NTSC - NTSC

Ushbu maqola televizion tizim haqida. Indoneziya hukumat agentligi uchun qarang Milliy transport xavfsizligi qo'mitasi.
Analog televizion kodlash tizimlari millatlar bo'yicha; NTSC (yashil), SECAM (to'q sariq) va PAL (ko'k).

NTSCnomi bilan nomlangan Milliy televizion tizim qo'mitasi,[1] bo'ladi analog televizor kiritilgan rang tizimi Shimoliy Amerika 1954 yilda va raqamli konversiyaga qadar ishlatilgan. Bu uchta analog analog televizion standartlardan biri edi, boshqalari esa PAL va SECAM.

NTSC-dan foydalanadigan barcha mamlakatlar hozirda konversiya jarayoni, yoki allaqachon ga o'zgartirilgan ATSC standart yoki to DVB, ISDB, yoki DTMB.

Ushbu sahifada birinchi navbatda NTSC rang kodlash tizimi muhokama qilinadi. Haqida maqolalar efirga uzatiladigan televizion tizimlar va analog televideniye kadr stavkalari, tasvir o'lchamlari va audio modulyatsiyani yanada tavsiflaydi.

Geografik qamrov

NTSC standarti ko'pchiligida ishlatilgan Shimoliy Amerika, g'arbiy Janubiy Amerika, Liberiya, Myanma, Janubiy Koreya, Tayvan, Filippinlar, Yaponiya va ba'zi Tinch okeanidagi orol davlatlari va hududlari (xaritaga qarang).

Raqamli konvertatsiya

NTSC standartidan foydalanadigan aksariyat mamlakatlar, shuningdek boshqa mamlakatlar analog televizion standartlar, yangisiga o'tgan yoki o'tish bosqichida raqamli televidenie standartlari, dunyo bo'ylab kamida to'rt xil standartlar mavjud. Shimoliy Amerika, uning qismlari Markaziy Amerika va Janubiy Koreya kabi ATSC standartlarini qabul qilmoqdalar yoki qabul qildilar, masalan, boshqa mamlakatlar Yaponiya, ATSC o'rniga boshqa standartlarni qabul qilmoqdalar yoki qabul qildilar. Taxminan 70 yildan so'ng, Qo'shma Shtatlardagi NTSC translyatsiyasining aksariyati 2010 yil 1 yanvarda to'xtatildi,[2] va 2011 yil 31 avgustgacha[3] yilda Kanada va boshqa ko'plab NTSC bozorlari.[4] NTSC translyatsiyalarining aksariyati 2011 yil 24 iyulda Yaponiyada tugadi, Yaponiya prefekturalari bilan Ivate, Miyagi va Fukusima keyingi yil tugaydi.[3] 2013 yildagi sinov dasturidan so'ng, Meksikadagi aksariyat to'liq quvvatli analog stantsiyalar 2015 yilda o'n sanada havoni tark etishdi, 500 ga yaqin kam quvvatli va takroriy stantsiyalar 2016 yil oxirigacha analogda qolishga ruxsat berishdi. Raqamli eshittirish imkon beradi yuqori aniqlikdagi televizor, lekin raqamli standart ta'rifi televizor analog NTSC standarti tomonidan belgilangan kvadrat tezligi va o'lchamlari qatorlaridan foydalanishda davom etmoqda.

Tarix

Shuningdek qarang: Televizion tarixi

Birinchi NTSC standarti 1941 yilda ishlab chiqilgan va rang uchun hech qanday shart yo'q edi. 1953 yilda ikkinchi NTSC standarti qabul qilindi, bunga imkon berdi rangli televizor mavjud bo'lgan oq-qora qabul qiluvchilar zaxirasiga mos keladigan eshittirish. NTSC birinchi bo'lib qabul qilingan keng tarqalgan efirga uzatiladigan rangli tizim bo'lib, 2000-yillarga qadar hukmron bo'lib qoldi almashtirildi boshqacha bilan raqamli kabi standartlar ATSC va boshqalar.

Milliy televizion tizim qo'mitasi 1940 yilda AQSh tomonidan tashkil etilgan Federal aloqa komissiyasi (FCC) Qo'shma Shtatlarda milliy analog televizion tizimni joriy qilish bo'yicha kompaniyalar o'rtasidagi ziddiyatlarni hal qilish. 1941 yil mart oyida qo'mita uchun texnik standart chiqarildi qora va oq Radio ishlab chiqaruvchilar assotsiatsiyasi (RMA) tomonidan 1936 yildagi tavsiyasiga binoan qurilgan televizor. Ning texnik yutuqlari vestigial yon tasma texnika tasvir o'lchamlarini oshirish imkoniyatini yaratdi. NTSC o'zaro kelishuv sifatida 525 ta skanerlash liniyasini tanladi RCA 441-ko'rish chizig'i standart (allaqachon RCA tomonidan ishlatilgan NBC Televizion tarmoq) va Philco va DuMont skanerlash liniyalari sonini 605 dan 800 gacha oshirish istagi.[5] Standart tavsiya etilgan a kvadrat tezligi ikkitadan iborat soniyada 30 kvadrat (rasm) interlaced dalalar har bir kvadrat uchun 262,5 chiziq va soniyada 60 ta maydon. Yakuniy tavsiyadagi boshqa standartlar an tomonlar nisbati 4: 3 va chastota modulyatsiyasi (FM) ovozli signal uchun (o'sha paytda bu juda yangi edi).

1950 yil yanvar oyida qo'mita standartlashtirish uchun qayta tuzildi rangli televizor. 1950 yil oktyabr oyida FCC tomonidan ishlab chiqarilgan rangli televizion standart qisqacha tasdiqlangan edi CBS.[6] CBS tizimi mavjud qora va oq qabul qiluvchilar bilan mos kelmadi. Unda aylanadigan rangli g'ildirak ishlatilgan, soni kamaytirilgan skanerlash chiziqlari 525 dan 405 gacha va maydon stavkasini 60 dan 144 gacha oshirdi, ammo samarali bo'ldi kvadrat tezligi soniyada atigi 24 kvadrat. Raqobatchi RCA tomonidan amalga oshirilgan huquqiy harakatlar tizimdan tijorat maqsadlarida foydalanishni 1951 yil iyungacha ushlab turdi va muntazam ko'rsatuvlar faqat bir necha oy davom etdi va barcha rangli televizorlar ishlab chiqarilishi taqiqlandi. Mudofaani safarbar qilish boshqarmasi tufayli oktyabr oyida, go'yo tufayli Koreya urushi.[7] CBS 1953 yil mart oyida o'z tizimini bekor qildi,[8] va FCC uni 1953 yil 17-dekabrda bir nechta kompaniyalar, shu jumladan RCA va Philco tomonidan birgalikda ishlab chiqilgan NTSC rang standarti bilan almashtirdi.[9]

1953 yil dekabrda FCC bir ovozdan hozirgi deb nomlangan narsani ma'qulladi NTSC rangli televizion standart (keyinchalik RS-170a deb belgilangan). Mos rang standarti o'sha paytda mavjud bo'lgan oq-qora televizorlar bilan to'liq orqaga qarab muvofiqligini saqlab qoldi. Rang haqida ma'lumot oq-qora tasvirga rang kiritish orqali qo'shildi subcarrier aniq 315/88 MGts (odatda 3,579545 MGts ± 10 Hz deb ta'riflanadi[10] yoki taxminan 3,58 MGts). To'g'ri chastota shunday tanlanganki, xrominans signalining gorizontal chiziqli tezlik modulyatsiyasi komponentlari yorug'lik signalining gorizontal chiziqli tezlikli modulyatsiya tarkibiy qismlari o'rtasida to'liq tushib, shu bilan xrominans signalini yorug'lik darajasidan kichik degradatsiyaga uchragan holda filtrlashga imkon beradi. nashrida signali. (Shuningdek, uni filtrlamaydigan mavjud to'plamlarda ko'rinishni minimallashtiring.) Cheklovlar tufayli chastotani ajratuvchi rang standarti e'lon qilingan vaqtdagi sxemalar, rangli subcarrier chastotasi kichik tamsayılardan yig'ilgan kompozit chastota sifatida qurilgan, bu holda 5 × 7 × 9 / (8 × 11) MGts.[11] Gorizontal chiziq tezligi soniyasiga 15,750 chiziqdan sekundiga taxminan 15 734 ta chiziqqa (3,579545 × 2/455 MGts = 9/572 MGts) qisqartirildi va kvadrat tezligi sekundiga 30 / 1.001 ≈ 29.970 kvadratgacha qisqartirildi (gorizontal chiziq soniya 30 kvadratdan 525 qatorga / kvadratga bo'lingan). Ushbu o'zgarishlar 0,1 foizni tashkil etdi va o'sha paytdagi televizion qabul qiluvchilar tomonidan osonlikcha toqat qilindi.[12][13]

