ATSC
Cac tieu chuan cua Uy ban He thong Truyen hinh Tien tien (ATSC) la mot bo cac tieu chuan de truyen hinh ky thuat so qua cac mang mat dat, cap va ve tinh. No phan lon la su thay the cho tieu chuan NTSC tuong tu, va giong nhu tieu chuan do, duoc su dung chu yeu o Hoa Ky, Mexico va Canada. Nhung nguoi dung truoc day cua NTSC, nhu Nhat Ban, da khong su dung ATSC trong qua trinh chuyen doi truyen hinh ky thuat so cua ho vi ho da ap dung he thong cua rieng ho duoc goi la ISDB.
Cac tieu chuan ATSC duoc phat trien vao dau nhung nam 1990 boi Grand Alliance, mot tap doan gom cac cong ty dien tu va vien thong duoc lap rap de phat trien mot dac diem ky thuat cho cai ma ngay nay goi la HDTV. Tieu chuan nay hien duoc quan ly boi Uy ban He thong Truyen hinh Tien tien. Tieu chuan bao gom mot so yeu to duoc cap bang sang cheva viec cap phep la bat buoc doi voi cac thiet bi su dung cac phan nay cua tieu chuan. Diem mau chot trong so nay la he thong dieu che 8VSB duoc su dung de phat song qua khong trung. Cong nghe ATSV duoc phat trien chu yeu voi su dong gop bang sang che cua LG Electronics, cong ty nam giu hau het cac bang sang che cho tieu chuan ATSV.
ATSC bao gom hai dinh dang video do net cao chinh, 1080i va 720p. No cung bao gom cac dinh dang do net tieu chuan, mac du ban dau chi co cac dich vu HDTV duoc ra mat o dinh dang ky thuat so. ATSC co the mang nhieu kenh thong tin tren mot luong va thong thuong co mot tin hieu do phan giai cao va mot so tin hieu do phan giai tieu chuan duoc phan bo tren mot phan bo kenh 6 MHz (NTSC cu).
Mo ta ve ATSC
[sua | sua ma nguon]Cac tieu chuan truyen hinh do net cao duoc xac dinh boi ATSC tao ra hinh anh man hinh rong 16:9 co kich thuoc len toi 1920 x 1080 pixel - gap hon sau lan do phan giai man hinhcua tieu chuan truoc do. Tuy nhien, nhieu kich co hinh anh khac nhau cung duoc ho tro. Yeu cau bang thong giam cua hinh anh do phan giai thap hon cho phep toi da sau "kenh con" do net tieu chuan duoc phat tren mot kenh TV6 MHz duy nhat.
Cac tieu chuan ATSC duoc danh dau A / x (xla so tieu chuan) va co the duoc tai xuong mien phi tu trang web cua ATSC tai ATSC.org. ATSC Standard A / 53, duoc trien khai he thong do Grand Alliance phat trien, duoc xuat ban nam 1995; tieu chuan duoc Uy ban Truyen thong Lien bang tai Hoa Ky ap dung vao nam 1996. No da duoc sua doi vao nam 2009. Tieu chuan ATSC A / 72 da duoc phe duyet nam 2008 va gioi thieu ma hoa video H.264 / AVC cho he thong ATSC.
ATSC ho tro am thanh vom 5.1 kenh su dung dinh dang AC-3 cua Dolby Digital. Nhieu dich vu du lieu phu tro cung co the duoc cung cap.
Nhieu khia canh cua ATSC duoc cap bang sang che, bao gom cac yeu to cua ma hoa video MPEG, ma hoa am thanh AC-3 va dieu che 8VSB.Chi phi cap phep bang sang che, uoc tinh len toi $50 moi dau thu TV ky thuat so,da khien cac nha san xuat phan nan.
Cung nhu cac he thong khac, ATSC phu thuoc vao nhieu tieu chuan dan xen, vi du tieu chuan EIA-708 cho chu thich dong ky thuat so, dan den cac thay doi trong trien khai.
