131-749: Advanced Television Systems Committee ( ATSC ) standards are an international set of standards for broadcast and digital television transmission over terrestrial, cable and satellite networks. It is largely a replacement for the analog NTSC standard and, like that standard, is used mostly in the United States , Mexico , Canada , South Korea and Trinidad & Tobago . Several former NTSC users, such as Japan , have not used ATSC during their digital television transition , because they adopted other systems such as ISDB developed by Japan, and DVB developed in Europe, for example. The ATSC standards were developed in
262-552: A 16:9 aspect ratio. HDTV cannot be transmitted over analog television channels because of channel capacity issues. SDTV, by comparison, may use one of several different formats taking the form of various aspect ratios depending on the technology used in the country of broadcast. NTSC can deliver a 640 × 480 resolution in 4:3 and 854 × 480 in 16:9 , while PAL can give 768 × 576 in 4:3 and 1024 × 576 in 16:9 . However, broadcasters may choose to reduce these resolutions to reduce bit rate (e.g., many DVB-T channels in
393-495: A 1990 FIFA World Cup broadcast in March 1990. An American company, General Instrument , also demonstrated the feasibility of a digital television signal in 1990. This led to the FCC being persuaded to delay its decision on an advanced television (ATV) standard until a digitally based standard could be developed. When it became evident that a digital standard might be achieved in March 1990,
524-528: 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
655-402: A scattering effect as the digital processing dithers and is unable to consistently allocate a value of either absolute black or the next step up the greyscale. Changes in signal reception from factors such as degrading antenna connections or changing weather conditions may gradually reduce the quality of analog TV. The nature of digital TV results in a perfectly decodable video initially, until
786-429: A subwoofer bass channel, producing broadcasts similar in quality to movie theaters and DVDs. Digital TV signals require less transmission power than analog TV signals to be broadcast and received satisfactorily. DTV images have some picture defects that are not present on analog television or motion picture cinema, because of present-day limitations of bit rate and compression algorithms such as MPEG-2 . This defect
917-490: A television set with digital capabilities, using integrated circuit chips such as a microprocessor to convert analog television broadcast signals to digital video signals, enabling features such as freezing pictures and showing two channels at once . In 1986, Sony and NEC Home Electronics announced their own similar TV sets with digital video capabilities. However, they still relied on analog TV broadcast signals, with true digital TV broadcasts not yet being available at
1048-537: A TV set in the following year. The digital television transition, migration to high-definition television receivers and the replacement of CRTs with flat screens are all factors in the increasing number of discarded analog CRT-based television receivers. In 2009, an estimated 99 million analog TV receivers were sitting unused in homes in the US alone and, while some obsolete receivers are being retrofitted with converters, many more are simply dumped in landfills where they represent
1179-411: A cable network as cable television . All broadcast television systems used analog signals before the arrival of DTV. Motivated by 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
1310-509: 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 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
1441-570: 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,
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#17328456606611572-517: 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
1703-597: A maximum possible MPEG-2 bitrate of 10.08 Mbit/s (7 Mbit/s typical) allowed in the DVD standard and 48 Mbit/s (36 Mbit/s typical) allowed in the Blu-ray disc standard. Although the ATSC A/53 standard limits MPEG-2 transmission to the formats listed below (with integer frame rates paired with 1000/1001-rate versions), the U.S. Federal Communications Commission declined to mandate that television stations obey this part of
1834-488: 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,
1965-436: A more efficient means of converting filmed programming into digital formats. For their part, the consumer electronics industry and broadcasters argued that interlaced scanning was the only technology that could transmit the highest quality pictures then (and currently) feasible, i.e., 1,080 lines per picture and 1,920 pixels per line. Broadcasters also favored interlaced scanning because their vast archive of interlaced programming
2096-399: 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
2227-450: A recent proposal from Thomson /Micronas; all of these systems have been submitted as candidates for a new ATSC standard, ATSC-M/H . After one year of standardization, the solution merged between Samsung's AVSB and LGE's MPH technology has been adopted and would have been deployed in 2009. This is in addition to other standards like the now-defunct MediaFLO , and worldwide open standards such as DVB-H and T-DMB . Like DVB-H and ISDB 1seg ,