NTSC "mos rang" tizimidan foydalangan holda dasturning birinchi bo'lib e'lon qilingan tarmoq televidenie translyatsiyasi NBC telekanalining epizodi bo'ldi Kukla, Fran va Olli 1953 yil 30-avgustda, garchi uni faqat tarmoqning shtab-kvartirasida ko'rish mumkin edi.[14] NTSC rangini birinchi marta mamlakat bo'ylab tomosha qilish keyingi 1-yanvar kuni qirg'oqdan qirg'oqqa translyatsiya bilan sodir bo'ldi Roses Parad turniri, mamlakat bo'ylab o'tkazilgan maxsus taqdimotlarda rangli qabul qiluvchilar prototipida ko'rish mumkin. Birinchi rang NTSC televizion kamera edi RCA TK-40, 1953 yilda eksperimental eshittirishlar uchun ishlatilgan; 1954 yil mart oyida taqdim etilgan takomillashtirilgan versiyasi - TK-40A, sotuvga qo'yilgan birinchi rangli televizion kameradir. O'sha yilning oxirida takomillashtirilgan TK-41 1960-yillarning ko'p qismida ishlatilgan standart kameraga aylandi.

NTSC standarti boshqa mamlakatlar tomonidan, shu jumladan, ko'pchilik tomonidan qabul qilingan Amerika va Yaponiya.

Kelishi bilan raqamli televidenie, analog eshittirishlar bekor qilinmoqda. Ko'pgina AQSh NTSC translyatorlari FCC tomonidan 2009 yilda analog transmitterlarini o'chirishni talab qilishgan. Kam quvvatli stantsiyalar, A sinfidagi stantsiyalar va tarjimonlar 2015 yilgacha yopilishi kerak edi.

Texnik ma'lumotlar

Chiziqlar va yangilanish tezligi

Bilan NTSC rang kodlash ishlatiladi Tizim M iborat bo'lgan televizion signal30⁄1.001 (taxminan 29.97)interlaced ramkalari video per ikkinchi. Har bir ramka ikkita maydondan iborat bo'lib, ularning har biri 262,5 ta skanerlash liniyasidan iborat bo'lib, jami 525 ta skanerlash liniyasiga ega. 486 skanerlash liniyasi ko'rinadigan joyni tashkil qiladi raster. Qolgan (the vertikal bo'shliq oralig'i ) vertikalga imkon beradi sinxronizatsiya va orqaga qaytish. Ushbu bo'shliq oralig'i dastlab oddiy analog zanjirlar va dastlabki televizor qabul qiluvchilarning vertikal qayta tiklanishini ta'minlash uchun qabul qiluvchining CRT elektron nurlarini bo'shatish uchun mo'ljallangan edi. Biroq, ushbu qatorlarning ba'zilari endi boshqa ma'lumotlarni o'z ichiga olishi mumkin yopiq taglavha va vertikal oraliq vaqt kodi (VITC). To'liq raster (tufayli yarim chiziqlarni e'tiborsiz qoldirish interlacing ) skanerlashning juft raqamli chiziqlari (video signalda hisoblangan bo'lsa ham, boshqa har qanday satr, masalan, {2, 4, 6, ..., 524}) birinchi maydonda chizilgan va toq raqamli ( agar video signalida hisoblansa g'alati bo'lgan har qanday boshqa satr, masalan, {1, 3, 5, ..., 525}) ikkinchi maydonda chizilgan va natijada miltillovchi yo'q maydonidagi rasm yangilanadi chastota ning60⁄1.001 Hz (taxminan 59,94 Hz). Taqqoslash uchun, 576i tizimlari kabi PAL-B / G va SECAM 625 satrdan foydalaning (576 ko'rinadigan) va shuning uchun vertikal o'lchamlari yuqori, ammo vaqtinchalik o'lchamlari pastroq 25 kvadrat yoki soniyada 50 ta maydon.

Oq-qora tizimdagi NTSC maydonini yangilash chastotasi dastlab nominal 60 Gts ga to'g'ri keldi chastota ning o'zgaruvchan tok Qo'shma Shtatlarda ishlatiladigan quvvat. Maydonga mos kelish yangilanish tezligi quvvat manbaiga yo'l qo'ymaslik kerak intermodulyatsiya (shuningdek, deyiladi urish), bu ekranda prokat majmuasi ishlab chiqaradi. Yangilanish tezligini quvvatga sinxronlashtirish tasodifan yordam berdi kineskop kameralar erta jonli televizion ko'rsatuvlarni yozib olishadi, chunki a-ni sinxronlashtirish juda oddiy edi film o'zgaruvchan tok chastotasi yordamida sinxron o'zgaruvchan tok dvigatelining harakatlantiruvchi kamerasining tezligini o'rnatish orqali har bir plyonkada bitta videoni olish uchun kamera. Tizimga rang qo'shilganda, yangilanish chastotasi quyida izohlanganidek tovush va rang tashuvchilar o'rtasidagi farq chastotasidagi statsionar nuqta naqshlarini yo'q qilish uchun 0,1% ga taxminan 59,94 Gts gacha ozaytirildi. "Ranglarni kodlash ". Rangni moslash uchun kvadrat tezligi o'zgargan paytgacha, video signalning o'zi kameraning deklanşörünü ishga tushirish deyarli oson edi.

Vakuum-trubka asosidagi texnologiyalarning cheklanganligi natijasida 525 qatordan iborat haqiqiy kun tanlandi. Dastlabki televizion tizimlarda usta kuchlanish bilan boshqariladigan osilator gorizontal chiziq chastotasining ikki baravarida ishlagan va bu chastota ishlatilgan chiziqlar soniga bo'lingan (bu holda 525) maydon chastotasini berish uchun (bu holda 60 Hz). Keyinchalik bu chastota 60 Hz bilan taqqoslandi elektr uzatish chastotasi va asosiy osilatorning chastotasini sozlash bilan tuzatilgan har qanday kelishmovchilik. Interlaced skanerlash uchun vertikal retrasiya masofasini toq va juft maydonlar uchun bir xil qilish uchun har bir kvadrat uchun toq sonli chiziqlar kerak edi, bu asosiy osilator chastotasini toq songa bo'lishini anglatadi. faqat chastotalarni taqsimlashning amaliy usuli zanjirdan foydalanish edi vakuum trubkasi multivibratorlar, zanjirning bo'linish nisbatlarining matematik mahsuloti bo'lgan umumiy bo'linish nisbati. Toq sonning barcha omillari ham toq sonlar bo'lishi kerak ekan, demak, zanjirdagi barcha bo'linuvchilar ham toq sonlarga bo'linishi kerak edi va ular muammolari tufayli nisbatan kichik bo'lishi kerak edi. termal drift vakuum trubkasi qurilmalari bilan. Ushbu mezonlarga mos keladigan 500 ga yaqin amaliy ketma-ketlik edi 3×5×5×7=525. (Xuddi shu sababli, 625 qatorli PAL-B / G va SECAM foydalanadi 5×5×5×5, ishlatilgan eski ingliz 405 qatorli tizim 3×3×3×3×5, ishlatilgan frantsuzcha 819 qatorli tizim 3×3×7×13 va boshqalar.)

