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
#277 ·
LoREvanescence said:
What would happen though, if you have a dvr stb forsay, and are not home while it's recording. If it were to get polled while recording event could the station get pulled? Just a interesting thought.
Once again, the engineers are working many use-cases. STBs with recordings are assumed to be using the channel and will not be polled.
 
#278 ·
ah30k said:
Statistical analysis shows that if you offer an x channel pool for y offerings with a node size of z you will be able to satisfy all of the users 99.9% of the time. The x can be much less than y. You can choose not to believe it if you want.
Most users would never notice the difference and it would rarely happen anyway. Once again, you can choose to disagree if you want.
The only way you can guarantee 99.9% availability is if the channel pool, x, is equal to, or slightly less than, the lesser of the number of offerings, y, or the node size, z. Since y is most likely less than z, this means that x must be equal to, or slightly less than y. In other words, the size of the channel pool must be very close to the number of offerings. So what has the expense of the SDV equipment bought you?
 
#279 ·
wbertram said:
The only way you can guarantee 99.9% availability is if the channel pool, x, is equal to, or slightly less than, the lesser of the number of offerings, y, or the node size, z. Since y is most likely less than z, this means that x must be equal to, or slightly less than y. In other words, the size of the channel pool must be very close to the number of offerings. So what has the expense of the SDV equipment bought you?
Sorry, can't argue with you any more on this. You are right. All of the cable operators are stupid and pissing millions away on this with no payback.
 
#280 ·
ah30k said:
Once again, the engineers are working many use-cases. STBs with recordings are assumed to be using the channel and will not be polled.
The smarter thing to do would make the protocol that requests the channel include the expected time on that channel. Alternatively, an STB making a recording could just renew the channel request every 15 minutes.
 
#282 ·
vman41 said:
The smarter thing to do would make the protocol that requests the channel include the expected time on that channel. Alternatively, an STB making a recording could just renew the channel request every 15 minutes.
I should caveat my responses... Although I am generally aware of the SDV design, exact details may be slightly different. The exact implementation of the protocols and sequence diagrams for switching and the DVR recording are a good example of specifics which I may be wrong on.
 
#283 ·
wbertram said:
The only way you can guarantee 99.9% availability is if the channel pool, x, is equal to, or slightly less than, the lesser of the number of offerings, y, or the node size, z. Since y is most likely less than z, this means that x must be equal to, or slightly less than y. In other words, the size of the channel pool must be very close to the number of offerings. So what has the expense of the SDV equipment bought you?
Well to me at least. This all makes since when there comes a point where bandwidth could start becoming an issue. Sadly, I wish it wasn't the direction things were going or that tivo supports it now.

What is the latest with turning off analog cable. In systems where they turn it off is this an alternative to sdv or will they still use sdv after turning off analog cable.

From reading through the avsforum today it seams that Comcast have already pulled the plug for analog cable in Chicago leaving only local access channels as analog. They are making this move becuase the majority of homes in the city already have digital cable, for those who don't, comcast is providing a free STB as a solution. It seams that they are now turnign off analog channels in the suburbs over the next few months.

Is this a likely trend that we will see in more cities in the near future to a lot for more space for digital content? What is the latest information as to what the cable industry is doing in terms of analog cable over the next few years.
 
#284 ·
LoREvanescence said:
What is the latest with turning off analog cable. In systems where they turn it off is this an alternative to sdv or will they still use sdv after turning off analog cable.

From reading through the avsforum today it seams that Comcast have already pulled the plug for analog cable in Chicago leaving only local access channels as analog.
And people started screaming that their S2DTs were now rendered merely single-tuners and they needed STBs for every TV. You are always going to piss someone off. It is just a matter of who.
 
#287 ·
jordanz said:
Why don't they go to a packet-switched type of protocol (ala TCP/IP)? This SDV thing seems like a big hack to me.
Incremental changes to the headend and STB base over time as opposed to a massive switch-out of the entire infrastructure. Cable company investors would not tolerate the kind of cost impacts necessary to switch the underlying tech.
 
#288 ·
ah30k said:
And people started screaming that their S2DTs were now rendered merely single-tuners and they needed STBs for every TV. You are always going to piss someone off. It is just a matter of who.
Well, it's true, there is always someone thats going to be pissed off. Such is the life of adapting new technology to replace a older one. I just wish this one 1 way 2 way ocap thing could have been settled by now, not changing every couple of months leaving third party devices out of the circle.
 
#289 ·
ah30k said:
Incremental changes to the headend and STB base over time as opposed to a massive switch-out of the entire infrastructure. Cable company investors would not tolerate the kind of cost impacts necessary to switch the underlying tech.
I see. This does, however, seem like an interim solution. They're banking on each SDV "node" only needing a subset of the total available channels. At some point in the future they'll need to look at a better technology.
 
