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Communications Laboratory Lecture Series

Communications Laboratory Lecture Series

Digital television Digital television broadcastingbroadcasting

Presentation by: Neil PickfordPresentation by: Neil Pickford

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Digital Television Broadcasting DTB

Digital Television Broadcasting DTB

What is digital TVWhat is digital TV How was it developedHow was it developed What are the systemsWhat are the systems Enabling technologiesEnabling technologies

Transmission technologyTransmission technology Compression technologyCompression technology

Content & servicesContent & services What is happening in australiaWhat is happening in australia The futureThe future

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Broad Objectives of DTBBroad Objectives of DTB

Overcome limitations of the existing Overcome limitations of the existing analog television systemsanalog television systems

Improved picture Improved picture High quality (no interference)High quality (no interference) Resolution (HDTV)Resolution (HDTV) Format (16:9)Format (16:9)

Enhanced service related featuresEnhanced service related features Additional data capacity available for other Additional data capacity available for other

value added servicesvalue added services

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Digital MediaDigital Media

First media systems were First media systems were analoganalog

Most media are converting Most media are converting to digitalto digital Computer storageComputer storage Music (LP-CD)Music (LP-CD) TelecommunicationsTelecommunications MultimediaMultimedia Radio (DAB)Radio (DAB) Television Television

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Standard Definition Television SDTV

Standard Definition Television SDTV

The current television display systemThe current television display system 4:3 aspect ratio picture, interlace scan4:3 aspect ratio picture, interlace scan Australia/EuropeAustralia/Europe

625 lines - 704 pixels x 576 lines displayed625 lines - 704 pixels x 576 lines displayed 50 frames/sec 25 pictures/sec50 frames/sec 25 pictures/sec 405504 pixels total405504 pixels total

USA/JapanUSA/Japan 525 lines - 704 pixels x 480 lines displayed525 lines - 704 pixels x 480 lines displayed 60 frames/sec 30 pictures/sec60 frames/sec 30 pictures/sec 337920 pixels total337920 pixels total

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Enhanced Definition Television EDTV

Enhanced Definition Television EDTV

Intermediate step to HDTVIntermediate step to HDTV Doubled scan rate - reduce flickerDoubled scan rate - reduce flicker Double lines on picture - calculatedDouble lines on picture - calculated Image processing - ghost cancellingImage processing - ghost cancelling Wider aspect ratio - 16:9Wider aspect ratio - 16:9 Multi-channelMulti-channel

soundsound

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High Definition Television HDTVHigh Definition Television HDTV

Not exactly defined - number of systemsNot exactly defined - number of systems System with a higher picture resolutionSystem with a higher picture resolution Greater than 1000 lines resolutionGreater than 1000 lines resolution Picture with less artefacts or distortionsPicture with less artefacts or distortions Bigger picture to give a viewing experienceBigger picture to give a viewing experience Wider aspect ratio to use peripheral visionWider aspect ratio to use peripheral vision Progressive instead of interlaced picturesProgressive instead of interlaced pictures

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HDTV - Have We Heard This Before?HDTV - Have We Heard This Before? The first TV system had just 32 linesThe first TV system had just 32 lines When the 405 line system was introducedWhen the 405 line system was introduced

it was called it was called HDTVHDTV!! When 625 line black & white came alongWhen 625 line black & white came along

it was called it was called HDTVHDTV!! When the PAL colour system was introducedWhen the PAL colour system was introduced

it was called it was called HDTVHDTV by some people. by some people. Now we have 1000+ line systems and digitalNow we have 1000+ line systems and digital

television - guess what? Its called television - guess what? Its called HDTVHDTV!!

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Interlaced Vs Progressive ScanInterlaced Vs Progressive Scan

Interlaced pictures. - Interlaced pictures. - 1/2 the lines presented each scan1/2 the lines presented each scan

1,3,5,7,9,11,13...............623,625 field 11,3,5,7,9,11,13...............623,625 field 12,4,6,8,10,12,14.............622,624 field 22,4,6,8,10,12,14.............622,624 field 2

Because the fields are recorded at separate Because the fields are recorded at separate times this leads to picture twitter & juddertimes this leads to picture twitter & judder

Progressive pictures - Progressive pictures - all the lines sent in the one scanall the lines sent in the one scan..1,2,3,4,5,6,7,8................623,624,625 picture1,2,3,4,5,6,7,8................623,624,625 picture

No twitter or judder. No twitter or judder. But twice the information rate.But twice the information rate.

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Question - HDTVQuestion - HDTV

Have you seen Have you seen HDTV pictures?HDTV pictures?

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Do You Use A PC?Do You Use A PC?

All Current Generation PCs use Progressive

Scan and display Pictures which match

or exceed HDTVresolutions although thepixel pitch, aspect ratio

and colorimetry are not correct.