2358-399: 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
2489-459: 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
2620-473: A similar benefit. In spite of ATSC's fixed transmission mode, it is still a robust signal under various conditions. 8VSB was chosen over COFDM in part because many areas are rural and have a much lower population density , thereby requiring larger transmitters and resulting in large fringe areas. In these areas, 8VSB was shown to perform better than other systems. COFDM is used in both DVB-T and ISDB-T, and for 1seg , as well as DVB-H and HD Radio in
2751-593: A single 6 MHz TV channel . ATSC standards are marked A/ x ( x is the standard number) and can be downloaded for free from the ATSC's website at ATSC.org . ATSC Standard A/53, which implemented the system developed by the Grand Alliance, was published in 1995; the standard was adopted by the Federal Communications Commission in the United States in 1996. It was revised in 2009. ATSC Standard A/72
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#17328456606612882-463: A single HDTV feed or multiple lower-resolution feeds is often referred to as distributing one's bit budget or multicasting. This can sometimes be arranged automatically, using a statistical multiplexer . With some implementations, image resolution may be less directly limited by bandwidth; for example in DVB-T , broadcasters can choose from several different modulation schemes, giving them the option to reduce
3013-410: A single frame often results in black boxes in several subsequent frames, making viewing difficult. For remote locations, distant channels that, as analog signals, were previously usable in a snowy and degraded state may, as digital signals, be perfectly decodable or may become completely unavailable. The use of higher frequencies add to these problems, especially in cases where a clear line-of-sight from
3144-459: A sixth channel for low-frequency effects (the so-called "5.1" configuration). In contrast, Japanese ISDB HDTV broadcasts use MPEG's Advanced Audio Coding (AAC) as the audio codec, which also allows 5.1 audio output. DVB (see below ) allows both. MPEG-2 audio was a contender for the ATSC standard during the DTV " Grand Alliance " shootout, but lost out to Dolby AC-3 . The Grand Alliance issued
3275-442: A source of toxic metals such as lead as well as lesser amounts of materials such as barium , cadmium and chromium . Analog television Analog television 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
3406-400: A standard-definition (SDTV) digital signal instead of an HDTV signal, because current convention allows the bandwidth of a DTV channel (or " multiplex ") to be subdivided into multiple digital subchannels , (similar to what most FM radio stations offer with HD Radio ), providing multiple feeds of entirely different television programming on the same channel. This ability to provide either
3537-523: A statement finding the MPEG-2 system to be "essentially equivalent" to Dolby, but only after the Dolby selection had been made. Later, a story emerged that MIT had entered into an agreement with Dolby whereupon the university would be awarded a large sum of money if the MPEG-2 system was rejected. Dolby also offered an incentive for Zenith to switch their vote (which they did); however, it is unknown whether they accepted
3668-410: 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
3799-502: A terrestrial transmitter in range of their antenna. Other delivery methods include digital cable and digital satellite . In some countries where transmissions of TV signals are normally achieved by microwaves , digital multichannel multipoint distribution service is used. Other standards, such as digital multimedia broadcasting (DMB) and digital video broadcasting - handheld (DVB-H), have been devised to allow handheld devices such as mobile phones to receive TV signals. Another way
3930-438: 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
4061-477: 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
ATSC standards - Misplaced Pages Continue
4192-503: Is Internet Protocol television (IPTV), which is the delivery of TV over a computer network. Finally, an alternative way is to receive digital TV signals via the open Internet ( Internet television ), whether from a central streaming service or a P2P (peer-to-peer) system. Some signals are protected by encryption and backed up with the force of law under the WIPO Copyright Treaty and national legislation implementing it, such as
4323-501: 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
4454-411: 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
4585-440: Is a crucial regulatory tool for controlling the placement and power levels of stations. Digital TV is more tolerant of interference than analog TV. People can interact with a DTV system in various ways. One can, for example, browse the electronic program guide . Modern DTV systems sometimes use a return path providing feedback from the end user to the broadcaster. This is possible over cable TV or through an Internet connection but
