Վիքիպեդիա

Մասնակից:GrigorGB/Ավազարկղ11

< Մասնակից:GrigorGB
Սա GrigorGB մասնակցի սևագրության էջն է՝ «ավազարկղը», և մասնակցի էջի ենթաէջերից մեկն է։ Այն ծառայում է որպես սևագիր և փորձարկումների վայր։ Սա հանրագիտարանային հոդված չէ։

Ձեր անձնական ավազարկղը ստեղծելու համար սեղմեք այստեղ։

Այլ ավազարկղեր՝ Ընդհանուր ավազարկղ
Այս էջը Internet Protocol Television մասին է․ public television broadcasting in Iowa տես՝ Iowa Public Television։

Այ-փի (ինտերնետային պրոտոկոլով) հեռուստատեսություն, IPTV համակարգ, որի միջոցով ի տարբերություն ավանդական մետրային կամ արբանյակային ալեհավաքներով, մալուխային տարբերակով հեռուստատեսության ծառայություններ մատուցելու փոխարեն ծառայությունները մատուցվում են լոկալ կամ ինտերնետային ցանցի միջոցով ինտերնետային պրոտոկոլներ օգտագործելու միջոցով: Ի տարբերություն բեռնվող մեդիայի, Այ-փի հեռուստատեսությունը հնարավորություն է տալիս անիմջապես աղբյուրից մեդիայի փոքր ծավալներ ստանալ: Սա հնարավորություն է ընձեռում դիտել տեսանյութը առանց սպասելու, որ այն ամբողջությամբ հեռարձակվելուց հետո ձայնագրվի և ամբողջական ֆայլ դառնա: Այս ֆունկցիան հայտնի է որպես «հոսքային մեդիա»:

Այ-փի հեռուստատեսության ծառայությունները կարելի է բաժանել երեք հիմնական խմբի.

  1. ուղիղ հեռարձակում
  2. եթերի կառավարման ֆունկցիա,
    1. վերսկսել ընթացիկ ցուցադրվող հաղորդումը (start-over TV)
    2. նախկին հաղորդումների դիտում (հայտնի որպես catch-up TV)
  3. Տեսավարձույթ (հայտնի որպես VOD)

Այ-Փի հեռուստատեսությունը ինտերնետ հեռուստատեսությունից տարբերվում է ստանդարտացման գործընթացով, ինչպես նաև բաժանորդներին ծառայությունները մատուցելու եղանակներով: Այ-փի հեռուստատեսության մատուցման համար ծառայությունների մատակարարները բարձր արագությամբ ցանցերի միջոցով բաժանորդի բնակարանում տեղադրված set-top box ընդունիչ սարքերի, կամ ծառայությունների մատուցման ստանդարտներին համապատասխանեցված այլ սարքերի միջոցով:

Անվանումը խմբագրել

Այ-փի հեռուստատեսության գործածության ընթացքում այն ստացել է բազմաթիվ անվանումներ, ինչպես օրինակ՝ «Այ-փի ցանցերի միջոցով պարզ հոսքեր», սակայն Հեռահողորդակցության ոլորտի լուծումների միջազգային միությունը տվել է հետևյալ սահմանումը.

«Այ-փի հեռուստատեսությունը մուլտիմեդիայի՝ (ինչպես հեռուստատեսություն, վիդեո, աուդիո, տեքստային, գրաֆիկական, տվյալների) Այ-փի ցանցերի միջոցով փոխանցման ծառայություն է, որը կարողացել է ապահովել օգտագործման և ծառայության անհրաժեշտ որակ, անվտանգություն, ինտերակտիվություն և կայունություն»[1]

Այ-փի հեռուստատեսության մեկ այլ՝ ավելի մանրամասն սահմանում 2005 թվականին տրվել է Հեռահողորդակցության ոլորտի լուծումների միջազգային միության կողմից:

Another more detailed definition of IPTV is the one given by Alliance for Telecommunications Industry Solutions (ATIS) IPTV Exploratory Group on 2005:

"Այ-փի հեռուստատեսությունը համարվում է վիդեո և հարակից ծառայությունների փոխանցում բաժանորդներին անվտանգ և կայուն փոխանցման միջոցով: Հարակից ծառայությունները կարող են ընդգրկել հեռուստատեսային ուղիղ հեռարձակում, տեսավարձույթ (VoD), ինտերակտիվ հեռուստատեսություն (iTV). Այս ծառայությունները այ-փի պրոտոկոլի միջոցով փոխանցում են պատկեր, ձայն և կառավարման ազդանշաններ: Ի տարբերություն ինտերնետային հանրային ցանցերի, այ-փի հեռուստատեսության կառուցումը, ցանցի անվտանգությունը և թողունակությունը հաջողությամբ կարողանում են ապահովել ժամանցային բարձր մակարդակ, որը պրովայդերների, գոզադային գործակալությունների համար ստեղծում է բիզնես միջավայր:[2]

Պատմություն խմբագրել

Այ-փի հեռուստատեսություն անվանումը առաջին անգամ օգտագործվել է 1995 թվականին, Precept Software ընկերության հիմնադրմանը համատեղ: Precept ընկերությունը մշակել էր ինտերնետային վիդեո պրոդուկտ, որն անվանել էին այ-փի/թի-վի (IP/TV). developed an Internet video product named IP/TV. IP/TV was a multicast backbone (MBONE) compatible Windows and Unix-based application that transmitted single and multi-source audio and video traffic, ranging from low to DVD quality, using both unicast and IP multicast Real-time Transport Protocol (RTP) and Real time control protocol (RTCP). The software was written primarily by Steve Casner, Karl Auerbach, and Cha Chee Kuan. Precept was acquired by Cisco Systems in 1998.[3] Cisco retains the IP/TV trademark.

