implemented quickly because the more channels that are switched the more valuable it is.

ESPN Classic was recently removed from the analog tier(probably as part of the TWC agreement to get ESPNU and ESPN2 HD) here in Charlotte. My guess is that it was removed to make way for SDV because that one analog channel could support 6 simultaneous SDV channels.
 
#43 ·
JimSpence said:
Interesting topic. One question comes to mind. What happens if you request a channel and there isn't a free frequency from the "hub" you're attached to?
I've heard there is a spike in support calls.

Some implementers are of the opinion you should never be consistently over 80% (or some percentage) of capacity allocated to SDV. Basically just like the phone company doesn't actually have switching capacity to handle every phone call (as evidenced by circuits being down during a natural disaster), but 99% of the time you don't get an all circuits are busy message.
 
#44 ·
sfhub said:
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.
I agree. I mean, who is watching PBS? Or that new UPN+WB channel? Or PAX? These would otherwise appear to be prime candidates for SDV, but it's probably less hassle to leave them alone for now. The cable companies don't want to press their luck by entering the gray areas of the law.
 
#45 ·
sfhub said:
I've heard there is a spike in support calls.

Some implementers are of the opinion you should never be consistently over 80% (or some percentage) of capacity allocated to SDV. Basically just like the phone company doesn't actually have switching capacity to handle every phone call (as evidenced by circuits being down during a natural disaster), but 99% of the time you don't get an all circuits are busy message.
'zactly the bean counters figure out what they need to provide to get a bunch of nine's for reliability.

I suspect it's not so tough to go bulletproof though once you go whole hog though. Figure 125 qam slices on a 750mhz system. Take out the slots for the “always on” locals and internet and voip and you still probably have like spots for 200 HD channels. (or 1,000+ SD).

I think I’ve read a typical switched node has 150 houses. Lets assume 3 tv’s per house (made up WAG). 450 tv’s per node. IF I understand the ratings- during the most watched time of the day – primetime- when the most possible tv’s are on then 25% of the tv’s are tuned to the big 4 (which are always one). So that leaves 337 tv’s left to be serves by the remaining 200 HD channels. If I understand correctly, HBO, Disney, ESPN and a couple other ‘big gun’ cable channels peel off another 20% of cable households. So that’ gets you down to like 270 tv’s with 190+ possible pipe’s. No statistician but I’d feel pretty comfy that with the tv’s that are off and the fact that each node is likely serving a similar socioeconomic class (with similar tastes probably) that you can easily assure everyone the slice of bandwidth that they need.

Again not a bean counter myself But I’d suspect you could easily make 20 channels fixed and then do 180 switched slots and provide an unlimited amount of channels to each node.

And all that assumes 100% HD with SD viewers giving you like 6 times the headroom.
 
#46 ·
TiVoMonkey said:
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.
What does it really cost for them to have a channel be switched? If it is effectively always in use, then when someone tunes to that channel, there will be a request from the set-top box to the SDV controller for its node, who will respond with the existing frequency assignment for that channel. Why bother trying to figure out which channels are in use at what time in which nodes; just switch everything and let the actual usage pattern sort it out.
 
#47 ·
Using SDV for popular changes doesn't make any sense, there is a worse case and then there is unplausable.

Here's a question, if you try to tune to a SDV channel on your S3, that someone else on the same node is currently watching, can you see it? I would suspect no, since the CableCARD doesn't tell the TiVo what QAM channel it is on. The reason I think you might though, is because I've been able to watch VOD and PPV with my PC QAM tuner before.
 
#48 ·
CharlesH said:
Why bother trying to figure out which channels are in use at what time in which nodes; just switch everything and let the actual usage pattern sort it out.
They bother, cause it's the entire point, to save bandwidth. There was a post on the Official Moto blog about trying to figure out what channels to go SDV with, but it was pulled, here is the text.

Nielsen ratings measure the most popular television programming. Preparing for switched digital video (SDV) requires exactly the opposite. No cable operator is going to move content to a switched system that is never going to be switched off. The best channels for SDV are the ones at the tail end of the popularity curve.

This has two major implications. First, cable operators need a very accurate system for measuring which channels will give them the most bandwidth return when moved to a switched network. I was on a call last week where Motorola’s Bill Bradley described the monitoring technology that Motorola uses with operators. It’s wild. The software actually shows a running feed of which channels consumers tune to in any given service group. (I’ll post a screen shot when I have one.) Operators run the software to determine which channels to switch initially, but also continue running the software so they can make changes dynamically based on subscriber viewing habits.

Second, the current kerfuffle going on about whether consumers with retail CableCARD devices will be able to access SDV channels seems to deflate a bit in light of what will actually be available in switched form.
http://connectedhome2go.com/2007/07...rt-1-choosing-your-switched-digital-channels/
 
#49 ·
bdraw said:
Using SDV for popular changes doesn't make any sense, there is a worse case and then there is unplausable.

Here's a question, if you try to tune to a SDV channel on your S3, that someone else on the same node is currently watching, can you see it? I would suspect no, since the CableCARD doesn't tell the TiVo what QAM channel it is on. The reason I think you might though, is because I've been able to watch VOD and PPV with my PC QAM tuner before.
Currently with CableCards my S3 actually has 80 VOD channels assigned (VOD1->VOD80 and distributed over 8 256 QAMs). At any point in time I can channel up and down to find currently active channels. There is no discernable pattern to the assigned channels, they are spread out across the entire range. However, the only reason I can see them is the VOD channels are unencrypted. I would imagine that most channels on SDV would have encryption and therefore even if I knew which frequency (or frequency range) to check it wouldn't do me much good, not to mention the fact that it can skip to a different frequency at any moment anyway just as happens with VOD channels.
 
#51 ·
bdraw said:
Why bother trying to figure out which channels are in use at what time in which nodes; just switch everything and let the actual usage pattern sort it out.
bdraw said:
They bother, cause it's the entire point, to save bandwidth. There was a post on the Official Moto blog about trying to figure out what channels to go SDV with, but it was pulled, here is the text.
Doesn't switching everything and allowing the system to sort itself out at worse use the the *same* bandwidth (minus some small switching overhead) as having a mix of static/switched channels? They do need to make sure they have enough unused SDV capacity to handle peaks, so total SDV bandwidth usage should not be above some number, let's say 80% of total SDV bandwidth allocation.

I'm not seeing why bandwidth would be the reason a cable company decided not to switch everything. Could someone explain this, since it appears multiple people have this opinion.

On the other hand, I could understand keeping UDCP CableCARD users happy being a reason not to switch popular channels.

In the TW Austin article in your first post, there were 2 examples given
http://www.multichannel.com/article/CA6454447.html
1) deploying a popular channel on SDV could end up eating up all your SDV bandwidth
This seems just like a configuration issue. If you have room for 20 channels on SDV and decide to move a potentially popular channel to SDV, you should allocate room just freed up from the static channel into your SDV pool, so that it now has capacity for 21 channels. It seemed the TW Austin moved a popular channel to SDV but instead of expanding SDV capacity, they left it the same.

2) popular PPV channels on SDV
It seemed the problem they were describing was a problem with the SDV client updates not being distributed to all their customers causing a flood of support when the event occurred. This seems like a short term deployment issue, rather than a long term reason why all channels wouldn't be on SDV.

Again, I'm *not* arguing to have all channels on SDV. I'm trying to understand why it makes absolutely no sense as some folks are asserting. I can see pros and cons of doing that, while others are saying there are only cons.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top