73-508: The digital television transition , also called the digital switchover ( DSO ), the analogue switch/sign-off ( ASO ), the digital migration , or the analogue shutdown , is the process in which older analogue television broadcasting technology is converted to and replaced by digital television . Conducted by individual nations on different schedules, this primarily involves the conversion of analogue terrestrial television broadcasting infrastructure to Digital terrestrial television (DTT),
146-414: A digital television (DTV) signal remains good until the signal level drops below a threshold where reception is no longer possible or becomes intermittent. Analog television may be wireless ( terrestrial television and satellite television ) or can be distributed over a cable network as cable television . All broadcast television systems used analog signals before the arrival of DTV. Motivated by
219-490: A spectrum auction . The program was managed by the Department of Commerce through its National Telecommunications and Information Administration . Televisions with integrated digital tuners have been available for a considerable time. This means that a set-top box is usually no longer necessary with a new TV set. Satellite broadcasting switched to digital much earlier than terrestrial broadcasting. The switchover process
292-627: A given bandwidth. This is because sophisticated comb filters in receivers are more effective with NTSC's 4 color frame sequence compared to PAL's 8-field sequence. However, in the end, the larger channel width of most PAL systems in Europe still gives PAL systems the edge in transmitting more picture detail. In the SECAM television system, U and V are transmitted on alternate lines, using simple frequency modulation of two different color subcarriers. In some analog color CRT displays, starting in 1956,
365-527: A given signal completely, it is necessary to quote the color system plus the broadcast standard as a capital letter. For example, the United States, Canada, Mexico and South Korea used (or use) NTSC-M , Japan used NTSC-J , the UK used PAL-I , France used SECAM-L , much of Western Europe and Australia used (or use) PAL-B / G , most of Eastern Europe uses SECAM-D / K or PAL-D/K and so on. Not all of
438-448: A major benefit being extra frequencies on the radio spectrum and lower broadcasting costs, as well as improved viewing qualities for consumers. The transition may also involve analogue cable conversion to digital cable or Internet Protocol television , as well as analog to digital satellite television. Transition of land based broadcasting had begun in some countries around 2000. By contrast, transition of satellite television systems
511-503: A means of television channel selection. Analog broadcast television systems come in a variety of frame rates and resolutions. Further differences exist in the frequency and modulation of the audio carrier. The monochrome combinations still existing in the 1950s were standardized by the International Telecommunication Union (ITU) as capital letters A through N. When color television was introduced,
584-489: A mobile newsgathering vehicle to a central receive point. It is also used in the US by Amateur television operators. Rather than carrying one data carrier on a single radio frequency (RF) channel, COFDM works by splitting the digital data stream into a large number of slower digital streams, each of which digitally modulates a set of closely spaced adjacent sub-carrier frequencies. In the case of DVB-T, there are two choices for
657-399: A number of different broadcast television systems are in use worldwide, the same principles of operation apply. A cathode-ray tube (CRT) television displays an image by scanning a beam of electrons across the screen in a pattern of horizontal lines known as a raster . At the end of each line, the beam returns to the start of the next line; at the end of the last line, the beam returns to
730-399: A second demodulator, the Z demodulator, also extracts an additive combination of U plus V, but in a different ratio. The X and Z color difference signals are further matrixed into three color difference signals, (R-Y), (B-Y), and (G-Y). The combinations of usually two, but sometimes three demodulators were: In the end, further matrixing of the above color-difference signals c through f yielded
803-485: A separate date to switch off. In others, the whole country switches on one date, such as the Netherlands. On 3 August 2003, Berlin became the world's first city to switch off terrestrial analogue signals. Luxembourg was the first country to complete its terrestrial switchover, on 1 September 2006. Different standards have been developed for the broadcast transmission of digital terrestrial television, comparable to
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#1732781131414876-462: A signal would not be compatible with monochrome receivers, an important consideration when color broadcasting was first introduced. It would also occupy three times the bandwidth of existing television, requiring a decrease in the number of television channels available. Instead, the RGB signals are converted into YUV form, where the Y signal represents the luminance of the colors in the image. Because
949-502: A switchover to happen by a given deadline. In addition, governments can also have a say with the broadcasters as to what digital standard to adopt – either DVB-T , ATSC , ISDB-T , or DTMB . Governments can also require all receiving equipment sold in a country to support the necessary digital 'tuner'. Before digital television, PAL and NTSC were used for both video processing within TV stations and for broadcasting to viewers. Because of this,
