ATSC-M/H ( Advanced Television Systems Committee - Mobile/Handheld ) is a U.S. standard for mobile digital TV that allows TV broadcasts to be received by mobile devices .
88-538: ATSC-M/H is a mobile TV extension to preexisting terrestrial TV broadcasting standard ATSC A/53. It corresponds to the European DVB-H and 1seg extensions of DVB-T and ISDB-T terrestrial digital TV standards respectively. ATSC is optimized for a fixed reception in the typical North American environment and uses 8VSB modulation . The ATSC transmission method is not robust enough against Doppler shift and multipath radio interference in mobile environments, and
176-507: A Finite impulse response (FIR) filter, while a recursive convolutional code might be considered an Infinite impulse response (IIR) filter. Convolutional codes are used extensively to achieve reliable data transfer in numerous applications, such as digital video , radio, mobile communications (e.g., in GSM, GPRS, EDGE and 3G networks (until 3GPP Release 7) ) and satellite communications . These codes are often implemented in concatenation with
264-478: A concatenated code with an inner convolutional code. The popular solution for this problem is to interleave data before convolutional encoding, so that the outer block (usually Reed–Solomon ) code can correct most of the errors. Several algorithms exist for decoding convolutional codes. For relatively small values of k , the Viterbi algorithm is universally used as it provides maximum likelihood performance and
352-480: A 'mother' code rate n / k = 1 / 2 {\displaystyle n/k=1/2} may be punctured to a higher rate of, for example, 7 / 8 {\displaystyle 7/8} simply by not transmitting a portion of code symbols. The performance of a punctured convolutional code generally scales well with the amount of parity transmitted. The ability to perform economical soft decision decoding on convolutional codes, as well as
440-469: A constraint length of 2 and a rate of 1/2 is used in GSM as an error correction technique. Convolutional code with any code rate can be designed based on polynomial selection; however, in practice, a puncturing procedure is often used to achieve the required code rate. Puncturing is a technique used to make a m / n rate code from a "basic" low-rate (e.g., 1/ n ) code. It is achieved by deleting of some bits in
528-409: A continuous bitstream, the value of t applies to a quantity of errors located relatively near to each other. That is, multiple groups of t errors can usually be fixed when they are relatively far apart. Free distance can be interpreted as the minimal length of an erroneous "burst" at the output of a convolutional decoder. The fact that errors appear as "bursts" should be accounted for when designing
616-474: A data stream. The sliding application represents the 'convolution' of the encoder over the data, which gives rise to the term 'convolutional coding'. The sliding nature of the convolutional codes facilitates trellis decoding using a time-invariant trellis. Time invariant trellis decoding allows convolutional codes to be maximum-likelihood soft-decision decoded with reasonable complexity. The ability to perform economical maximum likelihood soft decision decoding
704-451: A fixed duration of 968 ms, is divided into five M/H sub-frames and each sub-frame is further subdivided into sixteen M/H Slots. Each slot is the equivalent amount of time needed to transmit 156 TS packets. A slot may either carry all main ATSC data (A/53) or 118 packets of M/H data and 38 packets of main data. The collection of 118 M/H packets transmitted within a slot is called an M/H Group. Each of
792-456: A hard-decision code, particularly Reed–Solomon . Prior to turbo codes such constructions were the most efficient, coming closest to the Shannon limit . To convolutionally encode data, start with k memory registers , each holding one input bit. Unless otherwise specified, all memory registers start with a value of 0. The encoder has n modulo-2 adders (a modulo 2 adder can be implemented with
880-597: 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
968-451: 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 ,
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#17328514033301056-473: 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
1144-448: A single Boolean XOR gate , where the logic is: 0+0 = 0 , 0+1 = 1 , 1+0 = 1 , 1+1 = 0 ), and n generator polynomials — one for each adder (see figure below). An input bit m 1 is fed into the leftmost register. Using the generator polynomials and the existing values in the remaining registers, the encoder outputs n symbols. These symbols may be transmitted or punctured depending on
1232-602: 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
1320-459: 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
1408-523: 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
