HDTV

HDTV,  STANDARISASI
DAN  PENYELENGGARAANNYA
      KATA PENGANTAR    
               Seiring berjalannya waktu, teknologi pun semakin maju. Dari hari ke hari ada saja penemuan-penemuan mutakhir yang seolah bisa “merubah dunia”. Kebanyakan dari teknologi-teknologi mutakhir ini merupakan hasil konvergensi dari teknologi-teknologi terdahulu.
 
               Di antara sekian banyak teknologi canggih tersebut, di sini saya akan mencoba menguraikan tentang teknologi HDTV ( High-definition Television ) yang sebenarnya sudah mulai dikembangkan di Jepang pada sekitar tahun 1968, dan mulai masuk ke Indonesia sekitar tahun 90-an. 
 
               Adapun tujuan dibuatnya tulisan ini antara lain untuk menceritakan sedikit sejarahnya kemunculannya, kelebihannya, dan hal-hal lain seputar HDTV yang mungkin masih ada segelintir orang yang kurang mengetahuinya.
 
               Terlebih dahulu saya ucapkan terima kasih kepada dosen saya, Bang Vinsen Sitepu yang baik hati banget karena telah menugaskan saya membuat tulisan ini, sehingga saya jadi tau lebih banyak lagi tentang HDTV. 
 
               Semoga tulisan yang sumbernya saya kutip dari wikipedia.org dan google.com ini bermanfaat dalam menambah pengetahuan dan wawasan tentangn teknologi bagi orang0orang yang membacanya. Lebih dan kurangnya  saya mohon maaf.
 
 
 
PENDAHULUAN         

            Selama ini kita sudah sangat familiar dengan sistem national television system committee (NTSC) yang dipergunakan televisi untuk menyajikan gambar. Tetapi, belakangan dengan munculnya teknologi high-definition television (HDTV) atau yang dalam bahasa Indonesia disebut televisi definisi tinggi, menyebabkan fungsi NTSC perlahan-lahan tergantikan. Apa sih sebenarnya teknologi HDTV ini?

HDTV adalah merupakan media komunikasi baru dan teknologinya masih dalam proses penggarapan yang sangat ramai, terutama pada awaltahun 90-an.  Secara singkat sejarah perkembangan  HDTV dimulai olehJepang yang dimotori oleh pusat riset dan pengembangan NHK (TVRI/RRI-nya Jepang) pada tahun 1968, kemudian diikuti oleh Masyarakat Eropasebagai pembanding dan akhirnya Amerika Serikat menjadi kompetitor yang harus diperhitungkan.

Sebenarnya sampai sekarang masih sulit untuk mendefinisikan secara tepat HDTV. Yang pasti, teknologi tayangan televisi yang dianggap terbaik sekarang ini adalah menggunakan sistem NTSC (National Television Systems Committee) yang menayangkan gambar analog, menghasilkan resolusi sebanyak 525 garis pada layar televisi. Sedangkan HDTV menghasilkan resolusi 1.125 garis tayangan yang lebih padat dan mampu menghasilkan informasi video lima kali lebih banyak dibanding sistem NTSC.

Namun, walaupun memiliki keunggulan yang luar biasa dalam menghasilkan resolusi yang rapat, tajam, dan jelas, transmisi HDTV memerlukan bandwith yang lebih besar sampai lima kali dibanding kapasitas sinyal televisi konvensional. Meski masih sulit mendefinisikannya, HDTV dapat diartikan sebagai suatu sistem media komunikasi bergambar dan atau bersuara dengan tingkat kualitas ketajaman gambar (resolusi) yang sangat tinggi (hampir sama dengan kualitas film 35 mm) dan kualitas suaranya juga menyerupai CD (Compact Disk).

            Pesatnya kemajuan teknologi digital, terutama di bidang gambar digital yang mengkombinasikan foto dan video, memang tidak diduga sebelumnya. Kehadiran teknologi HDTV, bukan saja mendorong produk-produk dengan kualitas digital pada beberapa merek perangkat televisi yang sudah punya nama, tetapi juga pada cara perekamannya untuk ditayangkan di HDTV.  

 

PEMBAHASAN

Dalam hal ini teknologi pemrosesan sinyal digital dan displai memberikan peran yang sangat penting. Diharapkan juga nantinya bisa melayani multi bahasa dan multi media. Karena HDTV merupakan sistem komunikasi, maka seperti juga sistem komunikasi konvensional lainnya, untuk penyelenggaraannya memerlukan beberapa komponen dasar seperti pusat produksi (studio), pemroses/penyimpan, sistem transmisi dan pesawat penerima.

Konsep dasar HDTV di sisi lain sebenarnya tidak dimaksudkan hanya untuk meningkatkan definisi per wilayah unit tayangan layar televisi, tetapi juga untuk meningkatkan persentase bidang visual yang menayangkan gambar tersebut. Pengembangan HDTV diarahkan pada peningkatan 100 persen jumlah piksel horizontal dan vertikal, misalnya bingkai gambar 1 MB seharusnya memiliki jumlah 1.000 garis x 1.000 titik horizontal.

Hasil yang didapat dari perluasan ini adalah faktor perbaikan 2-3 kali dalam sudut bidang vertikal dan horizontal. Dengan demikian, perbaikan sudut ini pada HDTV juga mengubah rasio menjadi 16:9 dari 4:3 dan menjadi imej yang ditayangkan seperti di “bioskop”. HDTV memang merupakan media komunikasi baru dan teknologinya sedang dalam proses penyempurnaan, terutama pada awal dekade 90-an.

Secara singkat sejarah perkembangan  HDTV dimulai oleh Jepang yang dimotori oleh pusat riset dan pengembangan NHK (TVRI/RRI-nya Jepang) pada tahun 1968. Kemudian diikuti oleh masyarakat Eropa sebagai pembanding dan akhirnya Amerika Serikat menjadi kompetitor yang harus diperhitungkan.

Diperkirakan teknologi HDTV ini akan menjadi standar televisi masa depan, sehingga seorang peneliti senior dalam bidang sistem strategi dan manajemen Dr. Indu Singh  meramalkan bahwa pasar dunia untuk HDTV ini akan mencapai 250 milyar dolar per tahun (tahun 2010).

 

Kompetisi Standar HDTV

Di samping aspek pasar yang menggiurkan, dalam sistem penyelenggaran HDTV  mempunyai dampak yang luas pada bidang budaya, sosial, politik sampai pada pertahanan. Karena itu negara-negara maju telah berlomba agar sistem yang mereka kembangkan itu nantinya dapat dipakai sebagai standar dunia (global).

Standar yang telah masuk dalam agenda rapat CCIR (badan internasional yang menangani standarisasi sistem penyiaran),  baru dua yaitu MUSE (Jepang) dan HD-MAC (Eropa). Sementara itu Amerika Serikat yang diatur oleh FCC (Komisi Komunikasi) sedang ditegangkan untuk memutuskan satu standar dari masing-masing team (konsorsium) yang sedang berkompetisi.

Karena kepentingan masing-masing negara yang berbeda-beda apakah CCIR bisa memutuskan pemakaian standar yang tunggal? Pengalaman dari sistem TV konvensional yaitu adanya PAL/SECAM di Eropa & ASEAN, NTSC di Amerika dan Jepang, rasanya sulit CCIR untuk bisa memutuskan pemakaian tunggal sistem penyiaran HDTV ini. Disamping itu juga ada badan standarisasi di bawah ISO yaitu MPEG yang menangani standarisasi pengkodean dan pemampatan sinyal gambar bergerak.

 

HDTV di Negara Berkembang

Setiap negara tentu saja menginginkan bahwa negaranya bisa maju dalam segala hal, termasuk teknologi HDTV. Bagi negara maju yang infrastruturnya sudah lengkap yang menjadi masalah penerapan adalah kompetisi. Namun demikian bagaimana dengan negara berkembang yang infrastrukturnya masih terbatas (lihat idealisasi sistem siaran di atas), apakah mau menciptakan standar sendiri ataukah mengikuti standar yang sedang dikembangkan oleh bangsa maju. apankah HDTV tersebut layak diterapkan?

