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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.
 
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#1,453 ·
As for TiVo, will they not have to write drivers for each TR like they do with USB-ethernet adapters?
No--one of the purposes of the Tuning Adapter is to normalize the interface (the other purpose being to give access to the backchannel to hosts with unidirectional CC interfaces). TiVo only talks and listens to the Tuning Adapter through its USB interface, and every Tuning Adapter talks exactly the same language through that interface. The Tuning Adapters also exchange messages with the cable network through backchannel communications over the coax; when TiVo makes a request of the network, the TA's job is to convert that into terms of the specific network's SDV system and send the appropriate message out over the backchannel; when the reply is received from the network, it's converted into a message in the TA USB connection protocol and passed on to TiVo.

It's a bit like being in the United Nations--a participant there just talks into his or her microphone and listens to responses as rendered into English (or whatever his or her language is) by translators, without having to consider what languages the people who give those responses are actually speaking.

CableCARD itself is similar; CableCARDs manufactured by Motorola and SA deal with different proprietary encryption schemes used on the wire (Motorola's DigiCipher and SA's PowerKey), decrypting content received in those proprietary formats and re-encrypting it using the open standard DFAST system to be passed back over the CableCARD host interface. CableCARDs in bidirectional host devices can send messages on behalf of the host, passed to the CableCARD by the host device using an ANSI/SCTE standard API; the CableCARD repackages such messages for transmission as appropriate for whatever vendor's host network they're operating on.
 
#1,454 ·
I don't believe the TR will be viewed as another device but take on the personality of the host device to which it speaks for.
The network will probably have some awareness of the Tuning Adapters as a separate entities, since it will probably be able to download firmware upgrades into them. Beyond that, I'd think that the interaction between the network and the TR would be indistinguishable from the network performing SDV negotiations with a leased cable STB. Those interactions are vendor-proprietary and explicitly not in within the scope of the OpenCable Tuning Resolver Interface Specification, so they could be as aware or unaware of the existence of the Tuning Adapter as the vendor cares to make them.
 
#1,455 ·
No--one of the purposes of the Tuning Adapter is to normalize the interface (the other purpose being to give access to the backchannel to hosts with unidirectional CC interfaces). TiVo only talks and listens to the Tuning Adapter through its USB interface, and every Tuning Adapter talks exactly the same language through that interface.
Thanks, that is an important piece of info.
 
#1,456 ·
The network will probably have some awareness of the Tuning Adapters as a separate entities, since it will probably be able to download firmware upgrades into them. Beyond that, I'd think that the interaction between the network and the TR would be indistinguishable from the network performing SDV negotiations with a leased cable STB.
Hmm, that makes me wonder if the cableCARDS and the TA will talk to each other somehow. Currently if you bring up the cableCARD menus on the TiVo, the cards report that the device they are connected to does not have two way capabilities and that there is no associated IP address. After the TA is installed would this update to indicate that there is a two way interface or is it still considered one way from the card's perspective?
 
#1,457 ·
Cisco announces their version of the SDV tuning adapter - STA-1520:
http://www.lightreading.com/document.asp?doc_id=152093
Looks like Tivo has already done some limited testing with the prototype:
Cisco has already conducted some interface testing with TiVo and expects to provide some samples to MSOs soon for their internal testing. "So we're pretty far along," Kasten says.
 
#1,459 ·
Cisco announces their version of the SDV tuning adapter - STA-1520:
http://www.lightreading.com/document.asp?doc_id=152093
Looks like Tivo has already done some limited testing with the prototype:
Although it will operate with different SDV platforms, the STA-1520 will work only on systems that use the Cisco digital cable platform.
That's interesting. Must be programmable on the network side. I guess if a cable provider plans to buy some tens of thousands of these things, customizing it to his particular brand of SDV isn't that much to ask.

It's great news, though, inasmuch as TWC, the prime purveyor of SDV, is on Cisco networks. So many people in these forums have been freaking out because there'd been no press release on development of an SA compatible product.
 
#1,460 ·
It's still fascinating to me that people--on a TiVo forum no less--seem to have such a hard-on for VOD. Personally it doesn't bother me that it exists, but it's irrelevant to me because I have a DVR. I can't imagine I'm part of some tiny minority, especially since everyone I know and work with seems to have one, too, and has had for quite a while. If I'm 10 minutes late getting to my favorite shows or am on a date or running errands or whatever, it doesn't affect me. Only selected programming is available on VOD anyway, and other than the novelty factor of being able to order up Showtime late-night soft-core on a whim when I first got the service, it's of little use.
That could be because the content available over VOD is also available over normal channels. VOD is currently primarily a way to re-access content that has already been transmitted. If, however, VOD is used to provide first-access to content that is no being transmitted on another channel, which is how many envision VOD to untimately develop, then your DVR becomes a hindrance to the access of VOD content.

This shift to SDV (which exists to save bandwidth on less veiwed channels) is driven (my opinion) by the current idustry structure of "channels" being owned by people who aggregate themed content (example -Food Network). This is an old paradigm - the content aggregators ("channels") were required to bundled themed content and sell targeted advertising into the gaps between the shows.

The apparent new model (content owners themselves providing content in single bites for a fee) removes the aggregator (TV channel) and is more appropriate to the VOD delivery model. The internet & IP transmission technology, the low cost of video blogging, the eruption of youtube, etc - all point to a more self-serve model that individualizes content aggregation. Note that the biggest adopters of VOD so far have been those companies not reliant on the aggragator-that-enbeds-commericals business model - HBO, Movie releases, etc.

