Standar ATSC

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(Dialihkeun ti ATSC Standards)
Luncat ka: pituduh, sungsi
“ATSC” dialihkeun ka dieu. Keur kagunaan sejen, tingali ATSC (disambiguasi).

Standar ATSC ngadokumentasi hiji format televisi digital nu bakal ngaganti sistim televisi NTSC analog (di Amerika Sarikat)[1] ti mimiti 17 Pebruari, 2009.[2] 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 — leuwih ti genep kalieun resolusi pidangan standar samemehna. Ukuran gambar lianna oge dirojong, sahingga panglobana genep standard-definition "virtual channel" bisa disiarkeun dina hiji saluran TV tunggal 6 MHz.

ATSC oge ngarojong audio "kualitas theater" sabab make format AC-3 Dolby Digital keur nyadiakeun surround sound 5.1 kanal. Sababaraha jasa datacasting tambahan bisa disadiakeun oge.

Nu nyiarkeun make ATSC, lamun hayang keneh mertahankeun sinyal analog, kudu nyiarkeun dina dua saluran nu misah, sabab sistim ATSC kudu make saluran sagemblengna. Sababaraha saluran bisa dipetakeun deui make saluran virtual tina saluran RF fisik jadi nomer-nomer ti 1 nepi ka 99, sahingga stasion ATSC bisa diasosiasikeun jeung nomer saluran NTSC nu patali, atawa bisa oge sakabeh stasion dina hiji jaringan make nomer nu sarua. Aya oge hiji standar keur transmisi nu sumebar (DTx) nu ngidinan booster station.

Standar ATSC dicirian ku A/x (x nyaeta nomer standarna) tur bisa dicokot kalayan bebas tina ramatloka ATSC (tempo tumbu luar di handap).

Loba aspek ATSC nu dipatenkeun, kaasup unsur koding video MPEG, koding audio AC-3, sarta modulasi 8VSB.[3] Kawas sistim lianna, ATSC gumantung kana sababaraha standar nu patula-patali, contona standar EIA-708 keur closed captioning digital, geus bareda dina implementasina.

Daptar eusi

[édit] Resolusi

Sistim ATSC ngarojong sababaraha resolusi, rasio aspék, jeung frame rate pidangan nu beda. Formatna didaptar di dieu dumasar resolusi, wangun scanning (progresif atawa interlace), sarta jumlah frame (atawa field) per detikna (tempo oge sawangan resolusi TV dina pungkasan artikel ieu):

Resolusi Rasio aspék Rasio aspék piksel Form of scanning Framerate (Hz)
Vertikal Horizontal
288 352 4:3 atawa 16:9 henteu pasagi progresif 25
480 640 4:3 pasagi interlace 29.97 (59.94 fields/s)
30 (60 fields/s)
progresif 23.976
24
29.97
30
59.94
60
704 4:3 or 16:9 henteu pasagi interlace 29.97 (59.94 fields/s)
30 (60 fields/s)
progresif 23.976
24
29.97
30
59.94
60
576 352 4:3 or 16:9 henteu pasagi interlace 25 (50 fields/s)
progresif 25
480 4:3 or 16:9 henteu pasagi interlace 25 (50 fields/s)
progresif 25
544 4:3 or 16:9 henteu pasagi interlace 25 (50 fields/s)
progresif 25
720 4:3 or 16:9 henteu pasagi interlace 25 (50 fields/s)
progresif 25
50
720 1280 16:9 pasagi progresif 23.976
24
25
29.97
30
50
59.94
60
1080 1920 16:9 pasagi interlace 25 (50 fields/s)
29.97 (59.94 fields/s)
30 (60 fields/s)
progresif 23.976
24
25
29.97
30

Resolusi nu beda 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 hade teuing keur mangsa kiwari, katambah-tambah kualitas gambarna oge 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 "EDTV" bisa ngareproduksi eusi progressive scan sarta sacara frekuentif boga format layar lega 16:9. Resolusi nu kawas kieu nyaeta 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). Video 1080 gurat sabenerna mah dienkode make frame 1920×1088 piksel, tapi dalapan gurat pangpandeurina dipiceun dina pidangannana. Hl ieu alatan wawates format video MPEG-2, nu nyaratkeun yen jumlah sampel luma nu dikodekeun (contona piksel) bisa dibagi ku 16.

[édit] Kodek

Keur transpor, ATSC make spesifikasi sistim MPEG-2, nu katelah transport stream, keur nga-enkapsulasi data, make wawates tinangtu. ATSC make paket trnsport stream 188 bita keur mawa data. Samemeh ngadekode audio jeung video, panarima kudu ngademodulasi jeung nerapkeun koreksi kasalahan kana sinyal. Tuluy, transport stream bisa didemultipleks jadi stream poko.