Kolorimetriya

1953 yilgi asl NTSC spetsifikatsiyasi, hanuzgacha Qo'shma Shtatlarning bir qismi Federal qoidalar kodeksi, belgilangan kolorimetrik tizimning qiymatlari quyidagicha:[15]

Asl NTSC kolorimetri (1953)CIE 1931 xCIE 1931 y
asosiy qizil0.670.33
asosiy yashil0.210.71
asosiy ko'k0.140.08
oq nuqta (CIE Standart yoritgich C) 6774 K0.3100.316

RCA kabi erta rangli televizion qabul qiluvchilar KT-100, ushbu spetsifikatsiyaga sodiq edi (u amaldagi kinofilmlar standartlariga asoslangan edi), bugungi monitorlarning aksariyatiga qaraganda kattaroq hajmga ega edi. Ularning past samaradorlikli fosforlari (xususan, Qizil rangda) zaif va uzoq muddatli bo'lib, harakatlanuvchi narsalardan keyin iz qoldirgan. 1950-yillarning oxiridan boshlab rasm naychali fosforlar yorqinligi oshishi uchun to'yinganlikni qurbon qiladi; qabul qiluvchida ham, translyatorda ham standartdan chetga chiqish ranglarning sezilarli o'zgarishi manbai bo'lgan.

SMPTE C

Ranglarni yanada ko'paytirishni ta'minlash uchun qabul qiluvchilar qabul qilingan signalni - yuqorida sanab o'tilgan kolorimetrik qiymatlar uchun kodlangan - monitorda aslida ishlatiladigan fosforlar uchun kodlangan signallarga aylantirgan ranglarni to'g'rilash davrlarini qo'shishni boshladilar. Bunday rangni tuzatish chiziqli bo'lmagan holda aniq bajarilishi mumkin emasligi sababli gamma tuzatildi signallari uzatilganda, sozlash faqat taxminiy bo'lishi mumkin, bu rang va rangni taqdim etadi nashrida juda to'yingan ranglar uchun xatolar.

Xuddi shu tarzda teleradioeshittirish bosqichida, 1968-69 yillarda RCA bilan ishlaydigan Conrac Corp., efirga uzatiladigan rangli rasmda foydalanish uchun boshqariladigan fosforlar to'plamini aniqladi video monitorlar.[16] Ushbu xususiyat bugungi kunda saqlanib qolgan SMPTE "C" fosforning spetsifikatsiyasi:

SMPTE "C" kolorimetriCIE 1931 yil xCIE 1931 y
asosiy qizil0.6300.340
asosiy yashil0.3100.595
asosiy ko'k0.1550.070
oq nuqta (CIE yoritgichi D65 )0.31270.3290

Uy qabul qiluvchilarida bo'lgani kabi, yana tavsiya etilgan[17] studiya monitorlari shu kabi ranglarni tuzatish sxemalarini o'z ichiga oladi, shunda translyatorlar FCC standartlariga muvofiq 1953 yilgi kolorimetrik qiymatlari uchun kodlangan rasmlarni uzatadilar.

1987 yilda Kinofilm va televideniye muhandislari jamiyati (SMPTE) Televizion texnologiyalar qo'mitasi, studiya monitor kolorimetri bo'yicha ishchi guruh, tavsiya etilgan 145-amaliyotda SMPTE C (Conrac) fosforlarini umumiy foydalanish uchun qabul qildi,[18] SMPTE "C" kolorimetrini ranglarni to'g'irlamasdan to'g'ridan-to'g'ri kodlash uchun ko'plab ishlab chiqaruvchilarni kamera dizaynlarini o'zgartirishga undash,[19] SMPTE standarti 170M da tasdiqlanganidek, "Kompozit analog video signal - Studio dasturlari uchun NTSC" (1994). Natijada, ATSC raqamli televideniye standarti shuni ta'kidlaydi 480i signallari, SMPTE "C" kolorimetri, agar transport oqimiga kolorimetrik ma'lumotlar kiritilmagan bo'lsa, qabul qilinishi kerak.[20]

Yaponiyaning NTSC hech qachon boshlang'ich va oq nuqtani SMPTE "C" ga o'zgartirmagan, 1953 yilgi NTSC boshlang'ich va oq nuqtadan foydalanishda davom etgan.[17] Ikkalasi ham PAL va SECAM tizimlar 1953 yilgi NTSC kolorimetriyasidan 1970 yilgacha ham foydalangan;[17] NTSC-dan farqli o'laroq, Evropa Teleradioeshittirishlar Birligi (EBU) o'sha yili qabul qiluvchilar va studiya monitorlarida ranglarni to'g'rilashni rad etdi va buning o'rniga barcha uskunalarni "EBU" kolorimetrik qiymatlari uchun signallarni to'g'ridan-to'g'ri kodlashni talab qildi,[21] ushbu tizimlarning ranglarning aniqligini yanada yaxshilash.

Ranglarni kodlash

Oq-qora televizor bilan orqaga qarab muvofiqligi uchun NTSC a dan foydalanadi nashrida -xrominans tomonidan 1938 yilda ixtiro qilingan kodlash tizimi Jorj Valensi. The uchta rangli rasm signallari yorqinlikka bo'linadi (matematik ravishda uchta alohida rangli signallardan (qizil, yashil va ko'k) olingan)[22] bu asl nusxaning o'rnini egallaydi monoxrom signal va Chrominance olib boradi faqat rang haqida ma'lumot. Ushbu jarayon qo'llaniladi har biri o'z-o'zidan rang manbai Colorplexer, shu bilan mos keladigan rang manbasini oddiy monoxrom manbai kabi boshqarishga imkon beradi. Bu qora va oq qabul qiluvchilarga xrominans signalini e'tiborsiz qoldirib, NTSC rangli signallarini ko'rsatishga imkon beradi. 1953 yilda rangli efirga uzatilgandan so'ng AQShda sotilgan ba'zi oq-qora televizorlar xromalarni filtrlash uchun mo'ljallangan edi, ammo dastlabki B&W to'plamlari buni qilmadi va xrominans rasmning juda rangli joylarida "nuqta naqshlari" sifatida ko'rish mumkin.

NTSC-da xrominans I (fazada) va Q (to'rtburchakda) deb nomlanuvchi ikkita rangli signal yordamida kodlanadi. QAM. Ikkala signal har bir amplituda 3,58 MGts tashuvchilarni modulyatsiya qiladi, ular bir-birlari bilan fazadan 90 daraja tashqarida va natijalar qo'shilib, lekin tashuvchilarning o'zlari bostirilmoqda. Natijada, mos yozuvlar tashuvchisiga nisbatan o'zgaruvchan faza va turli xil amplituda bo'lgan bitta sinus to'lqini sifatida qarash mumkin. O'zgaruvchan faza oniylikni anglatadi rang tusi televizor kamerasi tomonidan ushlangan va amplituda bir lahzani anglatadi ranglarning to'yinganligi. Bu 3,58 MGts subcarrier keyin video signalni modulyatsiya qiladigan "kompozit rangli signal" hosil qilish uchun Luminance-ga qo'shiladi tashuvchi xuddi monoxrom uzatishda bo'lgani kabi.

Rangli televidenie rangli subcarrier-dan rang ma'lumotlarini tiklashi uchun u ilgari bostirilgan tashuvchini almashtirish uchun nol fazali ma'lumotga ega bo'lishi kerak. NTSC signali ushbu mos yozuvlar signalining qisqa namunasini o'z ichiga oladi rang portlashi, har bir gorizontal sinxronizatsiya impulsining "orqa ayvonida" joylashgan. Rang portlashi modullanmagan (qat'iy faza va amplituda) rangli subcarrierning kamida sakkiz tsiklidan iborat. Televizion qabul qilgichda "mahalliy osilator" mavjud bo'lib, u ushbu rang portlashlari bilan sinxronlashtiriladi. Rang portlashidan kelib chiqadigan ushbu mos yozuvlar fazasi signalini xrominans signalining amplitudasi va fazasi bilan birlashtirish 'I' va 'Q' signallarini tiklashga imkon beradi, ular Luminance ma'lumotlari bilan birgalikda ekrandagi rangli tasvirni qayta tiklashga imkon beradi. Rangli televizor haqiqatan ham rangli deb aytilgantahrir Rasmning yorqinligini rang qismidan to'liq ajratish sababli televizor. CRT televizorlarida NTSC signali uchta rangli signalga aylantiriladi Red, Green va BLue, ularning har biri bu rangli elektron qurolni boshqaradi. Raqamli elektronli televizorlarda signallarni qayta ishlash uchun namuna olish texnikasi qo'llaniladi, ammo yakuniy natija bir xil. Analog NTSC signalini qayta ishlaydigan analog va raqamli to'plamlar uchun asl uchta rangli signal (Qizil, Yashil va Moviy) uchta diskret signal (Luminance, I va Q) yordamida uzatiladi va keyin uchta alohida rang sifatida tiklanadi va rangli tasvir sifatida birlashtiriladi .