1496-912: A strict requirement, but a common practice. The example encoder in Img. 2. is an 8-state encoder because the 3 registers will create 8 possible encoder states (2 ). A corresponding decoder trellis will typically use 8 states as well. Recursive systematic convolutional (RSC) codes have become more popular due to their use in Turbo Codes. Recursive systematic codes are also referred to as pseudo-systematic codes. Other RSC codes and example applications include: Useful for LDPC code implementation and as inner constituent code for serial concatenated convolutional codes (SCCC's). Useful for SCCC's and multidimensional turbo codes. Useful as constituent code in low error rate turbo codes for applications such as satellite links. Also suitable as SCCC outer code. A convolutional encoder
1584-410: Is a finite state machine . An encoder with n binary cells will have 2 states. Imagine that the encoder (shown on Img.1, above) has '1' in the left memory cell ( m 0 ), and '0' in the right one ( m −1 ). ( m 1 is not really a memory cell because it represents a current value). We will designate such a state as "10". According to an input bit the encoder at the next turn can convert either to
1672-415: 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
1760-580: Is a service for mobile TV receivers and partly uses the 19.39 Mbit/s ATSC 8VSB stream. The mobile data is carried in an unreferenced Packet ID, so legacy receivers ignore the mobile data. ATSC-M/H bandwidth consumes fixed chunks of 917 kbit/s out of the total ATSC Bandwidth. Each such chunk is called an M/H Group. A data pipe called a parade is a collection of one to eight M/H groups. A parade conveys one or two ensembles which are logical pipes of IP datagrams. Those datagrams in turn carry TV services, System Signaling tables, OMA DRM key streams and
1848-438: 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
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#17328514033301936-462: Is called so because it performs a convolution of the input stream with the encoder's impulse responses : where x is an input sequence, y is a sequence from output j , h is an impulse response for output j and ∗ {\displaystyle {*}} denotes convolution. A convolutional encoder is a discrete linear time-invariant system . Every output of an encoder can be described by its own transfer function , which
2024-459: 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
2112-449: Is closely related to the generator polynomial. An impulse response is connected with a transfer function through Z-transform . Transfer functions for the first (non-recursive) encoder are: Transfer functions for the second (recursive) encoder are: Define m by where, for any rational function f ( z ) = P ( z ) / Q ( z ) {\displaystyle f(z)=P(z)/Q(z)\,} , Then m
2200-569: 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
2288-470: Is defined by the respective communication standard. Punctured convolutional codes are widely used in the satellite communications , for example, in Intelsat systems and Digital Video Broadcasting . Punctured convolutional codes are also called "perforated". Simple Viterbi-decoded convolutional codes are now giving way to turbo codes , a new class of iterated short convolutional codes that closely approach
2376-511: Is designed for highly directional fixed antennas. To overcome these issues, additional channel coding mechanisms are introduced in ATSC-M/H to protect the signal. As of 2021, ATSC-M/H is considered to have been a commercial failure. Several requirements of the new standard were fixed right from the beginning: Ten systems from different companies were proposed, and two remaining systems were presented with transmitter and receiver prototypes: To find
2464-546: Is highly parallelizable. Viterbi decoders are thus easy to implement in VLSI hardware and in software on CPUs with SIMD instruction sets. Longer constraint length codes are more practically decoded with any of several sequential decoding algorithms, of which the Fano algorithm is the best known. Unlike Viterbi decoding, sequential decoding is not maximum likelihood but its complexity increases only slightly with constraint length, allowing
2552-515: Is improved by an additional CRC checksum since bytes can be marked as defective before they are decoded (erasure decoding). The number of RS parity symbols can represent 24, 36 or 48. The symbols and the additional checksum form the outer elements of a data matrix which is allocated by the payload of the M/H Ensemble. The number of lines is fixed and the number of columns is variable according to how many slots per Subframe are occupied. The RS Frame
2640-548: 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
2728-684: 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-M/H - Misplaced Pages Continue
2816-470: 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
2904-415: Is one of the major benefits of convolutional codes. This is in contrast to classic block codes, which are generally represented by a time-variant trellis and therefore are typically hard-decision decoded. Convolutional codes are often characterized by the base code rate and the depth (or memory) of the encoder [ n , k , K ] {\displaystyle [n,k,K]} . The base code rate