4716-415: Is a media container format. It may contain a number of streams of audio or video content multiplexed within the transport stream. Transport streams are designed with synchronization and recovery in mind for potentially lossy distribution (such as over-the-air ATSC broadcast) in order to continue a media stream with minimal interruption in the face of data loss in transmission. When an over-the-air ATSC signal
4847-438: Is actually encoded with 1920×1088 pixel frames, but the last eight lines are discarded prior to display. This is due to a restriction of the MPEG-2 video format, which requires the height of the picture in luma samples (i.e. pixels) to be divisible by 16. The lower resolutions can operate either in progressive scan or interlaced mode, but not the largest picture sizes. The 1080-line system does not support progressive images at
4978-459: Is captured to a file via hardware/software the resulting file is often in a .TS file format. ATSC signals are designed to use the same 6 MHz bandwidth as analog NTSC television channels (the interference requirements of A/53 DTV standards with adjacent NTSC or other DTV channels are very strict). Once the digital video and audio signals have been compressed and multiplexed, the transport stream can be modulated in different ways depending on
5109-569: Is common for there to be a single high-definition signal and several standard-definition signals carried on a single 6 MHz (former NTSC) channel allocation. The high-definition television standards defined by the ATSC produce widescreen 16:9 images up to 1920×1080 pixels in size – more than six times the display resolution of the earlier standard. However, many different image sizes are also supported. The reduced bandwidth requirements of lower-resolution images allow up to six standard-definition "subchannels" to be broadcast on
5240-499: 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
5371-683: Is more prone to electromagnetic interference from engines and rapidly changing multipath conditions. ATSC 2.0 was a planned major new revision of the standard which would have been backward compatible with ATSC 1.0. The standard was to have allowed interactive and hybrid television technologies by connecting the TV with the Internet services and allowing interactive elements into the broadcast stream. Other features were to have included advanced video compression, audience measurement, targeted advertising , enhanced programming guides, video on demand services, and
ATSC standards - Misplaced Pages Continue
5502-470: Is more susceptible to changes in radio propagation conditions than DVB-T and ISDB-T . It also lacks true hierarchical modulation , which would allow the SDTV part of an HDTV signal (or the audio portion of a television program) to be received uninterrupted even in fringe areas where signal strength is low. For this reason, an additional modulation mode, enhanced-VSB ( E-VSB ) has been introduced, allowing for
5633-498: Is not possible with a standard antenna alone. Some of these systems support video on demand using a communication channel localized to a neighborhood rather than a city (terrestrial) or an even larger area (satellite). 1seg (1-segment) is a special form of ISDB . Each channel is further divided into 13 segments. Twelve are allocated for HDTV and the other for narrow-band receivers such as mobile televisions and cell phones . DTV has several advantages over analog television ,
5764-568: Is not readily compatible with a progressive format. DirecTV in the US launched the first commercial digital satellite platform in May 1994, using the Digital Satellite System (DSS) standard. Digital cable broadcasts were tested and launched in the US in 1996 by TCI and Time Warner . The first digital terrestrial platform was launched in November 1998 as ONdigital in the UK, using
5895-450: Is only used by TV networks . Very few teleports outside the U.S. support the ATSC satellite transmission standard, but teleport support for the standard is improving. The ATSC satellite transmission system is not used for direct-broadcast satellite systems; in the U.S. and Canada these have long used either DVB-S (in standard or modified form) or a proprietary system such as DSS or DigiCipher 2 . [REDACTED] ATSC coexists with
6026-504: Is sometimes referred to as mosquito noise . Because of the way the human visual system works, defects in an image that are localized to particular features of the image or that come and go are more perceptible than defects that are uniform and constant. However, the DTV system is designed to take advantage of other limitations of the human visual system to help mask these flaws, e.g., by allowing more compression artifacts during fast motion where
6157-465: 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,
6288-405: 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
6419-440: Is the format used in computers, scans lines in sequences, from top to bottom. The computer industry argued that progressive scanning is superior because it does not flicker in the manner of interlaced scanning. It also argued that progressive scanning enables easier connections with the Internet and is more cheaply converted to interlaced formats than vice versa. The film industry also supported progressive scanning because it offers