Transmitter NTSC signalini efirga uzatganda, u hozirda tasvirlangan NTSC signali bilan radiochastota tashuvchisini amplituda-modulyatsiya qiladi, audio uzatish bilan esa 4,5 MGts balandroq tashuvchini chastota-modulyatsiya qiladi. Agar translyatsiya signalida chiziqli bo'lmagan buzilish sodir bo'lsa, 3.579545 MGts rang tashuvchisi bo'lishi mumkin mag'lub etish ekranda nuqta naqshini yaratish uchun ovoz tashuvchisi bilan. Olingan naqshni unchalik sezilmaydigan qilish uchun dizaynerlar 15,750 Gts skanerlash tezligini 1,001 (0,1%) faktorga kamaytirib, audio tashuvchisi chastotasini 286 faktorga bo'lishiga moslashtirishdi, natijada maydon tezligi taxminan 59,94 Hz. Ushbu sozlash ovoz tashuvchisi va rang subcarrier (eng muammoli) o'rtasidagi farqni ta'minlaydi intermodulyatsiya Ikkala tashuvchining mahsuloti) chiziq chizig'ining yarmining toq ko'paytmasi bo'lib, bu ketma-ket chiziqlardagi nuqtalarning fazada qarama-qarshi bo'lishining zaruriy sharti bo'lib, ularni eng kam seziladi.

59.94 stavkasi quyidagi hisob-kitoblardan kelib chiqadi. Dizaynerlar xrominans subcarrier chastotasini an qilishni tanladilar n + Yorug'lik signali va xrominans signali orasidagi shovqinlarni minimallashtirish uchun chiziq chastotasining 0,5 ko'paytmasi. (Buni tez-tez aytadigan yana bir usul - bu subcarrier rangining chastotasi chiziq chastotasining yarmining g'alati ko'paytmasi.) Keyin ular audio o'rtasidagi ko'rinadigan (intermodulyatsiya) shovqinlarni minimallashtirish uchun audio subcarrier chastotasini chiziq chastotasining tamsayı ko'pligiga aylantirishni tanladilar. signal va xrominans signali. 15,750 Gts chastota chastotasi va 4,5 MGts audio subcarrier bilan original oq-qora standart bu talablarga javob bermaydi, shuning uchun dizaynerlar audio subcarrier chastotasini oshirishi yoki chiziq chastotasini pasaytirishi kerak edi. Audio subcarrier chastotasini oshirish mavjud (qora va oq) qabul qiluvchilarni audio signalni to'g'ri sozlashni oldini oladi. Tarmoq chastotasini pasaytirish nisbatan zararsizdir, chunki NTSC signalidagi gorizontal va vertikal sinxronizatsiya ma'lumotlari qabul qiluvchiga chiziq chastotasining katta miqdordagi o'zgarishiga toqat qilishiga imkon beradi. Shunday qilib, muhandislar rang standarti uchun o'zgarishi kerak bo'lgan chiziq chastotasini tanladilar. Oq-qora standartda audio subcarrier chastotasining chiziq chastotasiga nisbati4,5 MGts⁄15,750 Hz = 285.71. Rang standartida bu 286 butun soniga yaxlitlanadi, ya'ni rang standartining satr darajasi4,5 MGts⁄286 ,7 15,734 Hz. Har bir maydon (va ramka) bo'yicha bir xil miqdordagi skanerlash satrlarini saqlab, pastki chiziq tezligi pastroq maydon tezligini berishi kerak. Bo'linish4500000⁄286 Bir soniyada 262,5 qatorga bir soniyada chiziqlar soniyada 59,94 maydonni beradi.

Transmissiyani modulyatsiya qilish usuli

NTSC rangidagi System M televizion kanalining spektri

NTSC televizion kanal chunki uzatilgan umumiy 6 MGts tarmoqli kengligini egallaydi. Haqiqiy video signal amplituda modulyatsiyalangan, 500 orasida uzatiladikHz va kanalning pastki chegarasidan 5,45 MGts. Video tashuvchi kanalning pastki chegarasidan 1,25 MGts balandlikda. Ko'pgina AM signallari singari, video operator ham ikkitasini ishlab chiqaradi yon tasmalar, biri tashuvchidan yuqorida va ikkinchisi pastda. Yon chiziqlar har birining kengligi 4,2 MGts. Butun yuqori yon tasma uzatiladi, lekin pastki tomonning atigi 1,25 MGts chastotasi atigi ma'lum vestigial yon tasma, uzatiladi. Rangli subcarrier, yuqorida ta'kidlab o'tilganidek, video tashuvchidan 3,579545 MGts yuqori va shunday kvadrat-amplituda-modulyatsiya qilingan bostirilgan tashuvchi bilan. Ovozli signal chastota bilan modulyatsiya qilingan, tomonidan uzatiladigan audio signallarga o'xshaydi FM radiosi stantsiyalar 88-108 MGts diapazonida, lekin maksimal 25 kHz bilan chastota og'ishi, 75 kHz dan farqli o'laroq FM diapazoni, analog televizion audio signallarni keng polosali qabul qilgichda qabul qilingan FM radio signallariga qaraganda jimroq qilish. Asosiy audio tashuvchisi video tashuvchidan 4,5 MGts balandlikda, kanalning yuqori qismidan 250 kHz pastda joylashgan. Ba'zan kanalda an bo'lishi mumkin MTS har biri chiziq chastotasining ko'pligi bilan sinxronlangan audio signalga bitta yoki ikkita subcarrier qo'shish orqali bir nechta audio signallarni taklif qiluvchi signal. Odatda bu qachon bo'ladi stereo audio va / yoki ikkinchi audio dastur signallari ishlatiladi. Xuddi shu kengaytmalar ishlatiladi ATSC, bu erda ATSC raqamli tashuvchisi kanalning pastki chegarasidan 0,31 MGts tezlik bilan uzatiladi.

"O'rnatish" - bu "qora" va "bo'shatish" darajalari orasidagi 54 mV (7,5 IRE) kuchlanishni almashtirish. Bu NTSC uchun o'ziga xosdir. CVBS Rang, Video, Blanking va Sinxronlashtirishni anglatadi.

Kadrlar stavkasini konvertatsiya qilish

Shuningdek qarang: Telecine

Ichida katta farq bor kvadrat tezligi sekundiga 24,0 kvadrat tezlikda ishlaydigan film va soniyasiga taxminan 29,97 (10 MGts × 63/88/455/525) kvadrat tezlikda ishlaydigan NTSC standarti o'rtasida. 25-soniyali televizion va video standartlardan foydalanadigan hududlarda bu farqni engib o'tish mumkin tezlikni oshirmoq.

