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|List of digital television broadcast standards|
|DVB standards (countries)|
|ATSC standards (countries)|
|ISDB standards (countries)|
|DTMB standards (countries)|
|DMB standard (countries)|
Digital Video Broadcasting - Satellite - Second Generation (DVB-S2) is a digital television broadcast standard that has been designed as a successor for the popular DVB-S system. It was developed in 2003 by the DVB Project, an international industry consortium, and ratified by ETSI (EN 302307) in March 2005. The standard is based on, and improves upon DVB-S and the electronic news-gathering (or Digital Satellite News Gathering) system, used by mobile units for sending sounds and images from remote locations worldwide back to their home television stations.
Digital television (DTV) is the transmission of television signals, including the sound channel, using digital encoding, in contrast to the earlier television technology, analog television, in which the video and audio are carried by analog signals. It is an innovative advance that represents the first significant evolution in television technology since color television in the 1950s. Digital TV transmits in a new image format called high definition television (HDTV), with greater resolution than analog TV, in a widescreen aspect ratio similar to recent movies in contrast to the narrower screen of analog TV. It makes more economical use of scarce radio spectrum space; it can transmit multiple channels, up to 7, in the same bandwidth occupied by a single channel of analog television, and provides many new features that analog television cannot. A transition from analog to digital broadcasting began around 2006. Different digital television broadcasting standards have been adopted in different parts of the world; below are the more widely used standards:
Digital Video Broadcasting – Satellite (DVB-S) is the original DVB standard for Satellite Television and dates from 1995, in its first release, while development lasted from 1993 to 1997. The first commercial application was by Galaxy in Australia, enabling digitally broadcast, satellite-delivered Television to the public.
The European Telecommunications Standards Institute (ETSI) is an independent, not-for-profit, standardization organization in the telecommunications industry in Europe, headquartered in Sophia-Antipolis, France, with worldwide projection. ETSI produces globally-applicable standards for Information and Communications Technologies (ICT), including fixed, mobile, radio, converged, broadcast and internet technologies.
DVB-S2 is envisaged (contemplate) for broadcast services including standard and HDTV, interactive services including Internet access, and (professional) data content distribution. The development of DVB-S2 coincided with the introduction of HDTV and H.264 (MPEG-4 AVC) video codecs.
Standard-definition television is a television system which uses a resolution that is not considered to be either high or enhanced definition. SDTV and high-definition television (HDTV) are the two categories of display formats for digital television (DTV) transmissions.
High-definition television (HDTV) is a television system providing an image resolution that is of substantially higher resolution than that of standard-definition television. This can be either analog or digital. HDTV is the current standard video format used in most broadcasts: terrestrial broadcast television, cable television, satellite television, Blu-rays, and streaming video.
H.264 or MPEG-4 Part 10, Advanced Video Coding is a block-oriented motion-compensation-based video compression standard. As of 2014, it is one of the most commonly used formats for the recording, compression, and distribution of video content. It supports resolutions up to 8192×4320, including 8K UHD.
Two new key features that were added compared to the DVB-S standard are:
In telecommunication, information theory, and coding theory, forward error correction (FEC) or channel coding is a technique used for controlling errors in data transmission over unreliable or noisy communication channels. The central idea is the sender encodes the message in a redundant way by using an error-correcting code (ECC).
In information theory, a low-density parity-check (LDPC) code is a linear error correcting code, a method of transmitting a message over a noisy transmission channel. An LDPC is constructed using a sparse bipartite graph. LDPC codes are capacity-approaching codes, which means that practical constructions exist that allow the noise threshold to be set very close to the theoretical maximum for a symmetric memoryless channel. The noise threshold defines an upper bound for the channel noise, up to which the probability of lost information can be made as small as desired. Using iterative belief propagation techniques, LDPC codes can be decoded in time linear to their block length.
Other features include enhanced modulation schemes up to 32APSK, additional code rates, and the introduction of a generic transport mechanism for IP packet data including MPEG-4 audio–video streams, while supporting backward compatibility with existing MPEG-2 TS based transmission.
In electronics and telecommunications, modulation is the process of varying one or more properties of a periodic waveform, called the carrier signal, with a modulating signal that typically contains information to be transmitted. Most radio systems in the 20th century used frequency modulation (FM) or amplitude modulation (AM) for radio broadcast.
