Témbongkeun sumber pikeun Standar ATSC

{{redirect|ATSC}}
'''Standar ATSC''' ngadokumentasi hiji format [[televisi digital]] nu bakal ngaganti sistim televisi [[NTSC]] analog (di [[Amerika Sarikat]])<ref>[http://home.businesswire.com/portal/site/home/index.jsp?ndmViewId=news_view&ndmConfigId=1000001&newsId=20071017005469&newsLang=en Major retailer stops selling analog sets]{{Dead link|date=December 2023 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> ti mimiti [[17 Pebruari]], [[2009]].<ref>http://www.dtvtransition.org/</ref> Standar ieu dijieun ku [[Advanced Television Systems Committee]].

Standar televisi definisi luhur nu ditetepkeun ku ATSC ngahasilkeun gambar [[layar lega]] [[16:9]] tepi ka ukuran 1920×1080 [[piksel]] &mdash; leuwih ti genep kalieun [[display resolution|resolusi pidangan]] standar saméméhna. Ukuran gambar lianna ogé dirojong, antukna panglobana genep [[SDTV|standard-definition]] "[[virtual channel]]" bisa disiarkeun dina hiji [[saluran TV]] tunggal 6 [[MegaHertz|MHz]].

ATSC ogé ngarojong audio "kualitas [[movie theater|theater]]" sabab maké format [[AC-3]] [[Dolby Digital]] keur nyadiakeun ''[[surround sound]]'' 5.1 kanal. Sababaraha jasa [[datacasting]] tambahan bisa disadiakeun oge.

Nu nyiarkeun maké ATSC, lamun hayang kénéh mertahankeun sinyal analog, kudu nyiarkeun dina dua saluran nu misah, sabab sistim ATSC kudu maké saluran sagemblengna. Sababaraha saluran bisa dipetakeun deui maké saluran virtual tina saluran [[Frékuénsi radio|RF]] fisik jadi nomer-nomer ti 1 nepi ka 99, antukna stasion ATSC bisa diasosiasikeun jeung nomer saluran NTSC nu patali, atawa bisa ogé sakabéh stasion dina hiji jaringan maké nomer nu sarua. Aya ogé hiji standar keur ''[[distributed transmission|transmisi nu sumebar]]'' (DTx) nu ngidinan [[broadcast translator|booster station]].

Standar ATSC dicirian ku A/x (x nyaéta nomer standarna) tur bisa dicokot kalayan bébas tina ramatloka ATSC (tempo [[#Tumbu luar|tumbu luar]] di handap).

Loba aspek ATSC nu [[paten|dipatenkeun]], kaasup unsur koding vidéo [[MPEG]], koding audio AC-3, sarta modulasi [[8VSB]].<ref>http://www.chinadaily.com.cn/bizchina/2006-12/27/content_768603.htm</ref> Kawas sistim lianna, ATSC gumantung kana sababaraha standar nu patula-patali, contona standar [[EIA-708]] keur [[closed captioning]] digital, geus bareda dina implementasina.

==Resolusi==
Sistim ATSC ngarojong sababaraha resolusi, [[rasio aspék]], jeung [[frame rate]] pidangan nu béda. Formatna didaptar di dieu dumasar resolusi, wangun scanning ([[progressive scan|progresif]] atawa [[interlacing|interlace]]), sarta jumlah frame (atawa field) per detikna (tempo ogé sawangan resolusi TV dina pungkasan artikel ieu):