#291 ·
ah30k said:
Sorry, can't argue with you any more on this. You are right. All of the cable operators are stupid and pissing millions away on this with no payback.
Are you saying no business every makes costly mistakes?

I guess I just don't see the benefit of this in the long run, vs going all digital and building out capacity. I see the near-term benefits. I guess the costs are small enough that they feel they are OK.
 
#292 ·
ah30k said:
Any channel with inactivity for a period of time is able to be polled to see if the watcher is still there. "Please hit the enter button if you still want this channel". If no response is received the channel will be reclaimed and the STB will be sent to a safe channel.
Is my dongle going to send back the proper response if Tivo is recording a SDV channel and I'm not home?
 
#294 ·
jrm01 said:
Is my dongle going to send back the proper response if Tivo is recording a SDV channel and I'm not home?
Reading your post, it sounds like you have one already, so maybe you should tell us :)

If the dongle didn't provide this basic functionality, then it wouldn't be a solution for TiVo. I doubt that TiVo would deploy the dongle if it didn't support TiVo's most basic functions.
 
#296 ·
wbertram said:
Re the often made statement "SDV makes more channels available."

I fail to see the logic here.
Well, this is how your cell phone service has worked. Voice channels are only dedicated to your phone one a call is established. Once the call is completed, the channel is released back into the pool of available channels. The channels that are used to handshake between your phone and the tower are much smaller in nature, so the system can support many more of those channels than voice channels. The same technology is used for landline phones too.

Yes, if everybody who owned a phone tried to call at the exact same time, the system gets congested. But unless a disaster occurs (9/11, hurricanes, etc.), no more than x% of people are using the service at any one time. In the past two years, the cable company has been busy watching your viewing habits and conducting trials in some markets to determine how many channels they can switch to SDV. If they implement it correctly, you won't notice a thing. Unless you're using an S3.

The benefit is that it is a quick way to boost capacity without rewiring everyone's house to bring fiber directly to the house. They need a solution ASAP. I have FIOS -- my uplink speed is probably faster than your downlink speed. And it's the same price as your service. DirecTV will release a bunch of HD channels any day now. Cable is just trying to keep up.
 
#297 ·
BobCamp1 said:
Well, ...SNIP

Yes, if everybody who owned a phone tried to call at the exact same time, the system gets congested. ...SNIP.
Of course, that is exactly how the SDV system works! Everybody who owns a TV sits down at 8:00PM and tries to tune to their favorite channel. And, the system gets congested, just like the phone system gets congested on Mother's Day, or after a catastrophe like 9/11.

SDV only "increases capacity" when relatively few people are viewing TV.
 
#298 ·
wbertram said:
Of course, that is exactly how the SDV system works! Everybody who owns a TV sits down at 8:00PM and tries to tune to their favorite channel. And, the system gets congested, just like the phone system gets congested on Mother's Day, or after a catastrophe like 9/11.

SDV only "increases capacity" when relatively few people are viewing TV.
In practice, not everyone sits down to watch every channel on the map at 8:00. Most people tune to x channels at any given time where x is much smaller than y offered. SDV will and is working just fine in the areas where it is deployed without running out of slots. I don't know what else to tell you to make you feel any different. SDV actually works better during peak times because there is more concentration on fewer channels.

When was the last time you could not reach you mother on Mothers Day on the first attempt?
 
#299 ·
bicker said:
That really points out the no-win situation that a la carte is, especially if it is to be driven by consumers wanting it. They'll go from complaining about "having to pay for channels they don't watch" :rolleyes: to complaining about how all the channels now cost $3-$4 each.
Maybe so, but if your pricing is correct, my bill would go down by 2/3. I don't watch any HBO types, no sports (I am told that ESPN type channels would cost $70+) I long for the "a la carte" system
 
#301 ·
Early reports indicate that SDV does not save as much bandwidth as hoped. To simplify things a bit, think about the demographics in your area -- there are probably high income neighborhoods and lower income neighborhoods (rich people don't build big houses in trailer parks). Thus, hoseholds with HDTV tend to be grouped togther in the same neighborhoods. Moreover, people with HDTVs tend to watch a heck of a lot more hdtv than sd analog. If only HDTV stations are put on sdv, chances are that the people in these high income neighborhoods are watching a good number of the HD channels at the same time.

To get the bandwidth savings, the entire lineup needs to be placed on sdv. This means an all digital lineup. However, going all digital, in and of itself, makes room for 150-200 or so HD stations without the use of sdv.

So, it really makes little sense to use sdv at this point without going all digital. Nevertheless, one particular company is going full steam ahead, while most others seem to be adopting a wait and see approach.
 
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