Karena tingkatan teknologi HDTV yang ada sudah demikian maju, kemungkinan membuat standar sinyal sendiri hanyalah membuang waktu dan dana. Alangkah bijaksananya kalau negara berkembang bisa mempelajari sistem HDTV ini baik dari segi produksi, transmisinya, pesawat penerima bahkan sampai industri pembuatan komponen-komponen tersebut. Karena tanpa bisa memproduksi, negara tesebut akan selalu bergantung.

Sebagai contoh keterpaduan yang dilakukan di Jepang untuk pengembangan industri televisi yang dimulai dekade 50-an. Dengan dimotori oleh Pusat Riset dan Pengembangan NHK, Jepang memaksa industri-industri dalam negeri (Sony, Matsuhita, dll) untuk bisa memproduksi televisi dan komponen terkait dengan orientasi permulaan pasar dalam negeri.

Dengan dilaksanakan siaran secara langsung  melalui media televisi upacara pernikahan kaisar (emperor) Akihito pada tahun 1959, meledaklah industri televisi di Jepang. Akhirnya seperti kita ketahui dengan baik bahwa Jepang telah bisa merajai teknologi televisi dan pasar dunia. Bahkan telah berhasil menayangkan program HDTV 8 jam sehari (mulai 25 Nopember 1991).

               Contoh lain adalah Korea Selatan. Mereka tidak terburu-buru mengadakan penyelenggaraannya di saat standar belum mapan. Namun yang mereka kejar adalah bagaimana memproduksi HDTV untuk bisa diekspor, sehingga mereka mengirimkan para ahli yang bisa membuat HDTV ke Jepang , Eropa dan Amerika. Kegiatan ini merupakan konsorsium dari pemerintah dan industri terkait seperti Golden Star, Samsung, Daewo, dan Korean Telecom. Proyek pengembangan produksi HDTV di Korea ini dimulai sejak tahun 1989, dengan biaya 100 milyar won, 60 persen di antaranya dikeluarkan dari kocek pemerintah. Target yang mereka harapkan adalah, konfigurasi dasar (prototipe) akan selesai dilaksanakan pada tahun 1993, sedangkan secara ambisius pada tahun 1995 bisa membuat produksi secara massal.
               
               Kelihatannya sangat netral dan beralasan sekali ,saran seorang mantan peneliti  dari NHK yang sekarang menjadi guru besar di salah satu perguruan tinggi  di Jepang, yang menyatakan bahwa kalau negara berkembang ingin mengembangkan sistem siaran HDTV, maka yang perlu dibenahi dulu antara lain  adalah , perbanyaklah ahli elektronika (pendidikan) dan yang terkait sehingga bisa membuat , menjalankan dan memasarkan industri elektronika secara mandiri. Menurut beliau  kalau ini dikerjakan mulai sekarang dengan  kerja keras (Gambate /bahasa Jepang),  mudah-mudahan penyelenggaraan sistem siaran HDTV ini bisa dilaksanakan dalam  kurun 10 tahun yang akan datang.

 

 Syarat Penyelenggaraan HDTV

Untuk dapat menyelenggarakan sistem siaran HDTV baik secara nasional maupun global yang ideal, diperlukan beberapa kriteria antara lain sebagai berikut:

– Penggunaan sinyal standar yang sama (di dunia /dalam satu negara).

– Biaya pesawat penerima yang murah /terbeli oleh khalayak umum.

– Kompatibel dengan sistem yang sudah ada.

– Bisa dihubungkan dengan media lain (multi-media).

– Dapat terjangkau secara meluas (aspek pemerataan).

Memindahkan Bioskop ke Rumah

            Banyak orang yang hobi menonton film di bioskop dibandingkan menonton film di televisi. Kegemaran banyak orang ini memang tidak bisa disalahkan. Tetapi seiring kemajuan teknologi di bidang perangkat televisi, sekarang kita bisa memindahkan segenap keistimewaan bioskop ke rumah melalui layar plasma. Layar plasma ini pun jadi identik dengan teknologi HDTV. Meski tidak semua TV plasma menyandang teknologi ini.

Dalam prinsipnya, layar plasma tersusun atas dua lembar kaca. Di antara keduanya diisi ribuan sel, yang ratusan di antaranya berisi gas xenon dan neon. Dua jenis elektroda panjang, address electrode dan transparent display electrode, direntangkan di antara lempengan kaca tersebut.

Saat layar plasma dihidupkan, elektroda-elektroda yang saling berpotongan di atas sel itu diberi muatan listrik oleh komputer layar untuk mengionisasi gas dalam sel. Ini berlangsung ribuan kali dalam sepersekian detik. Arus listrik pun melewati gas di dalam sel dan menghasilkan aliran partikel bermuatan listrik yang cepat, yang merangsang atom gas tersebut melepaskan foton ultraviolet.

Kemudian, foton ultraviolet berinteraksi dengan fosfor yang akhirnya melepaskan energi di dalam bentuk sinar foton yang jelas. Setiap pixel tersusun atas tiga sel sub pixel yang terpisah. Masing-masing dengan fosfor yang berbeda warna, yaitu merah, hijau, biru yang akan bercampur menghasilkan warna pixel.

Untuk menyeragamkan kekuatan arus listrik yang mengalir melalui sel berbeda, sistem kontrolnya akan menambah atau mengurangi intensitas warna setiap sub pixel. Hal ini untuk menghasilkan ratusan kombinasi merah, hijau, dan biru yang berbeda. Dengan cara ini, sistem kontrol dapat menghasilkan warna dalam spektrum luas, sekira ada 16,77 juta warna bisa dihasilkan sebuah layar plasma. Inilah yang membuat tampilan gambar plasma sangat tajam dan jelas.

Selain itu, TV layar plasma memiliki resolusi lebih tinggi ketimbang layar tv konvensional. Kebanyakan mampu menampilkan siaran HDTV (high definition television) dan non-HDTV, serta bingkainya pun mampu menghasilkan sinyal gambar XGA, SVGA, dan VGA untuk sebuah komputer. Layar plasma pun memungkinkan kita menonton film dari VCD/DVD dalam format layar lebar, seperti terlihat di layar bioskop.

Pasalnya, layar plasma dibuat dengan rasio 16 : 9 (lebar : tinggi). Permukaan layarnya betul-betul datar sehingga menghilangkan distorsi gambar di bagian sudut seperti biasa terjadi pada layar CRT (catode ray tube) cembung. Apabila materi yang ditonton tidak dalam format layar lebar pun tidaklah menjadi masalah.

Layar plasma akan merentangkan itu untuk mengisi penuh layar atau memperbesar gambar untuk membatasi perentangan gambar. Bahkan, beberapa merek layar plasma dapat ditonton secara vertikal. Dengan demikian, layar plasma disertai perangkat lunak (software) komputer. Dengan software tersebut, sekitar 40% gambar bagian tengah akan ditampilkan di layar secara vertikal. Sebagian lainnya, yang berada di kiri dan kanan, tidak ditampilkan di layar.

Keistimewaan lain dari teknologi layar plasma ini adalah bahwa layar plasma tidak menghasilkan medan magnet seperti layar berteknologi CRT. Masalahnya, tidak ada tembakan elektron dalam menghasilkan gambar. Speaker, yang bermedan magnet kuat dan dapat mendistorsi gambar TV CRT pun membuat gambar pada layar plasma mengalami distorsi. Inilah sebenarnya kunci keunggulan dari teknologi layar plasma.

Tidak semua layar plasma mampu menangkap siaran HDTV, beberapa memang dilengkapi namun ada pula yang tidak. Di Indonesia sendiri hampir semua merek layar plasma yang dipasarkan beresolusi HDTV, termasuk merek Sony, Panasonic, Pioneer, Sharp, Philips, Samsung, Sanyo, Hitachi, LG, Toshiba dan lain sebagainya.

