Switched Video, also called Switched Digital Video or SDV, is a telecommunications industry term for a network scheme for distributing digital video via a cable with limited capacity. Switched video sends the digital video in a more efficient manner so that additional uses may be made of the freed up bandwidth. The scheme applies to digital video distribution both on typical cable TV systems using QAM channels, or on IPTV systems. Users of analog video transmitted on the cable are unaffected. See diagram below for an illustration of how Switched Video saves bandwidth on a cable company's cables in the last mile where channels are transmitted via coaxial cable.In a Switched Video system, the unwatched channels do not need to be sent.
In cable TV systems in the United States, equipment in the home sends a channel request signal back to the distribution hub. If a channel is not currently being transmitted on the coaxial line, the distribution hub allocates a new QAM channel and transmits the new channel to the coaxial cable via the fiber optic node. For this to work, the equipment in the home must have two-way communication ability. Switched video uses the same mechanisms as Video on Demand and may be viewed as a non-ending video on demand show that any number of users may share.
Two-way communication is handled differently between cable and IPTV schemes. IPTV use communication protocols used on the internet but requires entirely new video distribution infrastructure. Cable companies in the United States elected the less costly approach of upgrading existing infrastructure, and European operators may well take the same approach. In the upgrade approach, various proprietary schemes use specific frequencies for passing messages back to the distribution hub. In the United States, there is currently no standard for two-way communications from consumer electronics devices using CableCARDs, such as Digital video recorders, High-definition televisions and Home Theater Computers.
For a switched video system to work on cable systems, all digital television users in a subscription group must have devices capable of communicating to the distribution hub in a compatible manner. Unlike other features dependent on two-way communication such as Video on Demand, the requirement to upgrade all digital set-top boxes within a group makes conversion to switched video extremely expensive. CableLabs proposed in the CableCARD 2.0 specification that two-way communication be supported with a scheme which required more powerful hardware capable of running Java programs. Many cable companies have indicated they will build lower cost devices that do not require this OCAP programing environment, so that upgrading to a switched video system would not be as costly. Consumer electronics companies also prefer a more light weight solution for two-way communication, and so absent a standard for two-way communication, the conversion to switched video may require many years to complete.
Switched video is sometimes abbreviated as SDV for switched digital video, or SVB, for switched video broadcast.
wikipedia.orgUsing Bandwidth More Efficiently with Switched Digital Video - Motorola White Paper
Switched Digital Video: The Elements of an Architecture
Scientific AtlantaTo understand how SDV works, we'll first need a quick lesson on how cable companies traditionally provide service to customers. In older cable systems, the cable company broadcasts every channel in a single stream of programming to every section of its network all the time. When you use your set-top box (STB) to tune to a particular channel, the STB searches the stream for the channel's frequency and carries the signal to your television.
Because the cable company sends every channel through the entire network, there's not much spare bandwidth available for Internet service or digital video channels. High definition channels take up more bandwidth than normal digital video, so spare bandwidth decreases as cable companies add HD channels to their lineups. Because HDTVs have become more affordable and more households have acquired them, demand for HD programming has increased. Cable companies have to find ways to meet customer expectations, particularly in light of the fact that HD television providers already offer dozens of channels in HD format.
In a traditional video delivery system, the cable company
combines all channels into one data stream,
even if no one is watching most of them.
Switched Digital Video Advantages and Disadvantages
Switched digital video systems' most obvious advantage is that they address one of the biggest problems cable companies have -- running out of bandwidth. As more people sign up for HDTV services, high speed cable modems and VOD, cable companies have to find a way to deliver. An SDV system helps cable companies implement a solution without replacing miles of cable, since the system can work on top of an existing infrastructure.
Increased bandwidth can also lead to more services. A cable company could choose to increase the number of channels it offers, allowing it to compete more effectively with satellite television companies. Additional channels could include more HD feeds or programming catered to a particular region.
Cable companies provide Internet access in much the same way they provide television feeds. Companies feed Internet downstream through 6-megahertz (MHz) channels in the cable bandwidth. Upstream feeds, the information sent back through your modem to the Internet, goes into a 2 MHz channel. When customer demand gets heavy, the cable company creates a new 6 MHz channel to relieve stress on the system. With SDV, cable companies have more bandwidth available to convert into Internet channels during periods of high customer demand.
howstuffworks.com
Switched Digital Video (SDV) technologies provide an excellent, long-term approach that is helping cable operators keep up the pace with expanding High Definition TV and super-high-speed data services, reports In-Stat.
SDV is a new technology that distributes video more efficiently over cable TV coaxial lines, the high-tech market research firm says. SDV will enable cable operators to better compete with rivals in digital broadcast satellite and telco TV.
"Initial deployments will create a strong market for upgrades, which will become dominant in 2012," says Gerry Kaufhold, In-Stat analyst. "The strategic key to success for vendors will be winning early deployments, because follow-on upgrades will be lucrative. World-class professional services, staff training, and the ability to remotely monitor and repair SDV installations will be the winning formula."
Recent research by In-Stat found the following:
* The market for SDV equipment, software, and services is expected to grow from about US$165 million during 2008, up to more than US$1 billion in 2012.
* North America will be the biggest market, with Asia coming on strong later.
* Large cable TV systems will drive early growth for SDV.
* Medium cable TV systems will become an important segment as early as 2009.