Internet radio company AudioNet started the first continuous live webcasts with content from WFAA-TV in January 1998 and KCTU-LP on January 10, 1998.[4]

Kingston Communications, a regional telecommunications operator in the UK, launched KIT (Kingston Interactive Television) the brainchild of Matt Child, an IPTV over digital subscriber line (DSL) broadband interactive TV service in September 1999 after conducting various TV and video on demand (VoD) trials. The operator added additional VoD service in October 2001 with Yes TV, a VoD content provider. Kingston was one of the first companies in the world to introduce IPTV and IP VoD over ADSL as a commercial service. The service became the reference for various changes to UK Government regulations and policy on IPTV. In 2006, the KIT service was discontinued, subscribers having declined from a peak of 10,000 to 4,000.[5][6]

In 1999, NBTel (now known as Bell Aliant) was the first to commercially deploy Internet protocol television over DSL in Canada[7][8] using the Alcatel 7350 DSLAM and middleware created by iMagic TV (owned by NBTel's parent company Bruncor[9]). The service was marketed under the brand VibeVision in New Brunswick, and later expanded into Nova Scotia in early 2000[10] after the formation of Aliant. iMagic TV was later sold to Alcatel.[11]

In 2002, Sasktel was the second in Canada to commercially deploy Internet Protocol (IP) video over DSL, using the Lucent Stinger DSL platform.[12] In 2006, it was the first North American company to offer high-definition television (HDTV) channels over an IPTV service.[13]

In 2003, Total Access Networks Inc launched an IPTV service, consisting of 100 free IPTV stations worldwide.[փա՞ստ]

In 2005, Bredbandsbolaget launched its IPTV service as the first service provider in Sweden. As of January 2009, they are not the biggest supplier any longer; TeliaSonera, who launched their service later now has more customers.[14]

Կաղապար:Cnspan By 2010, iiNet and Telstra launched IPTV services in conjunction to internet plans but with extra fees.[15]

In 2008, PTCL launched IPTV under the brand name of PTCL Smart TV. This service is available in 50 major cities of the country offering 140 live channels and more than 500 titles for VOD with key features such as

In 2009, the company ZaapTV™ came out with the IPTV receiver ZaapTV™ HD1009N, a receiver that could bring live channels from all over the world. Successfully now in 2013 (now at its fourth generation model) it is still in the market as one of the leading brands in the industry with streaming of over 1,200 live channels. Its wide success is accredited by the strong impact it has in the United States market.[17]

In 2010, CenturyLink – after acquiring Embarq (2009) and Qwest (2010) – entered five U.S. markets with an IPTV service called Prism.[18] This was after successful test marketing in Florida. During the 2014 Winter Olympics Shortest path bridging (IEEE 802.1aq) was used to deliver 36 IPTV HD Olympic channels.

Promise խմբագրել

The technology was hindered by low broadband penetration and by the relatively high cost of installing wiring capable of transporting IPTV content reliably in the customer's home.[փա՞ստ] However, residential IPTV was expected to growԿաղապար:Or as broadband was available to more than 200 million households worldwide in 2005.[19]

In December 2009, the FCC began looking into using set-top boxes to make TVs with cable or similar services into network video players. FCC Media Bureau Chief Bill Lake had said earlier that TV and the Internet would soon be the same, but only 75 percent of homes had computers, while 99 percent had TV. A 2009 Nielsen survey found 99 percent of video viewing was done on TV.[20]

Markets խմբագրել

 
Map of IPTV countries of the world.[փա՞ստ]      Countries where IPTV is available in at least some parts of the country

The number of global IPTV subscribers was expected to grow from 28 million in 2009 to 83 million in 2013. Europe and Asia are the leading territories in terms of the over-all number of subscribers. But in terms of service revenues, Europe and North America generate a larger share of global revenue, due to very low average revenue per user (ARPU) in China and India, the fastest growing (and ultimately, the biggest markets) is Asia. The global IPTV market revenues are forecast to grow from US$12 billion in 2009 to US$38 billion in 2013.[21]

Services also launched in Bosnia and Herzegovina, Bulgaria, Pakistan, Canada, Croatia, Lithuania, Moldova, Macedonia, Montenegro, Poland, Mongolia, Romania, Serbia, Slovenia,[22] the Netherlands,[23] Georgia, Greece, Denmark, Finland, Estonia, Czech Republic, Slovakia, Hungary,[24][25] Norway, Sweden, Iceland, Lithuania, Turkey, Colombia, Chile and Uzbekistan.[26] The United Kingdom launched IPTV early and after a slow initial growth, in February 2009 BT announced that it had reached 398,000 subscribers to its BT Vision service.[27] Claro has launched their own IPTV service called "Claro TV". This service is available in several countries in which they operate, such as Dominican Republic, El Salvador, Guatemala, Honduras, Nicaragua. IPTV is just beginning to grow in Central and Eastern Europe and Latin America, and now it is growing in South Asian countries such as Sri Lanka, Pakistan and especially India.[28] but significant plans exist in countries such as Russia. Kazakhstan introduced[29] its own IPTV services by the national provider Kazakhtelecom JSC[30] and content integrator Alacast under the "iD TV" brand in two major cities Astana and Almaty in 2009 and is about to go nationwide starting 2010.Կաղապար:Update after Australian ISP iiNet launched Australia's first IPTV with fetchtv.[31]

The first IPTV service to launch on the Chinese mainland sells under the "BesTV" brand and is currently available in the cities of Shanghai and Harbin.[32] In India, IPTV was launched by Airtel and the government service provider MTNL and BSNL through tie up with AKSH and is available in most of the major cities of the country. Meanwhile, UF Group which is the franchise owner for UFO movies in Southern India plans to offer multiple host of services such as customer's movies on demand, shopping online, video conferencing, media player, e-learning on their single IPTV set top box branded as Emagine.[33]

In Sri Lanka, IPTV was launched by Sri Lanka Telecom (operated by SLT VisionCom) in 2008, under the brand name of PEO TV. This service is available in whole country.