Digital HDTV
Jepang Pindah Haluan
 
               Akhir Februari lalu, Kementrian Pos dan Telekomunikasi Jepang mengeluarkan dua arahan kebijaksanaan sehubungan dengan penyelenggaraan media baru yang berhubungan dengan media siaran, telekomunikasi dan komputasi di Jepang.
Arahan pertama yang dikeluarkan oleh Biro Administrasi Siaran kementrian tersebut adalah kebijaksanaan pengembangan HDTV di Jepang , dan yang keduaadalah penyiapan naskah undang-undang penyelenggaraan multimedia.
 
               Meskipun kedua arahan kebijaksanaan tersebut kelihatannya berbeda namun kalauditelaah lebih lanjut kemungkinan merupakan upaya terpadu pemerintah Jepang dalam mengantisipasi digitalisasi bisnis media pada masa yang akan datang.Arahan pertama yang menyangkut HDTV (High Definition Television = Televisi berketajaman gambar sangat tinggi) adalah rencana kepindahan Jepang dari penggunaan sistem analog ke sistem digital. Arahan baru ini menjadi polemic yang cukup hangat masyarakat Jepang seperti Assosiasi Industri Elektronika Jepang sebagai produsen, NHK sebagai pelopor riset dan pengembangan HDTV dan
masyarakat pengguna televisi baik yang sudah mempunyai maupun yang belum mempunyai HDTV di Jepang. Polemik ini menghangat disebabkan Jepang yang selama ini dikenal sebagai 
pelopor pengembangan teknologi HDTV, sistemnya masih belum digital penuh, dengan kata lain masih analog. Sementara itu rival-rivalnya sudah beralih ke sistem digital penuh, bahkan Eropa yang dulunya menggunakan teknologi analog akhir tahun lalu telah beralih ke sistem digital penuh.
                Dalam pengembangan tahap awal, Eropa masih menggunakan teknologi Analog (HD-Mac). Sementara Amerika meskipun terlambat dalam mengembangkan teknologi ini, ternyata dengan kejeliannya mampu memanfaatkan kelemahan sistem yang ada.
               Jepang mulai November 1991 berhasil mengadakan siaran percobaan delapanjam sehari. Beberapa kejadian penting juga telah disiarkan secara langsung di Jepang melalui sistem HDTV ini diantaranya Olimpiade Bercelelona 1992, pesta pernikahan Putra Mahkota Naruhito  dengan Masako Owada dll-nya. Sedangkan aplikasi HDTV selain untuk sistem siaran adalah untuk hiburan ("mini-cinema"), museum, pendidikan dan latihan sebagai contoh opersai bedah (kedokteran) dan lain-lain.
 
 
 
" Digital Penuh"
               
               Untuk menyelenggarakan sistem siaran HDTV, secara teknologi diperlukan tiga komponen utama yaitu studio produksi, transmisi dan tentu saja pesawat penerima yang biasa dikenal sebagai pesawat televisi. Suatu sistem siaran HDTV disebut "full digital" jika semua komponen sistem siaran tersebut digital.
Sistem digital mempunyai beberapa keunggulan dibandingkan sistem analog, di antaranya adalah perbaikan ketajaman gambar maupun kualitas suara, hal ini disebabkan sinyal distorsi yang disebabkan "interference" lebih mudah dieliminasi. Di samping itu, karena representasi digital menggunakan bahasa nol dan satu, sistem digital mudah dimanipulasi untuk tujuan tertentu. Selain sinyal gambar (citra), sinyal lain seperti suara, teleponi, komputasi dengan menggunakan pengubah analog to digital dapat didigitalisasi menjadi bahasa yang seragam yaitu nol dan satu.
               Kesamaan reperesentasi beberapa sinyal tersebut, memnungkinkan untuk mengembangkan kemampuan pemrosesan menjadi suatu kerangka yang disebut sistem multimedia, baik untuk transmisi multimedia, displai multimedia maupun komputasi multimedia.
Namun demikian untuk mengimplementasikan sistem digital diperlukan beberapa prasyarat, di antaranya tersedianya fasilitas transmisi dengan laju tinggi dan juga kapasitas ruang penyimpanan yang besar. Sebagai contoh, gambar hitam-putih digital dengan ukuran 512x512 pixel ("picture element" = elemen gambar), setiap pixel dikodekan dengan 8 bit akan memerlukan 2.100.000 bit. Kamera televisi biasa dengan laju 30 frame/detik jika disusun secara digital memerlukan laju bit sekitar 180.000.000 bit/detik. Sedangkan sinyal HDTV yang mempunyai ketajaman gambar lebih dua kali dan laju framenya 60 frame/detik memerlukan laju lebih dari 1 giga bit/detik.
               
               Prasyarat tersebut menyebabkan sulitnya melaksanakan transmisi sinyal HDTV begitu saja melalui sistem transimisi yang ada.
 
 
" Transmisi Analog"
 
               Jepang yang telah mengembangkan studio dan pesawat penerima secara digital telah membuat strategi dengan mengubah kembali sinyal digital menjadi sinyal analog untuk keperluan tranmisi dan dikenal dengan nama MUSE ("multiple subnyquist sampling encoding"). Sistem Muse inilah yang dikenal oleh khalayak sebagai sistem yang masih anlog namun paling tidak telah menjadi kebanggaan Jepang untuk empat tahun terakhir ini. HDTV Jepang ini juga bisa dipakai untuk menayangkan televisi konvensional seperti NTSC.
Sebetulnya industri manufaktur Jepang juga telah menghasilkan produk "Video Cassete Tape recorder" untuk sistem HDTV MUSE tersebut.
                                                “Teknologi Pemampatan Sinyal”
 
               Untuk mengatasi persoalan laju transmisi digital agar semua pemrosesan dapat dilakukan secara digital pada awal dekade ini telah dikembangkan suatu metode untuk memampatkan sinyal digital yang berukuran besar menjadi susunan bit yang rendah. Teknik ini dikenal sebagai "Video/Signal Compression", teknik ini masih menjadi topik riset cukup ramai baik algoritma maupun implementasinya. 
               Teknik pemampatan sinyal inilah yang akan menjadi modal Amerika Serikat untuk bersaing dengan HDTV yang telah dikembangkan Jepang maupun Eropa.
               Negara-negara Eropa yang telah bergabung dalam Masyarakat Eropa juga sedang berjuang keras mendapatkan teknik transmisi HDTV yang efisien. Mereka melibatkan lebih dari 5.000 orang/tahun untuk mengembangkan teknologi ini.
               Persoalan akan muncul lagi pada standardisasi sedunia yang akan dipakai. Apakah MPEG (Motion Picture Expert Group) yang merupakan badan resmi di bawah ISO (organisasi internasional untuk standardisasi) bisa memberikan algoritma standar resmi dan bisa diterima oleh semua pihak? Yang jelas untuk sinyal gambar dengan resolusi rendah seperti "Video-phone, teleconference" dan lain-lain, MPEG telah berhasil mengeluarkan standarnya melalui MPEG1.
               Kembali pada persoalan pengembangan di Jepang. Dengan arahan Kementrian
Pos dan Telekomunkasi Jepang itu, apakah Jepang akan mengubah haluan strategi pengembangan penyelenggaraan sistem HDTV-nya menjadi  digital penuh ataukah tetap mempertahankan MUSE-nya dengan memodifikasi-nya?
               Persolan ini kelihatannya sulit dijawab pihak yang telah mengeluarkan dana besar untuk riset dan pengembangan , produsen yang telah memproduksi HDTV, bahkan juga pengguna HDTV yang diperkiran sudah membeli 20.000 pesawat.
               Perlu dicatat, harga satu set HDTV di Jepang berkisar antara 650.000 - 1 juta yen. Pihak peneliti Jepang masih berjjuang keras untuk lebih mengefisienkan komponen pendukung sehingga harga masih bisa lebih ditekan.
               Bagi negara berkembang yang ingin mengembangkan teknologi HDTV atau media sejenis, persolan ini bisa dipakai bahan pelajaran untuk bisa menyiapkan strategi lebih lanjut.
(Kompas, April 1994)
 
Penulis : Suhono Harso Supangkat, adalah staf Lab. Sinyal dan Sistem Jurusan 
Teknik Elektro ITB, saat ini sedang menempuh program Doktor di The University
of Electro=communications Tokyo. Anggota Himpunan Ahli Pertelevision Jepang 
dan IEEE USA.
 

