Videotext

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Teletext is an information retrieval service provided by Television broadcast companies. Teletext pages can be viewed on television sets with suitable Decoder s. They offer a range of text-based information, usually including national, international and sporting news, weather and TV schedules. Subtitle (or closed caption) information is also transmitted in the teletext signal.

Teletext has gained great popularity across Europe (and was for a short while in the USA ), with every major television station having its own teletext service. On some commercial stations, the teletext is also used as a publicity channel, advertising products such as travel destinations. Common teletext services include TV schedules, regularly updated current affairs and sport news, simple games (like quizzes) and subtitling for deaf people or in different languages. In Australia , there is one Teletext service which is owned and operated by the Seven Network .

While Teletext is, in most aspects, technologically inferior to the Internet, it is still very popular due to its ease of use and integration into the TV. Another benefit is that, unlike web servers, Teletext doesn't slow down as the number of users increase. This is relevant during great news events which often block access to the webpages of major news sites. Also, the Teletext system is used for carrying special packets interpreted by TVs and video recorders, containing information about channels, programming etc. (see "Other Teletext-related services").

Although teletext tends to refer to one specific system, or variants, the recent availability of Digital Television has led to more advanced systems being provided that perform the same task, such as MHEG-5 (the UK system) and Multimedia Home Platform .

HISTORY—1970S

Development of Teletext

In about 1970 the BBC had a brainstorming session in which it was decided to start researching ways to send Closed Captioning information to audience. As the Teledata research continued they became increasingly interested in using the same system for delivering any sort of information, not just closed captioning. Displaying subtitles requires limited Bandwidth , at a rate of perhaps a few words per second. However, by combining even a slow data rate with a suitable memory, pages of information could be sent and stored in the TV for later recall.

Meanwhile the General Post Office (whose telecommunications division later became British Telecom ) had been researching a similar concept since the late 1960s, known as Viewdata. Unlike Ceefax which was a one-way service carried in the existing TV signal, Viewdata was a two-way system using telephones. Since the Post Office owned the telephones, this was considered to be an excellent way to drive more customers to use the phones.

In 1972 the BBC demonstrated their system, now known as Ceefax ("see facts", the departmental stationary used the curious "Cx" logo), on various news shows. The Independent Television Authority (ITA) announced their own service in 1973 , known as ''' ORACLE ''' (Optional Reception of Announcements by Coded Line Electronics). Unlike Ceefax, ORACLE content was provided by a separate company formed by Philips and Associated Newspapers.

In 1974 all the services agreed a standard for displaying the information. The display would be a simple 40x24 grid of text, with some ''graphics characters'' for constructing simple graphics. This standard was called CEPT1 . The standard did not define the delivery system, so both Viewdata-like and Teledata-like services could at least share the TV-side hardware (which at that point in time was quite expensive). The standard also introduced a new term that covered all such services, Teletext .

The "Broadcast Teletext Specification" was published in September 1976 jointly by the IBA, the BBC and the British Radio Equipment Manufacturers's Association. Not to be outdone the GPO immediately announced a 1200/75 baud videotext service under the name Prestel .

Recent versions of the CEPT1 standard are called ''World System B'' (also known as WST , or World System Teletext) and commonly known as European teletext.

At roughly the same time a similar system called Telidon was developed in Canada. It used a simple graphics language that would allow a more complex circuit in the TV to decode not only characters, but simple graphics as well. To do this the graphic was encoded as a series of instructions (graphics primitives) like "polyline" which was represented as the characters PL followed by a string of digits for the X and Y values of the points on the line. This system was referred to as PDI (Picture Description Instructions). Later improved versions of Telidion were called NAPLPS .

Introduction of Teletext

Following test transmissions in 1973 – 74 , towards the end of 1974 the BBC news department put together an editorial team of nine, including and led by Editor Colin McIntyre, to develop a news and information service. Initially limited to 30 pages, the Ceefax service was later expanded to 100 pages and was launched formally in 1976. It was followed quickly by ORACLE and Prestel . Development was limited until the first TV sets with built-in decoders started appearing in 1977 , but by 1982 there were two million such sets, and by the Mid-80s they were available as an option for almost every European TV set. It took another decade before the decoders became a standard feature on almost all sets over 15" (Teletext is still usually only an option for smaller "portable" sets). From the Mid-80s both Ceefax and ORACLE were broadcasting several hundred pages on every channel, slowly changing them throughout the day.

HISTORY—1980S

North America

Teletext was first demonstrated in the USA in 1978 by American television network CBS , which decided to try both the British Ceefax and French Antiope software for preliminary tryouts for a teletext service using station KMOX (now KMOV ) in St. Louis, Missouri as a testing ground. CBS decided on Antiope, and the service premiered on station KNXT (now KCBS ) in Los Angeles .

