Switched video
Encyclopedia
Telecommunications network
A telecommunications network is a collection of terminals, links and nodes which connect together to enable telecommunication between users of the terminals. Networks may use circuit switching or message switching. Each terminal in the network must have a unique address so messages or connections...
scheme for distributing digital video
Digital video
Digital video is a type of digital recording system that works by using a digital rather than an analog video signal.The terms camera, video camera, and camcorder are used interchangeably in this article.- History :...
via a cable. Switched video sends the digital video in a more efficient manner so that additional uses may be made of the freed up bandwidth
Bandwidth (computing)
In computer networking and computer science, bandwidth, network bandwidth, data bandwidth, or digital bandwidth is a measure of available or consumed data communication resources expressed in bits/second or multiples of it .Note that in textbooks on wireless communications, modem data transmission,...
. The scheme applies to digital video distribution both on typical cable TV systems using QAM channels, or on IPTV
IPTV
Internet Protocol television is a system through which television services are delivered using the Internet protocol suite over a packet-switched network such as the Internet, instead of being delivered through traditional terrestrial, satellite signal, and cable television formats.IPTV services...
systems. Users of analog video transmitted on the cable are unaffected. See diagram to the right for an illustration of how Switched Video saves bandwidth on a cable company's cables in the last mile
Last mile
The "last mile" or "last kilometer" is the final leg of delivering connectivity from a communications provider to a customer. The phrase is therefore often used by the telecommunications and cable television industries. The actual distance of this leg may be considerably more than a mile,...
where channels are transmitted via coaxial cable
Coaxial cable
Coaxial cable, or coax, has an inner conductor surrounded by a flexible, tubular insulating layer, surrounded by a tubular conducting shield. The term coaxial comes from the inner conductor and the outer shield sharing the same geometric axis...
.
In current hybrid fibre-coaxial
Hybrid fibre-coaxial
Hybrid fiber-coaxial is a telecommunications industry term for a broadband network which combines optical fibre and coaxial cable. It was commonly employed globally by cable television operators since the early 1990s.-Description:...
systems, a fiber optic network extending from the operator's central office carries all video channels out to a fiber optic node which services any number of homes ranging from 1 to 2000. From this point, all channels are sent via coaxial cable to each of the homes. Note that only a percentage of these homes are actively watching channels at a given time. Rarely are all channels being accessed by the homes in the service group.
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
Video on demand
Video on Demand or Audio and Video On Demand are systems which allow users to select and watch/listen to video or audio content 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 uses Internet communication protocols but requires an 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 a recent standard for two-way communications from consumer electronics devices using CableCARD
CableCARD
CableCARD is a special-use PCMCIA card that allows consumers in the United States to view and record digital cable television channels on digital video recorders, personal computers and television sets without the use of other equipment such as a set top box provided by a cable television company...
s, such as digital video recorder
Digital video recorder
A digital video recorder , sometimes referred to by the merchandising term personal video recorder , is a consumer electronics device or application software that records video in a digital format to a disk drive, USB flash drive, SD memory card or other local or networked mass storage device...
s, high-definition television
High-definition television
High-definition television is video that has resolution substantially higher than that of traditional television systems . HDTV has one or two million pixels per frame, roughly five times that of SD...
s and home theater computers known as OpenCable
OpenCable
OpenCable is a set of hardware and software specifications under development in the United States by CableLabs to "define the next-generation digital consumer device" for the cable television industry...
(or tru2way
Tru2Way
Tru2way is a brand name for interactive digital cable services delivered over the cable video network, for example interactive program guides, interactive ads, games, chat, web browsing, and t-commerce. The brand also appears as “'” and is used to market cable services, applications, and devices...
) which require three things to work:
- Hardware that implements one of three standards which allow the cable receiver to communicate with the cable head end,
- SCTE 55-1 which is the ALOHA protocol-based standard used by General InstrumentGeneral InstrumentGeneral Instrument was an electronics manufacturer based in Horsham, PA specializing in semiconductors and cable television equipment. The company was active until 1997, when it split into which was later acquired by Vishay Intertechnology in 2001, CommScope and NextLevel Systems General...
and MotorolaMotorolaMotorola, Inc. was an American multinational telecommunications company based in Schaumburg, Illinois, which was eventually divided into two independent public companies, Motorola Mobility and Motorola Solutions on January 4, 2011, after losing $4.3 billion from 2007 to 2009...
equipment, - SCTE 55-2 a.k.a. DAVIC which is a slotted ALOHA-based standard used by CiscoCiscoCisco may refer to:Companies:*Cisco Systems, a computer networking company* Certis CISCO, corporatised entity of the former Commercial and Industrial Security Corporation in Singapore...
cable boxes, and - DOCSIS Set-top GatewayDOCSIS Set-top GatewayDOCSIS Set-top Gateway is a specification describing how out of band data is delivered to a cable set-top box. Cable set-top boxes need a reliable source of out of band data for information such as program guides, channel lineups, and updated code images.- Features :DSG is an extension of the...
, an extension to the DOCSISDOCSISData Over Cable Service Interface Specification is an international telecommunications standard that permits the addition of high-speed data transfer to an existing cable TV system...
cable modem standard to make it degrade gracefully under adverse conditions and still provide as much functionality as possible;
- SCTE 55-1 which is the ALOHA protocol-based standard used by General Instrument
- A CableCARD that decrypts the channel for the cable receiver; and
- A Java-based OpenCable Application PlatformOpenCable Application PlatformThe OpenCable Application Platform, or OCAP, is an operating system layer designed for consumer electronics that connect to a cable television system, the Java-based middleware portion of the platform. Unlike operating systems on a personal computer, the cable company controls what OCAP programs...