In Pakistan, IPTV was launched by PTCL in 2008, under the brand name of Smart TV. This service is available in most major cities of the country.

In Malaysia, various companies have attempted to launch IPTV services since 2005. Failed PayTV provider MiTV attempted to use an IPTV-over-UHF service but the service failed to take off. Hypp.TV was supposed to use an IPTV-based system, but not true IPTV as it does not provide a set-top box and requires users to view channels using a computer. True IPTV providers available in the country at the moment are Fine TV and DETV. In Q2 2010, Telekom Malaysia launched IPTV services through their fiber to the home product UniFi in select areas. In April 2010, Astro began testing IPTV services on TIME dotCom Berhad's high-speed fiber to the home optical fibre network. In December 2010, Astro began trials with customers in high-rise condominium buildings around the Mont Kiara area. In April 2011, Astro commercially launched its IPTV services under the tag line "The One and Only Line You'll Ever Need", a triple play offering in conjunction with TIME dotCom Berhad that provides all the Astro programming via IPTV, together with voice telephone services and broadband Internet access all through the same fibre optic connection into the customer's home.

In Turkey, TTNET launched IPTV services under the name IPtivibu in 2010. It was available in pilot areas in the cities of Istanbul, İzmir and Ankara. As of 2011, IPTV service is launched as a large-scale commercial service and widely available across the country under the trademark "Tivibu EV".[34][35] Superonline plans to provide IPTV under the different name "WebTV" in 2011. Türk Telekom started building the fiber optic substructure for IPTV in late 2007.

For hospitality խմբագրել

Besides targeting the homes, vendors target IPTV services to the hospitality sector. IPTV is a natural progression from the pay-per-view and video on demand offerings. Some players such as Locatel, Select-TV, VDA, and Tivus have started offering IPTV to the hotels before moving into the homes. In 2013 Locatel Company launched the most comprehensively integrated IPTV platform available into new markets in Australia, Philippines, Malaysia, Thailand, Ethiopia and Sri Lanka.[փա՞ստ]

Architecture խմբագրել

 
A simplified network diagram for IPTV

Elements խմբագրել

  • TV head-end: where live TV channels are encoded, encrypted and delivered in the form of IP multicast streams.
  • VOD platform: where on-demand video assets are stored and served when a user makes a request in the form of IP unicast stream.
  • Interactive portal: allows the user to navigate within the different IPTV services, such as the VOD catalog.
  • Delivery network: the packet switched network that carries IP packets (unicast and multicast).
  • Home TV gateway: the piece of equipment at the user's home that terminates the access link from the delivery network.
  • User's set-top box: the piece of equipment at the user's home that decodes and decrypts TV and VOD content and displays it on the TV screen.

Architecture of a video server network խմբագրել

Կաղապար:Home networking standards Depending on the network architecture of the service provider, there are two main types of video server architecture that can be considered for IPTV deployment: centralized and distributed.

The centralized architecture model is a relatively simple and easy to manage solution. For example, as all contents are stored in centralized servers, it does not require a comprehensive content distribution system. Centralized architecture is generally good for a network that provides relatively small VOD service deployment, has adequate core and edge bandwidth and has an efficient content delivery network (CDN).

Distributed architecture is just as scalable as the centralized model, however it has bandwidth usage advantages and inherent system management features that are essential for managing a larger server network. Operators who plan to deploy a relatively large system should therefore consider implementing a distributed architecture model right from the start. Distributed architecture requires intelligent and sophisticated content distribution technologies to augment effective delivery of multimedia contents over service provider's network.[36]

Home networks խմբագրել

In many cases, the residential gateway that provides connectivity with the Internet access network is not located close to the IPTV set-top box. This scenario becomes very common as service providers start to offer service packages with multiple set-top boxes per subscriber.

Networking technologies that take advantage of existing home wiring (such as power lines,[37][38] phone lines or coaxial cables[39][40]) or of wireless hardware have become common solutions for this problem, although fragmentation in the wired home networking market has limited somewhat the growth in this market.[41][42]

In December 2008, ITU-T adopted Recommendation G.hn (also known as G.9960), which is a next-generation home networking standard that specifies a common PHY/MAC that can operate over any home wiring (power lines, phone lines or coaxial cables).[43] During 2012 IEC will adopt a prenorm for POF networking at Gigabit speed. This pre standard will specify a PHY that operates at an adaptable bit rate between 100 Mbit/s and 1 Gbit/s depending on the link power budget.

Groups such as the Multimedia over Coax Alliance, HomePlug Powerline Alliance, Home Phoneline Networking Alliance, and Quasar Alliance (Plastic Optical Fiber)[44] each advocate their own technologies.

