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{{Short description|Japanese teletext standard}}
[[File:JTES example.png|thumb|Example of Japanese JTES teletext]]
'''JTES''', the '''Japanese Teletext Specification''', is a protocol used for encoding [[teletext]] pages, as well as other types of digital data, within the [[vertical blanking interval]] (VBI) of an analog video signal in Japan. It was adopted into the international standard [[ITU-R|CCIR]] 653 (now [[ITU-R]] BT.653) of 1986 as '''CCIR Teletext System D'''.<ref name="auto">{{Cite book |url=https://www.itu.int/dms_pubrec/itu-r/rec/bt/R-REC-BT.653-3-199802-I!!PDF-E.pdf |title=Recommendation ITU-R BT.653-3 (02/1998) Teletext systems |publisher=ITU |year=2011}}</ref><ref>{{Cite web |date=October 10, 2006 |title=EIA516 NABTS MODULE - NABTS DATA BROADCAST SOFTWARE FOR NORPAK ENCODER PLATFORMS |url=http://www.norpak.ca/Nabts.htm |url-status=dead |archive-url=https://web.archive.org/web/20061010042356/http://www.norpak.ca/Nabts.htm |archive-date=10 October 2006 |website=Norpak Corporation}}</ref>
It supports the display of [[Kanji]], [[Katakana]] and [[Hiragana]] characters. The service can be used to display subtitles, cyclic text pages or pseudo interactive programs. There's support for presentation of photographs, geometry or sound.<ref name="auto"/><ref name="nii">{{Cite web |title=DBNSTJ : Teletext for Japan |url=https://dbnst.nii.ac.jp/english/detail/1107 |archive-url=https://web.archive.org/web/20211202093835/https://dbnst.nii.ac.jp/english/detail/1107 |archive-date=2 December 2021 |access-date=24 January 2023 |website=Database on Noteworthy Contributions for Science and Technology (Japan)}}</ref>
==History==
The development of teletext in Japan started in 1972,<ref name="jst">{{Cite news |year=2011 |title=テレビ文字多重放送の研究開発を振り返って |language=ja |volume=65 |pages=907–911 |work=映像情報メディア学会誌 |issue=7 |url=https://www.jstage.jst.go.jp/article/itej/65/7/65_907/_pdf/-char/ja}}</ref> followed by the announcement of the world's first teletext system ([[Ceefax]]) by the [[BBC]] in the United Kingdom.
Because [[Japanese characters]] are different from the [[Western culture|western]] [[alphabets]], Japan proceeded with research and development of a specific transmissions method. Called ''"pattern method"'',<ref name="google">{{Cite book |last1=Bens |first1=E. de |url=https://books.google.com/books?id=APrrCAAAQBAJ&dq=teletext+on+NHK&pg=PA519 |title=Electronic Mass Media in Europe. Prospects and Developments: A Report from the FAST Programme of the Commission of the European Communities |last2=Knoche |first2=Manfred |date=December 6, 2012 |publisher=Springer Science & Business Media |isbn=9789400939493 |pages=519 |via=Google Books}}</ref> it sends scanning signals similar to a [[fax]], at a rate 20 times faster than existing methods, but required a [[character generator]] with a large (at the time) 1-[[megabit]] [[ROM]]. This method was adopted in 1982.
The first receiver prototype was capable of displaying 1258 characters, and a 48-[[kilobyte]] character generation ROM, integrated into a single chip. During the 1970s the problem of [[error correction]] (causing wrong characters to be displayed) was studied. These problems were solved in the early 1980s, allowing the service to start.<ref name="jst"/>
An alternative method of transmission, called ''"hybrid method"'' was developed by NHK in 1979. It allowed faster transmissions rated, and was adopted as a standard in October 1985.<ref name="google"/>
Experimental broadcasts started on October 3, 1983, by [[NHK]] in [[Tokyo]] and [[Osaka]] using the ''"pattern method"''.<ref name="nii"/><ref name="google"/><ref>{{Cite journal |last=Takashiro |first=Akiyama |date=3 December 1984 |title=Teletext and TV Programs for the Deaf and Hard of Hearing in Japan |url=https://eric.ed.gov/?id=ED263897 |journal=Studies of Broadcasting |issue=20 |pages=17–38}}</ref> This included subtitles and other so called "supplementary" or "independent programs", where information unrelated to the TV program being show is displayed.<ref name="web-japan">{{Cite web |date=October 19, 1995 |title=Teletext Back in the Limelight {{pipe}} Society and Culture {{pipe}} Trends in Japan |url=https://web-japan.org/trends95/45.html |website=Web Japan}}</ref> For example, at the time of the [[Great Hanshin Earthquake]], information about vital services and victim names was broadcast for days.<ref name="web-japan"/> To accompany the introduction of the system, [[Sony]] released the "TXT-10" decoder with a cost of 119,000 yen, and [[Sharp Corporation|Sharp]] released "21C-L1", a TV with a built in decoder.
In 1984 [[Nippon TV]] (NTV) experimented teletext between March and July.
Regular transmissions started on November 29, 1985 (covering the entire country by 1986) by [[NHK]] (''"Telemo Japan"'' service) and NTV (''"AXES4"'' service), using the ''"hybrid method".''<ref>{{Cite web |title=歴史 {{pipe}} NHK放送文化研究所 |url=https://www-nhk-or-jp.translate.goog/bunken/about/history.html?_x_tr_sch=http&_x_tr_sl=ja&_x_tr_tl=en&_x_tr_hl=pt-PT&_x_tr_pto=wapp |website=NHK (Japan Broadcasting Corporation)}}</ref><ref>{{Cite web|url=http://www.nhk.or.jp/saga/|title=NHK佐賀放送局|website=Nhk.or.jp}}</ref> NHK broadcast 759 hours of teletext per week during 1985, with eight different programs such as news, weather, public announcements and subtitles.<ref name="google" />
In 1986, [[TV Asahi]] started broadcasts with a service named ''"TV Asahi Data Vision"'', that remained active up to 24 July 2011.