Chuyen doi ky thuat so
[sua | sua ma nguon]ATSC da thay the phan lon he thong truyen hinh NTSC tuong tu tai Hoa Ky vao ngay 12 thang 6 nam 2009, vao ngay 31 thang 8 nam 2011 tai Canada, vao ngay 31 thang 12 nam 2012 tai Han Quoc va vao ngay 31 thang 12 nam 2015 tai Mexico.
Cac dai truyen hinh da su dung ATSC va muon giu lai tin hieu tuong tu da tam thoi bi buoc phai phat tren hai kenh rieng biet, vi he thong ATSC yeu cau su dung toan bo mot kenh rieng biet. So kenh trong ATSC khong tuong ung voi dai tan so RF, nhu da lam voi truyen hinh analog. Thay vao do, cac kenh ao, duoc gui nhu mot phan cua sieu du lieu cung voi (cac) chuong trinh, cho phep cac so kenh duoc anh xa tu kenh RF vat ly cua chung sang bat ky so 1 den 99 nao khac, de cac tram ATSC co the duoc lien ket voi NTSC lien quan so kenh hoac tat ca cac tram tren mang co the su dung cung mot so. Ngoai ra con co mot tieu chuan cho cac he thong truyen dan phan tan (DTx), mot dang cua mang don tancho phep van hanh dong bo nhieu tram tang ap tren kenh.
Am thanh
[sua | sua ma nguon]Dolby Digital AC-3 duoc su dung lam codec am thanh, mac du no duoc tieu chuan hoa la A / 52 boi ATSC. No cho phep truyen toi da nam kenh am thanh voi kenh thu sau cho cac hieu ung tan so thap (cau hinh duoc goi la "5.1"). Nguoc lai, cac chuong trinh phat song HDTV ISDB cua Nhat Ban su dung Ma hoa am thanh nang cao (AAC) cua MPEG lam codec am thanh, cung cho phep phat ra am thanh 5.1. DVB (xem ben duoi) cho phep ca hai.
Am thanh MPEG-2 la mot ung cu vien cho tieu chuan ATSC trong loat ban sung " Lien minh lon " cua DTV, nhung da thua Dolby AC-3. Lien minh Grand da dua ra tuyen bo tim thay he thong MPEG-2 "ve co ban tuong duong" voi Dolby, nhung chi sau khi lua chon Dolby duoc thuc hien. Sau do, mot cau chuyen noi len rang MIT da tham gia mot thoa thuan voi Dolby, trong do truong dai hoc se duoc trao mot khoan tien lon neu he thong MPEG-2 bi tu choi. Dolby cung dua ra mot dong luc de Zenith chuyen doi phieu bau cua ho (dieu ho da lam); tuy nhien, khong biet lieu ho co chap nhan loi de nghi hay khong.
Video
[sua | sua ma nguon]He thong ATSC ho tro mot so do phan giai man hinh, ty le khung hinh va toc do khung hinh khac nhau. Cac dinh dang duoc liet ke o day theo do phan giai, hinh thuc quet (luy tienhoac xen ke) va so khung hinh (hoac truong) moi giay.
De truyen tai, ATSC su dung dac ta he thong MPEG, duoc goi la luong truyen tai MPEG, de dong goi du lieu, chiu cac rang buoc nhat dinh. ATSC su dung cac goi luong truyen tai MPEG 188 byte de mang du lieu. Truoc khi giai ma am thanh va video dien ra, may thu phai giai dieu che va ap dung sua loi cho tin hieu. Sau do, luong van chuyen co the duoc phan tach thanh cac luong cau thanh cua no.
MPEG-2
[sua | sua ma nguon]Co bon kich thuoc hien thi co ban cho ATSC, thuong duoc biet den bang cach tham khao so luong dong cua chieu cao hinh anh. Kich thuoc hinh anh NTSC va PAL la nho nhat, voi chieu rong 720 (hoac 704) va chieu cao 480 hoac 576 dong. Kich thuoc thu ba la hinh anh HDTV co chieu cao quet 720 va rong 1280 pixel. Kich thuoc lon nhat co chieu cao 1080 dong va rong 1920 pixel. Video 1080 dong thuc su duoc ma hoa voi khung hinh 1920 x 1088 pixel, nhung tam dong cuoi cung bi loai bo truoc khi hien thi. Dieu nay la do han che dinh dang video MPEG-2, yeu cau chieu cao cua hinh anh trong cac mau luma (tuc la pixel) phai chia het cho 16.