 

 

High-definition Television

 

 

Projection screen in a home theater, displaying a high-definition television image.

Projection screen in a home theater, displaying a high-definition television image.

High-definition television (HDTV) is a digital television broadcasting system with greater resolution than traditional television systems (NTSC, SECAM, PAL). HDTV is digitally broadcast because digital television (DTV) requires less bandwidth if sufficient video compression is used.

History of high-definition television

The term high definition described the television systems of the 1930s and 1940s beginning with the British 405-line black-and-white system, introduced in 1936; however, it and the American 525-line NTSC system established in 1941, were high definition in comparison with previous mechanical and electronic television systems. Today, the American 525-line NTSC system and the European 625-line PAL and SECAM systems are standard definition television, whereas the post–WWII French 819-line black-and-white system, was high definition in the contemporary sense, it required more bandwidth and was discontinued in 1986, a year after the final British 405-line broadcast.

In 1958, the U.S.S.R. created Трансформатор (Transformer), the first high-resolution (definition) television system capable of producing an image composed of 1,125 lines of resolution for the purpose of television conferences among military commands; as it was a military product, it was not commercialised.

In 1969, NHK of Japan first developed commercial, high-definition television. However, the system was not commercialized until late in the 1990s.

In 1981, the first HDTV demonstration in the United States was held. It had 5:3 aspect ratio like the Japanese system.

In 1983, the International Telecommunication Union‘s radiotelecommunications sector (ITU-R) set up a working party (IWP11/6) with the aim of setting a single international HDTV standard. This WP considered many views and through the 1980s served to encourage development in a number of video digital processing areas such as conversion between 30/60 and 25/50 picture rates using motion vectors that led to other outcomes. While a single standard was never finalized, a common aspect ratio of 16:9 was agreed to at the first meeting at the BBC‘s R & D establishment at Kingswood Warren. Initially the Japanese 5:3 ratio was considered but a proposal to widen it to 16:9 was accepted. 16:9 aspect ration was seen as a good compromise between the European 1.66 cinema aspect ratio and the 1.85 aspect ratio used in motion pictures in the United States.

The resulting ITU-R Recommendation ITU-R BT.709-2 (“Rec. 709“) includes the 16:9 aspect ratio, specified colorimetry, and 1080i (1,080 actively-interlaced lines of resolution) and 1080p (1,080 progressively-scanned lines) scanning modes. It also includes the 1440 x 1152 HDMAC scanning format. According to some reports, 720p format was viewed by some at the ITU, unofficially, as an “enhanced” television format rather than an HDTV format, and was not standardized there. Both 1920×1080 and 1280x720p (720 progressively-scanned lines) systems for a range of frame and field rates are also defined by several SMPTE standards.

However, the standardization of HDTV did not lead to its adoption. Early HDTV commercial experiments such as NHK’s MUSE required over four times the bandwidth of a standard definition broadcast, and despite the effort made to shrink the required bandwidth into about 2 times of that of the SDTV’s, it still was distributable only by satellite. In addition, recording and reproducing an HDTV signal was also a technical challenge in the early years of HDTV.

HDTV technology was introduced in the United States in the 1990s by the Digital HDTV Grand Alliance, a group of television companies and MIT.

On, April 6, 1997 CBS went on the air with WCBS-HD from the top of the Empire State Building, New York, doing demos and evaluations. The first HDTV sets went on sale in the United States in 1998.

Japan is the only country with successful commercial analog HDTV, known as “Hi-vision”, featuring a 5:3 aspect ratio screen with 1,125 interlaced lines (1,035 active lines) at the rate of 60 fields per second. Elsewhere, in Europe, analog 1,125-line HD-MAC television failed in its test broadcasts in the early 1990s.

However, it was not until the early 2000s that storage means of enough capacity and computer processing power for dense compression algorithms made commercial applications of HDTV affordable for consumers and profitable for TV channels or the video rental industry.

HDTV became viable due to the transition from analog to digital TV broadcasting. Digital compression methods such as MPEG-2 and MPEG-4 allow the bandwidth of a single TV channel (in the US, 6 MHz) to carry up to 5 TV programs of standard definition or up to 2 channels of high definition.

Current HDTV broadcast standards include ATSC (US) and DVB (Europe, and most of the rest of the world). HDTV can also provide 5.1-channel surround sound audio using e.g. the Dolby Digital (AC-3) format.

On February 17, 2009, the US will terminate all full power station (some smaller local stations have later deadlines) terrestrial analog broadcasting in favor of digital broadcasting, which can be standard-definition (SDTV) or HDTV.

HDTV sources

The rise in popularity of large screens and projectors has made the limitations of conventional Standard Definition TV (SDTV) increasingly evident. A HDTV compatible television set will not improve the quality of SDTV channels. To display a superior picture, high definition televisions require a High Definition (HD) signal. Typical sources of HD signals are as follows:

  • Over the air with an antenna. Most cities in the US with major network affiliates broadcast over the air in HD. To receive this signal an HD tuner is required. Most newer high definition televisions have an HD tuner built in. For HDTV televisions without a built in HD tuner, a separate set-top HD tuner box can be rented from a cable or satellite company or purchased.
  • Cable television companies often offer HDTV broadcasts as part of their digital broadcast service. This is usually done with a set-top box or CableCARD issued by the cable company. Alternatively one can usually get the network HDTV channels for free with basic cable by using a QAM tuner built into their HDTV or set-top box. Some cable carriers also offer HDTV on-demand playback of movies and commonly viewed shows.
  • Satellite-based TV companies, such as DirecTV and Dish Network (both in North America), Sky Digital (in the UK and Ireland), Bell ExpressVu and StarChoice (both in Canada) and NTV Plus (in Russia), offer HDTV to customers as an upgrade. New satellite receiver boxes and a new satellite dish are often required to receive HD content.
  • Video game systems, such as the Xbox (NTSC only), Playstation 3, and Xbox 360 can output an HD signal. The Xbox Live Marketplace and Playstation Network services offers HD movies, TV shows, movie trailers, and clips for download to their respective consoles.
  • Most newer computer graphics cards have either HDMI or DVI interfaces, which can be used to output images or video to an HDTV.
  • Two optical disc standards, Blu-ray Disc (25GB-50GB) and HD DVD (15GB-30GB), can provide enough digital storage to store hours of HD video content.

Notation

HDTV broadcast systems are defined threefold, by:

  • The scanning system: progressive scanning (p) or interlaced scanning (i). Progressive scanning redraws an image frame (all of its lines) when refreshing each image. Interlaced scanning redraws the image field (every second line) per each image refresh operation, and then redraws the remaining lines during a second refreshing. Interlaced scanning yields greater image resolution if subject is not moving, but loses up to half of the resolution and suffers “combing” artifacts on progressive displays when subject is moving – in case no appropriate deinterlacing applied. (There is an advantage, though: the alternating fields can hold different movement phases, effectively doubling them (1 [logical] frame = 2 field), compared to a given frame/sec progressive mode.)
  • The number of frames per second or fields per second.

The 720p60 format is 1280 × 720 pixels, progressive encoding with 60 frames per second (60 Hz). The 1080i50 format is 1920 × 1080 pixels (ie 2 MP), interlaced encoding with 50 fields per second. Sometimes interlaced fields are called half-frames, but they are not, because two fields of one frame are temporally shifted. Frame pulldown and segmented frames are special techniques that allow transmitting full frames by means of interlaced video stream.

