TELEVISION TRANSMISSION Program Studi S1 Teknik Telekomunikasi Jurusan Teknik Elektro STT Telkom

BACKGROUND   Television was developed prior to World War II   monochrome television   Color television began to come on the market about 1960   The next step in television evolvement was high-definition television (HDTV), and 1998 is considered to be the year when HDTV was launched OBJECTIVES  provide the reader with a clear understanding of how TV works  describe how television is transmitted and distributed over long distances  provide an overview of digital television, and we cover several generic methods of digitizing original analog television signals

AN APPRECIATION OF VIDEO TRANSMISSION A video transmission system must deal with four factors when transmitting images of moving objects: 1. Perception of the distribution of luminance or simply the distribution of light and shade 2. Perception of depth or a three-dimensional perspective 3. Perception of motion relating to the first two factors above 4. Perception of color (hues and tints) Monochrome TV deals with the first three factors. Color TV includes all four factors.

Scanning process from TV camera to receiver display.   National Television Systems Committee (US) (NTSC) practice divides an image into 525 horizontal scanning lines   The aspect ratio used almost universally is 4:3 and an image divided into 525 (491) vertical elements would then have 700 (652) horizontal elements   rate of display is called the frame rate   60 frames per second. In Europe it is 50 frames per second

Following North American practice, some other important parameters 1. A field period is 1/60 sec. This is the time required to scan a full picture on every horizontal line. 2. The second scan covers the lines not scanned on the first period, offset one-half horizontal line. 3. Thus 1/30 sec is required to scan all lines on a complete picture. 4. The transmit time of exploring and reproducing scanning elements or spots along each scanning line is 115,750 sec (525 lines in 1/30 sec) = 63.5 µsec.

THE COMPOSITE SIGNAL

CRITICAL VIDEO PARAMETERS   Transmission Standard—Level 1. Excellent (no perceptible snow) 45 dB 2. Fine (snow just perceptible) 35 dB 3. Passable (snow definitively perceptible but not objectionable) 29 dB 4. Marginal (snow somewhat objectionable) 25 dB

Citra dan Video

VIDEO TRANSMISSION STANDARDS (CRITERIA FOR BROADCASTERS) Color Transmission   NTSC National Television System Committee (North America, Japan, and many Latin American countries)   SECAM Sequential color and memory (Europe)   PAL Phase alternation line (Europe)

  RF amplitude characteristics of TV picture transmission, NTSC/US practice. Field strength at points A do not exceed 20 dB below the picture carrier. Drawing not to scale.

Television Standards, NTSC/US

Basic European TV Standard

Allocation and applications of electromagnetic spectrum.

Interconnection at Video Frequencies (Baseband)

Interconnection at Intermediate Frequency (IF)

METHODS OF PROGRAM CHANNEL TRANSMISSION   For point-to-point transmission on coaxial cable, radiolink, and earth station systems,   the audio program channel is generally transmitted separately from its companion video   providing the following advantages:   It allows for individual channel level control.   It provides greater control over crosstalk.   It increases guardband between video and audio.   It saves separation at broadcast transmitter.   It leaves TV studio at separate channel.   It permits individual program channel preemphasis.

THE TRANSMISSION OF VIDEO OVER LOS MICROWAVE   Video/TV transmission over line-of-sight microwave has two basic applications:   For studio-to-transmitter link. This connects a TV studio to its broadcast transmitter.   To extend CATV systems to increase local programming content.

TV TRANSMISSION BY SATELLITE RELAY   Satellite Relay TV Performance

DIGITAL TELEVISION Basic Digital Television   there are four components that make up a color video signal. These are R for red, G for green, B for blue, and Y for luminance. The output signals of a TV camera are converted by a linear matrix into luminance (Y) and two color difference signals R-Y and B-Y.   sampling rate is based on the color subcarrier frequency called fsc. For NTSC television the color subcarrier is at 3.58 MHz. In some cases the sampling rate is three times this frequency (3fsc) or (4fsc). For PAL television, the color subcarrier is 4.43 MHz.   Based on 8-bit PCM words, the bit rates are 3 × 3.58 × 106 × 8 = Mbps and 4 × 3.58 × 106 × 8 = Mbps. In the case of PAL transmission system using 4fsc, the uncompressed bit rate for the video is 4 × 4.43 × 106 × 8 = Mbps.