Do phan giai thap hon co the hoat dong trong qua trinh quet luy tien hoac xen keche do, nhung khong phai la kich thuoc hinh anh lon nhat. He thong 1080 dong khong ho tro hinh anh luy tien o toc do khung hinh cao nhat la 50, 59,94 hoac 60 khung hinh moi giay, boi vi cong nghe nhu vay duoc xem la qua tien tien vao thoi diem do. Tieu chuan cung yeu cau video 720 dong phai quet lien tuc, vi dieu do cung cap chat luong hinh anh tot hon so voi quet xen ke o toc do khung hinh nhat dinh va khong co viec su dung quet xen ke cho dinh dang do. Ket qua la su ket hop giua toc do khung hinh toi da va kich thuoc hinh anh dan den xap xi cung so luong mau moi giay cho ca dinh dang xen ke 1080 dong va dinh dang 720 dong, vi 1920 * 1080 * 30 gan bang 1280 * 720 * 60. Mot moi quan he binh dang tuong tu ap dung cho 576 dong o 25 khung hinh moi giay so voi 480 dong o 30 khung hinh moi giay.
Truyen tren mat dat (truyen qua khong trung) mang 19,39 megabit du lieu moi giay (bang thong dao dong con lai khoang 18,3 Mbit / giay sau khi su dung nhu sua loi, huong dan chuong trinh, chu thich dong, v.v.), so voi muc toi da co the Toc do bit MPEG-2 la 10,08 Mbit / s (7 Mbit / s dien hinh) duoc cho phep trong tieu chuan DVD va 48 Mbit / s (dien hinh 36 Mbit / s) duoc cho phep trong tieu chuan dia Blu-ray.
Mac du tieu chuan ATSC A / 53 gioi han truyen MPEG-2 sang cac dinh dang duoc liet ke ben duoi (voi toc do khung hinh nguyen duoc ghep voi cac phien ban ty le 1000/1001), Uy ban Truyen thong Lien bang Hoa Ky da tu choi yeu cau cac dai truyen hinh tuan theo phan nay cua tieu chuan ATSC. Ve ly thuyet, cac dai truyen hinh o My co the tu do lua chon bat ky do phan giai, ty le khung hinh va toc do khung hinh / truong, trong gioi han cua Ho so chinh @ Cap cao. Nhieu tram vuot ra ngoai gioi han cua dac ta ATSC bang cach su dung cac do phan giai khac - vi du: 352 x 480 hoac 720 x 480.
" EDTV " hien thi co the tai tao noi dung quet lien tuc va thuong xuyen co mot dinh dang 16: 9 man hinh rong. Do phan giai nhu vay la 704 x 480 hoac 720 x 480 [ can dan nguon ] trong NTSC va 720 x 576 trong PAL, cho phep 60 khung hinh luy tien moi giay trong NTSC hoac 50 trong PAL.
| Nghi quyet | Ty le khung hinh | Ti le diem anh | Quet | Toc do khung hinh (Hz) | |
|---|---|---|---|---|---|
| Theo chieu doc | Ngang | ||||
| 1080 | 1920 | 16: 9 | 1: 1 | cap tien | 23.976
24 29.97 30 |
| xen ke | 29,97 (59,94 truong / s)
30 (60 truong / s) | ||||
| 720 | 1280 | 16: 9 | 1: 1 | cap tien | 23.976
24 29.97 30 59.94 60 |
| 480 | 704 hoac 858 | 4: 3 hoac 16: 9 | SMPTE 259M | cap tien | 23.976
24 29.97 30 59.94 60 |
| xen ke | 29,97 (59,94 truong / s)
30 (60 truong / s) | ||||
| 640 | 4: 3 | 1: 1 | cap tien | 23.976
24 29.97 30 59.94 60 | |
| xen ke | 29,97 (59,94 truong / s)
30 (60 truong / s) | ||||
ATSC cung ho tro toc do khung hinh PAL va do phan giai duoc xac dinh trong tieu chuan ATSC A / 63.