Other channels, such as [[Tokyo Broadcasting System]] ([[TBS Television (Japan)|TBS]]) with ''"Tokyo Data Vision"'' or [[TV Tokyo]] with ''"Nikkei Telepress"'', along with  [[Fuji TV]] and [[Tokyo MX|Tokyo Metropolitan Television]] also had teletext services.
As of 1995, 20 television models with built-in teletext receivers were available in the Japanese market.
==Description==
In a normal [[NTSC]] video signal there are 525 [[Scan line|scan lines]] of video signal. These are split into two half-images, known as "[[Field (video)|fields]]", sent every 60th of a second. These images merge on-screen, and in-eye, to form a single frame of video updated every 30th of a second. Each line of each field takes 63.5 μs to send; 50.3 μs of video and 13.2 μs amount of "dead time" on each end used to signal the television that the line is complete, known as the [[horizontal blanking interval]] (HBI). When the scanning process reaches the end of the screen it returns to the top during the [[vertical blanking interval]] (VBI), which, like the HBI requires some "dead time" to properly frame the signal on the screen. In this case, the dead time is represented by unused lines of the picture signal, normally the top 22 lines of the frame.
At the beginning of the service, JTES used four of these lines to transmit information, with 176 [[Bit|bits]] of data transmitted per scanning line.
JTES encodes data into the video signal as a series of dots at a fixed rate of 5.727272&nbsp;Mbit/s. Each line of a field has 50.3 μs of video area that can be used for transmission, which results in 296 bits per line.<ref name="auto"/>
It's possible to change the [[Character encoding|character code set]] ([[JIS C 6226]] Japanese Industrial Standard, containing 6879 graphic characters suitable for writing text, place names, personal names, etc. in the Japanese language, defined in 1978), in order to express appropriate characters or enhance transmission efficiency. If a character is not available in the teletext receiver character generator, it can be created  using ''"DRCS"'' (Dynamically Redefinable Character Sets).<ref name="nii"/><ref name="nii2">{{cite web|url=https://dbnst.nii.ac.jp/upload/images/research/1107/english/cc002c79a7da0dd4ea4a160eb5366a13/fig2030std-pro_en.png|format=PNG|title=(a) Character code set|website=Ddnst.nii.ac.jp|access-date=12 February 2022}}</ref>
Characters can be transmitted as a mosaic of [[semigraphic]] elements, with each element having a resolution of {{Resx|8|12}} pixels.<ref name="nii2"/><ref>{{cite web|url=https://dbnst.nii.ac.jp/upload/images/research/1107/english/8d883c86bf81c5549a9133b89a11b708/fig2032std.png|format=PNG|title=Characters|website=Ddnst.nii.ac.jp|access-date=12 February 2022}}</ref>
There was support for sound generation using the [[YM2413]] sound chip.<ref>{{cite web |title=Note table |url=https://dbnst.nii.ac.jp/upload/images/research/1107/english/2c2e25717e53eb94877cccaf5dcab112/fig2033std.png |access-date=12 February 2022 |website=Ddnst.nii.ac.jp |format=PNG}}</ref> Yet sound and images could be transmitted using [[PCM]], using an error correction system called ''"BEST"''.<ref>{{cite web|url=https://dbnst.nii.ac.jp/upload/images/research/1107/english/247da090eb828d56c37b139e07e5b626/fig2029std-pro_en.png|format=PNG|title=Signal arrangement of error-correction system|website=Ddnst.nii.ac.jp|access-date=12 February 2022}}</ref>
Several information codings are possible:<ref>{{cite web|url=https://dbnst.nii.ac.jp/upload/images/research/1107/english/09166c9cff705e9b614d600238a83df2/fig2031std-pro_en.png|format=PNG|title=Coding table|website=Ddnst.nii.ac.jp|access-date=12 February 2022}}</ref>
*Mosaic - a mosaic of semigraphic blocks, similar to how graphics are composed on other teletext systems
*DRCS - allows characters not available on the character generator
*Single layer photographic - transmits image data (pixels, limited number of colors) instead of blocks, significantly slower
*Multi layer photographic - transmits images or animations with a large number of colors, much slower
*Geometric - generates images from lines, arcs, rectangles and polygons. Similar to [[NABTS]] teletext.
==List of Japanese Teletext Services==
*''[[Telemo Japan]]'' ([[NHK]])
*''[[TV Asahi Data Vision]]'' ([[TV Asahi]]) (7 April 1986 – 24 July 2011)
*''[[AXES4]]'' ([[Nippon TV]]) (1985 – 31 March 2007)
*''[[Tokyo Data Vision]]'' ([[Tokyo Broadcasting System|TBS]])
*[[Fuji TV]]
*[[Tokyo Metropolitan Television]]
*''[[Nikkei Telepress]]'' ([[TV Tokyo]])
==See also==
* [[Antiope (teletext)|Antiope]] - French teletext standard (CCIR Teletext System A)
* [[NABTS]] – North American Broadcast Teletext Specification (CCIR Teletext System C)
* [[Captain (videotex)|CAPTAIN]] - Japanese videotex system created by NTT
* [[NAPLPS]] – North American Presentation Level Protocol Syntax
* [[Videotex character set]]
* [[Text semigraphics]]
== References ==
{{reflist}}
{{Teletext}}
[[Category:Television technology]]
[[Category:Teletext]]