Amplitude and phase-shift keying or asymmetric phase-shift keying (APSK) is a digital modulation scheme that conveys data by changing, or modulating, both the amplitude and the phase of a reference signal. In other words, it combines both amplitude-shift keying (ASK) and phase-shift keying (PSK) to increase the symbol-set. It can be considered as a superclass of quadrature amplitude modulation (QAM). The advantage over conventional QAM, for example 16-QAM, is lower number of possible amplitude levels.
In telecommunication and information theory, the code rate of a forward error correction code is the proportion of the data-stream that is useful (non-redundant). That is, if the code rate is for every bits of useful information, the coder generates a total of bits of data, of which are redundant.
DVB-S2 achieves significantly better performance than its predecessors – mainly allowing for an increase of available bitrate over the same satellite transponder bandwidth. The measured DVB-S2 performance gain over DVB-S is around 30% at the same satellite transponder bandwidth and emitted signal power. When the contribution of improvements in video compression is added, an (MPEG-4 AVC) HDTV service can now be delivered in the same bandwidth that supported an early DVB-S based MPEG-2 SDTV service only a decade before.
In March 2014, DVB-S2X specification has been published by DVB Project as an optional extension adding further improvements.
DVB-S2X is an extension of DVB-S2 satellite digital broadcasting standard.
Depending on code rate and modulation, the system can operate at a C/N between −2.4 dB (QPSK, 1/4) and 16 dB (32APSK, 9/10) with a quasi-error free goal of a 10−7 TS packet error rate. Distance to the Shannon limit ranges from 0.7 dB to 1.2 dB.
Modes and features of DVB-S2 in comparison to DVB-S:
|Input interface||Single transport stream (TS)||Multiple transport stream and generic stream encapsulation (GSE)|
|Modes||Constant coding & modulation||Variable coding & modulation and adaptive coding & modulation|
|FEC||Reed–Solomon (RS) 1/2, 2/3, 3/4, 5/6, 7/8||LDPC + BCH 1/4, 1/3, 2/5, 1/2, 3/5, 2/3, 3/4, 4/5, 5/6, 6/7, 8/9, 9/10|
|Modulation||Single-carrier QPSK||QPSK, 8PSK, 16APSK, 32APSK|
|Pilots||Pilot symbols||Pilot symbols|
Envisaged scenarios for DVB-S2 by the standard document are:
The conversion process from DVB-S to DVB-S2 is being accelerated, due to the rapid increase of HDTV and introduction of 3D-HDTV. The main factor slowing down this process is the need to replace or upgrade set-top boxes, or acquire TVs with DVB-S2 integrated tuners, which makes the transition slower for established operators.
Current direct-to-home broadcasters using DVB-S2 are:
These broadcasters have used DVB-S2 in their internal broadcast distribution networks, but may not have instituted DVB-S2 transmissions for consumers.
8VSB is the modulation method used for broadcast in the ATSC digital television standard. ATSC and 8VSB modulation is used primarily in North America; in contrast, the DVB-T standard uses COFDM.
Digital Video Broadcasting (DVB) is a set of international open standards for digital television. DVB standards are maintained by the DVB Project, an international industry consortium, and are published by a Joint Technical Committee (JTC) of the European Telecommunications Standards Institute (ETSI), European Committee for Electrotechnical Standardization (CENELEC) and European Broadcasting Union (EBU).
A satellite modem or satmodem is a modem used to establish data transfers using a communications satellite as a relay. A satellite modem's main function is to transform an input bitstream to a radio signal and vice versa.
DVB-T is an abbreviation for "Digital Video Broadcasting — Terrestrial"; it is the DVB European-based consortium standard for the broadcast transmission of digital terrestrial television that was first published in 1997 and first broadcast in the UK in 1998. This system transmits compressed digital audio, digital video and other data in an MPEG transport stream, using coded orthogonal frequency-division multiplexing modulation. It is also the format widely used worldwide for Electronic News Gathering for transmission of video and audio from a mobile newsgathering vehicle to a central receive point.