| Nghi quyet | Ty le khung hinh | Ti le diem anh | Quet | Toc do khung hinh (Hz) | |
|---|---|---|---|---|---|
| Theo chieu doc | Ngang | ||||
| 1080 | 1920 | 16: 9 | 1: 1 | xen ke | 25 (50 truong / giay) |
| cap tien | 25 | ||||
| 720 | 1280 | 16: 9 | 1: 1 | cap tien | 50 |
| 576 | 720 | 4: 3 hoac 16: 9 | SMPTE 259M | cap tien | 25
50 |
| xen ke | 25 (50 truong / giay) | ||||
| 544 | 4: 3 hoac 16: 9 | SMPTE 259M
ba phan tu |
cap tien | 25 | |
| xen ke | 25 (50 truong / giay) | ||||
| 480 | 4: 3 hoac 16: 9 | SMPTE 259M
hai phan ba |
cap tien | 25 | |
| xen ke | 25 (50 truong / giay) | ||||
| 352 | 4: 3 hoac 16: 9 | SMPTE 259M
mot nua |
cap tien | 25 | |
| xen ke | 25 (50 truong / giay) | ||||
| 288 | 352 | 4: 3 hoac 16: 9 | CIF | cap tien | 25 |
Dac ta ATSC A / 53 ap dat cac rang buoc nhat dinh doi voi luong video MPEG-2:
- Gia tri toc do bit toi da trong tieu de chuoi cua luong video MPEG-2 la 19,4 Mbit / s cho truyen hinh phat song va 38,8 Mbit / s cho che do "toc do du lieu cao" (vi du: truyen hinh cap). Toc do bit video MPEG-2 thuc te se thap hon, vi luong video MPEG-2 phai nam gon trong luong truyen tai.
- So luong bo dem luong MPEG-2 duoc yeu cau tai bo giai ma (vbv_buffer_size_value) phai nho hon hoac bang 999.424 byte.
- Trong hau het cac truong hop, may phat khong the bat dau gui hinh anh duoc ma hoa cho den trong vong nua giay khi no duoc giai ma (vbv_delay nho hon hoac bang muc tang xung nhip 45000 90 kHz).
- Luong phai bao gom thong tin so mau (duong cong gamma, mau RGB chinh xac duoc su dung va moi quan he giua RGB va YCbCr duoc ma hoa).
- Video phai la 4: 2: 0 (do phan giai sac do phai bang 1/2 do phan giai ngang luma va 1/2 do phan giai doc luma).
Dac ta ATSC va MPEG-2 cho phep su dung cac khung luy tien duoc ma hoa trong mot chuoi video xen ke. Vi du: cac tram NBC truyen mot chuoi video 1080i60, nghia la dau ra chinh thuc cua qua trinh giai ma MPEG-2 la sau muoi truong 540 dong moi giay. Tuy nhien, doi voi cac chuong trinh truyen hinh thoi gian chinh, 60 truong do co the duoc ma hoa bang 24 khung hinh luy tien lam co so - thuc te, mot luong video 1080p24 (chuoi 24 khung hinh lien tuc moi giay) duoc truyen di va sieu du lieu MPEG-2 huong dan bo giai ma de xen ke cac truong nay va thuc hien keo xuong 3: 2 truoc khi hien thi, nhu trong telecine mem.
Dac diem ky thuat ATSC cung cho phep cac chuoi 1080p-1080p 1080p va 1080p24, tuy nhien chung khong duoc su dung trong thuc te, vi cac dai truyen hinh muon co the chuyen doi giua 60 Hz xen ke (tin tuc), 30 Hz tien bo hoac PsF (vo opera xa phong) va 24 Hz noi dung luy tien (thoi gian chinh) ma khong ket thuc chuoi 1080i60 MPEG-2.
Cac dinh dang 1080 dong duoc ma hoa voi ma tran luma 1920 x 1088 pixel va ma tran sac do 960 x 540, nhung 8 dong cuoi cung bi loai bo boi qua trinh giai ma va hien thi MPEG-2.