Also in 1978, station KSL in Salt Lake City, Utah , also premiered a teletext service using Ceefax.

Later on, an official North American standard of teletext, called NABTS (North American Broadcast Teletext Specification) was developed in the early 80s by Norpak , a Canadian company. NABTS provided improved graphic and text capability over WST, but was quite short-lived. This was mainly due to the expensive cost of NABTS decoders, costing in the thousands of dollars upon their release to the public. NABTS, however, was adopted for a short while by American TV networks NBC & CBS throughout the early-to-mid 80s, CBS using it for their short-lived ''' ExtraVision ''' teletext service, which premiered after the early Antiope & Ceefax trials by CBS & KNXT, and NBC, who had a NABTS-based service for a very short time in the mid-80s. NBC discontinued their service in 1986 due to the cost of NABTS decoders not dropping to an affordable level for the consumer public.

WST was also used for a short time in the USA as well, with services provided throughout the late 70s and early 80s by several regional American TV networks (such as the University Of Wisconsin 's ''Infotext'' service in the mid 80s, which was carried on several TV stations across Wisconsin , and provided agriculturally oriented information) & large-market US TV stations (such as ''Metrotext'', which was formerly carried on station KTTV in Los Angeles , and ''KeyFax'', formerly on WFLD in Chicago ), but the most prominent of American teletext providers was the '' Electra '' teletext service, which was broadcast starting in the early 1980s on the Vertical blanking interval ( VBI ) of the famed American cable channel Superstation WTBS (now TBS Superstation ). Electra was owned and operated by Taft Broadcasting and Satellite Syndicated Systems ( SSS ). Electra ran up until 1993, when it was shut down due to the prominent (and only) American TV manufacturer offering teletext features in their sets, Zenith , discontinuing such sets (more info on this in the next paragraph), a lack of funding, and lagging interest in teletext by the American consumer.

Zenith manufactured models of television sets in the USA in the 1980s, most notably their ''Digital System 3'' line, that had built-in WST teletext decoders as a feature, much like most British/European TV sets. Teletext services in the USA like Electra could be received with one of these sets, but these were mostly more expensive higher-end sets offered by Zenith, posibly causing Electra (and American teletext in general) to never catch on with the public. Another reason for the demise of American teletext was when Zenith introduced built-in Closed Captioning decoders in TVs in the early 90s, as mandated by the FCC . Apparently, it was not practical for Zenith to re-design their TV chassis models that previously had teletext decoder support to have both teletext and closed captioning support. So Zenith decided to drop the teletext features, therefore ending teletext service in the US in the early 1990s, considering Zenith was the only major manufacturer of teletext-equipped sets in America.

Australian company Dick Smith Electronics (DSE) also offered through their USA distributors a set-top WST teletext decoder kit. The kit used as its core the same teletext Decoding Module (manufactured by UK electronics company Mullard ) installed in most British TV sets, with additional circuitry to adapt it for American NTSC video, and to utilize it in a separate set-top box.

Germany

The German TV channels ARD and ZDF began broadcasting a teletext service on 1 June 1980. The German teletext service was initially called Videotext, to avoid confusion with the "Teletex" electronic messaging service offered at the time by German telecom.

A closely related service is the Video Program System (VPS), which was introduced in Germany in 1985. Like teletext, this signal is also broadcast in the vertical blank interval. It consists only of 32 bits of data, primarily the date and time for which the broadcast of the currently running TV programme was originally scheduled. Video recorders can use this information (instead of a simple timer) in order to automatically record a scheduled programme, even if the broadcast time changes after the user programmes the VCR. VPS also provides a PAUSE code; broadcasters can use it to mark interruptions and pause the recorders, however advertisement-financed broadcasters tend not to use it during their ad breaks.

HISTORY—1990S

North America

The NABTS protocol received a revival of sorts in the late 90s, when it was used for the Datacasting features of WebTV For Windows under Windows 98 , and for Intel 's now-defunct InterCast service (also for Windows as well), using a proper TV Card (such as the ATI All-In-Wonder or Hauppauge 's Win-TV).

InterCast was a modern teletext-like system created by Intel in 1996 , using a TV card installed in a desktop PC running Windows with the InterCast Viewer software. The software would receive data representing HTML pages via the VBI (Vertical Blanking Interval) of a television channel's video, while displaying in a window in the InterCast software the TV channel itself. The HTML data received would then be displayed in another window in the Intercast software. It usually was extra supplemental information relevant to the TV program being viewed, such as extra clues for the viewer during a murder mystery show, or extra news headlines or extended weather forecasts during a newscast.

NBC , as well as The Weather Channel , CNN and M2 (now MTV2), utilized InterCast technology to complement their programming. InterCast, however, fell into disuse, and Intel discontinued support of InterCast a few years later.