For commercial naming of the product, either the frame rate or the field rate is dropped, e.g. a “1080i television set” label indicates only the image resolution. Often, the rate is inferred from the context, usually assumed to be either 50 or 60, except for 1080p, which denotes 1080p24, 1080p25, and 1080p30, but also 1080p50 and 1080p60 in the future.

A frame or field rate can also be specified without a resolution. For example 24p means 24 progressive scan frames per second and 50i means 25 interlaced frames per second, consisting of 50 interlaced fields per second. Most HDTV systems support some standard resolutions and frame or field rates. The most common are noted below.

 

Standard Display Resolutions

Standard Definition usually refers to 480 vertical lines of resolution or more.

Resolution (W×H)

Active Frame (W×H)

Canonical Name(s)

Pixels (Advertised Megapixels)

Display Aspect Ratio (X:Y)

Pixel Aspect RatioStandard “4:3” (X:Y)

Pixel Aspect Ratio – Widescreen “16:9” (X:Y)

Description

ITU-R BT.601

MPEG-4

ITU-R BT.601

MPEG-4

720×480

710.85×486

480i/p

345,600 (0.3)

3:2

4320:4739

10:11

5760:4739

40:33

Used for 525-line/ (60 * 1000/1001) Hz video, e.g. NTSC-M

720×576

702×576

576i/p

414,720 (0.4)

5:4

128:117

12:11

512:351

16:11

Used for 625-line/50 Hz video, e.g. PAL-I

When resolution is considered, both the resolution of the transmitted signal and the (native) displayed resolution of a TV set are taken into account. Most HDTVs contain video scalers and will “upscale” or “upconvert” the transmitted signal to that of the TV’s native format.

Sometimes the progressive versions of these video formats are referred to as EDTV, or “Enhanced Definition Television.” This is slightly misleading, for although a progressive frame contains double the image information as that of an interlaced frame, Standard Definition is already capable of displaying progressive frames, for example in MPEG video with the appropriate “Progressive” flag set. Despite this, 480p/576p signals are not currently broadcast.

 

High-Definition Display Resolutions

High Definition usually refers to 720 vertical lines of video format resolution or more.

Pixel Resolution (W×H)

Video Format Supported

Pixels (Advertised Megapixels)

Aspect Ratio (X:Y)

Description

Image

Pixel

1024×768

HD Ready

786,432 (0.8)

16:9

4:3

Typically a computer resolution XGA; also exists as a standardized “HD-Ready” TV size on the Plasma display with non-square pixels.

1248×702

720p Clean Aperture

876,096 (0.9)

16:9

1:1

Used for 750-line video with raster artifact/overscan compensation, as defined in SMPTE 296M.

1280×720

720p

921,600 (0.9)

16:9

1:1

Typically a computer resolution WXGA, also used for 750-line video, as defined in SMPTE 296M, ATSC A/53, ITU-R BT.1543, Digital television, DLP, LCD and LCOS projection HDTV displays.

1366×768

720p/1080i, HD Ready

1,049,088 (1.0)

683:384
(Approx 16:9)

1:1
Approx

Typically a TV resolution WXGA; also exists as a standardized “HD-Ready” TV size. HDTV common pixel resolution, that used on LCD HDTV displays.

 

 

 

 

 

 

1280×1080

HD Ready 1080p

1,382,400 (1.4)

32:27
(Approx 16:9)

3:2

Non-standardized “HD-Ready” TV size. Used on HDTV Plasma display.

1440×1080

HDCAM/HDV 1080i

1,555,200 (1.6)

4:3

4:3:1

Used for anamorphic 1152-line video in the HDCAM and HDV formats introduced by Sony and defined (also as a luminance subsampling matrix) in SMPTE D11.

1888×1062

1080p Clean Aperture

2,001,280 (2.0)

16:9

1:1

Used for 1152-line video with raster artifact/overscan compensation, as defined in SMPTE 274M.

1920×1080

1080i/1080p, HD Ready 1080p, Full HD

2,073,600 (2.1)

16:9

1:1

Used for 1152-line video, as defined in SMPTE 274M, ATSC A/53, ITU-R BT.709. HDTV common pixel resolution, that used on LCD HDTV displays.

3840×2160

2160p

8,294,400 (8.3)

16:9

1:1

Quad HDTV, (there is no HD Ready 2160p Quad HDTV format).

It should be noted that the numbers used for “HD-Ready” image resolutions do not constitute acceptable 750- or 1152-line video signals in most standards-compliant hardware; in this respect terms such as “720p” and “1080p” are mostly used for advertising, though that does not necessarily mean that HD-Ready TVs labeled in this manner are incapable of accepting those formats as input.

Additionally, the “Clean Aperture” numbers are almost always contained within the frames of their respective “Production Aperture” numbers (e.g., a 1888×1062 rectangle would be contained within a 1920×1080 frame). This is to maintain compatibility with analogue signals, which can often become distorted close to the edge of the frame. It also increases the chance that a digital signal being played on overscan-enabled equipment will display the entire picture visibly.

A common pixel resolution used in HD Ready LCD TV panels is 1366 x 768 pixels instead of the ATSC Standard 1280 x 720 pixels. This is due to maximization of manufacturing yield and resolution of VGA, VRAM that comes with a 768 pixel format. Hence, LCD manufacturers adopt the 16:9 ratio compatible for the HD Ready 1080p video standard. Nevertheless, every HDTV has an overscan processing chipset to fix resolution scaling and color rendering, eg LG😄 Engine, SONY BRAVIA Engine. Only when viewing 1080i/1080p HD contents under HD Ready 1080p where there is true pixel-for-pixel reproduction, and for HD ready LCD TV, do some signals undergo a scaling process which results in a 3-5% loss of picture.

Standard frame or field rates

  • 23.976p (allow easy conversion to NTSC)
  • 24p (cinematic film)
  • 25p (PAL, SECAM DTV progressive material)
  • 30p (29.97p in drop frame) (NTSC DTV progressive material)
  • 50p (PAL, SECAM DTV progressive material)
  • 60p (59.94p in drop frame) (NTSC DTV progressive material)
  • 50i (PAL & SECAM)
  • 60i (59.94i in drop frame) (NTSC, PAL-M)

 

Broadcast station format considerations

Close-up view

HDTV resolution

SDTV resolution

At the least, HDTV has twice the linear resolution of standard-definition television (SDTV), thus showing greater detail than either analog television or regular DVD. The technical standards for broadcasting HDTV also handle the 16:9 aspect ratio images without using letterboxing or anamorphic stretching, thus increasing the effective image resolution.

The optimum format for a broadcast depends upon the type of videographic recording medium used and the image’s characteristics. The field and frame rate should match the source and the resolution. A very high resolution source may require more bandwidth than available in order to be transmitted without loss of fidelity. The lossy compression that is used in all digital HDTV storage and transmission systems will distort the received picture, when compared to the uncompressed source.

Types of medium

The high resolution photographic film used for cinema projection is exposed at the rate of 24 frames per second. Depending upon available bandwidth and the amount of detail and movement in the image, the optimum format for video transfer is either 720p24 or 1080p24. When shown on television in PAL system countries, film must be projected at the rate of 25 frames per second by accelerating it by 4.1 per cent. In NT SC standard countries, the projection rate is 30 frames per second, and using a technique called 3:2 pull-down. One film frame is held for three video fields (1/20 of a second), and the next is held for two video fields (1/30 of a second) and then the process is repeated, thus achieving the correct film projection rate with two film frames shown in 1/12 of a second. Template:Cf.

Older (pre-HDTV) recordings on video tape such as Betacam SP are often either in the form 480i60 or 576i50. These may be upconverted to a higher resolution format (720i), but removing the interlace to match the common 720p format may distort the picture or require filtering which actually reduces the resolution of the final output.