6550-453: Is the modulation scheme used on the cable: cable operators in the U.S. (and to a lesser extent Canada) can determine their own method of modulation for their plants. Multiple standards bodies exist in the industry: the SCTE defined 256-QAM as a modulation scheme for cable in a cable industry standard, ANSI/SCTE 07 2006: Digital Transmission Standard For Cable Television Archived July 5, 2010, at
6681-566: 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
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#17328456606616812-456: Is transmitted, and MPEG-2 metadata instructs the decoder to interlace these fields and perform 3:2 pulldown before display, as in soft telecine . The ATSC specification also allows 1080p30 and 1080p24 MPEG-2 sequences, however they are not used in practice, because broadcasters want to be able to switch between 60 Hz interlaced (news), 30 Hz progressive or PsF (soap operas), and 24 Hz progressive (prime-time) content without ending
6943-542: 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
7074-582: Is used in the Netflix VMAF video quality monitoring system. Quantising effects can create contours—rather than smooth gradations—on areas with small graduations in amplitude. Typically, a very flat scene, such as a cloudless sky, will exhibit visible steps across its expanse, often appearing as concentric circles or ellipses. This is known as color banding . Similar effects can be seen in very dark scenes, where true black backgrounds are overlaid by dark gray areas. These transitions may be smooth, or may show
7205-472: 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
7336-413: 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
7467-497: The DVB-T standard, and with ISDB-T . A similar standard called ADTB-T was developed for use as part of China 's new DMB-T/H dual standard. While China has officially chosen a dual standard, there is no requirement that a receiver work with both standards and there is no support for the ADTB modulation from broadcasters or equipment and receiver manufacturers. For compatibility with material from various regions and sources, ATSC supports
7598-780: The DVB-T standard. Digital television supports many different picture formats defined by the broadcast television systems which are a combination of size and aspect ratio (width to height ratio). With digital terrestrial television (DTT) broadcasting, the range of formats can be broadly divided into two categories: high-definition television (HDTV) for the transmission of high-definition video and standard-definition television (SDTV). These terms by themselves are not very precise and many subtle intermediate cases exist. One of several different HDTV formats that can be transmitted over DTV is: 1280 × 720 pixels in progressive scan mode (abbreviated 720p ) or 1920 × 1080 pixels in interlaced video mode ( 1080i ). Each of these uses
7729-641: The EIA-708 standard for digital closed captioning , leading to variations in implementation. ATSC replaced much of the analog NTSC television system in the United States on June 12, 2009, on August 31, 2011 in Canada , on December 31, 2012 in South Korea , and on December 31, 2015 in Mexico . Broadcasters who used ATSC and wanted to retain an analog signal were temporarily forced to broadcast on two separate channels, as
7860-630: The Federal Communications Commission requires cable operators in the United States to carry the analog or digital transmission of a terrestrial broadcaster (but not both), when so requested by the broadcaster (the " must-carry rule"). The Canadian Radio-television and Telecommunications Commission in Canada does not have similar rules in force with respect to carrying ATSC signals. However, cable operators have still been slow to add ATSC channels to their lineups for legal, regulatory, and plant & equipment related reasons. One key technical and regulatory issue
7991-489: 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
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#17328456606618122-468: The Wayback Machine . Consequently, most U.S. and Canadian cable operators seeking additional capacity on the cable system have moved to 256-QAM from the 64-QAM modulation used in their plant, in preference to the 16VSB standard originally proposed by ATSC. Over time 256-QAM is expected to be included in the ATSC standard. There is also a standard for transmitting ATSC via satellite; however, this
8253-430: 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
8384-461: 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
8515-528: 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
8646-687: The 1080i60 MPEG-2 sequence. The 1080-line formats are encoded with 1920 × 1088 pixel luma matrices and 960 × 540 chroma matrices, but the last 8 lines are discarded by the MPEG-2 decoding and display process. In July 2008, ATSC was updated to support the ITU-T H.264 video codec. The new standard is split in two parts: The new standards support 1080p at 50, 59.94 and 60 frames per second; such frame rates require H.264/AVC High Profile Level 4.2 , while standard HDTV frame rates only require Levels 3.2 and 4, and SDTV frame rates require Levels 3 and 3.1. The file extension ".TS" stands for "transport stream", which