{|class="wikitable" style="text-align:center;"
|-style="background:#eee;"
!colspan="2"|Resolusi
!rowspan="2"|Rasio aspék
!rowspan="2"|[[Pixel aspect ratio|Rasio aspék piksel]]
!rowspan="2"|Form of scanning
!rowspan="2"|Framerate ([[Hertz|Hz]])
|-style="background:#eee;"
!Vertikal
!Horizontal
|-
|288
|352
|4:3 atawa 16:9
|henteu pasagi
|progresif
|25
|-
|rowspan="4"|480
|rowspan="2"|640
|rowspan="2"|4:3
|rowspan="2"|pasagi
|interlace
|29.97 (59.94 fields/s)<br />30 (60 fields/s)
|-
|progresif
|23.976<br />24<br />29.97<br />30<br />59.94<br />60
|-
|rowspan="2"|704
|rowspan="2"|4:3 or 16:9
|rowspan="2"|henteu pasagi
|interlace
|29.97 (59.94 fields/s)<br />30 (60 fields/s)
|-
|progresif
|23.976<br />24<br />29.97<br />30<br />59.94<br />60
|-
|rowspan="8"|576
|rowspan="2"|352
|rowspan="2"|4:3 or 16:9
|rowspan="2"|henteu pasagi
|interlace
|25 (50 fields/s)
|-
|progresif
|25
|-
|rowspan="2"|480
|rowspan="2"|4:3 or 16:9
|rowspan="2"|henteu pasagi
|interlace
|25 (50 fields/s)
|-
|progresif
|25
|-
|rowspan="2"|544
|rowspan="2"|4:3 or 16:9
|rowspan="2"|henteu pasagi
|interlace
|25 (50 fields/s)
|-
|progresif
|25
|-
|rowspan="2"|720
|rowspan="2"|4:3 or 16:9
|rowspan="2"|henteu pasagi
|interlace
|25 (50 fields/s)
|-
|progresif
|25<br />50
|-
|720
|1280
|16:9
|pasagi
|progresif
|23.976<br />24<br />25<br />29.97<br />30<br />50<br />59.94<br />60
|-
|rowspan="2"|1080
|rowspan="2"|1920
|rowspan="2"|16:9
|rowspan="2"|pasagi
|interlace
|25 (50 fields/s)<br />29.97 (59.94 fields/s)<br />30 (60 fields/s)
|-
|progresif
|23.976<br />24<br />25<br />29.97<br />30
|}

Resolusi nu béda bisa jalan dina mode ''[[progressive scan]]'' atawa ''[[interlace]]'', sanajan sistim 1080-gurat nu pangluhurna henteu bisa midangkeun gambar progresif dina laju 59.94 atawa 60 frame per detik oge. (Tehnologi kawas kieu katempona hadé teuing keur mangsa kiwari, katambah-tambah kualitas gambarna ogé goreng teuing lamun dibandingkeun jeung jumlah data nu bisa dikirimkeun.) Pangiriman terestrial (ngaliwatan udara) mawa 19.39 [[megabit]] data per detik, bandingkeun jeung bitrate maksimm nu mungkin, 10.08 Mbit/s kabawa dina standar [[DVD]].

Pidangan "[[Enhanced-definition television|EDTV]]" bisa ngaréproduksi eusi progressive scan sarta sacara frekuentif boga format layar lega 16:9. Resolusi nu kawas kieu nyaéta 720×480 dina NTSC atawa 720×576 dina PAL, nu ngidinan 60 frame progresif per detik dina NTSC atawa 50 dina PAL.

Aya tilu ukuran pidangan dasar keur ATSC. Ukuran gambar NTSC jeung PAL ''basic'' jeung ''enhanced'' aya dina hambalan handap 480 atawa 576 gurat. Gambar ukuran sedeng mibanda resolusi 720 gurat sarta legana 960 atawa 1280 piksel (rasio aspek, patuturut keur [[4:3]], versi tradisional, jeung [[16:9]], versi layar lega). Pangluhurna boga 1080 gurat boh legana 1440 atawa 1920 piksel (di dieu oge, patuturut keur rasio aspek [[4:3]] jeung [[16:9]]). Vidéo 1080 gurat sabenerna mah dienkode maké frame 1920×1088 piksel, tapi dalapan gurat pangpandeurina dipiceun dina pidangannana. Hl ieu alatan wawates format vidéo MPEG-2, nu nyaratkeun yén jumlah sampel luma nu dikodekeun (contona piksel) bisa dibagi ku 16.

==Kodek==
Keur transpor, ATSC maké spesifikasi sistim [[MPEG-2]], nu katelah [[transport stream]], keur nga-enkapsulasi data, maké wawates tinangtu. ATSC maké paket trnsport stréam 188 bita keur mawa data. saméméh ngadekode audio jeung vidéo, panarima kudu [[demodulasi|ngademodulasi]] jeung nerapkeun [[koreksi kasalahan]] kana sinyal. Tuluy, transport stréam bisa [[demultipleks|didemultipleks]] jadi stréam poko.

Vidéo MPEG-2 dipaké minangka [[video codec]], ogé kalayan wawates tinangtu.