IMS architecture խմբագրել

There is a growing standardization effort on the use of the 3GPP IP Multimedia Subsystem (IMS) as an architecture for supporting IPTV services in carriers networks. Both ITU-T and ETSI are working on so-called "IMS-based IPTV" standards (see e.g. ETSI TS 182 027[45]). Carriers will be able to offer both voice and IPTV services over the same core infrastructure and the implementation of services combining conventional TV services with telephony features (e.g. caller ID on the TV screen) will become straightforward.[46] The MultiService Forum recently conducted interoperability of IMS-based IPTV solutions during its GMI event in 2008.[47]

Պրոտոկոլներ խմբագրել

IPTV covers both live TV (multicast) as well as stored video-on-demand/VoD (unicast). Playback requires a broadband device connected to either a fixed or wireless IP network in the form of either a standalone personal computer or limited embedded OS device such as a smartphone, touch screen tablet, game console, connected TV or set-top box. Video compression is provided by either a H.263 or H.264 derived codec, audio compressed via a MDCT based codec and then encapsulated in either an MPEG transport stream or RTP packets or Flash Video packets for live or VoD streaming. IP multicasting allows for live data to be sent to multiple receivers using a single multicast group address. H.264/MPEG-4 AVC is commonly used for internet streaming over higher bit rate standards such as H.261 and H.263 which were more designed for ISDN video conferencing. H.262/MPEG-1/2 is generally not used as the bandwidth required would quite easily saturate a network which is why they are only used in single link broadcast or storage applications.

In standards-based IPTV systems, the primary underlying protocols used are:

  • Service provider based streaming:
    • IGMP for subscribing to a live multicast stream (TV channel) and for changing from one live multicast stream to another (TV channel change). IP multicast operates within LANs (including VLANs) and across WANs also. IP multicast is usually routed in the network core by Protocol Independent Multicast (PIM), setting up correct distribution of multicast streams (TV channels) from their source all the way to the customers who wants to view them, duplicating received packets as needed. On-demand content uses a negotiated unicast connection. RTP over UDP or the lower overhead H.222 transport stream over TCP are generally the preferred methods of encapsulation.

A telecommunications company IPTV service is usually delivered over an investment-heavy walled garden network.

Local IPTV, as used by businesses for audio visual AV distribution on their company networks is typically based on a mixture of:

  1. Conventional TV reception equipment and IPTV encoders
  2. IPTV gateways that take broadcast MPEG channels and IP wrap them to create multicast streams.

Via satellite խմբագրել

Although IPTV and conventional satellite TV distribution have been seen as complementary technologies, they are likely to be increasingly used together in hybrid IPTV networks that deliver the highest levels of performance and reliability. IPTV is largely neutral to the transmission medium, and IP traffic is already routinely carried by satellite for Internet backbone trunking and corporate VSAT networks.[48] The use of satellite to carry IP is fundamental to overcoming the greatest shortcoming of IPTV over terrestrial cables – the speed/bandwidth of the connection, as well as availability.

The copper twisted pair cabling that forms the last mile of the telephone and broadband network in many countries is not able to provide a sizeable proportion of the population with an IPTV service that matches even existing terrestrial or satellite digital TV distribution. For a competitive multi-channel TV service, a connection speed of 20 Mbit/s is likely to be required, but unavailable to most potential customers.[49] The increasing popularity of high-definition television (with twice the data rate of SD video) increases connection speed requirements, or limits IPTV service quality and connection eligibility even further.

However, satellites are capable of delivering in excess of 100 Gbit/s via multi-spot beam technologies, making satellite a clear emerging technology for implementing IPTV networks. Satellite distribution can be included in an IPTV network architecture in several ways. The simplest to implement is an IPTV-direct to home (DTH) architecture, in which hybrid DVB-broadband set-top boxes in subscriber homes integrate satellite and IP reception to give near-infinite bandwidth with return channel capabilities. In such a system, many live TV channels may be multicast via satellite (IP-encapsulated or as conventional DVB digital TV) with stored video-on-demand transmission via the broadband connection. Arqiva’s Satellite Media Solutions Division suggests “IPTV works best in a hybrid format. For example, you would use broadband to receive some content and satellite to receive other, such as live channels”.[50]

Hybrid IPTV խմբագրել

Կաղապար:Update

Hybrid IPTV refers to the combination of traditional broadcast TV services and video delivered over either managed IP networks or the public Internet. It is an increasing trend in both the consumer and pay TV [operator] markets.[51][52][53]

Hybrid IPTV has grown in popularity in recent yearsԿաղապար:When as a result of two major drivers. Since the emergence of online video aggregation sites, like YouTube and Vimeo in the mid-2000s, traditional pay TV operators have come under increasing pressure to provide their subscribers with a means of viewing Internet-based video [both professional and user-generated] on their televisions. At the same time, specialist IP-based operators [often telecommunications providers] have looked for ways to offer analogue and digital terrestrial services to their operations, without adding either additional cost or complexity to their transmission operations. Bandwidth is a valuable asset for operators, so many have looked for alternative ways to deliver these new services without investing in additional network infrastructures.

A hybrid set-top allows content from a range of sources, including terrestrial broadcast, satellite, and cable, to be brought together with video delivered over the Internet via an Ethernet connection on the device. This enables television viewers to access a greater variety of content on their TV sets, without the need for a separate box for each service.

Hybrid IPTV set-top boxes also enable users to access a range of advanced interactive services, such as VOD / catch-up TV, as well as Internet applications, including video telephony, surveillance, gaming, shopping, e-government accessed via a television set.