* Even small cable TV systems will turn to SDV in large numbers after 2010.
broadcastbuyer.tv
IPTV and Switched Digital Video Equipment Market to Reach $9.8B in 2011
"With each quarter, the battle for video subscribers gets more heated," said Jeff Heynen, directing analyst for IPTV at Infonetics Research. "Buoyed by the success of rollouts by Orange, Free, Neuf, Fastweb, PCCW, Telefonica, and China Telecom, IPTV service providers continue to build out headends and spend on IP set-top boxes to aggressively court video subscribers. Meanwhile, North American cable MSOs, such as Comcast and Cablevision, are leading the charge in switched digital video, to free up bandwidth and offer more HD content to their subscribers."
Other highlights from the report:
- Total worldwide IPTV and SDV equipment revenue hit $1.1 billion in 4Q07
- The number of IPTV subscribers is forecast by Infonetics to top 97 million worldwide by 2011
- Worldwide service provider revenue from IPTV services is expected to grow nearly 10-fold in the 5 years between 2007 and 2011
- Worldwide pure IP set-top box revenue grew 16% in 4Q07 over 3Q07 and is set to skyrocket in 2008
- Motorola leads the worldwide IP set-top box market in 2007, Microsoft leads the IPTV middleware and content delivery platform market, and UTStarcom leads the integrated digital headend platform market
- In 2007, the regional breakdown for worldwide IPTV equipment revenue was 40% North America, 30% EMEA, 28% Asia Pacific, and 2% CALA
Companies tracked include 2Wire, ADB, Alcatel-Lucent, Amino, ARRIS, Celrun, Cisco, Dasan Networks, Ericsson, Huawei, Microsoft, Motorola, Netgem, Nokia Siemens, OptiBase, Pace, Phillips, Sagem, Samsung, Scientific Atlanta, Sumitomo, Tatung, Telsey, Thomson, Tilgin, UTStarcom, Yuxing, and others.
www.tvover.net
Digital (All vs. Switched) EconomicsWhether and when to deploy switched digital video (SDV) are questions on the minds of strategists at cable operators both large and small. The variables of this puzzle are costs, budgets and alternatives.
One window into the thinking at a second-tier cable op came during Mediacom's earnings call last week. As reported by sister pub CableFAX Daily, Mediacom CEO Rocco Commisso explained his company's planned 2008 expenditures as directed toward "a lot more digital simulcasting, going all-digital in some systems, beginning our switched digital video initiative and FCC mandated requirements."
One takeaway is that Mediacom, reflecting the industry as a whole, is pursuing multiple options. Of course, each operator is on its own timetable.
Whereas there are only a couple of Comcast systems, for instance, that have yet to deploy digital simulcasting, Mediacom is at the front end of that cycle: currently at 25 percent of its footprint, with the expectation of growing to 50 percent by year end.
Once having deployed digital simulcast, generally regarded as an interim solution in that it consumes rather than reclaims spectrum, an operator is better off either to launch a switched digital solution or drop the analog tier entirely.
That Commisso indicated that some systems were going all digital is also telling. That approach has strong appeal, especially among tier 3 operators.
Massillon Cable
As reported previously here, all digital was a strong theme at last month's National Cable Television Cooperative Winter Educational Conference (WEC) in Phoenix. The presentation by Massillon Cable TV President Bob Gessner explicitly ruled out three other bandwidth expansion options: SDV, spectrum overlay and 1 GHz upgrade.
Gessner operates two systems in northeast Ohio that pass about 70,000 homes from a single consolidated headend that transmits, a la simulcast, both analog and all-digital video signals. Massillon has 45,500 video subscribers, a third of whom take digital video.
In a matrix that included capital expenditure, cost of customer premises equipment, operating expenditure, level of disruption, timeframe for completion, amount of spectrum reclaimed or freed up, confidence in success and level of unknowns, the analog elimination option came out on top of Gessner's analysis.
Gessner emphasized that a key and as yet missing component to this preferred path is a low-cost digital-to-analog (DTA) converter that can serve all TV sets in a subscriber's home. It may not go missing for long.
At WEC, Brent Smith, CTO of Evolution Canada, held up a model of an NTIA converter with a quadrature amplitude modulation (QAM) tuner. Discussion that Comcast had slipped into hardware developer mode and was specifying such a device followed the MSO's 4Q 2007 earnings call three weeks ago.
Like others at WEC, Smith emphasized the all-digital approach. "(Switched digital video) is not a solution for independent operators," he said. "Maybe if you're Time Warner Cable in Manhattan .…"
Not surprisingly, SDV pioneer BigBand Networks underscores the favorable economics of switching. According to Biren Sood, BigBand VP and Manager of Cable Video, the math works out to $0.90 per QAM channel per home passed for SDV, vs. $3 for all digital.
One cable engineer familiar with this technology roughly confirmed that figure, saying that with some add-ons, it could be closer to $1.00 per QAM signal.
How that translates into homes passed appears to be a matter of headend economics. At least one MSO is pegging that number at $15, which is about half as much as the capex number that Gessner used in his analysis. (Total capex of $2 million divided by 65,500 homes passed = $30.50.)
Another difference in views is estimates in how much spectrum SDV is able to make available. Whereas Gessner put 25 MHz to 50 MHz in his matrix, Sood talks about SDV's ability to reach enable a "virtually infinite, capacity by demand."
That is a worthy goal, Sood said. "At some point," he said, "you're always going to hit the wall with a broadcast architecture."
Jonathan Tombes
cable360.net