30 fps standartlari uchun "deb nomlangan jarayon3: 2 tugadi "bitta videokamera uchta video maydon uchun uzatiladi (davomiyligi davom etadi)1 1⁄2 videofilmlar), keyingi kadr esa ikkita video maydon uchun uzatiladi (davomiyligi 1 ta video kadr). Shunday qilib, o'rtacha ikkita film plyonkasi beshta video maydonida uzatiladi2 1⁄2 har bir kvadrat uchun video maydonlar. Shunday qilib o'rtacha kvadrat tezligi soniyada 60 ÷ 2,5 = 24 kvadratni tashkil qiladi, shuning uchun filmning o'rtacha tezligi nominal ravishda aynan shunday bo'lishi kerak. (Haqiqatda, bir soatlik real vaqt davomida, 86330,88 kvadrat kadrlarni aks ettiruvchi 215 827,2 video maydon namoyish etiladi, bir soat ichida haqiqiy 24 kvadrat / soatlik film proektsiyasida aynan 86 400 kadr ko'rsatilgan: shuning uchun 29,97-fps NTSC 24 kadr / pikselli filmning uzatilishi filmning odatdagi tezligining 99,92 foizida ishlaydi.) Ijro paytida ham kadrlar ikki xil plyonkali maydonlarni o'z ichiga olgan videofilmni namoyish qilishi mumkin, shuning uchun kadrlar orasidagi har qanday farq tez orqaga va orqaga qarab paydo bo'ladi. oldinga miltillash. Bundan tashqari, sekin kameralar panasida sezilarli titroq / "duduqlanish" bo'lishi mumkin (telecine sudyasi ).

3: 2 buzilishidan saqlanish uchun NTSC televideniesi uchun maxsus suratga olingan film ko'pincha 30 kvadrat / s tezlikda olinadi.[iqtibos kerak ]

25 kadr / kvadrat materialni ko'rsatish (masalan, Evropa kabi) teleseriallar va ba'zi Evropa filmlari) NTSC uskunalarida har beshinchi kadr takrorlanadi va keyin hosil bo'lgan oqim interlaced qilinadi.

NTSC televideniesi uchun sekundiga 24 kadrda suratga olingan film an'anaviy ravishda 25-fps televizion standartlardan foydalaniladigan hududlarda uzatilishi uchun odatdagidek 1/24 ga (normal tezlikning 104,17% gacha) tezlashtirildi. Rasm tezligining bu o'sishi an'anaviy ravishda ovoz balandligi va tempining shunga o'xshash o'sishi bilan birga kelgan. Yaqinda freymlarni aralashtirish tezligini o'zgartirmasdan 24 FPS videoni 25 FPS ga aylantirish uchun ishlatilgan.

25 kadrli televizion standartlardan foydalanadigan mintaqalarda televizion filmlar uchun suratga olish quyidagi ikki usulda amalga oshirilishi mumkin:

  • Filmni soniyasiga 24 kadrda suratga olish mumkin. Bunday holda, o'z mintaqasida uzatilganda, film yuqorida tavsiflangan analog texnikasi bo'yicha 25 kvadrat / soatgacha tezlashtirilishi yoki yuqorida tavsiflangan raqamli texnikada 24 kvadrat / soat davomida saqlanishi mumkin. Xuddi shu film 30 fps nominal televizion standartdan foydalanadigan hududlarda uzatilganda, tezlik, temp va balandlikda sezilarli o'zgarish bo'lmaydi.
  • Filmni soniyasiga 25 kadrda suratga olish mumkin. Bunday holda, o'z mintaqasida uzatilganda, film odatdagi tezlikda namoyish etiladi, unga qo'shiladigan soundtrack o'zgartirilmaydi. Xuddi shu film 30 fps nominal televizion standartdan foydalanadigan hududlarda namoyish etilganda, har beshinchi kadr takrorlanadi va tezlik, temp va balandlikda hali ham sezilarli o'zgarish bo'lmaydi.

Ikkala film tezligi 25 kadr tezlikda ishlatilganligi sababli, tomoshabinlar ushbu mintaqalardan olingan televizion filmlarda video va audio haqiqiy tezligi, ovozlarning balandligi, ovoz effektlari va musiqiy ijrolar to'g'risida chalkashliklarga duch kelishlari mumkin. Masalan, ular hayron bo'lishlari mumkin Jeremi Bret qatorlari Sherlok Xolms 1980-yillarda va 1990-yillarning boshlarida suratga olingan televizion filmlar 24 kvadrat / soat tezlikda suratga olingan va keyin 25 kvadrat / soat tezlikda sun'iy tezlikda uzatilgan yoki mahalliy sifatida 25 kvadrat tezlikda suratga olinganmi va keyin NTSC ko'rgazmasi uchun 24 kadrgacha sekinlashtirilganmi.

Ushbu tafovutlar nafaqat televidenie orqali efirda va kabel orqali, balki uy-video bozorida ham lentada, ham diskda, shu jumladan mavjud. lazer disk va DVD.

O'z analog analoglarini almashtirgan raqamli televidenie va videofilmlarda kadr stavkalarining keng doirasiga mos keladigan yagona standartlar hanuzgacha analog mintaqaviy standartlarning chegaralarini ko'rsatadi. Ning dastlabki versiyasi ATSC standart, masalan, 23.976, 24, 29.97, 30, 59.94 va 60 kvadrat kadrlar soniyasiga ruxsat berilgan, lekin 25 va 50 emas. Zamonaviy ATSC 25 va 50 FPSga ruxsat beradi.

Analog sun'iy yo'ldosh uzatish uchun modulyatsiya

Sun'iy yo'ldosh quvvati juda cheklanganligi sababli, sun'iy yo'ldosh orqali analog video uzatish quruqlikdagi televizion uzatishdan farq qiladi. AM chiziqli modulyatsiya usuli hisoblanadi, shuning uchun berilgan modullangan signal-shovqin nisbati (SNR) bir xil darajada yuqori qabul qilingan RF SNR ni talab qiladi. Studiya sifatli videoning SNR darajasi 50 dB dan yuqori, shuning uchun AM juda katta quvvat va / yoki katta antennalarni talab qiladi.

Keng tarmoqli FM kamaytirilgan quvvat uchun chastota chastotasi o'tkazuvchanligini almashtirish uchun ishlatiladi. Kanalning o'tkazuvchanligini 6 dan 36 MGts gacha oshirish RF SNR-ni atigi 10 dB yoki undan kam bo'lishiga imkon beradi. Kengroq shovqin o'tkazuvchanligi, bu 40 dB quvvat tejashni 36 MGts / 6 MGts = 8 dB ga kamaytiradi va 32 dB ni aniq pasaytiradi.

Ovoz quruqlikdagi uzatishda bo'lgani kabi FM subcarrier-da, lekin 4,5 MGts dan yuqori chastotalar eshitish / ko'rish shovqinlarini kamaytirish uchun ishlatiladi. Odatda 6,8, 5,8 va 6,2 MGts ishlatiladi. Stereo multipleksli, diskretli yoki matritsali bo'lishi mumkin va bir-biri bilan bog'liq bo'lmagan audio va ma'lumotlar signallari qo'shimcha tashuvchilarga joylashtirilishi mumkin.

Modulyatsiyadan oldin kompozitsion tayanch tasmali signaliga (video plyus audio va ma'lumot subcarrierlari) uchburchak shaklida 60 gts dispersiyali to'lqin shakli qo'shiladi. Bu sun'iy yo'ldoshning pastga yo'nalishini cheklaydi quvvat spektral zichligi video signal yo'qolgan taqdirda. Aks holda sun'iy yo'ldosh butun kuchini bitta chastotada uzatishi va bir xil chastota diapazonidagi er usti mikroto'lqinli ulanishlariga xalaqit berishi mumkin.

Yarim transponder rejimida kompozitsion tayanch tarmoqli signalining chastota og'ishi 18 MGts ga kamaytirilib, 36 MGts transponderning ikkinchi yarmida boshqa signalga imkon beradi. Bu FM foydasini biroz pasaytiradi va tiklangan SNRlar yanada kamayadi, chunki sun'iy yo'ldosh transponderidagi intermodulyatsiya buzilishining oldini olish uchun birlashgan signal kuchini "zaxira qilish" kerak. Yagona FM signal doimiy amplituda, shuning uchun u transponderni buzilmasdan to'ydirishi mumkin.

Dala buyurtmasi

[23] NTSC "ramkasi" "juft" maydondan keyin "g'alati" maydondan iborat. Analog signalni qabul qilish masalasiga kelsak, bu shunchaki odatiy narsadir va farq qilmaydi. Bu xuddi yo'lning o'rtasidan o'tib ketgan singan chiziqlarga o'xshaydi, bu chiziq / kosmik juftlikmi yoki bo'shliq / chiziq juftligi muhim emas; haydovchiga ta'siri aynan bir xil.

