ISDBT
integrated Services Digital Broadcasting (ISDB) is a Japanese standard for digital television (DTV) and digital radio used by the country's radio and television stations. ISDB replaced the previously used MUSE "Hi-vision" analogue HDTV system.
ISDB is maintained by the Japanese organization ARIB. The standards can be obtained for free at the Japanese organization 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 the name of an ISDB-T service for reception on cell phones, laptop computers and vehicles.
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. Brazil is using ISDB for terrestrial broadcasting (ISDB-T) with video encoded with MPEG-4 AVC (H.264) and audio with HE-AAC ([2]). Other countries in South America are following Brazil adopting ISDB-T with H.264 and HE-AAC.
[edit] 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.
[edit] 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).
[edit] Interfaces and Encryption
The ISDB specification describes a lot of (network) interfaces, but most importantly the Common Interface for Conditional Access (ARIB STD-B25) with the Common Scrambling Algorithm (CAS) system called MULTI2 required for (de-)scrambling television.
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 television program. That is why it is commonly called "Pay per view system without charge".[citation needed] An interface for mobile reception is under consideration.[citation needed]
ISDB supports RMP (Rights management and protection). Since all digitial television (DTV) systems carry digital data content, a DVD or high-definition (HD) recorder could easily copy content losslessly. Hollywood[who?] requested copy protection; this was the main reason for RMP being mandated. 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 further copied; only moved to another copy-protected media—and this move operation will mark the content “copy one generation”, which is mandated to permanently prevent further copying. “Copy never” programming may only be timeshifted and cannot be permanently stored. Currently[when?], the Japanese government is evaluating using the Digital Transmission Content Protection (DTCP) "Encryption plus Non-Assertion" mechanism, to allow making multiple copies of digital content between compliant devices[3