Information AboutIsdb |
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Integrated Services Digital Broadcasting ( ISDB ) is the digital television ( DTV ) and digital audio broadcasting ( DAB ) format that Japan has created to allow Radio and Television Station s there to convert to Digital . INTRODUCTION ISDB is maintained by ARIB . The Standards can be obtained for free at the DiBEG website and at ARIB. The core standards of ISDB are ISDB-S (satellite television), ISDB-T (terrestrial), ISDB-C (cable) and 2.6GHz Band Mobile Broadcasting which are all based on MPEG-2 video and audio coding as well as the transport stream described by the MPEG-2 standard, and are capable of high definition television ( HDTV ). ISDB-T and ISDB-Tsb are for mobile reception in TV bands. 1seg is name of an ISDB-T service for repection on Cell Phone , Laptop Computer and Vehicle . The concept was named for its similarity to ISDN , because both allow multiple channels of data to be transmitted together (a process called multiplexing). This is also much like another Digital Radio system, Eureka 147 , which calls each group of stations on a transmitter an Ensemble ; this is very much like the multi-channel digital TV standard DVB-T . ISDB-T operates on unused TV channels, an approach taken by other countries for TV but never before for radio. Video and audio compression ISDB has adopted the MPEG-2 video and audio compression system. ATSC and DVB also adopted the same system. DVB and ISDB also provide for other video compression methods to be used, including JPEG and MPEG-4 , although JPEG is only a required part of the MHEG standard. Transmission The various flavors of ISDB differ mainly in the modulations used, due to the requirements of different frequency bands. The 12 GHz band ISDB-S uses PSK modulation, 2.6 GHz band digital sound broadcasting uses CDM and ISDB-T (in VHF and/or UHF band) uses COFDM with PSK/QAM. Interaction Besides audio and video transmission, ISDB also defines data connections (Data broadcasting) with the internet as a return channel over several media (10Base-T/100Base-T, Telephone line modem, Mobile phone, Wireless LAN (IEEE 802.11) etc.) and with different protocols. This is used, for example, for interactive interfaces like data broadcasting (ARIB STD B-24) and electronic program guides (EPG). Interfaces and Encryption ISDB describes a lot of (network) interfaces, but most importantly the Common Interface for Conditional Access (ARIB STD-B25) with the Common Scrambling Algorithm (Multi-2) required for (de-)scrambling TV. The ISDB CAS system is operated by a company named B-CAS in Japan; the CAS card is called ''B-CAS'' card. The Japanese ISDB signal is always encrypted by the B-CAS system even if it is a free TV program. That is why it is commonly called "Pay per view system without charge". An interface for mobile reception is under consideration. ISDB supports RMP (Rights management and protection). Since all DTV systems carry digital data content, a DVD or HD recorder could easily copy content losslessly, so that a great deal of pirated content could be circulating the market. Hollywood requested copy protection; this was the main reason for RMP. The content has three modes: “Copy once”, “Copy free” and “Copy never”. In “Copy once” mode a program can be stored on a hard disc recorder, but cannot be copied. RECEIVER There are two types of ISDB receiver: TV and STB (Set top box). The aspect ratio of ISDB television is 16:9; televisions fulfilling these specs are called Hi-vision TVs. There are three TV types: CRT (Cathode ray tube), PDP (Plasma display panel) and LCD (Liquid crystal display), with LCD being most popular Hi-Vision format on the Japanese market right now. LCD share as measured by JEITA in November 2004 was about 60%. While PDP set occupies the high end market with units that are over 50 inches (1270 mm), PDP and CRT set shares are about 20% each. CRT set are considered low end for Hi-Vision. STB is sometimes referred to as digital tuner. High-end ISDB STB have several interfaces:
PROBLEMS Though ISDB is a feature-rich system, many problems have surfaced recently. Copy Protection Technology Almost every TV broadcast (including free TV) are encrypted with "Copy-Once", which allows users to record to a digital media (D-VHS, DVD, HDD, etc) but does not allow dubbing to another digital media. On the other hand, the "Copy-Once" technology does not prohibit all types of dubbing. It is possible to dub to an analog media (such as standard VHS) and if recorded to an HDD, it will allow users to "Move" the contents to a D-VHS, but not copy. Many users are also very worried about the recent news of severe protection in the future. There are modes in ISDB to now allow the output of signal from an Analog connector (D-connector, Component, Composite, S-Video, etc). There are already plans to not allow analog output for "Copyright Protection" reasons. (Same as Bluray and HD-DVD) This will make all currently sold STB Tuners, and the majority of LCD/Plasma TVs without HDMI inputs unusuable. Plus all analog VHS, D-VHS that can only record via analog input, and all DVD players will also become unusuable. These "unfair" copy protection technologies will all start after analog broadcasting ends (when there won't be any choice for viewers). Currently, no financial assistance are planned, and viewers without proper devices will be forced to buy a new compatible TV at their own cost. Though not clear, it is said that there are also plans to protect all programs with "Copy-Never". B-CAS Card The B-CAS card is required to decode all