View source for 1seg

{{Short description|Multimedia broadcasting service for mobile}}
{{More citations needed|date=March 2023}}
{{Infobox company
|name = 1seg
|type = [[Privately held company|Incentive]]
|foundation = 2005<br>[[Japan]]
|location = [[Japan]]
|logo = 1seg logo.svg
|logo_caption = 1seg logo in Japan
}}
{{Table Digital video broadcast standards}}
{{nihongo|'''1seg'''|ワンセグ|wansegu}} is a mobile terrestrial digital audio/video and data broadcasting service in [[Japan]], [[Argentina]], [[Brazil]], [[Chile]], [[Uruguay]], [[Paraguay]], [[Peru]] and the [[Philippines]]. Service began experimentally during 2005 and commercially on April 1, 2006. It is designed as a component of [[ISDB#ISDB-T|ISDB-T]], the terrestrial digital broadcast system used in those countries, as each channel is divided into 13 segments, with a further segment separating it from the next channel; an [[High-definition television|HDTV]] broadcast signal occupies 12 segments, leaving the remaining (13th) '''seg'''ment for mobile receivers, hence the name, "1seg" or "One Seg".

Its use in Brazil was established in late 2007 (starting in just a few cities), with a slight difference from the Japanese counterpart: it is broadcast under a 30 [[Frame rate|fps]] transmission setting (Japanese broadcasts are under the 15 fps transmission setting).

== Technical information ==
{{Unreferenced section|date=September 2017}}
{{main|ISDB}}
[[Image:ISDB-T CH Seg Prog allocation.svg|left|350px|The ISDB-T channel allocation scheme.]]
The [[ISDB]]-T system uses the [[Ultra high frequency|UHF]] band at frequencies between 470 and 770&nbsp;MHz (806&nbsp;MHz in Brazil), giving a total bandwidth 300&nbsp;MHz. The bandwidth is divided into fifty name channels 13 through 62. Each channel is 6&nbsp;MHz wide consisting of a 5.57&nbsp;MHz wide signalling band and a 430&nbsp;kHz guard band to limit cross channel interference. Each of these channels is further divided into 13 segments, each with 428&nbsp;kHz of bandwidth. 1 seg uses a single of these segments to carry the 1seg transport stream.

1seg, like ISDB-T uses [[Phase-shift keying#Quadrature phase-shift keying .28QPSK.29|QPSK]] for [[modulation]], with 2/3 [[Error correction code|forward error correction]] and 1/4 guard ratio. The total datarate is 416&nbsp;kbit/s.

The television system uses an [[Advanced Video Coding|H.264/MPEG-4 AVC]] video stream and an [[High-Efficiency Advanced Audio Coding|HE-AAC]] audio stream multiplexed into an [[MPEG transport stream]]. The maximum video resolution is 320x240 pixels, with a video bitrate of between 220 and 320&nbsp;kbit/s. Audio conforms to [[High-Efficiency Advanced Audio Coding|HE-AAC]] profile, with a bitrate of 48 to 64&nbsp;kbit/s. Additional data ([[Electronic program guide|EPG]], interactive services, etc.) is transmitted using [[Broadcast Markup Language|BML]] and occupies the remaining 10 to 100&nbsp;kbit/s of bandwidth.

Conditional access and copy control are implemented in 1seg broadcasting by the use of [[Broadcast flag|Broadcast Flag]]-like structure contained in the "Copy Control Descriptor" within the broadcast. The broadcast contents themselves are not encrypted, but  the Copy Control information forces the device to encrypt stored recordings and disallows making a copy of the recording.

== Broadcast Markup Language ==
[[Broadcast Markup Language]] (BML), is a data-transmission service allowing text to be displayed on a 1seg TV screen.

The text contains news, sports, weather forecasts, emergency warnings such as [[Earthquake Early Warning (Japan)|Earthquake Early Warning]], etc. free of charge. Further information can be found through links to content on websites, frequently those belonging to the television station itself.

[[Electronic program guide|EPG]] (program guides) is not included, but transmitted in separate stream (EIT).

== Multiple-program arrangement ==
On June 23, 2008, broadcaster [[Tokyo MX]] officially began using {{nihongo|''multiple-program arrangement''|マルチ編成|Maruchi hensei}} technology to simultaneously broadcast two programs on a single divided segment. Most 1seg receivers manufactured after September 2008 are compatible with this technology. Multiple-program arrangement in 1seg is named as {{nihongo|'''1seg2''' or '''Oneseg2'''|[[:ja:ワンセグ2|ワンセグ2]]|Wansegu tsū}}.

[[NHK Educational TV]] (from 1 April 2009) and {{nihongo|Nara Television|[[:ja:奈良テレビ放送|奈良テレビ放送]]|Nara terebi hōsō}} (from 1 December 2009) are also started for several number of programs.

== Popularity ==
Until the end of March 2008, Japanese regulation required that the programs on 1seg were fundamentally the same as those broadcast on the equivalent HDTV channel. On April 1 the regulation was revised, and experimental programs by 1seg or third parties have begun airing on several stations.