[[Dolby Digital]] AC-3 dipaké minangka [[audio codec]], sanajan resmina distandarkeun minangka A/52 ku ATSC. Hal ieu ngidinan transpor nepi ka lima saluran sora kalayan hiji saluran kagenep keur [[LFE|efek frekuensi handap]] (nu katelah konfigurasi "5.1"). Sabalikna, siaran HDTV [[ISDB]] Jepang mah maké [[Advanced Audio Coding]] (AAC) MPEG minangka audio codec, nu ogé bisa ngaluarkeun audio 5.1. [[DVB]] (tempo [[#Sistim séjén|di handap]]) bisa duanana.

==Modulasi jeung transmisi==
{{utama|8VSB|Tuner QAM}}

Sinyal ATSC dirancang pikeun maké [[lega pita]] 6&nbsp;MHz nu sarua jeung saluran televisi [[NTSC]] (sarat interferensi standar DTV A/53 jeung NTSC nu padeudeukeut atawa jeung saluran DTV lianna kacida ketatna). Lamun sinyal vidéo jeung audio geus dikompresi sarta dimultipleks, transport stréamna bisa [[modulasi|dimodulasi]] maké mangrupa-rupa cara gumantung kana cara pangirimannana.
{{tarjamahkeun|Inggris}}
* Terrestrial (local) broadcasters use [[8VSB]] modulation that can transfer at a maximum rate of 19.39 [[megabit|Mbit/s]], sufficient to carry several vidéo and audio programs and [[metadata]].
* [[Cable television]] stations can generally operate at a higher [[signal-to-noise ratio]] and can use [[16VSB]] or [[256-QAM]] to achieve a throughput of 38.78 Mbit/s, using the same 6&nbsp;MHz channel.

In recent yéars, cable operators have become accustomed to compressing standard-resolution vidéo for [[digital cable]] systems, making it harder to find duplicate 6&nbsp;MHz channels for local broadcasters on uncompressed "basic" cable.

Currently, 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 has similar rules in force with respect to carrying ATSC signals.

However, cable operators in the US (and to a lesser extent Canada) can determine their own method of modulation for their plants.
* Consequently, most North American cable operators have added [[256-QAM]] to the [[16VSB]] standard originally used.
* Cable operators have still been slow to add ATSC channels to their lineups for legal, regulatory, and plant & equipment related réasons.
* 256 QAM is a cable standard, not an ATSC standard; however, over time it is expected to be included in the ATSC standard

There is also a standard for transmitting ATSC via satellite; however, this is only used by [[TV network]]s. Very few teleports outside the US 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, which in North America have long used a system similar to [[DVB-S]].

==Sistim séjén==
Mayoritas nagara di dunya geus milih pikeun maké standar [[DVB]], kawas nu bisa ditingali dina  [http://www.dvb.org/about_dvb/dvb_worldwide/index.xml daptar status ngeunaan ramatloka Proyek DVB].

ATSC marengan ayana standar [[DVB-T]], sarta [[ISDB-T]] nu diterapkeun di Jepang. (modulasi ISDB dipaké ogé minangka dasar standar [[SBTVD-T]] di [[Brazil]].) Standar nu ampir sarua nuu katelah [[ADTB]] dikembangkeun pikeun dipaké minangka bagéantina standar ganda [[DMB-T/H]] anyar bogana [[China]]. Sanajan resmina milih standar ganda, taya persaratan yén hiji panarima bisa cocog jeung dua standar sarta taya rojongan ogé keur modulasi ADTB ti panyiar atawa pabrik alat jeung panarima. Taiwan (Républik China) milih [[DVB-T]] COFDM minangka modulasi resmina.

Sabab bisa dipaké di saluareun wewengkon NTSC nu aya kiwari, sistim ATSC mampuh mawa vidéo dina format [[PAL]] jeung [[SECAM]] (576 gurat nu bisa kapidangkeun, 50 field atwa 25 frame per detik) lian ti keur NTSC (486 gurat nu bisa kapidangkeun, 60 x 1000/1001 field atawa 30 x 1000/1001 frame per detik) jeung [[pilem]] (24 frame per detik).