Non-cinematic HDTV video recordings are recorded in either the 720p or the 1080i format. The format used is set by the broadcaster (if for television broadcast). In general, 720p is more accurate with fast action, because it progressively scans frames, instead of the 1080i, which uses interlaced fields and thus might degrade the resolution of fast images.

720p is used more for Internet distribution of high-definition video, because computer monitors progressively scan; 720p video has lower storage-decoding requirements than either the 1080i or the 1080p. 720p is also the medium for High Definition Broadcasts around the world. 1080p is used for Blu-Ray movies and HD-DVD.

List of stations

  • In Australia, the 576p50 format is also considered an HDTV format, as it has higher vertical resolution through the use of progressive scanning. When Australia started DVB-T in 2001 several networks broadcast high-definition in a 576p format as this could give better quality on 50 Hz scanning CRT TVs and was not as demanding on MPEG-2 bit-rate. Now that flat-screens are predominating and these have an interlace to progressive scan conversion there is little difference in picture quality. Also MPEG-2 encoders have improved so the more conventional 720p and 1080i formats are now used. Technically, the 576p format is internationally defined as Enhanced-definition television and many DVD players can provide a 576p signal usually on HDMI outputs.
  • In North America, FOX, MyNetworkTV (both owned by the News Corporation), ABC, and ESPN (ABC and ESPN are both owned by Disney) currently broadcast 720p content. NBC, Universal HD (both owned by the NBC Universal subsidiary of General Electric and Vivendi), CBS, The CW (co-owned by CBS and Time Warner), HBO (owned by Time Warner), Showtime (owned by CBS), Starz!, MOJO HD, HDNet ,TNT (owned by Time Warner), CNN (also owned by Time Warner), and Discovery HD Theater currently broadcast 1080i content. In Canada, virtually all over-the-air HD stations broadcast 1080i, as do most cable specialty channels. For list of local over the air HD channels visit http://www.antennaweb.org/.
  • In Singapore, MediaCorp TV HD5 is Singapore’s first over-the-air HDTV channel, simulcasting HD version of Channel 5 programming in 1080i. It is the first terrestrial broadcast HD channel in South-East Asia and also first in the world to use MPEG-4 AVC compression. Starhub, a Singapore cable provider also airs 3 HDTV channels: Discovery HD, National Geographic Channel HD and HD Showcase which features Barclays Premier League soccer matches.
  • In the United Kingdom on Sky Digital, there are BBC HD, Channel 4 HD, Sky One HD, Sky Arts HD, Sky Movies HD1 & 2, Sky Sports HD1,2 & X, Discovery HD, National Geographic Channel HD, The History Channel HD & Sky Box Office HD1 & 2. With MTV HD, FX HD, Living HD Rush HD, Ultra HD & Eurosport HD to come in the near future. BBC HD is also available on Virgin Media. The BBC Trust has given provisional approval for a BBC HD channel, which would be broadcast satellite, cable and DTT.
  • In Mexico TV Azteca began to broadcast HDTV in early 2005.
  • In Brazil all 5 major TV networks (Band, Rede Globo, Rede Record, RedeTV! and SBT) and the public television started to broadcast HDTV (1080i) in December 2007. Brazil uses an upgraded version of the Japanese ISDB-T system called ISDB-Tb that uses H.264 AVC video compression and as audio compression: HE-AAC on main program (or multi) and AAC-LC on mobile sub-program.
  • In Switzerland HD Suisse channel and Arte HD broadcasts started late 2007 on the cablecom network. Cablecom provides the HD mediabox receiver (UPC) manufactured by Philips. The HD Suisse and Arte HD channels are free of charge with the basic subscription to cablecom TV. Cablecom announced more HD channels to come during 2008.
  • In Russia on NTV Plus satellite television there are 3 HD channels: HD Sport, HD Life and HD Kino (HD Movies).

 

Technical details

One of the first DVB-S2 tuner cards.

One of the first DVB-S2 tuner cards.

HDTV signals and colorimetry are defined by Rec. 709. MPEG-2 is most commonly used as the compression codec for digital HDTV broadcasts. Although MPEG-2 supports up to 4:2:2 YCbCr chroma subsampling and 10-bit quantization, HD broadcasts use 4:2:0 and 8-bit quantization to save bandwidth. Some broadcasters also plan to use MPEG-4 AVC, such as the BBC which is trialing such a system via satellite broadcast, which will save considerable bandwidth compared to MPEG-2 systems. Some German broadcasters already use MPEG-4 AVC together with DVB-S2 (Pro 7, Sat.1 and Premiere). Although MPEG-2 is more widely used at present, it seems likely that in the future all European HDTV may be MPEG-4 AVC, and Norway, which is currently in the progress of implementing digital television broadcasts, is using MPEG-4 AVC for present SD Digital as well as for future HDTV on terrestrial broadcasts. In parts of Sweden the standard is already in use for HDTV terrestrial broadcasting, reaching about 25-30% of the population. Brasil was the first country in the American continent to begin broadcasting H.264 AVC video and HE-AAC audio as the main program (or multi) compression and the same H.264 AVC in LDTV 240p using AAC-LC as audio for mobile DTV devices, not only mobile phones.

HDTV is capable of “theater-quality” audio because it uses the Dolby Digital (AC-3) format to support “5.1” surround sound. The pixel aspect ratio of native HD signals is a “square” 1.0, in which each pixel’s height equals its width. New HD compression and recording formats such as HDV use rectangular pixels to save bandwidth and to open HDTV acquisition for the consumer market. For more technical details see the articles on HDV, ATSC, DVB, and ISDB but the ISDB-Tb used primarily in Brasil uses HE-AAC that is more flexible than AC-3 and lower royalty fees..

Television studios as well as production and distribution facilities, use the HD-SDI SMPTE 292M interconnect standard (a nominally 1.485 Gbit/s, 75-ohm serial digital interface) to route uncompressed HDTV signals. The native bitrate of HDTV formats cannot be supported by 6-8 MHz standard-definition television channels for over-the-air broadcast and consumer distribution media, hence the widespread use of compression in consumer applications. SMPTE 292M interconnects are generally unavailable in consumer equipment, partially due to the expense involved in supporting this format, and partially because consumer electronics manufacturers are required (typically by licensing agreements) to provide encrypted digital outputs on consumer video equipment, for fear that this would aggravate the issue of video piracy.

Newer dual-link HD-SDI signals are needed for the latest 4:4:4 camera systems (Sony Cinealta F23 & Thomson Viper), where one link/coax cable contains the 4:2:2 YCbCr info and the other link/coax cable contains the additional 0:2:2 CbCr information.

Advantages of HDTV expressed in non-technical terms

Plus, high-definition television (HDTV) yields a better-quality image than does standard television, because it has a greater number of lines of resolution. Because the signal is of a digital nature, it produces neither a snowy nor pale image from a weak signal or signal interference effects, such as herringbone patterns, or vertical rolling. Image colours are more realistic, because of the greater bandwidth. The visual information is some 2-5 times sharper because the gaps between the scan lines are narrower or invisible to the naked eye. Television content photographed and preserved on 35 mm film can be viewed at nearly its original resolution.

The lower-case “i” appended to the numbers denotes interlaced; the lower-case “p” denotes progressive. The interlaced scanning method, the 1,080 lines of resolution are divided into two, the first 540 lines are painted on a frame, the second 540 lines are painted on a second frame, reducing the bandwidth. The progressive scanning method simultaneously displays all 1,080 lines of resolution at 60 frames per second, on a greater bandwidth. (See: An explanation of HDTV numbers and laymen’s glossary)

Often, the broadcast HDTV video signal soundtrack is Dolby Digital 5.1 surround sound, enabling full, surround sound capabilities, while STBC television signals include either monophonic or stereophonic audio, or both. Stereophonic broadcasts can be encoded with Dolby Surround audio signal. Brasil opted to upgrade the ISDB-T Japanese standard to H.264 AVC Mpeg4 part 10 in the video compression and HE-AAC for audio compression because Dolby is not open and the royalty fees are more expensive that of Mpeg4 H.264 AVC and renamed the upgraded standard to ISDB-Tb that now became the International ISDB-T standard.