On January 16, 2008, [[Japan Electronics and Information Technology Industries Association|JEITA]] released their monthly shipping survey showing approx. 4.806 million [[mobile phone]]s were sold in [[Japan]] in November 2007. Of these, approx. 3.054 million phones, 63.5% of the total, can receive 1seg broadcasts.<!-- receivable capability as first record where as 34.3% of 2.286 million sets in October 2007 shipment. --><ref>Source; the [[Article (publishing)|article]] of [[Yomiuri Shimbun]] 2008-01-16, area version 13S page 8, and [http://www.jeita.or.jp/japanese/stat/cellular/2007/index.htm (Japanese language);2007 fiscal year monthly base shipment quantity] (2007年度移動電話国内出荷実績、ワンセグ搭載比率（%）)</ref>

In the fiscal year of 2007, on average 45% of mobile phones had 1seg reception capability out of the 22.284 million units sold. The percent increased from 26.8% in April 2007 to 64.2% at end of fiscal year March 2008.<ref>[http://www.jeita.or.jp/japanese/stat/cellular/2007/index.htm 2007年度移動電話国内出荷実績]; (2007 fiscal year mobile phone ship out record) (In Japanese)</ref>

== Receivers ==
[[Image:One_seg_reception_201209.jpg|right|thumb|250px|1seg TV reception image of [[weather forecasting]] on a touchscreen [[smartphone]], [[NTT DoCoMo]]'s [[NEC]] MEDIAS {{ill|N-04C|ja}}.]]
[[File:Nintendo DS with DSTV.jpg|thumb|[[Nintendo DS]] with "DS Terebi" 1seg tuner.]]
[[File:PSP Japan 1SEG.JPG|thumb|[[Sony]] [[PlayStation Portable|PSP Slim]] with 1seg tuner.]]
[[File:Pioneer AVIC-BZ500.jpg|thumb|Pioneer AVIC BZ500 with a large touchscreen, DVD, 1seg, and GPS]]
; [[Electronic dictionary]]
: {{in lang|ja}} Sharp Papyrus PW-TC900
: {{in lang|ja}} Sharp Papyrus PW-TC920
: {{in lang|ja}} Sharp Papyrus PW-TC930
: {{in lang|ja}} Sharp Papyrus PW-TC980
; PC connect type
: {{in lang|ja}} [[Pixela Corporation|Pixela]] PC
: {{in lang|ja}} Monster TV 1D [[PC Card|PC card]] Type II 1seg receiver by SKNET
: {{in lang|ja}} [[Cowon]] D2TV
: and more.
; [[Automotive navigation system|Car navigation system]]
: {{in lang|ja}} Sanyo One-seg & car navigation system
: {{in lang|ja}} [https://jpn.pioneer/ja/support/manual/manual_pdf.php?m_id=14290 Pioneer AVIC BZ500]
: and more.
; [[Handheld game console]]
: {{in lang|ja}} [https://web.archive.org/web/20070808004341/http://pspupdates.qj.net/-UPDATE-Sony-united-colors-of-the-PSP-2000-and-the-new-TV-tuner/pg/49/aid/97801 1seg PSP-2000 Tuner]
: {{in lang|ja}} [[Nintendo DS]] (via an add-on called "DS Terebi")
; [[Mobile device|Portable devices]]
; [[Set-top box|Set top box]]
; Others
: {{in lang|ja}} [[Sony]] [[Walkman]] NW-A919
: {{in lang|ja}} [[Kodak]] 3-inch OLED TV
: and more.
; [[Mobile phone]]s
: The first mobile phone to support 1seg was the [[Sanyo]] {{ill|W33SA|ja}} which was released by [[Au (mobile phone company)|au by KDDI]] to consumers in autumn 2005. Until around 2021, the vast majority of [[Japanese mobile phone culture|{{Transliteration|ja|italic=no|garakei}}]] and carrier-branded [[Android (operating system)|Android]] phones sold in Japan featured support for 1seg. While [[iOS]] users have always required to purchase a third-party 1seg antenna separately in order to access 1seg, the rise of [[5G]] [[5G NR|NR]] and unlimited data plans means that 1seg support is gradually becoming less important, hence it is increasingly omitted on newer Japanese iOS and Android mobile devices.

== See also ==
* [[Digital terrestrial television]]
* [[Digital Multimedia Broadcasting|DMB]] - South Korea
* [[DVB-H]]
* [[ISDB-T]]
** [[ISDB-T International]]

== References ==
<references/>

== External links ==
{{Commons category}}
<!-- Hide dead link * [http://www.sasase.ics.keio.ac.jp/jugyo/2006/print/One_segment_broadcasting_p.pdf What is “One Seg” ?], [[PDF]] File, Sasaki Laboratory, [[Keio University]]. -->
* {{cite news | title =TV programs go mobile as One Seg services begin | url =http://search.japantimes.co.jp/cgi-bin/nb20060401a2.html| archive-url =https://web.archive.org/web/20080110010101/http://search.japantimes.co.jp/cgi%2Dbin/nb20060401a2.html| publisher =[[The Japan Times]] | date =2006-04-01 | url-status =dead |archivedate =2008-01-10 }}
* [https://web.archive.org/web/20090225220811/http://www.dibeg.org/seminar/0702seminar_in_indonesia/Indonesia%20seminar%20Presentation%203.pdf ISDB-T, Application, Present and Future], [[PDF]] File
* {{in lang|ja}} [https://web.archive.org/web/20051218102907/http://1seg.jp/ 1seg official site (Japanese)]
* [http://wirelesswatch.jp/2011/02/15/access-ginga-edition-for-1seg-in-brazil/ ACCESS Ginga Edition for 1Seg in Brazil]
* [https://web.archive.org/web/20120204103419/http://nextvlatam.com/index.php/3-mobile-tv/gps-fitted-with-isdb-t-oneseg-sales-grow-in-brazil/ GPS fitted with ISDB-T OneSeg sales grow in Brazil]

{{Video formats}}

[[Category:ISDB|1seg]]
[[Category:Audiovisual introductions in 2006]]
[[Category:2005 establishments in Japan]]
[[Category:Broadcast engineering]]
[[Category:Digital television]]
[[Category:Mobile telephone broadcasting]]
[[Category:Mobile television]]
[[Category:Television transmission standards]]
[[Category:Japanese inventions]]