2992-451: 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
3080-407: Is performed on blocks of data. Convolutionally encoded block codes typically employ termination. The arbitrary block length of convolutional codes can also be contrasted to classic block codes , which generally have fixed block lengths that are determined by algebraic properties. The code rate of a convolutional code is commonly modified via symbol puncturing . For example, a convolutional code with
3168-405: Is the maximum of the polynomial degrees of the H i ( 1 / z ) {\displaystyle H_{i}(1/z)\,} , and the constraint length is defined as K = m + 1 {\displaystyle K=m+1\,} . For instance, in the first example the constraint length is 3, and in the second the constraint length is 4. A convolutional encoder
3256-453: 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
3344-600: Is then partitioned into several segments of different sizes and assigned to specified regions. The M/H data in these regions are protected by an SCCC (Series Concatenated Convolutional Code), incorporating a code rate of 1/2 or 1/4, and is specific to each region in a group. A 1/4 rate PCCC (Parallel Concatenated Convolutional Code) is also employed as an inner code for the M/H signaling channel, which includes FIC (Fast Information Channel) and TPC (Transmission Parameter Channel). The TPC carries various FEC modes and M/H Frame information. Once
3432-456: 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
3520-500: Is typically given as n / k {\displaystyle n/k} , where n is the raw input data rate and k is the data rate of output channel encoded stream. n is less than k because channel coding inserts redundancy in the input bits. The memory is often called the "constraint length" K , where the output is a function of the current input as well as the previous K − 1 {\displaystyle K-1} inputs. The depth may also be given as
3608-544: 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
ATSC-M/H - Misplaced Pages Continue
3696-646: 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
3784-473: The Electronic Service Guide . ATSC-M/H has an improved design based on detailed analyses of experiences with other mobile DTV standards. ATSC-M/H protocol stack is mainly an umbrella protocol that uses OMA ESG, OMA DRM, MPEG-4 in addition to many IETF RFCs. The ATSC-M/H standard defines a fixed transport stream structure, based on M/H Frames, which establishes the location of M/H content within
3872-630: 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
3960-484: The Viterbi algorithm . Other trellis-based decoder algorithms were later developed, including the BCJR decoding algorithm. Recursive systematic convolutional codes were invented by Claude Berrou around 1991. These codes proved especially useful for iterative processing including the processing of concatenated codes such as turbo codes . Using the "convolutional" terminology, a classic convolutional code might be considered
4048-522: The Voyager program , has a constraint length K of 7 and a rate r of 1/2. Mars Pathfinder , Mars Exploration Rover and the Cassini probe to Saturn use a K of 15 and a rate of 1/6; this code performs about 2 dB better than the simpler K = 7 {\displaystyle K=7} code at a cost of 256× in decoding complexity (compared to Voyager mission codes). The convolutional code with
4136-468: 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
4224-445: The "01" state or the "11" state. One can see that not all transitions are possible for (e.g., a decoder can't convert from "10" state to "00" or even stay in "10" state). All possible transitions can be shown as below: An actual encoded sequence can be represented as a path on this graph. One valid path is shown in red as an example. This diagram gives us an idea about decoding : if a received sequence doesn't fit this graph, then it
4312-688: 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
4400-641: The 118 M/H packets within an M/H Group are encapsulated inside a special TS packet, known as an MHE packet. An M/H Parade is a collection of M/H Groups and can carry one or two M/H Ensembles. These Ensembles are logical pipes for IP datagrams. Those datagrams in turn carry TV services and the signaling of mobile content. The M/H Groups from a single Parade are placed within M/H Slots according to an algorithm defined in A/153 Part 2. The Number of Groups per M/H Sub-Frame (NoG) for an M/H Parade ranges from 1 to 8 and therefore
4488-501: 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
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#17328514033304576-404: 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
4664-918: 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