H.264 / MPEG-4 AVC
[sua | sua ma nguon]Vao thang 7 nam 2008, ATSC da duoc cap nhat de ho tro codec video ITU-T H.264. Tieu chuan moi duoc chia thanh hai phan:
- A / 72 phan 1: Dac diem he thong video cua AVC trong He thong truyen hinh ky thuat so ATSC
- A / 72 phan 2: Dac diem cua he thong con truyen tai video AVC
Cac tieu chuan moi ho tro 1080p o muc 50, 59,94 va 60 khung hinh moi giay; toc do khung hinh nhu vay yeu cau Cap do cau hinh cao H.264 / AVC, trong khi toc do khung hinh HDTV tieu chuan chi yeu cau Cap do 3.2 va 4, va toc do khung hinh SDTV yeu cau Cap do 3 va 3.1.
| Nghi quyet | Ty le khung hinh | Ti le diem anh | Quet | Toc do khung hinh (Hz) | Cap do | |
|---|---|---|---|---|---|---|
| Theo chieu doc | Ngang | |||||
| 1080 | 1920 | 16: 9 | 1: 1 | cap tien | 23.976
24 29.97 30 25 |
4 |
| cap tien | 59,94
60 50 |
4.2 | ||||
| xen ke | 29,97 (59,94 truong / s)
30 (60 truong / s) 25 (50 truong / s) |
4 | ||||
| 1440 | 16: 9 | HDV
(4: 3) |
cap tien | 23.976
24 29.97 30 25 |
4 | |
| cap tien | 59,94
60 50 |
4.2 | ||||
| xen ke | 29,97 (59,94 truong / s)
30 (60 truong / s) 25 (50 truong / s) |
4 | ||||
| 720 | 1280 | 16: 9 | 1: 1 | cap tien | 23.976
24 29.97 30 59.94 60 25 50 |
3,2, 4 |
| 480 | 720 | 4: 3 hoac 16: 9 | SMPTE 259M
(10:11 hoac 40:33) |
cap tien | 23.976
24 29.97 30 59.94 60 25 50 |
3,1, 4 |
| xen ke | 29,97 (59,94 truong / s)
30 (60 truong / s) 25 (50 truong / s) |
3 | ||||
| 704 | 4: 3 hoac 16: 9 | SMPTE 259M
(10:11 hoac 40:33) |
cap tien | 23.976
24 29.97 30 59.94 60 25 50 |
3,1, 4 | |
| xen ke | 29,97 (59,94 truong / s)
30 (60 truong / s) 25 (50 truong / s) |
3 | ||||
| 640 | 4: 3 | 1: 1 | cap tien | 23.976
24 29.97 30 59.94 60 25 50 |
3,1, 4 | |
| xen ke | 29,97 (59,94 truong / s)
30 (60 truong / s) 25 (50 truong / s) |
3 | ||||
| 544 | 4: 3 | SMPTE 259M
ba phan tu (40:33) |
cap tien | 23.976
25 |
3 | |
| xen ke | 29,97 (59,94 truong / s)
25 (50 truong / s) | |||||
| 528 | 4: 3 | SMPTE 259M
ba phan tu (40:33) |
cap tien | 23.976
25 |
3 | |
| xen ke | 29,97 (59,94 truong / s)
25 (50 truong / s) | |||||
| 352 | 4: 3 | SMPTE 259M
mot nua (20:11) |
cap tien | 23.976
25 |
3 | |
| xen ke | 29,97 (59,94 truong / s)
25 (50 truong / s) | |||||
| 240 | 352 | 4: 3 | SIF
(10:11) |
cap tien | 23.976
25 |
3 |
| 120 | 176 | 4: 3 | [1] Mot nuaSIF
[2](10:11) |
cap tien | 23.976
25 |
1.1 |
Doc them
[sua | sua ma nguon]- Joel Brinkley (1998), Xac dinh tam nhin: Cuoc chien tuong lai cua truyen hinh, New York: Harcourt Brace.