Raqamli televizion formatlarning joriy etilishi vaziyatni biroz o'zgartirdi. Ko'pgina raqamli televidenie formatlari maydonlarni juftlikda bitta raqamli ramka sifatida saqlaydi va uzatadi. NTSC maydon stavkasiga mos keladigan raqamli formatlar, shu jumladan ommabop DVD formati,. bilan videoni yozib oling hatto birinchi maydon raqamli freymda, 625 liniya tizimining maydon tezligiga mos keladigan formatlarda ko'pincha video yoziladi birinchi navbatda toq ramka. Bu shuni anglatadiki, NTSC-ga asoslangan bo'lmagan ko'plab raqamli formatlarni ko'paytirishda maydon tartibini o'zgartirish kerak, aks holda harakatlanuvchi narsalarda qabul qilinishi mumkin bo'lmagan titroq "taroq" effekti paydo bo'ladi, chunki ular bir sohada oldinga surilib, so'ngra keyingi maydonga o'tishadi.

Bundan tashqari, NTSC bo'lmagan progressiv videoning interlaced formatiga transkodlanishi va aksincha, xavfli bo'lib qoldi. Progresiv kadrlarni yoki transkodli videoni tiklaydigan tizimlar "Maydon tartibi" ga rioya qilinishini ta'minlashi kerak, aks holda tiklangan kadr bitta kadrdan maydon va qo'shni kadrdan maydondan iborat bo'lib, natijada "taroq" armatura hosil bo'ladi. Bu ko'pincha kompyuterga asoslangan videofayl dasturlarida kuzatilishi mumkin, agar interlacing algoritmining noto'g'ri tanlovi amalga oshirilsa.

Qo'shma Shtatlarda o'nlab yillar davomida kuchli NTSC translyatsiyalari davomida ikkita kameraning ko'rinishini almashtirish ikkita natijaga ko'ra amalga oshirildi Dala ustunligi standartlar, ikkalasi o'rtasida tanlov geografiya tomonidan amalga oshiriladi, Sharq va G'arb. Bir mintaqada o'tish bitta ramkani tugatgan toq maydon bilan keyingi kadrni boshlagan juft maydon o'rtasida amalga oshirildi; ikkinchisida kalit juft maydondan keyin va toq maydondan oldin amalga oshirildi. Masalan, Sharqdagi mahalliy televizion xabarlardan olingan uydagi VHS yozuvi, to'xtatib qo'yilganda, faqat bitta kameradan ko'rinishni ko'rsatishi mumkin (agar eritish yoki boshqa ko'p kamerali tortishish mo'ljallanmagan bo'lsa), vaziyatni komediyasini VHS orqali ijro etish Los-Anjelesda lenta qilingan va tahrir qilingan, so'ngra butun mamlakat bo'ylab uzatiladigan kameralar o'rtasida yarim chiziqlar chiqayotgan kadrlar tasvirlangan, ikkinchisida esa keladigan kadrlar tasvirlangan vaqt o'tishi bilan to'xtatilishi mumkin.[iqtibos kerak ]

Variantlar

NTSC-M

PAL va SECAM-dan farqli o'laroq, uning ko'pgina asoslari mavjud efirga uzatiladigan televizion tizimlar butun dunyoda NTSC rang kodlash deyarli har doim ishlatiladi eshittirish tizimi M, NTSC-M berish.

NTSC-N / NTSC50

NTSC-N / NTSC50 - 625 qatorli videoni 3,58 MGts NTSC rang bilan birlashtirgan norasmiy tizim. NTSC-da ishlaydigan PAL dasturi Atari ST PAL rangini ko'rsatolmagani uchun ushbu tizimdan foydalanishni aks ettiradi. V-Hold tugmachasiga ega televizorlar va monitorlar ushbu tizimni vertikal ushlab turishni o'rnatgandan so'ng namoyish etishi mumkin.[24]

NTSC-J

Faqat Yaponiya variant "NTSC-J "biroz boshqacha: Yaponiyada signalning qora darajasi va bo'shliq darajasi bir xil (0 daIRE ), PAL-da bo'lgani kabi, Amerikaning NTSC-da qora daraja biroz yuqoriroq (7.5)IRE ) bo'shliq darajasidan. Farqi anchagina kichik bo'lgani uchun, nashrida tugmachasining engil burilishi NTSC ning "boshqa" variantini istalgan to'plamda kerakli tarzda to'g'ri ko'rsatish uchun zarur bo'lgan narsadir; aksariyat kuzatuvchilar birinchi navbatda farqni sezmasliklari ham mumkin. NTSC-J-da kodlovchi kanal NTSC-M-dan bir oz farq qiladi. Xususan, Yaponiyaning VHF diapazoni 1-12 kanallaridan (76-90 MGts Yaponiyaning to'g'ridan-to'g'ri yuqori chastotalarida joylashgan) FM radiosi Shimoliy Amerika VHF telekanali FM radioeshittirishga ajratilgan 88-108 MGts chastotali 2-13 (54-72 MGts, 76-88 MGts va 174-216 MGts) kanallaridan foydalanadi. Shuning uchun Yaponiyaning UHF telekanallari 13 dan 14 gacha emas, aks holda UHF radioeshittirish chastotalaridan foydalanadi. Shimoliy Amerika.

PAL-M (Braziliya)

Braziliyalik KAFT 1972 yil 19 fevralda taqdim etilgan tizim NTSC (525/60) bilan bir xil chiziqlar / maydondan va deyarli bir xil translyatsiya o'tkazuvchanligi va skanerlash chastotasidan (15,750 va 15,734 kHz) foydalanadi. Rangni taqdim etishdan oldin Braziliya standart oq-qora NTSC-da translyatsiya qildi. Natijada, KAFT signallari Shimoliy Amerika NTSC signallari bilan bir xil, faqat rangli subkarrierni kodlash bundan mustasno (3,575611 MGts uchun KAFT va NTSC uchun 3,579545 MGts). Ushbu yaqin xususiyatlar natijasida, KAFT monoxromda NTSC to'plamlarida ovoz bilan aks etadi va aksincha.

Eshittirish tizimi M
Rang tizimiKAFTNTSC
Transmissiya tasmasiUHF / VHF
Kadrlar tezligi30 Hz
Chiziqlar / maydonlar525/60
Portret chastota60 Hz60 / 1.001 Hz
Landshaft chastota15,750 kHz15,734 kHz
Rangli subcarrier3,575611 MGts3,579545 MGts
Video o'tkazuvchanligi4.2 MGts
Ovoz tashuvchisi chastotasi4,5 MGts
Kanalning o'tkazuvchanligi6 MGts

PAL-N

Asosiy maqola: PAL-N

Bu ishlatiladi Argentina, Paragvay va Urugvay. Bu juda o'xshash KAFT (ishlatilgan Braziliya ).

NTSC-M va NTSC-N o'xshashliklarini quyidagi ko'rinishda ko'rish mumkin ITU identifikatsiya qilish sxemasi bu erda qayta ishlab chiqarilgan jadval:

Jahon televizion tizimlari
TizimChiziqlarKadrlar tezligiKanal b / wVisual b / wOvoz ofsetVestigial yon tasmaVizyon rejimi.Ovoz rejimi.Izohlar
M52529.9764.2+4.50.75Salbiy.FMKo'pchilik Amerika va Karib dengizi, Janubiy Koreya, Tayvan, Filippinlar (barchasi NTSC-M) va Braziliya (KAFT). Kattaroq kvadrat tezligi yuqori sifatga olib keladi.
N6252564.2+4.50.75Salbiy.FMArgentina, Paragvay, Urugvay (barchasi PAL-N). Greater number of lines results in higher quality.

As it is shown, aside from the number of lines and sekundiga kadrlar, the systems are identical. NTSC-N/PAL-N are compatible with sources such as o'yin konsollari, VHS /Betamaks Videomagnitofonlar va DVD futbolchilar. Biroq, ular bilan mos kelmaydi tayanch tasma broadcasts (which are received over an antenna ), though some newer sets come with baseband NTSC 3.58 support (NTSC 3.58 being the frequency for color modulation in NTSC: 3.58 MHz).