1022-410: A television image is composed of scan lines drawn on the screen. The lines are of varying brightness; the whole set of lines is drawn quickly enough that the human eye perceives it as one image. The process repeats and the next sequential frame is displayed, allowing the depiction of motion. The analog television signal contains timing and synchronization information so that the receiver can reconstruct
1095-438: A two-dimensional moving image from a one-dimensional time-varying signal. The first commercial television systems were black-and-white ; the beginning of color television was in the 1950s. A practical television system needs to take luminance , chrominance (in a color system), synchronization (horizontal and vertical), and audio signals , and broadcast them over a radio transmission. The transmission system must include
1168-480: A volt. At this point the IF signal consists of a video carrier signal at one frequency and the sound carrier at a fixed offset in frequency. A demodulator recovers the video signal. Also at the output of the same demodulator is a new frequency modulated sound carrier at the offset frequency. In some sets made before 1948, this was filtered out, and the sound IF of about 22 MHz was sent to an FM demodulator to recover
1241-508: Is Sound-in-Syncs . The luminance component of a composite video signal varies between 0 V and approximately 0.7 V above the black level. In the NTSC system, there is a blanking signal level used during the front porch and back porch, and a black signal level 75 mV above it; in PAL and SECAM these are identical. In a monochrome receiver, the luminance signal is amplified to drive
1314-470: Is a COFDM transmission technique which includes the use of a Guard Interval. It allows the receiver to cope with strong multipath situations. Within a geographical area, DVB-T also allows single-frequency network (SFN) operation, where two or more transmitters carrying the same data operate on the same frequency. In such cases the signals from each transmitter in the SFN needs to be accurately time-aligned, which
1387-411: Is a brief (about 1.5 microsecond ) period inserted between the end of each transmitted line of picture and the leading edge of the next line's sync pulse . Its purpose was to allow voltage levels to stabilise in older televisions, preventing interference between picture lines. The front porch is the first component of the horizontal blanking interval which also contains the horizontal sync pulse and
1460-534: Is broadcast, or for a station to use digital equipment but convert the signal to analogue for broadcasting, or they may have a mix of both digital and analogue equipment. Digital TV signals require less transmission power to be broadcast and received satisfactorily. The switchover process is being accomplished on different schedules in different countries; in some countries it is being implemented in stages as in Australia, Greece, India or Mexico, where each region has
1533-467: Is done by sync information in the stream and timing at each transmitter referenced to GPS . The length of the Guard Interval can be chosen. It is a trade-off between data rate and SFN capability. The longer the guard interval the larger is the potential SFN area without creating intersymbol interference (ISI). It is possible to operate SFNs which do not fulfill the guard interval condition if
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#17327811314141606-506: Is easier to tune the picture without losing the sound. So the FM sound carrier is then demodulated, amplified, and used to drive a loudspeaker. Until the advent of the NICAM and MTS systems, television sound transmissions were monophonic. The video carrier is demodulated to give a composite video signal containing luminance, chrominance and synchronization signals. The result is identical to
1679-559: Is little used, the migration to digital satellite or cable is more realized. For instance, in Switzerland or the UAE, where terrestrial has low usage, the terrestrial switchover was not noticed by the general population. But in countries where terrestrial is the dominant method of watching TV, like Japan, Spain or Thailand, the switchover is a big deal as it affects the majority of the population. Analog television Analog television
1752-400: Is much easier for satellite since only changes to the earth station equipment are needed on the transmission side and consumers are already used to having a set top box/decoder. In many places, the satellite switchover was complete before terrestrial switchover was even started. Cable on the other hand would switch off months, if not years after terrestrial would. In countries where terrestrial
1825-468: Is that the U and V signals are zero when the picture has no color content. Since the human eye is more sensitive to detail in luminance than in color, the U and V signals can be transmitted with reduced bandwidth with acceptable results. In the receiver, a single demodulator can extract an additive combination of U plus V. An example is the X demodulator used in the X/Z demodulation system. In that same system,
1898-405: Is the difference between the B signal and the Y signal, also known as B minus Y (B-Y), and the V signal is the difference between the R signal and the Y signal, also known as R minus Y (R-Y). The U signal then represents how purplish-blue or its complementary color, yellowish-green, the color is, and the V signal how purplish-red or its complementary, greenish-cyan, it is. The advantage of this scheme