Another service in the USA similar in delivery and content to teletext was the WaveTop service, provided and operated by the Wavephore Corporation. It used the same types of InterCast-compatible TV tuner cards, and used an application that ran under Windows, like InterCast. In fact, WaveTop software was also bundled with TV cards that had InterCast software bundled with them as well.

However, Wavetop was an independent service from InterCast, and wasn't a complementary service to a television program or channel like the latter. In fact, TV viewing with a TV card was not possible while the WaveTop software was running, since the software utilized the TV card as a full-time data receiver.

WaveTop provided content from several different providers in the form of HTML pages displayed in the WaveTop software, such as news articles from the New York Times , weather information provided by The Weather Channel , and sports from ESPN . It also delivered short video clips, usually commercials, that could be viewed in the software as well.

When it was in operation, WaveTop's data was delivered on the VBI of local public TV stations affiliated with the PBS network through their PBS National Datacast {Link without Title} division, that the TV card & WaveTop software tuned into to receive the service.

Yet another service in the USA which relied on data delivery via the VBI like teletext, was the Guide+ ( Guide Plus , also referred to as GuidePlus+ as well) service provided and developed by Gemstar . There were several models of television sets made throughout the 90s by Thomson Consumer Electronics under the RCA and General Electric brands that had built-in Guide+ decoders. Guide+ was an on-screen interactive program guide that provided current TV schedule listings, as well as other information like news headlines. Some Guide+ equipped sets from RCA even had a IR -emitting sensor that could be plugged in to the back of the TV, to control a VCR to record programs which could be selected from the on-screen Guide+ listings. In some ways, this was very similar to the Video Programming By Teletext (VPT) , Video Program System (VPS), and Programme Delivery Control (PDC) features of British/European teletext.

Guide+ was a free service, supported by advertisements displayed on-screen in the Guide+ menu and listing screens, not unlike Banner Ads displayed on web pages. Guide+ was delivered over the VBI of select local American TV stations.

Guide+ was discontinued by Gemstar in June 2004, and soon afterwards, Thomson dropped the Guide+ features from all RCA and GE television sets made afterward.

However, Guide+ in America has now been replaced by Gemstar with a similar service (delivered in the same fashion via VBI like Guide+), called ''s, and PVR s (Personal Video Recorders) are now being released with ''TV Guide On Screen'' capabilities. The Guide+ name & service is still used in Europe by Gemstar. (The same service is known in Japan as G-Guide).

Similar to Guide+ in America, was , due to a lack of subscribers to the service. Star Sight's data was also delivered on the VBI of local PBS stations through the PBS National Datacast division, much like how WaveTop was delivered as mentioned previously in this article.

Nowadays, teletext or other similar technologies in the USA are practically non-existent, with the only technologies resembling such existing in the country being Closed Captioning , and XDS (eXtended Data Services).

Europe

The German Videotext service introduced by ARD and ZDF remains highly popular, and compatible teletext services are offered today by practically all Germany-language TV stations. The originally joint ARD and ZDF Videotext service was split into two individual services in 2000.

European teletext replaced the Antiope system in France at the beginning of the 1990s .

In 1993 ORACLE in the United Kingdom was replaced as content provider by Teletext Ltd, now owned by Daily Mail And General Trust and Media Ventures International . Branding themselves simply as "Teletext", they operate on ITV , Channel 4 and, more recently, Five .

Increasingly, the Internet is replacing teletext as a source of information on TV programmes, weather, news and travel. However, many broadcasters are now supplying their teletext feeds with content created for their websites, and put their complete set of teletext pages on the web— See Below .

DESCRIPTION

In the case of the Ceefax and Oracle systems and their successors in the UK, the teletext signal is transmitted as part of the ordinary analogue TV signal but concealed from view at the end of lines that are not visible on the screen. The teletext signal is digitally coded as 45-byte packets at the end of lines 6–22 and 318–335. The resulting data rate is about 600 Bit/s .

A teletext page comprises one or more ''frames'', each containing a screen-full of text. The pages are sent out one after the other in a continual loop. When the user requests a particular page the decoder simply waits for it to be sent, and then captures it for display. In order to keep the delays reasonably short, services typically only transmit a few hundred frames in total. Even with this limited number, waits can be up to 30 seconds.
Modern television sets however have a built-in memory, often for a few thousand different pages. This way, the teletext decoder captures every page sent out and stores it in memory, so when a page is requested by the user it can be loaded directly from memory instead of having to wait for the page to be transmitted. When the page is transmitted again, the television checks if the page in memory is still up-to-date and updates it if necessary.

The text can be displayed instead of the television image (but usually with the sound), or superimposed on it (a mode commonly called ''mix''). Some pages, such as subtitles ( Closed Captioning ) are ''in-vision'', meaning that text is displayed in a block on the screen covering part of the television image.