Mengapa Digital?  Exactness  Reproduksi sempurna tanpa degradasi  Duplikasi sempurna dari hasil pemrosesan  Pemrosesan berbasis komputer mudah & powerful  Dapat melakukan pemrosesan yg kompleks dg hardware/software  Penyimpanan dan Transmisi mudah

Pengolahan Citra: Mengapa?  Coding/compression  Penyimpanan dan transmisi (mis. mengirimkan citra via Internet)  Perbaikan & Restorasi (Enhancement & Restoration)  Menghilangkan artifact dan goresan dari foto/film lama  Memperbaiki contrast dan blurred images  Analysis, detection, recognition, understanding  Analisa informasi dan pengenalan otomatis  Memberikan kemampuan “human vision” ke mesin  Vizualisation  Encryption & watermarking  Keamanan & proteksi hak cipta  Aplikasi-Aplikasi lain  Visual mosaicing & virtual views  Error concealment & resilience pd transmisi video

Contoh-Contoh Pemrosesan Citra/Video: Compression Citra berwarna 600x800 pixels  Tanpa kompresi  600x800x24 bit/pixels = 11,52 Kbits = 1,44 Mbytes  Dg kompresi JPEG  Hanya 89 Kbytes  Rasio kompresi 16 : 1

Contoh-Contoh Pemrosesan Citra/Video: Denoising (Image Enhancement)

Contoh-Contoh Pemrosesan Citra/Video: Deblurring (Image Restoration)

Contoh-Contoh Pemrosesan Citra/Video: Visual Mosaicing

Contoh-Contoh Pemrosesan Citra/Video: Error Concealment

Contoh-Contoh Pemrosesan Citra/Video: Analysis, Detection, Recognition, Understanding

Fundamental Pengolahan Citra  Representasi  Acquisition, digitalisasi, dan display utk mendapatkan karakteristik matematis dari citra untuk pemrosesan selanjutnya  Persyaratan untuk teknik pemrosesan yang efisien seperti coding/compression, enhancement, filtering, restorasi, dsb  Teknik-Teknik Pemrosesan  Image compression, image restoration dan image reconstruction  Statistical image processing techniques  Komunikasi (comunications)

Aplikasi Utama

Perkembangan: 1990-an  Standard JPEG dan MPEG  Digital still cameras  Digital TV broadcasting  Digital video/versatile disk (DVD)  Integrasi komputer dan video  World Wide Web  Internet video streaming Setiap “perkembangan baru” tergantung pada kompresi yang efisien dari citra dan video

Motivasi Kompresi Citra  Digital video studio standard ITU-R Rec. 601  Some interesting bit-rates  Terrestrial TV broadcasting channel ~ 20 Mbps  Computer hard disk Mbps  DVD (max. 17 GB/length of movie) Mbps  Ethernet/Fast Ethernet < 10/100 Mbps  DSL downlink kbps  V.34 modem 28.8 kbps  Wireless cellular data kbps

Model Representasi Color  Menggunakan tiga primary color  RGB  CMY  Menggunakan luminance dan chrominance  HIS (Hue, saturation, intensity)  YIQ (digunakan pd TV warna NTSC)  YC b C r (digunakan TV warna digital)  Spesifikasi Amplituda:  8 bit utk tiap komponen warna, atau 24 bit total utk tiap pixel  Total 16 juta warna  Konversi antara set primary berbeda adalah linier  Konversi antara primary dan XYZ/YIQ/YUV juga linier  Formula konversi diantara banyak color coordinates dp dilihat di [Gonzales1992]

Primary Color

Luminance & Chrominance

Bit Rate Reduction— Compression Techniques   it is incumbent on the transmission engineer to reduce these bit rates without sacrificing picture quality if there is any long-distance requirements involved.   three basic bit rate reduction methods: - Removal of horizontal and vertical blanking intervals - Reduction of sampling frequency - Reduction of the number of bits per sample.

Specific Bit Rate Reduction Techniques.   Intraframe Coding. compression by removing redundant information within each video frame   Interframe Coding. technique that adds the dimension of time to compression by taking advantage of the similarity between adjacent frames   Intraframe and Interframe Coding Used in Combination. Intraframe and interframe coding used together provide a powerful compression technique.   Motion Compensation Coding. To improve image quality at low transmission rates, By focusing on the motion that has occurred between frames, motion compensation coding significantly reduces the amount of data that must be transmitted. Motion compensation coding compares each frame with the preceding frame to determine the motion that has occurred between the two frames. It compensates for this motion by describing the magnitude and direction of an object’s movement

MPEG-2 Compression Technique   based on the ATSC (Advanced Television System Committee) version of MPEG-2   system for the transmission of high-quality video, audio, and ancillary services   The ATSC system delivers 19 Mbps of throughput on a 6-MHz broadcasting channel and 38 Mbps on a 6-MHz CATV channel

ATSC (Advanced Television System Committee) system model consists of three subsystems: 1. Source coding and compression Refers to bit rate reduction methods (data compression), which are appropriate for the video, audio, and ancillary digital data bit streams 2. Service multiplex and transport Refers to dividing the bit stream into packets of information, the unique identification of each packet or packet type, and appropriate methods of multiplexing video bit stream packets, audio bit stream packets, and ancillary data bit stream packets into a single data stream. 3. RF/transmission subsystem Deals with channel coding and modulation.