1971-500: Is the original television technology that uses analog signals to transmit video and audio. In an analog television broadcast, the brightness, colors and sound are represented by amplitude , phase and frequency of an analog signal. Analog signals vary over a continuous range of possible values which means that electronic noise and interference may be introduced. Thus with analog, a moderately weak signal becomes snowy and subject to interference. In contrast, picture quality from
2044-566: Is the same as the original U signal at the corresponding time. In effect, these pulses are discrete-time analog samples of the U signal. The pulses are then low-pass filtered so that the original analog continuous-time U signal is recovered. For V, a 90-degree shifted subcarrier briefly gates the chroma signal every 280 nanoseconds, and the rest of the process is identical to that used for the U signal. Gating at any other time than those times mentioned above will yield an additive mixture of any two of U, V, -U, or -V. One of these off-axis (that is, of
2117-542: Is transmitted. Therefore, the receiver must reconstitute the subcarrier. For this purpose, a short burst of the subcarrier, known as the colorburst, is transmitted during the back porch (re-trace blanking period) of each scan line. A subcarrier oscillator in the receiver locks onto this signal (see phase-locked loop ) to achieve a phase reference, resulting in the oscillator producing the reconstituted subcarrier. NTSC uses this process unmodified. Unfortunately, this often results in poor color reproduction due to phase errors in
2190-475: Is used to build the image. This process doubles the apparent number of video frames per second and further reduces flicker and other defects in transmission. The television system for each country will specify a number of television channels within the UHF or VHF frequency ranges. A channel actually consists of two signals: the picture information is transmitted using amplitude modulation on one carrier frequency, and
2263-413: Is used to reduce the channel spacing, which would be nearly twice the video bandwidth if pure AM was used. Signal reception is invariably done via a superheterodyne receiver : the first stage is a tuner which selects a television channel and frequency-shifts it to a fixed intermediate frequency (IF). The signal amplifier performs amplification to the IF stages from the microvolt range to fractions of
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2336-696: The D-book in the UK, the Italian DGTVi, the ETSI E-Book and the Nordic countries and Ireland NorDig. DVB-T has been further developed into newer standards such as DVB-H (Handheld), which was a commercial failure and is no longer in operation, and DVB-T2 , which was initially finalised in August 2011. DVB-T as a digital transmission delivers data in a series of discrete blocks at the symbol rate. DVB-T
2409-492: The ITU in 1961 as: A, B, C, D, E, F, G, H, I, K, K1, L, M and N. These systems determine the number of scan lines, frame rate, channel width, video bandwidth, video-audio separation, and so on. A color encoding scheme ( NTSC , PAL , or SECAM ) could be added to the base monochrome signal. Using RF modulation the signal is then modulated onto a very high frequency (VHF) or ultra high frequency (UHF) carrier wave . Each frame of
2482-647: The VHF band which would be allowed until 17 June 2020. These deadlines set by the agreement have been difficult to reach in certain regions, like in Africa where most countries missed the 2015 deadline, as well as South East Asia. High upgrade costs are often a reason cited for the slow transition in those regions. The European Commission , on a different note, had recommended on 28 October 2009 that digital switchover should be completed by 1 January 2012. Analog-only TVs are incapable of receiving over-the-air broadcasts without
2555-430: The back porch . The back porch is the portion of each scan line between the end (rising edge) of the horizontal sync pulse and the start of active video. It is used to restore the black level (300 mV) reference in analog video. In signal processing terms, it compensates for the fall time and settling time following the sync pulse. In color television systems such as PAL and NTSC, this period also includes
2628-465: The colorburst signal. In the SECAM system, it contains the reference subcarrier for each consecutive color difference signal in order to set the zero-color reference. In some professional systems, particularly satellite links between locations, the digital audio is embedded within the line sync pulses of the video signal, to save the cost of renting a second channel. The name for this proprietary system
2701-534: The control grid in the electron gun of the CRT. This changes the intensity of the electron beam and therefore the brightness of the spot being scanned. Brightness and contrast controls determine the DC shift and amplification, respectively. A color signal conveys picture information for each of the red, green, and blue components of an image. However, these are not simply transmitted as three separate signals, because: such