The original standard provides a monospaced 40×24 character grid. The standard was improved in 1976 to allow for improved appearance and the ability to individually select the color of each character from a palette of 8. The proposed higher resolution Level 2 ( 1981 ) was not adopted in Britain (although in-vision services from Ceefax & ORACLE did use it at various times, though this use ceased by the BBC in 1996), although transmission rates were doubled from two to four lines a frame in 1981 . Britain also rejected Level 2.5 HiText .

Although it used the same page encoding and display methods, Prestel was quite a different system, using a modem and the phone system to transmit and receive the data. The modem was asymmetric, with data sent at 75 bit/s, and received 1200 bit/s. This two-way nature allowed pages to be served on request, in contrast to the TV-based systems' sequential rolling method. It also meant that a limited number of extra services were available such as booking event or train tickets and a limited amount of online banking. Prestel was in some ways similar to the French Minitel system.
Telkom in South Africa developed a similar system called Beltel - this was used by South African Banks to provide Home Banking .

"INTERACTIVE TELETEXT"

Some TV channels offer a service called interactive teletext to remedy some of the short-comings of standard teletext. To use interactive teletext, the user calls a special Telephone number with a regular telephone.
A computer then instructs the user to go to a certain teletext page which has been assigned to the customer for that session. Usually the page initially contains a menu with options and the user chooses among the options using the buttons on the telephone. When a choice has been made, the selected page is immediately broadcast and can be viewed by the user. This is in contrast with usual teletext where the customer has to wait for the selected page to be broadcast, because the pages are broadcast sequentially. This technology enables teletext to be used for games, Chat , access to databases etc. It allows one to overcome the limitations on the number of available pages. On the other hand, only a limited number of users can use the service at the same time, since one page is allocated per user. Some channels solve this by taking into account where the user is geographically calling from and by broadcasting different teletext pages in different geographical regions. In that way, two different users can be assigned the same page number at the same time as long as they don't receive the TV-signals from the same source. Another drawback to the technology is the privacy concerns in that many users can see what a user is doing because the interactive pages are received by all viewers. Also, the user usually has to pay for the telephone call to the TV-station. For these reasons, this type of service is gaining less and less popularity as more users turn to the Internet instead.

OTHER TELETEXT-RELATED SERVICES

Various other kinds of information are sent over the Teletext protocol. For instance, Programme Delivery Control signals—used by video recorders for starting/stopping recording at the correct time even during changes in programming—are sent as teletext packets. A similar, but different, standard Video Programming System is also used for this purpose.

Teletext pages may contain special packages allowing VCR's to interpret their contents. This is used in relation to the Video Programming By Teletext (also known as startext) system which allows users to program their videos for recording by simply selecting the program on a teletext page with a listing of programs.

Other standards define how special teletext packets may contain information about the name of the channel and the program currently being shown.

LEVEL 2.5 TELETEXT

Because teletext looks a bit outdated with its 80s-style graphics, a new standard found its way to the European market around . With Level 2.5 it's possible to set a background colour and have higher resolution text and images. However, very few television stations transmit their teletext in this new standard. One of the problems with Level 2.5 is that it often takes several transmission cycles before the higher resolution items show on the screen. In order to watch Level 2.5 teletext, a rather recent television set with a special decoder chip is required.

Television stations which are known to transmit teletext in Level 2.5 include the Dutch Public Television (background colour on all pages, and a test page with hi-res graphics) and the German ZDF (completely backwards-compatible Level 2.5 teletext, with higher quality text and graphics on nearly all pages).

DIGITAL TELETEXT

Digital television introduced "digital teletext" which, despite the previous teletext standard's digital nature, has entirely different standards, such as MHEG-5 and Multimedia Home Platform . Despite the age of the technology, VBI teletext (with its now quaint looking 1970s -style computer graphics) remains very popular; although the service may stop upon the cessation of European analogue TV broadcasting, sometime before 2012 . Some digital television platforms such as Sky Digital in the UK and Ireland incorporate separate teletext streams (used by the BBC from 1998 to 2004 , and still used by Irish broadcaster RTÉ ), which are provided to the television set in the normal analogue TV manner. Such emulation of analogue teletext on digital TV platforms may ensure its continued use for some time (particularly as there are no plans for an immediate transition to digital terrestrial transmission in some countries, such as the Republic Of Ireland ). This emulation is only possible due to the DVB-TXT and DVB-VBI sub-standards of DVB , which allow a set-top box or integrated DVB TV to emulate the VBI data in which teletext is carried. However, most DVB-T receivers do not support this.

ELECTRONIC PROGRAMME GUIDES BASED ON TELETEXT

Standard Electronic Programme Guide s, like NexTView , are based on teletext, using a compact Binary format instead of preformatted text pages.

SEE ALSO