NTSC 4.43

In what can be considered an opposite of PAL-60, NTSC 4.43 is a pseudo color system that transmits NTSC encoding (525/29.97) with a color subcarrier of 4.43 MHz instead of 3.58 MHz. The resulting output is only viewable by TVs that support the resulting pseudo-system (such as most PAL TVs[iqtibos kerak ] since around the mid-1990s). Using a native NTSC TV to decode the signal yields no color, while using an incompatible PAL TV to decode the system yields erratic colors (observed to be lacking red and flickering randomly). The format was used by the USAF TV based in Germany during the Sovuq urush.[25] It was also found as an optional output on some LaserDisc players and some game consoles sold in markets where the PAL system is used.

The NTSC 4.43 system, while not a broadcast format, appears most often as a playback function of PAL cassette format VCRs, beginning with the Sony 3/4" U-Matic format and then following onto Betamax and VHS format machines. As Hollywood has the claim of providing the most cassette software (movies and television series) for VCRs for the world's viewers, and as not barchasi cassette releases were made available in PAL formats, a means of playing NTSC format cassettes was highly desired.

Multi-standard video monitors were already in use in Europe to accommodate broadcast sources in PAL, SECAM, and NTSC video formats. The heterodin color-under process of U-Matic, Betamax & VHS lent itself to minor modification of VCR players to accommodate NTSC format cassettes. The color-under format of VHS uses a 629 kHz subcarrier while U-Matic & Betamax use a 688 kHz subcarrier to carry an amplituda modulyatsiya qilingan chroma signal for both NTSC and PAL formats. Since the VCR was ready to play the color portion of the NTSC recording using PAL color mode, the PAL scanner and capstan speeds had to be adjusted from PAL's 50 Hz field rate to NTSC's 59.94 Hz field rate, and faster linear tape speed.

The changes to the PAL VCR are minor thanks to the existing VCR recording formats. The output of the VCR when playing an NTSC cassette in NTSC 4.43 mode is 525 lines/29.97 frames per second with PAL compatible heterodyned color. The multi-standard receiver is already set to support the NTSC H & V frequencies; it just needs to do so while receiving PAL color.

The existence of those multi-standard receivers was probably part of the drive for region coding of DVDs. As the color signals are component on disc for all display formats, almost no changes would be required for PAL DVD players to play NTSC (525/29.97) discs as long as the display was frame-rate compatible.

OSKM

In January 1960 (7 years prior to adoption of the modified SECAM version) the experimental TV studio in Moscow started broadcasting using the OSKM system. The OSKM abbreviation means "Simultaneous system with quadrature modulation" (In Russian: Одновременная Система с Квадратурной Модуляцией). It used the color coding scheme that was later used in PAL (U and V instead of I and Q), because it was based on D/K monochrome standard, 625/50.

The color subcarrier frequency was 4.4296875 MHz and the bandwidth of U and V signals was near 1.5 MHz. Only circa 4000 TV sets of 4 models (Raduga, Temp-22, Izumrud-201 and Izumrud-203) were produced for studying the real quality of TV reception. These TV's were not commercially available, despite being included in the goods catalog for trade network of the USSR.

The broadcasting with this system lasted about 3 years and was ceased well before SECAM transmissions started in the USSR. None of the current multi-standard TV receivers can support this TV system.

NTSC-film

Asosiy maqola: 24p

Film content commonly shot at 24 frames/s can be converted to 30 frames/s through the telecine process to duplicate frames as needed.

Mathematically for NTSC this is relatively simple as it is only needed to duplicate every fourth frame. Various techniques are employed. NTSC with an actual frame rate of ​24⁄1.001 (approximately 23.976) frames/s is often defined as NTSC-film. A process known as pullup, also known as pulldown, generates the duplicated frames upon playback. This method is common for H.262 / MPEG-2 2-qism digital video so the original content is preserved and played back on equipment that can display it or can be converted for equipment that cannot.

Canada/US video game region

Ba'zan NTSC-U, NTSC-US, yoki NTSC-U/C is used to describe the video gaming region of North America (the U/C refers to US + Canada), as mintaqaviy lokavt usually restricts games from being playable outside the region.

Comparative quality

The SMPTE rangli chiziqlar, a misoli test pattern

Reception problems can degrade an NTSC picture by changing the bosqich of the color signal (actually differential phase distortion ), so the color balance of the picture will be altered unless a compensation is made in the receiver. The vacuum-tube electronics used in televisions through the 1960s led to various technical problems. Among other things, the color burst phase would often drift when channels were changed, which is why NTSC televisions were equipped with a tint control. PAL and SECAM televisions had no need of one, and although it is still found on NTSC TVs, color drifting generally ceased to be a problem for more modern circuitry by the 1970s. When compared to PAL in particular, NTSC color accuracy and consistency is sometimes considered inferior, leading to video professionals and television engineers jokingly referring to NTSC as Never The Same Color, Never Twice the Same Color, yoki No True Skin Colors,[26] while for the more expensive PAL system it was necessary to Pay for Additional Luxury.

PAL has also been referred to as Nihoyat tinchlik, Perfection At Last yoki Pictures Always Lovely in the color war. This mostly applied to vacuum tube-based TVs, however, and later-model solid state sets using Vertical Interval Reference signals have less of a difference in quality between NTSC and PAL. This color phase, "tint", or "hue" control allows for anyone skilled in the art to easily calibrate a monitor with SMPTE rangli chiziqlar, even with a set that has drifted in its color representation, allowing the proper colors to be displayed. Older PAL television sets did not come with a user accessible "hue" control (it was set at the factory), which contributed to its reputation for reproducible colors.

The use of NTSC coded color in S-Video systems completely eliminates the phase distortions. As a consequence, the use of NTSC color encoding gives the highest resolution picture quality (on the horizontal axis and frame rate) of the three color systems when used with this scheme. (The NTSC resolution on the vertical axis is lower than the European standards, 525 lines against 625.) However, it uses too much bandwidth for over-the-air transmission. The Atari 800 va Commodore 64 home computers generated S-video, but only when used with specially designed monitors as no TV at the time supported the separate chroma and luma on standard RCA raz'emlari. In 1987, a standardized four-pin mini-din socket was introduced for S-video input with the introduction of S-VHS players, which were the first device produced to use the four-pin plugs. However, S-VHS never became very popular. Video game consoles in the 1990s began offering S-video output as well.

The mismatch between NTSC's 30 frames per second and film's 24 frames is overcome by a process that capitalizes on the maydon rate of the interlaced NTSC signal, thus avoiding the film playback speedup used for 576i systems at 25 frames per second (which causes the accompanying audio to increase in pitch slightly, sometimes rectified with the use of a pitch shifter ) at the price of some jerkiness in the video. Qarang Frame rate conversion yuqorida.

Vertical interval reference

The standard NTSC video image contains some lines (lines 1–21 of each field) that are not visible (this is known as the Vertikal bo'shliq oralig'i, or VBI); all are beyond the edge of the viewable image, but only lines 1–9 are used for the vertical-sync and equalizing pulses. The remaining lines were deliberately blanked in the original NTSC specification to provide time for the electron beam in CRT-based screens to return to the top of the display.

VIR (or Vertical interval reference), widely adopted in the 1980s, attempts to correct some of the color problems with NTSC video by adding studio-inserted reference data for luminance and chrominance levels on line 19.[27] Suitably equipped television sets could then employ these data in order to adjust the display to a closer match of the original studio image. The actual VIR signal contains three sections, the first having 70 percent luminance and the same chrominance as the rang portlashi signal, and the other two having 50 percent and 7.5 percent luminance respectively.[28]

A less-used successor to VIR, GCR, also added ghost (multipath interference) removal capabilities.