From a pay-TV operator’s perspective, a hybrid IPTV set-top box gives them greater long-term flexibility by enabling them to deploy new services and applications as and when consumers require, most often without the need to upgrade equipment or for an engineer to visit and reconfigure or swap out the device. This minimises the cost of launching new services, increases speed to market and limits disruption for consumers.[54]

The Hybrid Broadcast Broadband TV (HbbTV) consortium of industry companies is currentlyԿաղապար:When promoting and establishing an open European standard for hybrid set-top boxes for the reception of broadcast and broadband digital TV and multimedia applications with a single user interface.[55] These trends led to the development of Hybrid Broadcast Broadband TV set-top boxes that included both a broadcast tuner and an Internet connection – usually an Ethernet port. The first commercially available hybrid IPTV set-top box was developed by Advanced Digital Broadcast, a developer of digital television hardware and software, in 2005. The platform was developed for Spanish pay TV operator Telefonica,[56] and used as part of its Movistar TV service, launched to subscribers at the end of 2005.

An alternative approach is the IPTV version of the Headend in the Sky cable TV solution. Here, multiple TV channels are distributed via satellite to the ISP or IPTV provider’s point of presence (POP) for IP-encapsulated distribution to individual subscribers as required by each subscriber.

This can provide a huge selection of channels to subscribers without overburdening Internet trunking to the POP, and enables an IPTV service to be offered to small or remote operators outside the reach of terrestrial high speed broadband connection. An example is a network combining fibre and satellite distribution via an SES New Skies satellite of 95 channels to Latin America and the Caribbean, operated by IPTV Americas.[57]

While the future development of IPTV probably lies with a number of coexisting architectures and implementations, it is clearԿաղապար:According to whom that broadcasting of high bandwidth applications such as IPTV is accomplished more efficiently and cost-effectively using satellite[58] and it is predicted that the majority of global IPTV growth will be fuelled by hybrid networks.[59]

Advantages խմբագրել

The Internet protocol-based platform offers significant advantages, including the ability to integrate television with other IP-based services like high speed Internet access and VoIP.

A switched IP network also allows for the delivery of significantly more content and functionality. In a typical TV or satellite network, using broadcast video technology, all the content constantly flows downstream to each customer, and the customer switches the content at the set-top box. The customer can select from as many choices as the telecomms, cable or satellite company can stuff into the “pipe” flowing into the home. A switched IP network works differently. Content remains in the network, and only the content the customer selects is sent into the customer’s home. That frees up bandwidth, and the customer’s choice is less restricted by the size of the “pipe” into the home. This also implies that the customer's privacy could be compromised to a greater extent than is possible with traditional TV or satellite networks. It may also provide a means to hack into, or at least disrupt (see Denial of service) the private network.

Economics խմբագրել

The cable industry's expenditures of approximately $1 billion per year are based on network updates to accommodate higher data speeds. Most operators use 2–3 channels to support maximum data speeds of 50 Mbit/s to 100 Mbit/s. However, because video streams require a high bit rate for much longer periods of time, the expenditures to support high amounts of video traffic will be much greater. This phenomenon is called persistency. Data persistency is routinely 5% while video persistency can easily reach 50%. As video traffic continues to grow, this means that significantly more CMTS downstream channels will be required to carry this video content. Based on today's market, it is likely that industry expenditures for CMTS expansion could exceed $2 billion a year, virtually all of that expenditure being driven by video traffic. Adoption of IPTV for carrying the majority of this traffic could save the industry approximately 75% of this capital expenditure.[60]

Interactivity խմբագրել

An IP-based platform also allows significant opportunities to make the TV viewing experience more interactive and personalized. The supplier may, for example, include an interactive program guide that allows viewers to search for content by title or actor’s name, or a picture-in-picture functionality that allows them to “channel surf” without leaving the program they’re watching. Viewers may be able to look up a player’s stats while watching a sports game, or control the camera angle. They also may be able to access photos or music from their PC on their television, use a wireless phone to schedule a recording of their favorite show, or even adjust parental controls so their child can watch a documentary for a school report, while they’re away from home.

In order that there can take place an interaction between the receiver and the transmitter, a feedback channel is needed. Due to this, terrestrial, satellite, and cable networks for television do not allow interactivity. However, interactivity with those networks can be possible by combining TV networks with data networks such as the Internet or a mobile communication network.

Video-on-demand խմբագրել

IPTV technology is bringing video on demand (VoD) to television,[61] which permits a customer to browse an online program or film catalog, to watch trailers and to then select a selected recording. The playout of the selected item starts nearly instantaneously on the customer's TV or PC.

Technically, when the customer selects the movie, a point-to-point unicast connection is set up between the customer's decoder (set-top box or PC) and the delivering streaming server. The signalling for the trick play functionality (pause, slow-motion, wind/rewind etc.) is assured by RTSP (Real Time Streaming Protocol).

The most common codecs used for VoD are MPEG-2, MPEG-4 and VC-1.

In an attempt to avoid content piracy, the VoD content is usually encrypted. Whilst encryption of satellite and cable TV broadcasts is an old practice, with IPTV technology it can effectively be thought of as a form of Digital rights management. A film that is chosen, for example, may be playable for 24 hours following payment, after which time it becomes unavailable.