===Babandingan===
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 is definitely more susceptible to changes in [[radio propagation]] conditions than [[DVB-T]] and [[ISDB-T]]. If ATSC were able to dynamically change its error correction modes, code rates, interléaver mode, and randomizer, the signal could be more robust even if the modulation itself did not change. It also lacks true [[hierarchical modulation]], which allows the SDTV part of an HDTV signal to be received even in fringe aréas where [[signal strength]] is low. For this réason, an additional modulation mode, enhanced-VSB ([[E-VSB]]) has been introduced, allowing for 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 aréas of North America are [[rural]] and have a much lower [[population density]], thereby requiring larger [[transmitter]]s and resulting in large fringe aréas.  In these aréas, 8VSB was shown to perform better than other systems.

COFDM is used in both DVB-T and ISDB-T, and for [[ISDB-H]], as well as [[DVB-H]] and [[HD Radio]] in the United States.  In [[metropolitan area]]s, where the gréat and incréasing majority of North Americans live, COFDM is said to be better at handling [[multipath]].  While ATSC is also incapable of true [[single-frequency network]] (SFN) operation, the distributed transmission mode, using on-channel repéaters, has been shown to improve reception under similar conditions. Thus, it may not require more [[spectrum]] allocation than [[DVB-T]] using SFNs.

==Mobile TV==
Because the FCC forced broadcasters to use 8VSB modulation instéad of COFDM, mobile reception of digital stations has (up till now) been difficult to impossible, especially when moving at vehicle speeds.  To overcome this, there are now at léast three standards which claim to improve mobile reception: [[Samsung]]'s [[A-VSB]], [[Harris Broadcast|Harris]] and [[LG]]'s [[MPH (ATSC)|MPH]], and now the ATSC's own [[ATSC-M/H]].  This is in addition to other proprietary standards like [[MediaFLO]], and worldwide open standards like [[DVB-H]] and [[DMB]]-T.  Like DVB-H and ISDB [[1seg]], 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 the FCC sold-off the rights to 18 of the UHF channels, forcing several broadcasters to stay on VHF.  This band requires larger antennas for reception, and is more prone to [[electromagnetic interference]] from [[engine]]s and rapidly-changing [[multipath]] conditions, aréas where ATSC's 8VSB is inferior to the COFDM of other standards.

== Nagara katut wewengkon nu make ATSC ==
=== Amérika ===
* {{flagcountry|Argéntina}} (uji coba)<ref>Argentina did reconsider its choice of [[8VSB]], but has been sitting on the fence for a number of years.  On November 17, 2006, the three standards (DVB, ATSC and ISDB) were presented to Argentinian Government officials, but no decision to change the standard has been made.  Brazil has now chosen [[ISDB-T]] and this decision may influence other Central and South American countries to follow their lead.{{Fact|date=Désémber 2007}}</ref>
* {{flagcountry|Bahama}}
* {{flagcountry|Kanada}}
* {{flagcountry|Kolombia}} (uji coba)
* {{flagcountry|Cili}} (ukur nyoba di [[Santiago, Chile|Santiago]])
* {{flagcountry|Guatemala}} (uji coba)
* {{flagcountry|Honduras}}
* {{flagcountry|Méksiko}}
* {{flagcountry|Péru}} (ukur nyoba di [[Lima Metropolitan Area|Lima]])
* {{flagcountry|Amérika Sarikat}}
** {{flagcountry|Puerto Rico}}
** {{flagcountry|Kapuloan Virgin A.S.}}

=== Asia/Pasifik ===
* {{flagcountry|Samoa Amérika}}
* {{flagcountry|Guam}}
* {{flagcountry|Kapuloan Mariana Kalér}}
* {{flagcountry|Pilipina}} (uji coba)
* {{flagcountry|Koréa Kidul}}

== Rujukan ==
{{reflist}}

==Tempo oge==
*[[Advanced Television Systems Committee]]
*[[Tuner ATSC]]
*[[Daptar standar ATSC]]
*[[Bandéra siaran]]
*[[DVB]] - Standar televisi digital Eropa
*[[EIA-708]]
*[[OpenCable]]

==Tumbu luar==
*[http://www.atsc.org ATSC website]
*[http://www.atsc.org/guide_default.html ATSC standards download page] {{Webarchive|url=https://web.archive.org/web/20060218161605/http://www.atsc.org/guide_default.html |date=2006-02-18 }}

{{TV resolution}}
{{Video formats}}

[[Kategori:ATSC|*]]
[[Kategori:MPEG]]
[[Kategori:Televisi digital]]
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[[Kategori:Téhnologi televisi]]