DVB-C stands for "Digital Video Broadcasting - Cable" and it is the DVB European consortium standard for the broadcast transmission of digital television over cable. This system transmits an MPEG-2 or MPEG-4 family digital audio/digital video stream, using a QAM modulation with channel coding. The standard was first published by the ETSI in 1994, and subsequently became the most widely used transmission system for digital cable television in Europe, Asia and South America. It is deployed worldwide in systems ranging from the larger cable television networks (CATV) down to smaller satellite master antenna TV (SMATV) systems.
The Integrated Services Digital Broadcasting is a Japanese standard for digital television (DTV) and digital radio used by the country's radio and television networks. ISDB replaced NTSC-J analog television system and the previously used MUSE Hi-vision analogue HDTV system in Japan, and will be replacing NTSC, PAL-M and PAL-N in South America and the Philippines. Digital Terrestrial Television Broadcasting (DTTB) services using ISDB-T started in Japan in December 2003 and in Brazil in December 2007 as a trial. Since then, many countries have adopted ISDB over other digital broadcasting standards.
Advanced Television Systems Committee (ATSC) standards are a set of standards for digital television transmission over terrestrial, cable, and satellite networks. It is largely a replacement for the analog NTSC standard, and like that standard, used mostly in the United States, Mexico and Canada. Other former users of NTSC, like Japan, have not used ATSC during their digital television transition because they adopted their own system called ISDB.
Digital Radio Mondiale is a set of digital audio broadcasting technologies designed to work over the bands currently used for analogue radio broadcasting including AM broadcasting, particularly shortwave, and FM broadcasting. DRM is more spectrally efficient than AM and FM, allowing more stations, at higher quality, into a given amount of bandwidth, using various MPEG-4 audio coding formats.
A single-frequency network or SFN is a broadcast network where several transmitters simultaneously send the same signal over the same frequency channel.
Digital Satellite System is the initialism expansion of the DSS digital satellite television transmission system used by DirecTV. Only when digital transmission was introduced did direct broadcast satellite (DBS) television become popular in North America, which has led to both DBS and DSS being used interchangeably to refer to all three commonplace digital transmission formats - DSS, DVB-S and 4DTV. Analog DBS services, however, existed prior to DirecTV and were still operational in continental Europe until April 2012.
In telecommunications, the (digital) cliff effect or brickwall effect is a sudden loss of digital signal reception. Unlike analog signals, which gradually fade when signal strength decreases or electromagnetic interference or multipath increases, a digital signal provides data which is either perfect or non-existent at the receiving end. It is named for a graph of reception quality versus signal quality, where the digital signal "falls off a cliff" instead of having a gradual rolloff. This is an example of an EXIT chart.
DVB-T2 is an abbreviation for "Digital Video Broadcasting — Second Generation Terrestrial"; it is the extension of the television standard DVB-T, issued by the consortium DVB, devised for the broadcast transmission of digital terrestrial television. DVB has been standardized by ETSI.
E-VSB or Enhanced VSB is an optional enhancement to the original ATSC Standards that use the 8VSB modulation system used for transmission of digital television. It is intended for improving reception where signals are weaker, including fringe reception areas, and on portable devices such as handheld televisions or mobile phones. It does not cause problems to older receivers, but they cannot take advantage of its features. E-VSB was approved by the ATSC committee in 2004. However, it has been implemented by few stations or manufacturers.
A free-to-air or FTA Receiver is a satellite television receiver designed to receive unencrypted broadcasts. Modern decoders are typically compliant with the MPEG-2/DVB-S and more recently the MPEG-4/DVB-S2 standard for digital television, while older FTA receivers relied on analog satellite transmissions which have declined rapidly in recent years.
Generic Stream Encapsulation, or GSE for short, is a Data link layer protocol defined by DVB. GSE provides means to carry packet oriented protocols such as IP on top of uni-directional physical layers such as DVB-S2, DVB-T2 and DVB-C2.
Satellite subcarrier audio is audio transmitted by way of satellite that utilizes a separate analog or digital signal carried on a main radio transmission on a specific satellite transponder. More technically, it is an already-modulated signal, which is then modulated into another signal of higher frequency and bandwidth. In a more general sense, satellite subcarrier audio is an early form of satellite radio not intended for the consumer market but was initially unencrypted, thus receivable to satellite hobbyists.
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