1seg
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1seg (ワンセグ wansegu?) is a mobile terrestrial digital audio/video and data broadcasting service in Japan. Service began experimentally during 2005 and commercially on April 1, 2006. The first mobile phone handsets for 1seg were sold by KDDI to consumers in autumn 2005.
ISDB-T, the terrestrial digital broadcast system used in Japan, is designed so that each channel is divided into 13 segments, with a further segment separating it from the next channel. A HDTV broadcast signal occupies 12 segments, leaving the remaining (13th) segment for mobile receivers. Thus the name, "1seg" or "One Seg".
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[edit] Technical information
ISDB-T uses UHF470MHz-770MHz, bandwidth 300 MHz. 50 channels, namely ch.13-62, are allocated. Each channel has a 6 MHz bandwidth (actually 5.57 MHz effective bandwidth and 430 kHz guard band between channels). Each channel is further divided into 13 segments, with each segment having 428 kHz bandwidth. 1seg uses a single segment. See ISDB#ISDB-T also.
1seg broadcasting uses H.264/MPEG-4 AVC video and HE-AAC audio encapsulated in a MPEG-2 Transport Stream. 1seg, like ISDB-T also uses QPSK for modulation, 2/3 FEC and 1/4 guard ratio. The total bit-rate is 416 kbit/s. The maximum video resolution avail.able is 320x240 pixels, with a video bitrate of 220-320 kbit/s. Audio conforms to HE-AAC profile, with a bitrate of 48-64 kbit/s. Additional data (EPG, interactive services, etc) is broadcast using BML and occupies the remaining 10-100 kbit/s.
Conditional access and copy control are not implemented in 1seg broadcasting. However, receiver device manufacturers may limit any recording function. For example, the W33SA receiver only allows recording 1seg broadcasts to its internal memory and disallows copying or moving recording to an external miniSD card.
[edit] 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, EPG (program guides), "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.
[edit] Criticism
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Mobile reception is difficult, especially in a moving vehicle/train, as the signal quality deteriorates quickly even at speeds around 20 km/h (12 mph).
This leaves the majority of the target audience for this service unable to receive it. In-car or vehicles reception requires use of diversity antenna and increases the receiver's complexity and price.
There is minimal to no reception in trains that are underground or go inside buildings, such as most of the commuter trains in Tokyo and other cities.[1]
In addition, long distance trains, especially the shinkansen, can move between broadcast service areas in a matter of half an hour. Each broadcast region uses different frequencies for a particular channel, requiring the viewer to regularly re-scan or pick from a table of stored frequencies to find whatever local channel may be broadcasting the program in question.
1seg is a part of UHF band of approx. 429 MHz bandwidths and inherently susceptible by various atmospheric conditions as with UHF.
Handheld 1seg receivers work well inside homes, although it may be necessary to be near a window and/or adjust the antenna for reception. 1seg was however developed as a mobile technology, and the relevance of watching it at home is reduced since the majority of viewers could watch the program on a larger high-definition screen TV instead.
Japanese regulation enforces that the programs on 1seg are fundamentally the same as those broadcast on the equivalent HDTV channel.
Even though 1seg signals are not encrypted, some receiver manufacturers have chosen to apply DRM to recorded files, preventing users from viewing or editing the recording in third party software.[2]
[edit] Popularity
On 2008-01-16, JEITA learned that the result of their monthly shipping out quantity survey showed 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. [3]
As of December 2007, approximately 13,905,000 mobile phones, 38.4% of the total number of phones sold, were capable of receiving 1seg transmissions.[4]
[edit] Receivers
- (Japanese) NTT DoCoMo P901iTV by Panasonic
- (Japanese) KDDI/Sanyo W33SA
- (Japanese) KDDI/Sanyo W33SAⅡ
- (Japanese) KDDI/Hitachi W41H
- (Japanese) Nintendo DS (via an add-on called "DS Telebi")
- (Japanese) Pixela PC
- (Japanese) Sanyo One-seg & car navigation system
- (English) Vodafone 905SH by SHARP
- (Japanese) Monster TV 1D PC card Type II 1seg receiver by SKNET
- (Japanese) Sharp Papyrus PW-TC900
- (Japanese) Sharp Papyrus PW-TC920
- (Japanese) 1seg PSP-2000 Tuner
- (Korean) Cowon D2TV
- (Japanese) Sony NW-A919
- (Japanese) Kodak [1]
[edit] See also
- Digital terrestrial television
- DMB - Europe
- DVB-H
- ISDB-T
- SBTVD - Brazil
[edit] References
- ^ http://www.wired.com/gadgets/wireless/news/2008/06/japan_phones
- ^ (Japanese) http://www.nowhow.net/1seg/010/ent71.html
- ^ Source; the article of Yomiuri Shimbun 2008-01-16, area version 13S page 8, and(Japanse 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（%）)
- ^ 2007年度移動電話国内出荷実績
[edit] External links
- What is “One Seg” ?, PDF File, Sasaki Laboratory, Keio University.
- TV programs go mobile as One Seg services begin, The Japan Times
- ISDB-T / One-Seg Receivers, PDF file,The Digital Broadcasting Experts Group (DiBEG)
- Digital Broadcasting Experts Group (DiBEG) promote ISDB-T
- ISDB-T, Application, Present and Future, PDF File
- [2] NTT DoCoMo web site
- [3] KDDI web site
- [4] SoftBank web site
- Advanced Silicon tuners for the digital TV era, RfStream Corporation
- (Japanese) Association for promotion of Digital Broadcasting (Japanese)
- (Japanese) 1seg promotion site (Japanese)
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