 

Disadvantages of HDTV expressed in non-technical terms

In practice, the best possible HD quality is not usually achieved. The main problem is that many operators do not follow HDTV specifications fully. They may use slower bitrates or lower resolution to pack more channels within the limited bandwidth. The operators may use format that is different from the original programming, introducing generation loss artifacts in the process of re-encoding. Also, image quality may be lost if the television is not properly connected to the input device or not properly configured for the input’s optimal performance, which may be difficult because of customer confusion regarding connections.

You will have to buy the appropriate cable for example in most cases an HDMI cable or component cables. These are often more expensive. For instance, if Composite or S-Video cables are used for connections from a cable box or satellite dish then only an SDTV quality picture will be seen. HDMI provides the best picture and sound but are also generally more expensive than Component cables.

As high-definition video broadcasts are digital, the disadvantages of digital video broadcasting also apply here. For example, digital video responds differently to analogue video when subject to interference. As opposed to a lower-quality signal one gets from interference in an analogue television broadcast, interference in a digital television broadcast will freeze, skip, or display “garbage” information. Broadcasters may aggressively compress video to save bandwidth and therefore broadcast more channels – this compression manifests itself as reduced video quality.

In order to view HDTV broadcasts, viewers may have to upgrade their TVs which come at expense. Adding a new aspect ratio makes for consumer confusion if their display is capable of one or more ratios but must be switched to the correct one by the user. Traditional standard definition TV shows and feature films (mostly movies from before 1953) originally filmed in the standard 4:3 ratio, when displayed correctly on an HDTV monitor, will have empty display areas to the left and right of the image. Many consumers aren’t satisfied with this unused display area and choose instead to distort their standard definition shows by stretching them horizontally to fill the screen, giving everything a too-wide or not-tall-enough appearance. Alternately, they’ll choose to zoom the image which removes content that was on the top and bottom of the original TV show.

As of 2007, broadcasters may demand, or cable-television operators may elect, to place HD signals in a premium band that requires higher cable fees. That some satellite companies offer the local HD channels as a service at additional cost (transmission comes from satellite) suggests to some broadcasters that on-air broadcasts of local HD signals must be a premium service to subscribers. Viewers may be denied some television channels that they expected, be allowed only access to the non-digital, and obviously sub-standard non-digital signal, or have to install an antenna to receive the digital broadcasts. Such issues more entail economic and legal disputes than they entail technology.

Another disadvantage of HDTV compared to traditional television has been consumer confusion stemming from the different standards and resolutions, such as 1080i, 1080p, and 720p. Complicating the matter have been the changes in television connections from component video, to DVI, then to HDMI. Finally, the HD-DVD vs. Blu-ray Disc high definition storage format war engenders even more animosity for consumers. The confusion has led to slower uptake of the technology as many people wait to see what becomes the “ultimate” standard.

 

 

 

 

 

 

Contemporary systems

1. HDTV Monitor 2. HD satellite receiver 3. Standard satellite dish 4. HDMI cable, DVI-D and audio cables, or audio and component video cables

Components of a typical satellite HDTV system:
1.HDTV Monitor
2.HD satellite receiver
3.Standard satellite dish
4.HDMI cable, DVI-D and audio cables, or audio and component video cables

Besides an HD-ready television set, other equipment is needed to view HD television. Cable-ready TV sets can display HD content without using an external box. They have a card slot for inserting a CableCARD.

High-definition image sources include terrestrial broadcast, direct broadcast satellite, digital cable, high definition discs (BD and HD DVD), internet downloads and the latest generation of video game consoles.

Recording and compression

Main article: High-definition pre-recorded media and compression

HDTV can be recorded to D-VHS (Data-VHS), W-VHS (analog only), to an HDTV-capable digital video recorder (for example DirecTV‘s high-definition Digital video recorder, Sky HD‘s set-top box, Dish Network‘s VIP 622 or VIP 722 high-definition Digital video recorder receivers, or TiVo‘s Series 3 or HD recorders), or an HDTV-ready HTPC. Some cable boxes are capable of receiving or recording two broadcasts at a time in HDTV format, and HDTV programming, some free, some for a fee, can be played back with the cable company’s on-demand feature. The massive amount of data storage required to archive uncompressed streams make it unlikely that an uncompressed storage option will appear in the consumer market soon. Realtime MPEG-2 compression of an uncompressed digital HDTV signal is also prohibitively expensive for the consumer market at this time, but should become inexpensive within several years (although this is more relevant for consumer HD camcorders than recording HDTV). Analog tape recorders with bandwidth capable of recording analog HD signals such as W-VHS recorders are no longer produced for the consumer market and are both expensive and scarce in the secondary market.

In the United States, as part of the FCC’s “plug and play” agreement, cable companies are required to provide customers who rent HD set-top boxes with a set-top box with “functional” Firewire (IEEE 1394) upon request. None of the direct broadcast satellite providers have offered this feature on any of their supported boxes, but some cable TV companies have. As of July 2004, boxes are not included in the FCC mandate. This content is protected by encryption known as 5C. This encryption can prevent duplication of content or simply limit the number of copies permitted, thus effectively denying most if not all fair use of the content.

Table of terrestrial HDTV transmission systems

Main characteristics of three DTTV systems

Systems

ATSC

DVB-T

ISDB-T

Source coding

Video

Main Profile syntax of ISO/IEC 13818-2 (MPEG-2 – Video)

Audio

ATSC Standard A/52 (Dolby AC-3)

As defined in ETSI DVB TS 101 154 – as H.264 AVC and/or ISO/IEC 13818-2 (MPEG-2 – Layer II Audio) and/or Dolby AC-3

ISO/IEC 13818-7 (MPEG-2 – AAC Audio)

Transmission system

Channel coding

 

Outer coding

R-S (207, 187, t = 10)

R-S (204, 188, t = 8)

Outer interleaver

52 R-S block

convolutional (I=12, M=17, J=1)

12 R-S block

Inner coding

rate 2/3 Trellis code

PCC: rate 1/2, 2/3, 3/4, 5/6, 7/8; constraint length = 7, Polynomials (octal) = 171, 133

Inner interleaver

12 to 1 Trellis code

bit-wise, frequency, selectable time

Data randomization

16-bit PRBS

Modulation

8VSB (Only used for over the air transmission)
16VSB (Designed for cable, but rejected by the cable industry, cable TV uses 64QAM or 256QAM modulation as a de facto standard)

COFDM
QPSK, 16QAM and 64QAM
Hierarchical modulation: multi-resolution constellation (16QAM and 64QAM)
Guard interval: 1/32, 1/16, 1/8 & 1/4 of OFDM symbol
Two modes: 2k and 8k FFT

BST-COFDM with 13 frequency segments
DQPSK, QPSK, 16QAM and 64QAM
Hierarchical modulation: choice of three different modulations on each segment
Guard interval: 1/32, 1/16, 1/8 & 1/4 of OFDM symbol
Three modes: 2k, 4k and 8k FFT

 

 

TV resolution

Digital Video Resolutions

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

HDTV, HD DVD, BD, HDV

720

 

24, 30, 60; 25, 50

1080

50, 60

24, 30; 25

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.

General references

 

 

 

High-definition television in the United State

The FCC has notified U.S. television broadcasters that the standard for transmitting TV over-the-air shall change from analog to digital. While there are many technical, political, and economic reasons for and implications of this change, the end-result for some segments of the American TV audience will be an improvement in picture and sound quality.