2774-408: The NTSC and PAL color systems, U and V are transmitted by using quadrature amplitude modulation of a subcarrier. This kind of modulation applies two independent signals to one subcarrier, with the idea that both signals will be recovered independently at the receiving end. For NTSC, the subcarrier is at 3.58 MHz. For the PAL system it is at 4.43 MHz. The subcarrier itself is not included in
2847-411: The NTSC system. PAL's color encoding is similar to the NTSC systems. SECAM, though, uses a different modulation approach than PAL or NTSC. PAL had a late evolution called PALplus , allowing widescreen broadcasts while remaining fully compatible with existing PAL equipment. In principle, all three color encoding systems can be used with any scan line/frame rate combination. Therefore, in order to describe
2920-405: The U and V axis) gating methods is called I/Q demodulation. Another much more popular off-axis scheme was the X/Z demodulation system. Further matrixing recovered the original U and V signals. This scheme was actually the most popular demodulator scheme throughout the 1960s. The above process uses the subcarrier. But as previously mentioned, it was deleted before transmission, and only the chroma
2993-848: The UK's Freeview . The DVB-T Standard is published as EN 300 744, Framing structure, channel coding and modulation for digital terrestrial television . This is available from the ETSI website, as is ETSI TS 101 154, Specification for the use of Video and Audio Coding in Broadcasting Applications based on the MPEG-2 Transport Stream , which gives details of the DVB use of source coding methods for MPEG-2 and, more recently, H.264/MPEG-4 AVC as well as audio encoding systems. Many countries that have adopted DVB-T have published standards for their implementation. These include
Digital television transition - Misplaced Pages Continue
3066-407: The Y signal) represents the approximate saturation of a color, and the chrominance phase against the subcarrier reference approximately represents the hue of the color. For particular test colors found in the test color bar pattern, exact amplitudes and phases are sometimes defined for test and troubleshooting purposes only. Due to the nature of the quadrature amplitude modulation process that created
3139-425: The addition of a set-top converter box. Consequently, a digital converter box – an electronic device that connects to an analog television – must be used to allow the television to receive digital broadcasts. In the United States, the government subsidized the purchase of such boxes for consumers via their coupon-eligible converter box program in 2009, funded by a small part of the billions of dollars brought in by
3212-435: The basic sound signal. In newer sets, this new carrier at the offset frequency was allowed to remain as intercarrier sound , and it was sent to an FM demodulator to recover the basic sound signal. One particular advantage of intercarrier sound is that when the front panel fine tuning knob is adjusted, the sound carrier frequency does not change with the tuning, but stays at the above-mentioned offset frequency. Consequently, it
3285-423: The beginning of the first line at the top of the screen. As it passes each point, the intensity of the beam is varied, varying the luminance of that point. A color television system is similar except there are three beams that scan together and an additional signal known as chrominance controls the color of the spot. When analog television was developed, no affordable technology for storing video signals existed;
3358-419: The brightness control signal ( luminance ) is fed to the cathode connections of the electron guns, and the color difference signals ( chrominance signals) are fed to the control grids connections. This simple CRT matrix mixing technique was replaced in later solid state designs of signal processing with the original matrixing method used in the 1954 and 1955 color TV receivers. Synchronizing pulses added to
3431-578: The chrominance information was added to the monochrome signals in a way that black and white televisions ignore. In this way backward compatibility was achieved. There are three standards for the way the additional color information can be encoded and transmitted. The first was the American NTSC system. The European and Australian PAL and the French and former Soviet Union SECAM standards were developed later and attempt to cure certain defects of
3504-436: The chrominance signal, at certain times, the signal represents only the U signal, and 70 nanoseconds (NTSC) later, it represents only the V signal. About 70 nanoseconds later still, -U, and another 70 nanoseconds, -V. So to extract U, a synchronous demodulator is utilized, which uses the subcarrier to briefly gate the chroma every 280 nanoseconds, so that the output is only a train of discrete pulses, each having an amplitude that
3577-425: The combining process, the low-resolution portion of the Y signals cancel out, leaving R, G, and B signals able to render a low-resolution image in full color. However, the higher resolution portions of the Y signals do not cancel out, and so are equally present in R, G, and B, producing the higher-resolution image detail in monochrome, although it appears to the human eye as a full-color and full-resolution picture. In
3650-486: The composite video format used by analog video devices such as VCRs or CCTV cameras . To ensure good linearity and thus fidelity, consistent with affordable manufacturing costs of transmitters and receivers, the video carrier is never modulated to the extent that it is shut off altogether. When intercarrier sound was introduced later in 1948, not completely shutting off the carrier had the side effect of allowing intercarrier sound to be economically implemented. Each line of