IPTV-based converged services խմբագրել

Another advantage of an IP-based network is the opportunity for integration and convergence. This opportunity is amplified when using IMS-based solutions.[62] Converged services implies interaction of existing services in a seamless manner to create new value added services. One example is on-screen Caller ID, getting Caller ID on a TV and the ability to handle it (send it to voice mail, etc.). IP-based services will help to enable efforts to provide consumers anytime-anywhere access to content over their televisions, PCs and cell phones, and to integrate services and content to tie them together. Within businesses and institutions, IPTV eliminates the need to run a parallel infrastructure to deliver live and stored video services.

Limitations խմբագրել

IPTV is sensitive to packet loss and delays if the streamed data is unreliable. IPTV has strict minimum speed requirements in order to facilitate the right number of frames per second to deliver moving pictures. This means that the limited connection speed and bandwidth available for a large IPTV customer base can reduce the service quality delivered.

Although a few countries have very high-speed broadband-enabled populations, such as South Korea with 6 million homes benefiting from a minimum connection speed of 100 Mbit/s, in other countries (such as the UK) legacy networks struggle to provide 3–5 Mbit/s[63]Կաղապար:Update after and so simultaneous provision to the home of TV channels, VOIP and Internet access may not be viable. The last-mile delivery for IPTV usually has a bandwidth restriction that only allows a small number of simultaneous TV channel streams – typically from one to three – to be delivered.[64]

Streaming IPTV across wireless links within the home has proved troublesome; not due to bandwidth limitations as manyԿաղապար:Who assume, but due to issues with multipath and reflections of the RF signal carrying the IP data packets. An IPTV stream is sensitive to packets arriving at the right time and in the right order. Improvements in wireless technology are nowԿաղապար:When starting to provide equipment to solve the problem.[65]

Due to the limitations of wireless, most IPTV service providers today use wired home networking technologies instead of wireless technologies like IEEE 802.11. Service providers such as AT&T (which makes extensive use of wireline home networking as part of its AT&T U-verse IPTV service) have expressed support for the work done in this direction by ITU-T, which has adopted Recommendation G.hn (also known as G.9960), which is a next-generation home networking standard that specifies a common PHY/MAC that can operate over any home wiring (power lines, phone lines or coaxial cables).[66][67]

Latency խմբագրել

The latency inherent in the use of satellite Internet is often held up as reason why satellites cannot be successfully used for IPTV, but in practice latency is not an important factor for IPTV. An IPTV service does not require real-time transmission, as is the case with telephony or videoconferencing services.

It is the latency of response to requests to change channel, display an EPG, etc. that most affects customers’ perceived quality of service, and these problems affect satellite IPTV no more than terrestrial IPTV. Command latency problems, faced by terrestrial IPTV networks with insufficient bandwidth as their customer base grows, may be solved by the high capacity of satellite distribution.

Satellite distribution does suffer from latency – the time for the signal to travel up from the hub to the satellite and back down to the user is around 0.25 seconds, and cannot be reduced. However, the effects of this delay are mitigated in real-life systems using data compression, TCP-acceleration, and HTTP pre-fetching.[68]

Satellite latency can be detrimental to especially time-sensitive applications such as on-line gaming (although it only seriously affects the likes of first-person shooters while many MMOGs can operate well over satellite Internet[69]), but IPTV is typically a simplex operation (one-way transmission) and latency is not a critical factor for video transmission.

Existing video transmission systems of both analogue and digital formats already introduce known quantifiable delays. Existing DVB TV channels that simulcast by both terrestrial and satellite transmissions experience the same 0.25-second delay difference between the two services with no detrimental effect, and it goes unnoticed by viewers.

Արագության պահանջները խմբագրել

 
Bandwidth capacity for simultaneously two HDTV streams, two SD streams, additional to HSD and voice

Թվային տեսագրությունը թվային պատկերների հաջորդականություն է, որոնք պատկերի էլեմենտրներից կամ պիքսելներից: Յուրաքանչյուր պիքսել ունի երկու արժեք. luminance and chrominance.


Each pixel has two values, which are luminance and chrominance. Luminance is representing intensity of the pixel; chrominance represents the colour of the pixel. Three bytes would be used to represent the colour of the high quality image for a true colour technique. A sequence of images is creating the digital video, in that case, images are called as frames.

Movies use 24 frames per second; however, the rate of the frames can change according to territories' electrical systems so that there are different kinds of frame rates, for instance, North America is using approximately 30 frames per second where the Europe television frame rate is 25 frames per second. Each digital video has dimensions width and height; when referred to analogue television, the dimension for SDTV is 720×480 pixels, on the other hand, numerous HDTV requires 1920×1080 pixels. Moreover, whilst for SDTV, two bytes (16 bits) is enough to create the colour depth, HDTV requires three bytes (24 bits) to create the colour depth.

Thereby, with a rate of 30 frames/second, the uncompressed data rate for SDTV becomes 30×640×480×16, in other words, 147,456,000 bits per second. Moreover, for HDTV, at the same frame rate, uncompressed date rate becomes 30×1920×1080×24 or 1,492,992,000 bits per second. With that simple calculation, it is obvious that without using a lossy compression methods service provider’s service delivery to the subscribers is limited.

There is no absolute answer for the bandwidth requirement for the IPTV service because the bandwidth requirement is increasing due to the devices inside the household. Thus, currently compressed HDTV content can be delivered at a data rate between 8 and 10 Mbit/s, but if the home of the consumer equipped with several HDTV outputs, this rate will be multiplied respectively.

The high-speed data transfer will increase the needed bandwidth for the viewer, at least 2 Mbit/s is needed to use web-based applications on the computer. Additionally to that, 64 kbit/s is required to use landline telephone for the property. In minimal usage, to receive an IPTV triple-play service requires 13 Mbit/s to process in a household.