From a technical standpoint, this change results in a more efficient management of the portions of the radio spectrum used for television. Even though the ATSC channel uses the same 6 MHz bandwidth as the NTSC channel it replaces, the ATSC channels can be packed in adjacent channel slots, whereas with NTSC transmission technology it is not possible to transmit on adjacent channels in the same geographic area. This allows the U.S. government to implement its plans of removing a portion of the VHF and UHF spectra from television uses and auctioning (resulting in a revenue stream of perhaps billions of dollars) some frequencies off to make them available for commercial voice and data services. Other frequencies will be reserved for government and public service.

From a consumer standpoint, every conventional TV with an antenna will become obsolete, unless connected to a digital tuner. After the switch to digital transmission, TVs will be unable to receive terrestrial analog RF TV broadcasts unless connected to a set-top box or other device that contains a digital tuner. Roughly 20% of viewers receive analog broadcasts over the air, and will be affected by the analog shutoff. The majority of TV watchers will not be affected. The 80% of television viewers that use cable or satellite television will not be immediately impacted. Virtually all satellite users and an increasing number of cable users already use set top boxes to view programming, and analog cable television is being phased out in many markets. For people unable to buy new digital TVs, Congress is arranging to offer cash vouchers for the purchase of digital tuners.

From a historical standpoint, this is the first time in over half a century that the basic format for TV transmission has changed. The last major change in TV transmission standards took place when compatible color broadcasts began in 1953. That change was engineered to be backwards-compatible, meaning that existing black-and-white TV sets would receive and display “compatible-color” broadcasts (in monochrome) without modification. The impending change to digital from analog is not backwards-compatible.

 

 

High definition versus Standard or Enhanced definition

Digital TV includes HDTV as a subset. The FCC has not mandated HDTV signals be broadcast; it only requires digital TV broadcasts. The prevailing expectation, however, is that native HDTV (i.e., programming recorded with a digital HDTV camera) during primetime will predominate. The great majority of primetime television shows in the United States are available in HDTV at the network level. It is up to the affiliates, not all of which have HDTV broadcast capability, to retransmit these shows at HDTV resolutions. A number of non-primetime shows, including morning news shows and some soap operas, are also available in HDTV.

It is not clear whether broadcasting HDTV or multiple standard definition (SD) channels during non-primetime hours will become common. Many Public Broadcasting Service member stations are now carrying SD multicasts when not broadcasting in HDTV; but unlike many commercial stations, most of these multicasts are suspended while HDTV programs are being broadcast.

The three main types of digital TV set are Standard Definition (“good”, offering the same resolution as the traditional analog system), Enhanced Definition (“better”), and High Definition (“best”). The resolution of viewers’ sets does not affect the logistics of the transition to digital TV since all sets with ATSC-compliant tuners will be able to receive and decode all resolutions, even though they might not be able to display the signal at full resolution.

From proposals to introduction

The Federal Communications Commission (FCC) began soliciting proposals for a new television standard for the U.S. in the late 1980s and later decided to ask companies competing to create the standard to pool their resources and work together, forming what was known as the Grand Alliance in 1993.

On July 23, 1996, WRAL-TV (the CBS affiliate in Raleigh, North Carolina) was the first television station in the United States to broadcast a digital television signal.

HDTV sets became available in the U.S. in 1998 and broadcasts began around November 1998. The first public HDTV broadcast was of the launch of the space shuttle Discovery and John Glenn‘s return to space; that broadcast was made possible in part by Harris Corporation.

Analog shutoff

Because HDTV requires extra broadcast spectrum during the transition period, it had become a topic of political controversy in the United States. Current stations have received a free channel, usually in the UHF range, on which to broadcast their digital signal, while still maintaining analog service.

According to the original FCC rules, all full power stations were to convert to digital by the beginning of 2007, followed by shutdown of analog broadcasting. An escape clause stipulated that 85% of receivers in the service area must be “capable” of receiving digital signals before the shutdown could occur. At the time of analog shutoff, one of the channels (digital or analog) would then be returned to the government, with the other channel remaining as a digital station; the freed spectrum could then be used for other TV stations, with UHF channels at the high end of the band being decommissioned and sold for other uses. The 2007 deadline could not be satisfied under many interpretations of 85% “capability” of digital signal reception.

On February 8, 2006, President Bush signed into law the “Digital Television Transition and Public Safety Act of 2005”, a section of the “Deficit Reduction Act of 2005“. This law mandated a hard shut-off date of February 17, 2009 for the end of all analog (NTSC) TV transmissions in the U.S., thus ending this uncertainty. The act also provided for the auctioning off of the frequencies associated with UHF channels 52 to 69, and set aside US$990 million for a voucher program enabling low-income households to purchase converter boxes. [1]

Existing analog TV sets would still work with cable or satellite service, or by using a converter box with an ATSC tuner that would convert digital over-the-air (OTA) signals to analog; the National Telecommunications and Information Administration is presently working on making a rule for a program that would give certain U.S. households up to two US$40 coupons towards the purchase of converter boxes.

Availability of HDTV sets

As of March 2006, all 25 inch and larger TVs for sale were required to have ATSC tuners capable of receiving the 8VSB modulation used for free terrestrial digital broadcasts in the United States. The final conversion step was a mandate that all televisions and TV-tuning devices have ATSC tuners by March 2007. Many of these are not capable of displaying HDTV signals at their full resolution, but they are capable of decoding and displaying these signals. No mandates exist for availability of digital set-top boxes enabling DTV reception and display on existing analog sets. However, it should be noted that VCRs and DVD recorders fall under the digital tuner mandate, and there will be considerable market demand by 2009 for set-top ATSC boxes for older analog TVs that are priced no more expensively (and presumably less so) than the recording devices on the market at that time.

 

Satellite and Cable

Satellite television companies in the United States, such as Dish Network and DirecTV, started to carry HD programming in 2002. Satellite transmissions in the U.S. use various forms of PSK modulation. A separate tuner is required to receive HD satellite broadcasts.

Cable television companies in the U.S. generally prefer to use 256-QAM to transmit HDTV. Many of the newer HDTVs with integrated digital tuners include support for decoding 256-QAM in addition to 8VSB. Some cable television companies, such as Comcast, started carrying HDTV in 2003. As of September 2005, HD programming is carried by all major television networks in at least some broadcast markets, including ABC, CBS, NBC, FOX, PBS, The CW, and MyNetworkTV.

CableCARD

Of those TVs with built-in QAM tuners, a subset also have CableCARD support. CableCARD enables the subscriber to access encrypted channels (generally premium channels), and ultimately (with a future version of the standard), interactive services such as video on demand, pay-per-view, and the cable operator’s interactive program guide. This eliminates the need for a separate, free standing cable box.

The broadcast flag rule

The FCC also instituted the broadcast flag rule through administrative rulemaking, which required that HDTV sets manufactured in July 2005 or later to include technology which would restrict the ability of viewers to record or time-shift broadcasts that the provider has flagged with a special signal, the broadcast flag. The mandate was highly controversial, with consumer and civil liberties advocates arguing that it stripped consumers of rights they had enjoyed in the past. In May 2005, the United States Court of Appeals for the District of Columbia Circuit struck down the Broadcast Flag mandate in a unanimous ruling, holding that the FCC overstepped its statutory authority when it asserted control of any device capable of receiving an HDTV signal.

 

 

Digital television deployments by country

Africa

Namibia · South Africa

Asia

China (PRC) · China (ROC) · Hong Kong · Japan  · South Korea  · Malaysia  · Philippines  · Saudi Arabia  · Singapore

Australiasia

Australia · New Zealand

Europe

Bulgaria · Czech Republic · Croatia · Denmark · Estonia · France · Germany · Greece · Finland · Ireland (ROI) · Malta · Italy · Netherlands · Norway · Poland · Portugal · Spain · Sweden · Switzerland · United Kingdom · Ukraine

North America

Canada  · Mexico  · United States of America (High-definition television in the United States)

Central America

El Salvador  · Honduras  · Guatemala

South America

Argentina  · Brazil  · Chile  · Uruguay

 

Retrieved from : http://en.wikipedia.org

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