3723-399: The date after which countries may use frequencies currently assigned for analog television transmission for digital services (specifically DVB-T ), without being required to protect the analog services of neighbouring countries against interference. This date was generally viewed as an internationally mandated analog switch-off date, at least along national borders—except for those operating on
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#17327811314143796-634: The development of the cathode-ray tube (CRT), which uses a focused electron beam to trace lines across a phosphor coated surface. The electron beam could be swept across the screen much faster than any mechanical disc system, allowing for more closely spaced scan lines and much higher image resolution. Also, far less maintenance was required of an all-electronic system compared to a mechanical spinning disc system. All-electronic systems became popular with households after World War II . Broadcasters of analog television encode their signal using different systems. The official systems of transmission were defined by
3869-503: The disc to scan an image. A similar disk reconstructed the image at the receiver. Synchronization of the receiver disc rotation was handled through sync pulses broadcast with the image information. Camera systems used similar spinning discs and required intensely bright illumination of the subject for the light detector to work. The reproduced images from these mechanical systems were dim, very low resolution and flickered severely. Analog television did not begin in earnest as an industry until
3942-417: The displayed image is transmitted using a signal as shown above. The same basic format (with minor differences mainly related to timing and the encoding of color) is used for PAL, NTSC , and SECAM television systems. A monochrome signal is identical to a color one, with the exception that the elements shown in color in the diagram (the colorburst , and the chrominance signal) are not present. The front porch
4015-526: The lower bandwidth requirements of compressed digital signals , beginning just after the year 2000, a digital television transition is proceeding in most countries of the world, with different deadlines for the cessation of analog broadcasts. Several countries have made the switch already, with the remaining countries still in progress mostly in Africa, Asia, and South America. The earliest systems of analog television were mechanical television systems that used spinning disks with patterns of holes punched into
4088-401: The luminance signal had to be generated and transmitted at the same time at which it is displayed on the CRT. It was therefore essential to keep the raster scanning in the camera (or other device for producing the signal) in exact synchronization with the scanning in the television. The physics of the CRT require that a finite time interval be allowed for the spot to move back to the start of
4161-435: The modulated signal ( suppressed carrier ), it is the subcarrier sidebands that carry the U and V information. The usual reason for using suppressed carrier is that it saves on transmitter power. In this application a more important advantage is that the color signal disappears entirely in black and white scenes. The subcarrier is within the bandwidth of the main luminance signal and consequently can cause undesirable artifacts on
4234-410: The negative side-effect of causing image smearing and blurring when there is rapid on-screen motion occurring. The maximum frame rate depends on the bandwidth of the electronics and the transmission system, and the number of horizontal scan lines in the image. A frame rate of 25 or 30 hertz is a satisfactory compromise, while the process of interlacing two video fields of the picture per frame
4307-451: The next line ( horizontal retrace ) or the start of the screen ( vertical retrace ). The timing of the luminance signal must allow for this. The human eye has a characteristic called phi phenomenon . Quickly displaying successive scan images creates the illusion of smooth motion. Flickering of the image can be partially solved using a long persistence phosphor coating on the CRT so that successive images fade slowly. However, slow phosphor has
4380-490: The number of carriers known as 2K-mode or 8K-mode. These are actually 1,705 or 6,817 sub-carriers that are approximately 4 kHz or 1 kHz apart. DVB-T offers three different modulation schemes ( QPSK , 16QAM , 64QAM ). DVB-T has been adopted or proposed for digital television broadcasting by many countries ( see map ), using mainly VHF 7 MHz and UHF 8 MHz channels whereas Taiwan, Colombia, Panama and Trinidad and Tobago use 6 MHz channels. Examples include
4453-546: The older TV. Usually during a transition, a simulcast service is operated where a broadcast is made available to viewers in both analogue and digital at the same time. As digital becomes more popular, it is expected that the existing analogue services will be removed. In most places this has already happened, where a broadcaster has offered incentives to viewers to encourage them to switch to digital. Government intervention usually involves providing some funding for broadcasters and, in some cases, monetary relief to viewers, to enable