4752-487: The ATSC-M/H multiplexer and the ATSC-M/H transmitter are synchronized by a GPS reference. The ATSC-M/H multiplexer operates as a network adapter and inserts time stamps in the MPEG transport stream . The transmitter analyzes the time stamp, delays the transport stream before it is modulated and transmitted. Eventually, all SFN transmitters generate a synchronized signal. Until its shutdown, MediaFLO had been available in parts of
4840-555: The Advanced Television Systems Committee elevated its specification for Mobile Digital Television to Candidate Standard status. In the following six months, the industry tested the standard. Before it became an official standard, additional improvements were proposed. The ATSC Mobile DTV standard ATSC-M/H (A/153) is modular in concept, with the specifications for each of the modules contained separate Parts. The individual Parts of A/153 are as follows: ATSC-M/H
4928-551: 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
5016-527: The SDP-File is transmitted within the SMT-Table. Most of the information is coded in binary, but some is coded in the original ASCII text format. The SMT-Table combines information that is typically in different tables and reduces the complexity for the network and the receivers. In case of signaling with ESG, the complete SDP-File is transmitted. In an SFN, two or more transmitters with an overlapping coverage send
5104-482: The TPC is extracted, the receiver then knows the code rates being employed and can decode each region at its specified rate. A modified trellis encoder is also employed for backwards compatibility with legacy A/53 receivers. The time interleaving of ATSC-M/H is 1 second. ATSC M/H Signaling and Announcement defines three different layers of signalling. The layers are organized hierarchically and optimized to characteristics of
5192-870: 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
5280-658: The United States. It was a premium service that required subscription. ATSC-M/H would be free to air , as are regular broadcast signals. Both Standards were designed without sufficient consideration of the continued growth of the internet and mobile platforms which today provide excellent multimedia capabilities using only web-centric codecs and protocols rather than repurposing of existing Standards suited to legacy broadcasting. ATSC 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
5368-565: The VSB Frames and allows for easier processing by an M/H receiver. This is contrary to the legacy ATSC transport stream, defined in A/53, in which there is no fixed structure to establish the phase of the data relative to VSB Frames. One M/H Frame is equivalent in size to 20 VSB Frames and has an offset of 37 transport stream (TS) packets relative to the beginning of the VSB Frame. Each M/H Frame, which has
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#17328514033305456-465: 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
5544-564: The best solution, the Advanced Television Systems Committee assigned the Open Mobile Video Coalition (OMVC) to test both systems. The test report was presented on May 15, 2008. As a result of this detailed work by the OMVC, a final standard draft was designed by the Advanced Television Systems Committee, specialist group S-4. ATSC-M/H will be a hybrid. Basically the following components of the proposed systems are used: On December 1, 2008,
5632-608: The bits that form the most likely codeword. An approximate confidence measure can be added to each bit by use of the Soft output Viterbi algorithm . Maximum a posteriori (MAP) soft decisions for each bit can be obtained by use of the BCJR algorithm . In fact, predefined convolutional codes structures obtained during scientific researches are used in the industry. This relates to the possibility to select catastrophic convolutional codes (causes larger number of errors). An especially popular Viterbi-decoded convolutional code, used at least since
5720-474: The block length and code rate flexibility of convolutional codes, makes them very popular for digital communications. Convolutional codes were introduced in 1955 by Peter Elias . It was thought that convolutional codes could be decoded with arbitrary quality at the expense of computation and delay. In 1967, Andrew Viterbi determined that convolutional codes could be maximum-likelihood decoded with reasonable complexity using time invariant trellis based decoders —
5808-552: 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,
5896-734: The desired code rate. Now bit shift all register values to the right ( m 1 moves to m 0 , m 0 moves to m −1 ) and wait for the next input bit. If there are no remaining input bits, the encoder continues shifting until all registers have returned to the zero state (flush bit termination). The figure below is a rate 1 ⁄ 3 ( m ⁄ n ) encoder with constraint length ( k ) of 3. Generator polynomials are G 1 = (1,1,1), G 2 = (0,1,1) , and G 3 = (1,0,1) . Therefore, output bits are calculated (modulo 2) as follows: Convolutional codes can be systematic and non-systematic: Non-systematic convolutional codes are more popular due to better noise immunity. It relates to