broadcasts. These cards are included with every digital TV or Tuner at no charge. To use this card, you must agree to the statement written on the registration card. Despite the fact that the card must be inserted to watch TV, if you don't agree to the statement, then the user cannot watch digital broadcasts. Essentially, users are "forced" to agree with the statement. Though registration is not required, it is recommended to fully enjoy interactive programs. However, many viewers worry about the leaking of personal information, and the power/rights the TV stations have to access personal information for almost every citizen in Japan. SERVICES # One HDTV or up to three SDTV services within one channel. # Provides Data Broadcasting . # Interactive services via Telephone Line or 10Base-T Broadband Internet. # EPG (Electronic Program Guide) # Ability to send firmware patches for the TV/tuner ISDB-S History Japan started digital broadcasting using the DVB-S standard by PerfecTV in October/1996 and DirecTV in December/1997 with communication satellites. Still, the DVB-S did not satisfy the requirements of Japanese broadcasters, among others 2000 . Today, SKY PerfecTV!, successor of Skyport TV, Sky D, CS burn, Platone, EP, DirecTV, J Sky B, and PerfecTV!, adopted ISDB-S system at the east longitude 110 degree wide band communication satellite. Technical specification Summary of ISDB-S (Satellite digital broadcasting)
Channel Frequency and channel specification of Japanese Satellite using ISDB-S
ISDB-T History HDTV was invented at NHK STRL . The research of HDTV started as early as in the 1960s, though only in 1973 a standard was proposed to the ITU-R (CCIR). In the 1980's, the television camera, high definition cathode-ray tube, video tape recorder and editing equipment among others have developed. In 1982 NHK developed MUSE (Multiple sub-nyquist sampling Encoding), the first HDTV video compression and transmission system. MUSE adopted digital video compression system, but for transmission Frequency Modulation had been adopted after a digital-to-analog converter converted the digital signal. In 1987, NHK made demonstration of MUSE in the Washington D.C and NAB. The demonstration made great impression on the U.S. As a result of this, the U.S. developed ATSC , a terrestrial digital DTV system. Europe also developed their own DTV system, DVB . Although the DVB-T service started operating a few weeks later than the ATSC system, it quickly outstripped ATSC in terms of user base. Japan started R&D of a completely digital system in the 1980s that led to ISDB. Japan started terrestrial digital broadcasting using ISDB-T standard by NHK and commercial broadcasting stations on the 1 December , 2003 . Feature ISDB-T is characterized by the following features:
Adoption ISDB-T was adopted in commercial transmissions in Japan in December 2003. It comprises a market of about 100 million television sets. ISDB-T had 10 million subscribers by the end of April 2005. Along with the wide use of ISDB-T, the price of STB is getting low. The price of ISDB-T STB in lower end of the market is ¥19800 that is worth $169 at 19 April 2006. uniden Brazil , which currently uses an Analogue TV System (PAL-M) that slightly differs from any other country's, is considering ISDB-T for its DTV format. Other than that, there are no other countries that are considering ISDB. Possibly because ISDB Tuners and TVs are way too expensive compared to other formats. However. it does seem to have an advantage over ATSC and DVB-T in reception tests. The ABERT/SET group in Brazil did system comparison tests of DTV under the supervision of the CPqD foundation. The comparison tests were done under the direction of a work group of SET (the Brazilian Television Engineering Society) and ABERT (the Brazilian Association of Radio and Television Broadcasters). The ABERT/SET group selected ISDB-T as the best in the digital broadcasting systems among ATSC, DVB-T and ISDB-T. ISDB-T was pointed out as the most flexible of all for better answering the necessities of mobility and portability. It is most efficient for mobile and portable reception. See SBTVD . Technical specification Segment struture ARIB has developed the segment structure called OFDM (see figure). ISDB-T divides the frequency band of one channel into thirteen segments. Broadcaster can select the combination of segments to use: this choice of segment structure allows for flexibility of services. For example, ISDB-T can transmit a LDTV and a HDTV using one TV channel or change to 3 SDTV, a switch that can be performed anytime. ISDB-T can also change the modulation scheme at the same time.
::::::FIGURE Spectrum segment structure of ISDB-T Summary of ISDB-T
Channel Specification of Japanese terrestrial digital broadcasting using ISDB-T
2.6 GHZ MOBILE SATELLITE DIGITAL AUDIO/VIDEO BROADCASTING MobaHo! is the name of the services that uses the Mobile satellite digital audio broadcasting specifications. MobaHo! started its service on 20th October, 2004. ISDB-TSB ISDB-Tsb is the terrestrial digital sound broadcasting specification. The technical specification is the same as ISDB-T. ISDB-Tsb supports the Coded Transmission Of OFDM Siginals . ISDB-C ISDB-C is cable digital broadcasting specification. The technical specification is developed by JCTEA . STANDARDS ARIB and JCTEA developed the following standards. Some part of standards are located on the pages of ITU-R and ITU-T .
TABLE OF TERRESTRIAL HDTV TRANSMISSION SYSTEMS SEE ALSO General category Transmission technology EXTERNAL LINKS |
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