Privacy implications խմբագրել

Due to limitations in bandwidth, an IPTV channel is delivered to the user one at a time, as opposed to the traditional multiplexed delivery. Changing a channel requires requesting the head-end server to provide a different broadcast stream, much like VOD (For VOD the stream is delivered using unicast, for the normal TV signal multicast is used). This could enable the service provider to accurately track each and every programme watched and the duration of watching for each viewer; broadcasters and advertisers could then understand their audience and programming better with accurate data and targeted advertising.

In conjunction with regulatory differences between IPTV and cable TV, this tracking could pose a threat to privacy according to critics.[70] For IP multicast scenarios, since a particular multicast group (TV channel) needs to be requested before it can be viewed, the same privacy concerns apply.

Vendors խմբագրել

A small number of companies supply most current IPTV systems. Some, such as Movistar TV, were formed by telecoms operators themselves, to minimise external costs, a tactic also used by PCCW of Hong Kong. Some major telecoms vendors are also active in this space, notably Alcatel-Lucent (sometimes working with Movistar TV), Ericsson (notably since acquiring Tandberg Television), NEC, Accenture (Accenture Video Solution), Thomson, Huawei, and ZTE, as are some IT houses, led by Microsoft. California-based UTStarcom, Inc., Tennessee-based Worley Consulting, Tokyo-based The New Media Group, Malaysian-based Select-TV and Oslo/Norway-based SnapTV also offer end-to-end networking infrastructure for IPTV-based services, and Hong Kong-based BNS Ltd. provides turnkey open platform IPTV technology solutions. Global sales of IPTV systems exceeded 2 billion USD in 2007.

Hospitality IPTV Ltd, having established many closed network IPTV systems, expanded in 2013 to OTT delivery platforms for markets in New Zealand, Australia and Asia Pacific region, bringing a European flair and sophistication to the delivery of OTT content.[փա՞ստ]

Google Fiber offers an IPTV service in Kansas City, MO and Kansas City, KS which includes Gigabit-speed internet and over 290 channels via the fiber optic network being built out in KCK and KCMO.

Many of these IPTV solution vendors participated in the biennial Global MSF Interoperability 2008 (GMI) event which was coordinated by the MultiService Forum (MSF) at five sites worldwide from 20 to 31 October 2008. Test equipment vendors including Netrounds, Codenomicon, Empirix, Ixia, Mu Dynamics and Spirent joined solution vendors such as the companies listed above in one of the largest IPTV proving grounds ever deployed.

Service bundling խմբագրել

For residential users, IPTV is often provided in conjunction with video on demand and may be bundled with Internet services such as Internet access and Voice over Internet Protocol (VoIP) telecommunications services. Commercial bundling of IPTV, VoIP and Internet access is sometimes referred to in marketing as triple play service. When these three are offered with cellular service, the combined service may be referred to as quadruple play.

Regulation խմբագրել

Historically, broadcast television has been regulated differently from telecommunications. As IPTV allows TV and VoD to be transmitted over IP networks, new regulatory issues arise.[71] Professor Eli M. Noam highlights in his report "TV or Not TV: Three Screens, One Regulation?" some of the key challenges with sector specific regulation that is becoming obsolete due to convergence in this field.[72]