Video MPEG-2 dipake minangka video codec, oge kalayan wawates tinangtu.

Dolby Digital AC-3 dipake 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 efek frekuensi handap (nu katelah konfigurasi "5.1"). Sabalikna, siaran HDTV ISDB Jepang mah make Advanced Audio Coding (AAC) MPEG minangka audio codec, nu oge bisa ngaluarkeun audio 5.1. DVB (tempo di handap) bisa duanana.

[édit] Modulasi jeung transmisi

Artikel utama: 8VSB

Sinyal ATSC dirancang pikeun make lega pita 6 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 video jeung audio geus dikompresi sarta dimultipleks, transport streamna bisa dimodulasi make mangrupa-rupa cara gumantung kana cara pangirimannana.

Panneau travaux.png Artikel ieu keur dikeureuyeuh, ditarjamahkeun tina basa Inggris.
Bantosanna diantos kanggo narjamahkeun.
  • Terrestrial (local) broadcasters use 8VSB modulation that can transfer at a maximum rate of 19.39 Mbit/s, sufficient to carry several video 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 MHz channel.

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, 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 reasons.
  • 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 networks. 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.

[édit] Sistim séjén

Mayoritas nagara di dunya geus milih pikeun make standar DVB, kawas nu bisa ditingali dina daptar status ngeunaan ramatloka Proyek DVB.

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

Sabab bisa dipake di saluareun wewengkon NTSC nu aya kiwari, sistim ATSC mampuh mawa video 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).

[édit] 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, interleaver 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 areas where signal strength is low. For this reason, 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 areas of North America 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 ISDB-H, as well as DVB-H and HD Radio in the United States. In metropolitan areas, where the great and increasing 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 repeaters, has been shown to improve reception under similar conditions. Thus, it may not require more spectrum allocation than DVB-T using SFNs.

[édit] Mobile TV

Because the FCC forced broadcasters to use 8VSB modulation instead 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 least three standards which claim to improve mobile reception: Samsung's A-VSB, Harris and LG's 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 engines and rapidly-changing multipath conditions, areas where ATSC's 8VSB is inferior to the COFDM of other standards.

[édit] Nagara katut wewengkon nu make ATSC

[édit] Amérika

[édit] Asia/Pasifik

[édit] Rujukan

  1. ↑ Major retailer stops selling analog sets
  2. ↑ http://www.dtvtransition.org/
  3. ↑ http://www.chinadaily.com.cn/bizchina/2006-12/27/content_768603.htm
  4. ↑ 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.[rujukan?]

[édit] Tempo oge

[édit] Tumbu luar

t·s·é
Résolusi Vidéo Digital
Designation
Usage Examples Definition (lines) Rate (Hz)
Interlaced (fields) Progressive (frames)
Low; MP@LL
LDTV, VCD 240; 288 (SIF)   24, 30; 25
Standard; MP@ML
SDTV, SVCD, DVD, DV 480 (NTSC, PAL-M) 60 24, 30
576 (PAL, SECAM) 50 25
Enhanced
EDTV 480; 576   60; 50
High; MP@HL
Ultra High
Quad HD, Chi Mei Optoelectronics LCD TV 1440  
2160
Visual comparison of common video/TV display resolutions
This table illustrates total horizontal and vertical pixel resolution via box size. It does not accurately reflect the screen shape (aspect ratio) of these formats, which is either 4:3, or 16:9.
t·s·é
Format video siaran
Siaran analog
525 gurat: NTSC • NTSC-J • PAL-M

625 gurat: PAL • PAL-N • PALplus • SECAM

Sistim nu geus teu dipaké: Pre-1940 • 405 lines • 819 lines • Baird-Nipkow • MAC • MUSE

Audio multikanal: BTSC (MTS) • NICAM-728 • Zweiton (A2, IGR) • EIAJ

Sinyal nu disumputkeun: Captioning • Teletext • CGMS-A • GCR • PDC • VBI • VEIL • VITC • WSS • XDS
Siaran digital
Interlace: SDTV (480i, 576i) • HDTV (1080i)

Progrésif: LDTV (240p, 288p, 1seg) • EDTV (480p, 576p) • HDTV (720p, 1080p)

Standar TV digital (MPEG-2):ATSC, DVB, ISDB, DMB-T/H

Standar TV digital (MPEG-4 AVC):DMB-T/H,DVB,SBTVD,ISDB (1seg)

Audio multikanal: AC3 (5.1) • Musicam • PCM • LPCM • AAC

Sinyal nu disumputkeun: Captioning • Teletext • (CPCM/Broadcast flag) • AFD • EPG

Bioskop digital: UHDV (2540p, 4320p) • DCI
Isu téhnis
Disalin ti "http://su.wikipedia.org/wiki/Standar_ATSC"