8777-453: The 480i video format used in the NTSC analog system (480 lines, approximately 60 fields or 30 frames per second), 576i formats used in most PAL regions (576 lines, 50 fields or 25 frames per second), and 24 frames-per-second formats used in film. While the ATSC system has been criticized as being complicated and expensive to implement and use, both broadcasting and receiving equipment are now comparable in cost with that of DVB. The ATSC signal
8908-404: The ATSC system requires the use of an entire separate channel. Channel numbers in ATSC do not correspond to RF frequency ranges, as they did with analog television . Instead, virtual channels , sent as part of the metadata along with the program(s), allow channel numbers to be remapped from their physical RF channel to any other number 1 to 99, so that ATSC stations can either be associated with
9039-871: The ATSC's standard. In theory, television stations in the U.S. are free to choose any resolution, aspect ratio, and frame/field rate, within the limits of Main Profile @ High Level. Many stations do go outside the bounds of the ATSC specification by using other resolutions – for example, 352 x 480 or 720 x 480. " EDTV " displays can reproduce progressive scan content and frequently have a 16:9 wide screen format. Such resolutions are 704×480 or 720×480 in NTSC and 720×576 in PAL, allowing 60 progressive frames per second in NTSC or 50 in PAL. ATSC also supports PAL frame rates and resolutions which are defined in ATSC A/63 standard. The ATSC A/53 specification imposes certain constraints on MPEG-2 video stream: The ATSC specification and MPEG-2 allow
9170-549: The Bootstrap component of ATSC 3.0 (System Discovery and Signalling) was upgraded from candidate standard to finalized standard. On June 29, 2016, NBC affiliate WRAL-TV in Raleigh, North Carolina , a station known for its pioneering roles in testing the original DTV standards, launched an experimental ATSC 3.0 channel carrying the station's programming in 1080p, as well as a 4K demo loop. The following organizations held patents for
9301-467: The FCC took several important actions. First, the Commission declared that the new TV standard must be more than an enhanced analog signal , but be able to provide a genuine HDTV signal with at least twice the resolution of existing television images. Then, to ensure that viewers who did not wish to buy a new digital television set could continue to receive conventional television broadcasts, it dictated that
9432-454: The FCC's final standard. This outcome resulted from a dispute between the consumer electronics industry (joined by some broadcasters) and the computer industry (joined by the film industry and some public interest groups) over which of the two scanning processes— interlaced or progressive —is superior. Interlaced scanning, which is used in televisions worldwide, scans even-numbered lines first, then odd-numbered ones. Progressive scanning, which
9563-408: 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
9694-411: 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
9825-405: 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
9956-639: The UK use a horizontal resolution of 544 or 704 pixels per line). Each commercial broadcasting terrestrial television DTV channel in North America is allocated enough bandwidth to broadcast up to 19 megabits per second. However, the broadcaster does not need to use this entire bandwidth for just one broadcast channel. Instead, the broadcast can use Program and System Information Protocol and subdivide across several video subchannels (a.k.a. feeds) of varying quality and compression rates, including non-video datacasting services. A broadcaster may opt to use
10087-572: The US Digital Millennium Copyright Act . Access to encrypted channels can be controlled by a removable card, for example via the Common Interface or CableCard . Digital television signals must not interfere with each other and they must also coexist with analog television until it is phased out. The following table gives allowable signal-to-noise and signal-to-interference ratios for various interference scenarios. This table
10218-868: The United States. In metropolitan areas , where population density is highest, COFDM is said to be better at handling multipath propagation . While ATSC is also incapable of true single-frequency network (SFN) operation, the distributed transmission mode, using multiple synchronized on-channel transmitters, has been shown to improve reception under similar conditions. Thus, it may not require more spectrum allocation than DVB-T using SFNs. A comparison study found that ISDB-T and DVB-T performed similarly, and that both were outperformed by DVB-T2 . Mobile reception of digital stations using ATSC has, until 2008, been difficult to impossible, especially when moving at vehicular speeds. To overcome this, there are several proposed systems that report improved mobile reception: Samsung / Rhode & Schwarz 's A-VSB , Harris / LG 's MPH, and
