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Sunday, June 22, 2008

Between DAB and DVB from Wiki, Try World Radio and TV tuner below!

Digital Audio Broadcasting (DAB), also known as Eureka 147, is a digital radio technology for broadcasting radio stations, used in several countries, particularly in Europe. As of 2006, approximately 1,000 stations worldwide broadcast in the DAB format[1].

The DAB standard was designed in the 1980s, and receivers have been available in many countries for several years. Proponents claim the standard offers several benefits over existing analogue FM radio, such as higher-fidelity audio, more stations in the same broadcast spectrum, and increased resistance to noise, multipath, fading, and co-channel interference. However, listening tests carried out by experts in the field of audio have shown that the audio quality on DAB is lower than on FM in the UK, which is the country that accounts for the vast majority of global DAB sales-to-date, due to 98% of stereo stations using a bit rate of 128 kbit/s with the MP2 audio codec, which is unable to match the audio quality provided by FM.[2][3][4]

An upgraded version of the system was released in February 2007, which is called DAB+. DAB+ is not backward-compatible with DAB, which means that only receivers that support the new standard will be able to receive DAB+ broadcasts. DAB+ is 2 - 3 times more efficient than DAB due to the adoption of the AAC+ audio codec[5], which means that DAB+ can provide higher audio quality and more radio stations than DAB allows. Reception quality will also be more robust on DAB+ than on DAB due to the addition of Reed-Solomon error correction coding.

Italy has started transmitting DAB+ stations, Malta and Switzerland are due to launch DAB+ stations in 2008, and Australia and Germany planning on launching DAB+ in 2009. The radio industry in the UK is expecting DAB+ stations to launch between 2010 - 2013[6], and podcast services using the DAB+ format will be launched in the UK in 2009[7].

Digital Video Broadcasting (DVB) is a suite of internationally accepted open standards for digital television. DVB standards are maintained by the DVB Project, an industry consortium with more than 270 members, and they are published by a Joint Technical Committee (JTC) of European Telecommunications Standards Institute (ETSI), European Committee for Electrotechnical Standardization (CENELEC) and European Broadcasting Union (EBU). The interaction of the DVB sub-standards is described in the DVB Cookbook (DVB-Cook).

DVB systems distribute data using a variety of approaches, including by satellite (DVB-S, DVB-S2 and DVB-SH; also DVB-SMATV for distribution via SMATV); cable (DVB-C); terrestrial television (DVB-T, DVB-T2) and digital terrestrial television for handhelds (DVB-H); and via microwave using DTT (DVB-MT), the MMDS (DVB-MC), and/or MVDS standards (DVB-MS)

These standards define the physical layer and data link layer of the distribution system. Devices interact with the physical layer via a synchronous parallel interface (SPI), synchronous serial interface (SSI), or asynchronous serial interface (ASI). All data is transmitted in MPEG-2 transport streams with some additional constraints (DVB-MPEG). A standard for temporally-compressed distribution to mobile devices (DVB-H) was published in November 2004.

These distribution systems differ mainly in the modulation schemes used and error correcting codes used, due to the different technical constraints. DVB-S (SHF) uses QPSK, 8PSK or 16-QAM. DVB-S2 uses QPSK, 8PSK, 16APSK or 32APSK, at the broadcasters decision. QPSK and 8PSK are the only versions regularly used. DVB-C (VHF/UHF) uses QAM: 16-QAM, 32-QAM, 64-QAM, 128-QAM or 256-QAM. Lastly, DVB-T (VHF/UHF) uses 16-QAM or 64-QAM (or QPSK) in combination with COFDM and can support hierarchical modulation.

The DVB-T2 standard will be published after march 2008 and is expected to be approved and submitted to ETSI during 2008.

The DVB-T2 standard will give more-robust TV reception and increase the possible bit-rate by over 30% for single transmitters (as in the UK) and is expected to increase the max bit-rate by over 50% in large SFN (as in Germany, Sweden...).

Besides audio and video transmission, DVB also defines data connections (DVB-DATA - EN 301 192) with return channels (DVB-RC) for several media (DECT, GSM, PSTN/ISDN, satellite etc.) and protocols (DVB-IPTV: Internet Protocol; DVB-NPI: network protocol independent).

Older technologies such as teletext (DVB-TXT) and vertical blanking interval data (DVB-VBI) are also supported by the standards to ease conversion. However for many applications more advanced alternatives like DVB-SUB for sub-titling are available.

You all may try this technology by installing this World Radio and TV Tuner software for free trials. Or you just wanna rip your favourite music from different Internet radio stations over the world.

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