Wikipedia / 1seg
Wikipedia / 1seg
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-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 HDTV broadcast signal occupies 12 segments, leaving the remaining (13th) segment 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 fps transmission setting (Japanese broadcasts are under the 15 fps transmission setting).
By 2014, approximately 62% of Brazil's population was covered by digital TV signals carrying 1seg, with the government targeting full national coverage by 2016. The standard, adopted regionally as ISDB-Tb, was also implemented in Argentina, Peru, Chile, Ecuador, Venezuela, Bolivia, and Paraguay following Brazil's lead, alongside the Philippines, which adopted the closely related ISDB-T International variant.
Technical information
The ISDB-T system uses the UHF band at frequencies between 470 and 770MHz (806MHz in Brazil), giving a total bandwidth 300MHz. The bandwidth is divided into fifty name channels 13 through 62. Each channel is 6MHz wide consisting of a 5.57MHz wide signalling band and a 430kHz guard band to limit cross channel interference. Each of these channels is further divided into 13 segments, each with 428kHz of bandwidth. 1 seg uses a single of these segments to carry the 1seg transport stream.
1seg, like ISDB-T uses QPSK for modulation, with 2/3 forward error correction and 1/4 guard ratio. The total datarate is 416kbit/s.
The television system uses an H.264/MPEG-4 AVC video stream and an 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 320kbit/s. Audio conforms to HE-AAC profile, with a bitrate of 48 to 64kbit/s. Additional data (EPG, interactive services, etc.) is transmitted using BML and occupies the remaining 10 to 100kbit/s of bandwidth.
Conditional access and copy control are implemented in 1seg broadcasting by the use of 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, etc. free of charge. Further information can be found through links to content on websites, frequently those belonging to the television station itself.
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 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 .
NHK Educational TV (from 1 April 2009) and (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, JEITA released their monthly shipping survey showing approx. 4.806 million mobile phones were sold in Japan in November 2007. Of these, approx. 3.054 million phones, 63.5% of the total, can receive 1seg broadcasts.
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.
Receivers
Sharp Papyrus PW-TC900
Sharp Papyrus PW-TC920
Sharp Papyrus PW-TC930
Sharp Papyrus PW-TC980
PC connect type
Pixela PC
Monster TV 1D PC card Type II 1seg receiver by SKNET
Cowon D2TV
and more.
Sanyo One-seg & car navigation system
Pioneer AVIC BZ500
and more.
1seg PSP-2000 Tuner
Nintendo DS (via an add-on called "DS Terebi")
Others
Kodak 3-inch OLED TV
and more.
The first mobile phone to support 1seg was the Sanyo which was released by au by KDDI to consumers in autumn 2005. Until around 2021, the vast majority of janogarakei and carrier-branded 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 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.
In Brazil, the long-term outlook for 1seg is also shifting: the country began commercial rollout of the ATSC 3.0-based DTV+ standard in 2026, though ISDB-T (and 1seg) is expected to remain in parallel use for the next 10–15 years.
See also
DMB - South Korea
References
External links