Block diagram of the digital terrestrial television broadcasting model ( ATSC system )

Video Compression.

ATSC Compression Formats Sampling Rate Summary

Bagaimana Kompresi Bekerja  Mengesploitir redundancy  Memanfaatkan pola (pattern) dari sinyal (statistical redundancy)  Memanfaatkan event yg sering muncul secara efisien  Lossless coding: reversible  “Memasukan” deviasi yg dp diterima (acceptable)  Membuang information yg tdk dp dipersepsi manusia  Menyesuaikan resolusi sinyal (dlm ruang, waktu, amplitude) ke aplikasi  Lossy coding: distorsi thd sinyal original irreversible

Lossless Compression  Meminimalkan jumlah bit yg diperlukan utk merepresentasikan citra digital original tanpa ada informasi yang hilang (loss)  Semua B bit dari tiap sampel harus direkonstruksi secara sempurna  Faktor kompresi yg dp dicapai biasanya terbatas  Aplikasi  Binary images (facsimile)  Medical images  Master copy sebelum editing

Lossy Compression  Sejumlah deviasi citra terkompresi dari original (“distorsi”) dp diterima (acceptable)  Persepsi sistem visual manusia mungkin tdk dapat mendeteksi loss atau bisa mentolelir  Input digital ke algoritma kompresi adalah representasi tdk sempurna dari real-world scene  Faktor kompresi lebih tinggi daripada kompresi lossless  Kompresi lossy luas digunakan utk citra natural (mis. JPEG) dan motion video (mis. MPEG)

Lossy Compression: Mengukur Distorsi  Paling banyak digunakan: Mean Squared Error  Atau secara ekivalen, Peak Signal to Noise Ratio  Keuntungan:  Kalkulasi mudah  Secara matematis mudah dipahami dlm masalah optimisasi  Baik utk perbandingan macam-macam algoritma  Kerugian  Mengabaikan properties dari human vision

Ukuran Kompresi  Citra direpresentasikan oleh “bit stream” c dg panjang ||c||  Bandingkan jumlah bit dengan dan tanpa kompresi  Alternatif lain  Utk lossy compression, bit rate lebih berarti drpd rasio kompresi, krn B kadang sembarang

Bit Rate Tipikal Setelah Kompresi  Secara substansial tergantung pd content citra: utk tipikal citra natural  Lossless compression: (B-3) bits/pixel  Lossy compression  Asumsi dilihat pd monitor komputer, 90 pixels/inch  high quality: 1 bpp  Moderate quality: 0.5 bpp  Usable quality: 0.25 bpp  Perceived distortion tergantung pd densitas sampling dan contrast

Lossless Compression dalam Sistem Lossy Compression  Hampir setiap sistem lossy compression mengandung sistem lossless compression

CONFERENCE TELEVISION Video conferencing (conference television) systems have seen phenomenal growth since Many of the world’s corporations have branches and subsidiaries that are widely dispersed. to make video conferencing cost effective : - Video compression techniques - Eroding cost of digital processing - Arrival of the all-digital network One of the compression schemes widely used for video conference systems is basedon ITU-T Rec. H.261 (Ref. 20), entitled Video Codec for Audiovisual Services at pX64 kbps

The pX64 kbps Codec   The pX64 codec has been designed for use with some of the common ISDN data rates, specifically the B channel (64 kbps), H0 channel (384 kbps), and H11/H12 channels (1.536/1.920 Mbps) for the equivalent DS1/E1 data rates.

Source Coder.   Source Coding Algorithm. Compression is based on interpicture prediction to utilize temporal redundancy, and transform coding of the remaining signal to reduce spatial redundancy

Functional block diagram of the source coder.

Video Multiplex Coder.   The video multiplex is arranged in a hierarchical structure with four layers. From top to bottom these layers are: - Picture - Group of blocks (GOB) - Macroblock - Block

BRIEF OVERVIEW OF FRAME TRANSPORT FOR VIDEO CONFERENCING

Sistem Komunikasi Digital Representasi sumber sinyal dg deretan simbol (biner) Adaptasi ke properties kanal transmisi Kita akan lihat bagian ini