See also խմբագրել

References խմբագրել

  1. ↑ «IPTV Standardization on Track Say Industry Experts». ITU-T Newslog. 2006-10-27. Վերցված է 2012-01-17-ին.
  2. ↑ «ATIS IPTV Exploratory Group Report and Recommendation to the TOPS Council» (PDF). Alliance for Telecommunications Industry Solutions. July 2006. Վերցված է 2012-01-17-ին. {{cite journal}}: Cite journal requires |journal= (օգնություն)
  3. ↑ Cisco - Summary of Acquisitions
  4. ↑ Hart, Timothy (February 15, 1998). «KCTU-TV earns a place in television, Internet history».
  5. ↑ http://www.theregister.co.uk/2006/02/27/kingston_iptv/
  6. ↑ KIT Kingston Interactive Television. Kitv.co.uk. Retrieved on 2014-03-12.
  7. ↑ NBTel Unveils Interactive TV
  8. ↑ NBTel leading the way in North America with Aliant's new interactive information and entertainment television service - VibeVision
  9. ↑ Bruncor launches iMagic TV
  10. ↑ Aliant Telecom Launches New Television Technology in Halifax
  11. ↑ «Alcatel Acquires iMagic TV». Communications Today. 2003.
  12. ↑ «Lucent Technologies Introduces First Commercial IP Video Over DSL Solution, Business Net». Business Wire. April 10, 2002. Վերցված է 2008-02-04-ին.
  13. ↑ «Internet HDTV unveiled, Regina Leader-Post». Վերցված է 2006-11-15-ին.
  14. ↑ Կաղապար:Se icon"Bredbandsbolaget is mobilizing for IP TV"
  15. ↑ Broadband Providers Plans
  16. ↑ Welcome to PTCL. Ptcl.com.pk (2008-08-14). Retrieved on 2014-03-12.
  17. ↑ ZAAPTV Receiver | Watch Arabic TV IPTV, Persian, Turkish, Greek, African Channels with ZAAPTV. Zaaptvusa.com. Retrieved on 2014-03-12.
  18. ↑ «CenturyLink Quietly Launches Prism IPTV Product». Telecompetitor.com. Վերցված է 2013-06-15-ին.
  19. ↑ Gartner - 2007 Press releases
  20. ↑ Eggerton, John (2009-12-14). «Broadcasters Squeezed by Convergence Push». Broadcasting & Cable. Վերցված է 2009-12-17-ին.
  21. ↑ IPTV Global Forecast (2008-2013) International Television Expert Group
  22. ↑ BHTelecom.ba
  23. ↑ KPN.com
  24. ↑ T-Home.hu
  25. ↑ InviTV.hu
  26. ↑ uzonline.uz
  27. ↑ BT Vision passes 398k subs in 4Q08
  28. ↑ "Salad days," Chris Dziadul, Broadband TV News, May 2, 2008
  29. ↑ Delivering IPTV System to Kazakhtelecom Article from the IPTV industrial portal
  30. ↑ iD TV services for broadband subscribers in Kazakhstan Kazakhtelecom JSC - iD TV service for Home users
  31. ↑ iiNet's Age of Terabyte PDF from iiNet press release 18 August 2010
  32. ↑ "BabyFirst launches on BesTV in China," Indiantelevision.com Team, May 2, 2008.
  33. ↑ "UF Group to launch E box for movies on demand, online shopping, e-learning " Netindian.in, Feb 1, 2012.
  34. ↑ "Turkey's iptv, Tivibu Ev is on air" ntvmsnbc.com, Feb 23, 2011.
  35. ↑ "Tivibu Ev's Official Homepage" tivibu.com/ev, March 13, 2011.
  36. ↑ Distributed Architecture vsCentralized Architecture for IP VoD, Annual Review of Communications, Vol. 58
  37. ↑ HomePlug Alliance keeps plugging away
  38. ↑ IPTV distribution using DS2 powerline networks
  39. ↑ «20 Million MoCA Nodes Have Been Shipped». Reuters. February 17, 2009.
  40. ↑ LightReading: Why AT&T Likes HomePNA
  41. ↑ Could MoCA/HomePlug win in-home networking wars?
  42. ↑ HomeGrid Forum Blog - Why do we need a unified standard at all?
  43. ↑ New global standard for fully networked home, ITU-T Press Release
  44. ↑ Quasar POF alliance
  45. ↑ ETSI TS 182 027
  46. ↑ IMS-based IPTV services - architecture and implementation
  47. ↑ MSforum.org
  48. ↑ Berlocher, Greg and Freyer, Dan. "IP And Satellite: Communications Worlds Merging" Via Satellite January 2009 p 24–28
  49. ↑ Taga, Karim. "Hybrid delivery of content for IPTV" InterComms Issue 11 August 2008 p 13–14
  50. ↑ Holmes, Mark. "Broadcast 2.0: The Changing Scene In Europe" Via Satellite September 2008 p 20–25
  51. ↑ October 14, 2009 19.46 Europe/London (2009-10-14). «UK and France lead with hybrid IPTV set-tops». Broadbandtvnews.com. Վերցված է 2013-06-15-ին.{{cite web}}: CS1 սպաս․ թվային անուններ: authors list (link)
  52. ↑ [1](չաշխատող հղում)
  53. ↑ «HYBRID Set Top Boxes for IPTV | Digital Media Strategy by Jeff Vinson». Jviptv.wordpress.com. 2009-06-25. Վերցված է 2013-06-15-ին.
  54. ↑ [2](չաշխատող հղում)
  55. ↑ «New European initiative merges television with the power of the Internet» (PDF) (Press release). HbbTV Consortium. August 27, 2009.
  56. ↑ «ADB Delivers World's First Hybrid, Single-Chip, Advanced Video Coding, High Definition IPTV Set-Top Boxes To TELEFÓNICA». Digitaltvnews.net. Վերցված է 2013-06-15-ին.
  57. ↑ «IPTV Americas Launches First IPTV Satellite Distribution Platform for Latin America and The Caribbean via SES NEW SKIES' NSS-806» (Press release). IPTV Americas. January 13, 2009.
  58. ↑ International Datacasting Corporation "Why IP Over Satellite?". Accessed January 18, 2009. Company factsheet
  59. ↑ "Future Looks Bright For IPTV" Satellite Today'.' Retrieved January 18, 2009.
  60. ↑ The Economics of IPTV
  61. ↑ Broadband Users Control What They Watch and When
  62. ↑ Session and Media Signalling for IPTV via IMS
  63. ↑ Bulkley, Kate. "IPTV’s Eastern Promise" Digital TV Europe October 2008 p 48
  64. ↑ Brown, Peter J. "Super Headends And High Expectations" Via Satellite April 2006 p 18–30
  65. ↑ Market Wire "ZyXEL Announces Industry's First ADSL2/2+ 802.11n Gateway and New IPTV Product Offerings" June 2008
  66. ↑ HomePNA and HomeGrid Sign Liaison Agreement, Groups Work to Promote New ITU G.hn Global Wired Home Networking Standard
  67. ↑ AT&T Participating in G.hn Standard Development
  68. ↑ Newtec Productions NV "TP210 Sat3Play Broadband Terminal" (Version R2/06.2010). Satellite Internet Modem factsheet
  69. ↑ Tom’s Hardware "How much latency is too much for Online Gaming?". Accessed January 23, 2009. Internet Forum
  70. ↑ IPTV privacy risks
  71. ↑ Կաղապար:PDFlink
  72. ↑ TV or Not TV

External links խմբագրել

Կաղապար:CATV


Category:Digital television Category:Film and video technology Category:Internet broadcasting Category:Internet radio Category:Internet television Category:Video on demand services Category:Television technology Category:Television terminology

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