5984-400: 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. Convolutional code In telecommunication , a convolutional code is a type of error-correcting code that generates parity symbols via the sliding application of a boolean polynomial function to
6072-617: 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
6160-401: The encoder output. Bits are deleted according to a puncturing matrix . The following puncturing matrices are the most frequently used: For example, if we want to make a code with rate 2/3 using the appropriate matrix from the above table, we should take a basic encoder output and transmit every first bit from the first branch and every bit from the second one. The specific order of transmission
6248-511: The free distance of the convolutional code. The encoder on the picture above is a non-recursive encoder. Here's an example of a recursive one and as such it admits a feedback structure: The example encoder is systematic because the input data is also used in the output symbols (Output 2). Codes with output symbols that do not include the input data are called non-systematic. Recursive codes are typically systematic and, conversely, non-recursive codes are typically non-systematic. It isn't
6336-436: 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
6424-439: 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,
6512-412: The number of Groups per an M/H Frame for a Parade ranges from 5 to 40 with a step of 5. The data of a Parade are channel coded and distributed by an interleaver during an M/H Frame. Mobile Data are protected by an additional FEC, as Interleaving and Convolutional codes . To improve the reception in the receiver, training sequences are introduced into the ATSC-M/H signal to allow channel estimation on
6600-399: The number of memory elements v in the polynomial or the maximum possible number of states of the encoder (typically: 2 v {\displaystyle 2^{v}} ). Convolutional codes are often described as continuous. However, it may also be said that convolutional codes have arbitrary block length, rather than being continuous, since most real-world convolutional encoding
6688-583: 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,
6776-403: 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
6864-544: 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
6952-419: The receiver side. Time slicing is a technique used by ATSC-M/H to provide power savings on receivers. It is based on the time- multiplexed transmission of different services. ATSC-M/H combines multiple error protection mechanisms for added robustness. One is an outer Reed–Solomon error correction code which corrects defective bytes after decoding the outer convolutional code in the receiver. The correction
7040-444: 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
7128-512: 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
7216-519: The same program content simultaneously on the same frequency . The 8VSB modulation used by ATSC allows SFN transmissions. To allow regular channel approximation, ATSC-M/H provides additional training sequences. ATSC A/110 defines a method to synchronize the ATSC modulator as part of the transmitter. The A/110 standard sets up the Trellis coder in a pre-calculated way to all transmitters of the SFN. In such an SFN,
7304-481: The transmission layer. Each video- or audio decoder needs information about the used coding parameters, for instance resolution, frame rate and IDR (Random Access Point) repetition rate. In MPEG-4/AVC, mobile TV systems the receiver uses information from the Session Description Protocol File (SDP-File). The SDP-file is a format which describes streaming media initialization parameters. In ATSC-M/H,
7392-421: 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)
7480-481: The use of strong, long-constraint-length codes. Such codes were used in the Pioneer program of the early 1970s to Jupiter and Saturn, but gave way to shorter, Viterbi-decoded codes, usually concatenated with large Reed–Solomon error correction codes that steepen the overall bit-error-rate curve and produce extremely low residual undetected error rates. Both Viterbi and sequential decoding algorithms return hard decisions:
7568-615: 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.,
7656-404: 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
7744-453: Was received with errors, and we must choose the nearest correct (fitting the graph) sequence. The real decoding algorithms exploit this idea. The free distance ( d ) is the minimal Hamming distance between different encoded sequences. The correcting capability ( t ) of a convolutional code is the number of errors that can be corrected by the code. It can be calculated as Since a convolutional code doesn't use blocks, processing instead
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