10349-407: 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
10480-461: The ability to store information on new receivers, including Non-realtime (NRT) content. However, ATSC 2.0 was never actually launched, as it was essentially outdated before it could be launched. All of the changes that were a part of the ATSC 2.0 revision were adopted into ATSC 3.0. ATSC 3.0 will provide even more services to the viewer and increased bandwidth efficiency and compression performance, which requires breaking backwards compatibility with
10611-435: 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
10742-423: 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;
10873-419: 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
11004-567: 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
11135-436: 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
11266-425: 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
11397-486: 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
11528-504: The current version. On November 17, 2017, the FCC voted 3–2 in favor of authorizing voluntary deployments of ATSC 3.0, and issued a Report and Order to that effect. ATSC 3.0 broadcasts and receivers are expected to emerge within the next decade. LG Electronics tested the standard with 4K on February 23, 2016. With the test considered a success, South Korea announced that ATSC 3.0 broadcasts would start in February 2017. On March 28, 2016,
11659-408: The development of ATSC 1.0 technology, as listed in the patent pool administered by MPEG LA . The latest patents expired on 16 September 2024. Patents for ATSC 3.0 are still active. Digital television Digital television ( DTV ) is the transmission of television signals using digital encoding, in contrast to the earlier analog television technology which used analog signals . At
11790-414: The digital signals. In the United States, a government-sponsored coupon was available to offset the cost of an external converter box. The digital television transition began around the late 1990s and has been completed on a country-by-country basis in most parts of the world. Prior to the conversion to digital TV, analog television broadcast audio for TV channels on a separate FM carrier signal from
11921-417: 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
12052-617: The early 1990s by the Grand Alliance , a consortium of electronics and telecommunications companies that assembled to develop a specification for what is now known as HDTV . The standard is now administered by the Advanced Television Systems Committee . It includes a number of patented elements, and licensing is required for devices that use these parts of the standard. Key among these is the 8VSB modulation system used for over-the-air broadcasts. ATSC 1.0 technology
12183-514: The early 1990s. In the mid-1980s, as Japanese consumer electronics firms forged ahead with the development of HDTV technology, and as the MUSE analog format was proposed by Japan's public broadcaster NHK as a worldwide standard. Japanese advancements were seen as pacesetters that threatened to eclipse US electronics companies. Until June 1990, the Japanese MUSE standard—based on an analog system—was
12314-482: The eye cannot track and resolve them as easily and, conversely, minimizing artifacts in still backgrounds that, because time allows, may be closely examined in a scene. Broadcast, cable, satellite and Internet DTV operators control the picture quality of television signal encoders using sophisticated, neuroscience-based algorithms, such as the structural similarity index measure (SSIM) video quality measurement tool. Another tool called visual information fidelity (VIF),
12445-522: The front-runner among the more than 23 different technical concepts under consideration. Between 1988 and 1991, several European organizations were working on DCT -based digital video coding standards for both SDTV and HDTV. The EU 256 project by the CMTT and ETSI , along with research by Italian broadcaster RAI , developed a DCT video codec that broadcast SDTV at 34 Mbit/s and near-studio-quality HDTV at about 70–140 Mbit/s . RAI demonstrated this with
12576-436: The highest frame rates of 50, 59.94 or 60 frames per second, because such technology was seen as too advanced at the time. The standard also requires 720-line video be progressive scan, since that provides better picture quality than interlaced scan at a given frame rate, and there was no legacy use of interlaced scan for that format. The result is that the combination of maximum frame rate and picture size results in approximately
12707-425: The image and sound, although the program material may still be watchable. With digital television, because of the cliff effect , reception of the digital signal must be very nearly complete; otherwise, neither audio nor video will be usable. Analog TV began with monophonic sound and later developed multichannel television sound with two independent audio signal channels. DTV allows up to 5 audio signal channels plus
12838-433: 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 the development of the cathode-ray tube (CRT), which uses a focused electron beam to trace lines across