Tis shift is already being seen in a small way on the Tivo platform - GeekbriefTV, CNET for Tivo, NYTimes movie reviews, etc - all these are essentially the first wave of post-TV-channel VOD.

As DVRs kill off the commercial they necessarily pave the way for their own destruction *unless* they are also equipped to survive in a post-commerical world. And post-commerical means a lage number of marginal chaneels will die, and their content will have to be VOD to survive that event.

So yes, VOD support matters, in the long run. (in my opinion)
 
#1,462 ·
That's actually already being done. There are a number of programs on Comcast's VOD that are only available through VOD.
without getting into politics- 2 words

Howard Stern.

Isn't his "howard TV channel" all vod?

I think VOD is a way for people to create new niche "channels". Maybe they wind up SDV when SDV is widely deployued- but for now VOD lets such a thing exist.
 
#1,463 ·
Virtually no one offers VOD unless it's SDV. It would be network suicide to do so, even on a small scale. I don't know for certain - sometimes businessmen do stupid things, but I strongly suspect there are no CATV systems anywhere which offer anything as VOD which is not SDV. Some systems may offer Howard as linear pay-per-view, in which case it would not have the network impact of a linear VOD channel, but there's a big difference between linear IPPV and non-SDV VOD.
 
#1,465 ·
Virtually no one offers VOD unless it's SDV. It would be network suicide to do so, even on a small scale. I don't know for certain - sometimes businessmen do stupid things, but I strongly suspect there are no CATV systems anywhere which offer anything as VOD which is not SDV.
Far, far from the truth.
 
#1,466 ·
Virtually no one offers VOD unless it's SDV. It would be network suicide to do so, even on a small scale. I don't know for certain - sometimes businessmen do stupid things, but I strongly suspect there are no CATV systems anywhere which offer anything as VOD which is not SDV. Some systems may offer Howard as linear pay-per-view, in which case it would not have the network impact of a linear VOD channel, but there's a big difference between linear IPPV and non-SDV VOD.
Wow, how far wrong could this statement be?

Since SDV is just getting launched, are you saying no one had any VOD prior to now?

Maybe there was just a mis-use of terms or something but you couldn't have meant what it seems.
 
#1,468 ·
Irhorer is correct. Most VOD systems use 4 qams for VOD delivery. The VOD system and cable box determine which qam is available and starts the stream. You can start 4 different movies in a row and have it stream on 4 different frequencies. This system has been around for a long time.
When we refer to SDV we are talking about the system just being launched that switches broadcast video. While it is true that VOD dynamically gets assigned to QAMs, we really don't call that SDV.

Hence my claim that this may just be a miscommunication of terms.
 
#1,470 ·
What lrhorer is saying is that VOD is a form of switched video which has been in use far longer than this fairly new "sharing-a-pool-of-bandwidth-on-a-network-edge-segment-between-many-linear-video-services" trick. No doubt modern systems use switching to implement scheduled pay-per-view as well--if no one in an edge segment has ordered a pay-per-view program, no bandwidth is used for that program on that segment. However, referring to VOD and IPPV as SDV, while it may be essentially true, is cheap semantic BS. The terms "switched video" and "switched digital video" are now exclusively used to refer to the "sharing-a-pool-of-bandwidth-on-a-network-edge-segment-between-many-linear-video-services" trick. When you find SDV in the tech literature today, that's what they're talking about, even though VOD and IPPV are provided using video switching. Maybe they should have come up with a brief three-or-four word phrase to describe "sharing-a-pool-of-bandwidth-on-a-network-edge-segment-between-many-linear-video-services" (maybe "shared bandwidth linear video", though that would describe IPPV as well :rolleyes:), but the fact is that they didn't--they co-opted the term "switched digital video" to mean specifically that.

It's similar to the way that, when people refer to "Americans" in common speech, they're talking about citizens of the United States of America, and not Canadians or Mexicans or Brazillians, even though those people also live on the continents of North and South America.

The discussion in this thread is about "non-PPV shared bandwidth linear video", the increasing use of which is a large problem for TiVo Series3 and TiVo HD users, who never expected to be able to access VOD or IPPV content with TiVo. Using the term "SDV" as an umbrella term for all services which involve video switching doesn't make any useful point and only serves to confuse the conversation and annoy people.
 
#1,471 ·
Virtually no one offers VOD unless it's SDV. It would be network suicide to do so, even on a small scale. I don't know for certain - sometimes businessmen do stupid things, but I strongly suspect there are no CATV systems anywhere which offer anything as VOD which is not SDV. Some systems may offer Howard as linear pay-per-view, in which case it would not have the network impact of a linear VOD channel, but there's a big difference between linear IPPV and non-SDV VOD.
Cox Omaha offers vod and doesn't have sdv yet.
 
#1,475 ·
The main difference is that SDV is coordinated between multiple viewers so each can simultaneously view the stream and there's no interactive control possible. VOD is exclusively viewed, only the customer who started the stream can view the stream and usually has the ability to interactively control the stream.
 
#1,476 ·
VOD is exclusively viewed, only the customer who started the stream can view the stream and usually has the ability to interactively control the stream.
While functionally that's they way it's supposed to work, there are exceptions. At times I've stumbled across VOD streams (which for whatever reason weren't encrypted) using the QAM tuner on my TV. Granted I couldn't control the playback, but I could still view it.

It did throw me the first time I saw a movie "rewind itself" while watching TV. :)
 
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