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#17327811314144526-478: The older analog standards they replace: NTSC , PAL and SECAM . Broadcasters around the world choose and adopt one of these to be the format and technology behind the transmission. The standards are: The " RRC-06 " agreement in Geneva (hosted by the International Telecommunication Union (ITU)) was signed by delegates from many countries, including most of Europe, Africa and Asia. The agreement set 17 June 2015 as
4599-452: The phase of the signal on each successive line, and averaging the results over pairs of lines. This process is achieved by the use of a 1H (where H = horizontal scan frequency) duration delay line. Phase shift errors between successive lines are therefore canceled out and the wanted signal amplitude is increased when the two in-phase ( coincident ) signals are re-combined. NTSC is more spectrum efficient than PAL, giving more picture detail for
4672-488: The picture, all the more noticeable in black and white receivers. A small sample of the subcarrier, the colorburst , is included in the horizontal blanking portion, which is not visible on the screen. This is necessary to give the receiver a phase reference for the modulated signal. Under quadrature amplitude modulation the modulated chrominance signal changes phase as compared to its subcarrier and also changes amplitude. The chrominance amplitude (when considered together with
4745-739: The possible combinations exist. NTSC is only used with system M, even though there were experiments with NTSC-A ( 405 line ) in the UK and NTSC-N (625 line) in part of South America. PAL is used with a variety of 625-line standards (B, G, D, K, I, N) but also with the North American 525-line standard, accordingly named PAL-M . Likewise, SECAM is used with a variety of 625-line standards. For this reason, many people refer to any 625/25 type signal as PAL and to any 525/30 signal as NTSC , even when referring to digital signals; for example, on DVD-Video , which does not contain any analog color encoding, and thus no PAL or NTSC signals at all. Although
4818-468: The received signal, caused sometimes by multipath, but mostly by poor implementation at the studio end. With the advent of solid-state receivers, cable TV, and digital studio equipment for conversion to an over-the-air analog signal, these NTSC problems have been largely fixed, leaving operator error at the studio end as the sole color rendition weakness of the NTSC system. In any case, the PAL D (delay) system mostly corrects these kinds of errors by reversing
4891-432: The rendering of colors in this way is the goal of both monochrome film and television systems, the Y signal is ideal for transmission as the luminance signal. This ensures a monochrome receiver will display a correct picture in black and white, where a given color is reproduced by a shade of gray that correctly reflects how light or dark the original color is. The U and V signals are color difference signals. The U signal
4964-415: The sound is transmitted with frequency modulation at a frequency at a fixed offset (typically 4.5 to 6 MHz) from the picture signal. The channel frequencies chosen represent a compromise between allowing enough bandwidth for video (and hence satisfactory picture resolution), and allowing enough channels to be packed into the available frequency band. In practice a technique called vestigial sideband
5037-465: The switchover process may also include the adoption of digital equipment using serial digital interface (SDI) on TV stations, replacing analogue PAL or NTSC component or composite video equipment. Digital broadcasting standards are only used to broadcast video to viewers; Digital TV stations usually use SDI irrespective of broadcast standard, although it might be possible for a station still using analogue equipment to convert its signal to digital before it
5110-434: The three color-difference signals, (R-Y), (B-Y), and (G-Y). The R, G, and B signals in the receiver needed for the display device (CRT, Plasma display, or LCD display) are electronically derived by matrixing as follows: R is the additive combination of (R-Y) with Y, G is the additive combination of (G-Y) with Y, and B is the additive combination of (B-Y) with Y. All of this is accomplished electronically. It can be seen that in
5183-498: The video signal at the end of every scan line and video frame ensure that the sweep oscillators in the receiver remain locked in step with the transmitted signal so that the image can be reconstructed on the receiver screen. DVB-T DVB-T , short for Digital Video Broadcasting – Terrestrial , is the DVB European-based consortium standard for the broadcast transmission of digital terrestrial television that
5256-543: Was first published in 1997 and first broadcast in Singapore in February 1998. This system transmits compressed digital audio , digital video and other data in an MPEG transport stream , using coded orthogonal frequency-division multiplexing (COFDM or OFDM) modulation. It is also the format widely used worldwide (including North America) for Electronic News Gathering for transmission of video and audio from
5329-423: Was well underway or completed in many countries by this time. It is an involved process because the existing analogue television receivers owned by viewers cannot receive digital broadcasts; viewers must either purchase new digital TVs, or digital converter boxes which have a digital tuner and change the digital signal to an analog signal or some other form of a digital signal (i.e. HDMI ) which can be received on
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