Qolganlari; qolgan vertikal bo'shliq oralig'i lines are typically used for ma'lumotlar to'plami or ancillary data such as video editing timestamps (vertical interval timecodes yoki SMPTE timecodes on lines 12–14[29][30]), sinov ma'lumotlari on lines 17–18, a network source code on line 20 and yopiq taglavha, XDS va V-chip data on 21-qator. Erta telematn applications also used vertical blanking interval lines 14–18 and 20, but teletext over NTSC was never widely adopted by viewers.[31]

Many stations transmit TV Guide On Screen (TVGOS ) data for an electronic program guide on VBI lines. The primary station in a market will broadcast 4 lines of data, and backup stations will broadcast 1 line. In most markets the PBS station is the primary host. TVGOS data can occupy any line from 10–25, but in practice its limited to 11–18, 20 and line 22. Line 22 is only used for 2 broadcast, DirecTV va CFPL-TV.

TiVo data is also transmitted on some commercials and program advertisements so customers can autorecord the program being advertised, and is also used in weekly half-hour paid programs kuni Ion Televizion va Discovery kanali which highlight TiVo promotions and advertisers.

Countries and territories that are using or once used NTSC

Qo'shimcha ma'lumotlar: Qo'shma Shtatlarda raqamli televizion o'tish

Below countries and territories currently use or once used the NTSC system. Many of these have switched or are currently switching from NTSC to digital television standards such as ATSC (United States, Canada, Mexico, Suriname, South Korea), ISDB (Japan, Philippines and part of South America), DVB-T (Taiwan, Panama, Colombia and Trinidad and Tobago) or DTMB (Cuba).

Tajriba qilingan

  •  Braziliya (Between 1962 and 1963, Redup Tupi va Rede Excelsior made the first unofficial transmissions in color, in specific programs in the city of San-Paulu, before the official adoption of KAFT by the Brazilian Government on February 19, 1972)
  •  Paragvay
  •  Birlashgan Qirollik (Experimented on 405-line variant of NTSC, then UK chose 625-line for PAL broadcasting.)

Countries and territories that have ceased using NTSC

The following countries and regions no longer use NTSC for terrestrial broadcasts.

MamlakatYoqilganO'tkazish tugallandi
 BermudDVB-T2016-03-012016 yil mart
 KanadaATSC2012-07-31August 31, 2011 (Select markets)
 YaponiyaISDB-T2012-03-312012 yil 31 mart
 Janubiy KoreyaATSC2012-12-312012 yil 31 dekabr
 MeksikaATSC2015-12-31December 31, 2015 (Full Power Stations)[51]
 Xitoy RespublikasiDVB-T2012-06-302012 yil 30 iyun
 Qo'shma ShtatlarATSC2009-06-12June 12, 2009 (Full Power Stations)[48]
September 1, 2015 (Class-A Stations)

Shuningdek qarang

Izohlar

  1. ^ National Television System Committee (1951–1953), [Report and Reports of Panel No. 11, 11-A, 12-19, with Some supplementary references cited in the Reports, and the Petition for adoption of transmission standards for color television before the Federal Communications Commission, n.p., 1953], 17 v. illus., diagrs., tables. 28 cm. LC Control No.:54021386 Kongress kutubxonasining onlayn katalogi
  2. ^ Raqamli televideniye. FCC.gov. 2014-05-11 da qabul qilingan.
  3. ^ a b DTV and Over-the-Air Viewers Along U.S. Borders. FCC.gov. 2014-05-11 da qabul qilingan.
  4. ^ Canada... PAL or NTSC?. VideoHelp Forum Retrieved on 2015-01-23.
  5. ^ What actually occurred was the RCA TG-1 synch generator system was upgraded from 441 lines per frame, 220.5 lines per field, interlaced, to 525 lines per frame 262.5 lines per field, also interlaced, with minimal additional changes, particularly not those affecting the vertical interval, which, in the extant RCA system, included serrated equalizing pulses bracketing the vertical sync pulse, itself being serrated. For RCA/NBC, this was a juda simple change from a 26,460 Hz master oscillator to a 31,500 Hz master oscillator, and minimal additional changes to the generator's divider chain. The equalizing pulses and the serration of the vertical sync pulse were necessary because of the limitations of the extant TV receiver video/sync separation technology, thought to be necessary because the sync was transmitted in band with the video, although at a quite different DC level. The early TV sets did not possess a DC restorer circuit, hence the need for this level of complexity. In-studio monitors were provided with separate horizontal and vertical sync, not composite synch and certainly not in-band synch (possibly excepting early color TV monitors, which were often driven from the output of the station's colorplexer ).
  6. ^ A third line sequential system from Color Television Inc. (CTI) was also considered. The CBS and final NTSC systems were called field-sequential and dot-sequential systems, respectively.
  7. ^ "Color TV Shelved As a Defense Step", The New York Times, October 20, 1951, p. 1. "Action of Defense Mobilizer in Postponing Color TV Poses Many Question for the Industry", The New York Times, October 22, 1951, p. 23. "TV Research Curb on Color Avoided", The New York Times, October 26, 1951. Ed Reitan, CBS Field Sequential Color System Arxivlandi 2010-01-05 da Orqaga qaytish mashinasi, 1997. A variant of the CBS system was later used by NASA to broadcast pictures of astronauts from space.
  8. ^ "CBS Says Confusion Now Bars Color TV," Vashington Post, March 26, 1953, p. 39.
  9. ^ "F.C.C. Rules Color TV Can Go on Air at Once", The New York Times, December 19, 1953, p. 1.
  10. ^ "73.682" (PDF). www.govinfo.gov. FCC. Olingan 22 yanvar 2019.
  11. ^ The master oscillator is 315/22 = 14.31818 MHz, from which the 3.579545 color burst frequency is obtained by dividing by four; and the 31 kHz horizontal drive and 60 Hz vertical drive are also synthesized from that frequency. This facilitated a conversion to color of the then common, but monochrome, RCA TG-1 synchronizing generator by the simple expedient of adding-on an external 14.31818 MHz temperature-controlled oscillator and a few dividers, and inputting the outputs of that chassis to certain test points within the TG-1, thereby disabling the TG-1's own 31500 Hz reference oscillator.
  12. ^ "Choice of Chrominance Subcarrier Frequency in the NTSC Standards," Abrahams, I.C., Proc. IRE, Vol. 42, Issue 1, p.79–80
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  15. ^ 47 CFR § 73.682 (20) (iv)
  16. ^ DeMarsh, Leroy (1993): TV Display Phosphors/Primaries — Some History. SMPTE Journal, December 1993: 1095–1098. doi:10.5594/J01650
  17. ^ a b v International Telecommunications Union Recommendation ITU-R 470-6 (1970–1998): Conventional Television Systems, Annex 2.
  18. ^ Society of Motion Picture and Television Engineers (1987–2004): Recommended Practice RP 145-2004. Color Monitor Colorimetry.
  19. ^ Society of Motion Picture and Television Engineers (1994, 2004): Engineering Guideline EG 27-2004. Supplemental Information for SMPTE 170M and Background on the Development of NTSC Color Standards, pp. 9
  20. ^ Advanced Television Systems Committee (2003): ATSC Direct-to-Home Satellite Broadcast Standard Doc. A/81, pp.18
  21. ^ European Broadcasting Union (1975) Tech. 3213-E.: E.B.U. Standard for Chromaticity Tolerances for Studio Monitors.
  22. ^ Poynton's Color FAQ by Charles Poynton
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  28. ^ Waveform Mons & Vectorscopes. Danalee.ca. 2014-05-11 da qabul qilingan.
  29. ^ SMPTE EBU timecode by Phil Rees. Philrees.co.uk. 2014-05-11 da qabul qilingan.
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  48. ^ a b "ATSC SALUTES THE 'PASSING' OF NTSC". NTSC. Arxivlandi asl nusxasi 2010 yil 24 mayda. Olingan 13 iyun, 2009.
  49. ^ "FCC Public Notice: "THE INCENTIVE AUCTION TASK FORCE AND MEDIA BUREAU ANNOUNCE PROCEDURES FOR LOW POWER TELEVISION, TELEVISION TRANSLATOR AND REPLACEMENT TRANSLATOR STATIONSDURING THE POST-INCENTIVE AUCTION TRANSITION", May 17, 2017" (PDF).
  50. ^ http://apps.fcc.gov/ecfs/document/view?id=60000976623
  51. ^ Transicion a TDT (Transition to DT) Arxivlandi 2010-09-19 at the Orqaga qaytish mashinasi (Ispancha)

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