12969-401: 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
13100-439: The method of transmission. The proposals for modulation schemes for digital television were developed when cable operators carried standard-resolution video as uncompressed analog signals. In recent years, cable operators have become accustomed to compressing standard-resolution video for digital cable systems, making it harder to find duplicate 6 MHz channels for local broadcasters on uncompressed "basic" cable. Currently,
13231-435: 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
13362-488: The most significant being that digital channels take up less bandwidth and the bandwidth allocations are flexible depending on the level of compression and resolution of the transmitted image. This means that digital broadcasters can provide more digital channels in the same space, provide high-definition television service, or provide other non-television services such as multimedia or interactivity. DTV also permits special services such as multiplexing (more than one program on
13493-410: 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
13624-408: The new ATV standard must be capable of being simulcast on different channels. The new ATV standard also allowed the new DTV signal to be based on entirely new design principles. Although incompatible with the existing NTSC standard, the new DTV standard would be able to incorporate many improvements. A universal standard for scanning formats, aspect ratios, or lines of resolution was not produced by
13755-451: 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
13886-628: The offer. The ATSC system supports a number of different display resolutions, aspect ratios , and frame rates . The formats are listed here by resolution, form of scanning ( progressive or interlaced ), and number of frames (or fields) per second (see also the TV resolution overview at the end of this article). For transport, ATSC uses the MPEG systems specification, known as an MPEG transport stream , to encapsulate data, subject to certain constraints. ATSC uses 188-byte MPEG transport stream packets to carry data. Before decoding of audio and video takes place,
14017-452: 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
14148-488: 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
14279-732: 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
14410-418: The problem of large numbers of analog receivers being discarded. One superintendent of public works was quoted in 2009 saying; "some of the studies I’ve read in the trade magazines say up to a quarter of American households could be throwing a TV out in the next two years following the regulation change." In Michigan in 2009, one recycler estimated that as many as one household in four would dispose of or recycle
14541-403: The proposed ATSC mobile standards are backward-compatible with existing tuners, despite being added to the standard well after the original standard was in wide use. Mobile reception of some stations will still be more difficult, because 18 UHF channels in the U.S. have been removed from TV service, forcing some broadcasters to stay on VHF. This band requires larger antennas for reception, and
14672-468: 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
14803-544: The receiver must demodulate and apply error correction to the signal. Then, the transport stream may be demultiplexed into its constituent streams. There are four basic display sizes for ATSC, generally known by referring to the number of lines of the picture height. NTSC and PAL image sizes are smallest, with a width of 720 (or 704) and a height of 480 or 576 lines. The third size is HDTV images that have 720 scan lines in height and are 1280 pixels wide. The largest size has 1080 lines high and 1920 pixels wide. 1080-line video
14934-422: The receiving antenna to the transmitter is not available, because usually higher frequency signals can't pass through obstacles as easily. Television sets with only analog tuners cannot decode digital transmissions. When analog broadcasting over the air ceases, users of sets with analog-only tuners may use other sources of programming (e.g., cable, recorded media) or may purchase set-top converter boxes to tune in
15065-445: The receiving equipment starts picking up interference that overpowers the desired signal or if the signal is too weak to decode. Some equipment will show a garbled picture with significant damage, while other devices may go directly from perfectly decodable video to no video at all or lock up. This phenomenon is known as the digital cliff effect. Block errors may occur when transmission is done with compressed images. A block error in
15196-444: The related NTSC channel numbers, or all stations on a network can use the same number. There is also a standard for distributed transmission systems (DTx), a form of single-frequency network which allows for the synchronised operation of multiple on-channel booster stations . Dolby Digital AC-3 is used as the audio codec , though it was standardized as A/52 by the ATSC. It allows the transport of up to five channels of sound with
15327-432: 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