(abbreviated as OCAP) stack that allows the cable company to download an application written in OCAP to run on any cable receiver which contains an OCAP stack.
The OCAP application programs the cable receiver on how to communicate with the switched video server, and does other tasks like running an interactive program guide and programming the receiver on how to perform video on demand. The cable company could choose whichever two-way communication standard it wants out of the three. It could choose the standard that its pre-OCAP hardware used in order to preserve its investment in legacy hardware, or could deploy DOCSIS Set-top Gateway in order to provide much more capacity and efficiency than either of the other two protocols.
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
Video on demand
Video on Demand or Audio and Video On Demand are systems which allow users to select and watch/listen to video or audio content on demand...
, the requirement to upgrade all digital set-top box
Set-top box
A set-top box or set-top unit is an information appliance device that generally contains a tuner and connects to a television set and an external source of signal, turning the signal into content which is then displayed on the television screen or other display device.-History:Before the...
es within a group makes conversion to switched video extremely expensive. CableLabs
CableLabs
Founded in 1988 by cable television operating companies, Cable Television Laboratories, Inc. is a not-for-profit research and development consortium that has cable operators as its members. System operators from around the world are eligible to be members. Members dues are based on revenue...
proposed in the CableCARD
CableCARD
CableCARD is a special-use PCMCIA card that allows consumers in the United States to view and record digital cable television channels on digital video recorders, personal computers and television sets without the use of other equipment such as a set top box provided by a cable television company...
2.0 specification that two-way communication be supported with a scheme which required more powerful hardware capable of running Java
Java (programming language)
Java is a programming language originally developed by James Gosling at Sun Microsystems and released in 1995 as a core component of Sun Microsystems' Java platform. The language derives much of its syntax from C and C++ but has a simpler object model and fewer low-level facilities...
programs. Many cable companies have indicated they will build lower cost devices that do not require this OCAP
OpenCable Application Platform
The OpenCable Application Platform, or OCAP, is an operating system layer designed for consumer electronics that connect to a cable television system, the Java-based middleware portion of the platform. Unlike operating systems on a personal computer, the cable company controls what OCAP programs...
programming 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.
History
BigBand NetworksBigBand Networks
BigBand Networks is a multinational corporation headquartered in Redwood City, California, United States. BigBand manufactures and sells digital video and data processing platforms and solutions in areas ranging from digital video to CMTS.-Locations:BigBand has 2 major development centers...
has been the first pioneer in the field of switched video, and received the Technology & Engineering Emmy Award
Technology & Engineering Emmy Award
A Technology and Engineering Emmy Award is given by the National Academy of Television Arts and Sciences for outstanding achievement in technical or engineering development...
in 2008 for revolutionizing the HFC market.
Today, major vendors like Motorola
Motorola
Motorola, Inc. was an American multinational telecommunications company based in Schaumburg, Illinois, which was eventually divided into two independent public companies, Motorola Mobility and Motorola Solutions on January 4, 2011, after losing $4.3 billion from 2007 to 2009...
and Cisco
Cisco
Cisco may refer to:Companies:*Cisco Systems, a computer networking company* Certis CISCO, corporatised entity of the former Commercial and Industrial Security Corporation in Singapore...
also provide SDV solutions for the cable operators.
See also
- IPTVIPTVInternet Protocol television is a system through which television services are delivered using the Internet protocol suite over a packet-switched network such as the Internet, instead of being delivered through traditional terrestrial, satellite signal, and cable television formats.IPTV services...
- Cable televisionCable televisionCable television is a system of providing television programs to consumers via radio frequency signals transmitted to televisions through coaxial cables or digital light pulses through fixed optical fibers located on the subscriber's property, much like the over-the-air method used in traditional...
- CableCARDCableCARDCableCARD is a special-use PCMCIA card that allows consumers in the United States to view and record digital cable television channels on digital video recorders, personal computers and television sets without the use of other equipment such as a set top box provided by a cable television company...
- Hybrid fibre-coaxialHybrid fibre-coaxialHybrid fiber-coaxial is a telecommunications industry term for a broadband network which combines optical fibre and coaxial cable. It was commonly employed globally by cable television operators since the early 1990s.-Description:...
- Quadrature amplitude modulationQuadrature amplitude modulationQuadrature amplitude modulation is both an analog and a digital modulation scheme. It conveys two analog message signals, or two digital bit streams, by changing the amplitudes of two carrier waves, using the amplitude-shift keying digital modulation scheme or amplitude modulation analog...
External links
- Using Bandwidth More Efficiently with Switched Digital Video - Motorola White Paper
- Switched Digital Video BigBand NetworksBigBand NetworksBigBand Networks is a multinational corporation headquartered in Redwood City, California, United States. BigBand manufactures and sells digital video and data processing platforms and solutions in areas ranging from digital video to CMTS.-Locations:BigBand has 2 major development centers...
Overview and White Papers - Switched Digital Video (SDV) Consulting & Analysis - A5 Consulting
- FCC fines TWC and Cox for deploying Switched Digital Video - FCC fines TWC and Cox for deploying Switched Digital Video