15458-433: The same bandwidth as a single analog channel, and provides many new features that analog television cannot. A transition from analog to digital broadcasting began around 2000. Different digital television broadcasting standards have been adopted in different parts of the world; below are the more widely used standards: Digital television's roots are tied to the availability of inexpensive, high-performance computers . It
15589-403: The same channel), electronic program guides and additional languages (spoken or subtitled). The sale of non-television services may provide an additional revenue source to broadcasters. Digital and analog signals react to interference differently. For example, common problems with analog television include ghosting of images, noise from weak signals and other problems that degrade the quality of
15720-512: The same number of samples per second for both the 1080-line interlaced format and the 720-line format, as 1920*1080*30 is roughly equal to 1280*720*60. A similar equality relationship applies for 576 lines at 25 frame per second versus 480 lines at 30 frames per second. A terrestrial (over-the-air) transmission carries 19.39 megabits of data per second (a fluctuating bandwidth of about 18.3 Mbit/s left after overhead such as error correction, program guide, closed captioning, etc.), compared to
15851-415: 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
15982-476: 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 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
16113-434: 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
16244-528: The time of its development it was considered an innovative advancement and represented the first significant evolution in television technology since color television in the 1950s. Modern digital television is transmitted in high-definition television (HDTV) with greater resolution than analog TV. It typically uses a widescreen aspect ratio (commonly 16:9 ) in contrast to the narrower format ( 4:3 ) of analog TV. It makes more economical use of scarce radio spectrum space; it can transmit up to seven channels in
16375-533: The time. A digital TV broadcast service was proposed in 1986 by Nippon Telegraph and Telephone (NTT) and the Ministry of Posts and Telecommunication (MPT) in Japan, where there were plans to develop an "Integrated Network System" service. However, it was not possible to practically implement such a digital TV service until the adoption of motion-compensated DCT video compression formats such as MPEG made it possible in
16506-435: The transmission bit rate and make reception easier for more distant or mobile viewers. There are several different ways to receive digital television. One of the oldest means of receiving DTV (and TV in general) is from terrestrial transmitters using an antenna (known as an aerial in some countries). This delivery method is known as digital terrestrial television (DTT). With DTT, viewers are limited to channels that have
16637-421: The use of progressive frames coded within an interlaced video sequence. For example, NBC stations transmit a 1080i60 video sequence, meaning the formal output of the MPEG-2 decoding process is sixty 540-line fields per second. However, for prime-time television shows, those 60 fields can be coded using 24 progressive frames as a base – actually, an 1080p24 video stream (a sequence of 24 progressive frames per second)
16768-451: The video signal. This FM audio signal could be heard using standard radios equipped with the appropriate tuning circuits. However, after the digital television transition , no portable radio manufacturer has yet developed an alternative method for portable radios to play just the audio signal of digital TV channels; DTV radio is not the same thing. The adoption of a broadcast standard incompatible with existing analog receivers has created
16899-612: Was approved in 2008 and introduces H.264 /AVC video coding to the ATSC system. ATSC supports 5.1-channel surround sound using Dolby Digital 's AC-3 format. Numerous auxiliary datacasting services can also be provided. Many aspects of ATSC were patented , including elements of the MPEG video coding, the AC-3 audio coding, and the 8VSB modulation. The cost of patent licensing, estimated at up to $ 50 per digital TV receiver, had prompted complaints by manufacturers. As with other systems, ATSC depends on numerous interwoven standards, e.g.,
17030-408: Was not until the 1990s that digital TV became a real possibility. Digital television was previously not practically feasible due to the impractically high bandwidth requirements of uncompressed video , requiring around 200 Mbit/s for a standard-definition television (SDTV) signal, and over 1 Gbit/s for high-definition television (HDTV). In the mid-1980s, Toshiba released
17161-403: Was primarily developed with patent contributions from LG Electronics , which held most of the patents for the ATSC standard. ATSC includes two primary high definition video formats, 1080i and 720p . It also includes standard-definition formats, although initially only HDTV services were launched in the digital format. ATSC can carry multiple channels of information on a single stream, and it
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