HDTV

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Digital TelevisionDigital Television

Why digital?Why digital? Noise free picturesNoise free pictures Higher resolution imagesHigher resolution images

Widescreen / HDTVWidescreen / HDTV No ghostingNo ghosting Multi-channel soundMulti-channel sound Other services.Other services.

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Digital Television - TypesDigital Television - Types

Satellite (DBS)Satellite (DBS) DVB-SDVB-S Program interchangeProgram interchange Direct view / pay TVDirect view / pay TV SMATVSMATV

Uplink

Downlink

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Digital Television - TypesDigital Television - Types

CableCable HFC - pay TVHFC - pay TV MATVMATV DVB-C / 16-VSBDVB-C / 16-VSB

Main Coax

Fibre

TeeSpurTap

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Digital Television - TypesDigital Television - Types

Terrestrial (DTTB)Terrestrial (DTTB) DVB-T / 8-VSBDVB-T / 8-VSB Free to air TV (broadcasting)Free to air TV (broadcasting) Narrowcasting/value added servicesNarrowcasting/value added services Untethered - portable receptionUntethered - portable reception

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Digital Terrestrial Television Broadcasting - DTTBDigital Terrestrial Television Broadcasting - DTTB Regional free to air televisionRegional free to air television Replacement of current analog PAL broadcast Replacement of current analog PAL broadcast

television servicestelevision services Operating in adjacent unused “taboo” channels Operating in adjacent unused “taboo” channels

to analog PAL serviceto analog PAL service Carries a range of services Carries a range of services

HDTV, SDTV, audio, teletext, dataHDTV, SDTV, audio, teletext, data Providing portable serviceProviding portable service

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Mobile Digital TV Onboard a Tram in Cologne - Germany

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How Was Digital TV DevelopedHow Was Digital TV Developed

Japanese & Europeans wanted to improve analog Japanese & Europeans wanted to improve analog TV - bigger pictures, more resolutionTV - bigger pictures, more resolution

Japanese developed muse 1125 lines 60 HzJapanese developed muse 1125 lines 60 Hz Europeans worked on HD-MAC 1250 linesEuropeans worked on HD-MAC 1250 lines Americans broadcasters wanted to protect spare Americans broadcasters wanted to protect spare

unused TV channels from the land mobile service unused TV channels from the land mobile service and told FCC they required the channels for a and told FCC they required the channels for a future analog compatible HDTV system.future analog compatible HDTV system.

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Development RaceDevelopment Race

Americans embarked on a HDTV race to Americans embarked on a HDTV race to develop an analog HDTV systemdevelop an analog HDTV system

Digital television was seen as impossible.Digital television was seen as impossible. General instruments developed first digital TV General instruments developed first digital TV

system for satellite pay TV from experience system for satellite pay TV from experience with NASA deep space probeswith NASA deep space probes

HDTV race became a digital HDTV race.HDTV race became a digital HDTV race. Race outcome - poor performance but Race outcome - poor performance but

demonstrated digital could be done.demonstrated digital could be done.

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DTTB Transmission SystemsDTTB Transmission Systems

3 systems are being developed at present.3 systems are being developed at present.

USAUSA ATSC ATSC 8-VSB8-VSB

EuropeEurope DVB DVB COFDMCOFDM

JapanJapan ISDBISDB band segmented band segmented

OFDMOFDM

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8-VSB - USA8-VSB - USA

Developed by the advance television systems Developed by the advance television systems committee - ATSCcommittee - ATSC

Developed for use in a 6 MHz channelDeveloped for use in a 6 MHz channel A 7 MHz variant is possible.A 7 MHz variant is possible.

Uses a single carrier with pilot toneUses a single carrier with pilot tone 8 level amplitude modulation system8 level amplitude modulation system Payload data rate of 19.3 Mb/sPayload data rate of 19.3 Mb/s Relies on adaptive equalisationRelies on adaptive equalisation Existing technology developed to near limitExisting technology developed to near limit

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COFDM - EuropeCOFDM - Europe Developed by the digital video Developed by the digital video

broadcasting project group - DVBbroadcasting project group - DVB Uses similar technology to DRBUses similar technology to DRB Uses 1705 or 6817 carriersUses 1705 or 6817 carriers Variable carrier modulation types are defined allowing data Variable carrier modulation types are defined allowing data

rates of 5-27 Mb/s in 7 MHzrates of 5-27 Mb/s in 7 MHz Developed for 8 MHz channelsDeveloped for 8 MHz channels

A 7 MHz variant has been produced and testedA 7 MHz variant has been produced and tested

Can use single frequency networks - SFNsCan use single frequency networks - SFNs New technology with scope for continued improvement & New technology with scope for continued improvement &

developmentdevelopment

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ISDB - JapanISDB - Japan Japanese are developing integrated services digital Japanese are developing integrated services digital

broadcasting (ISDB)broadcasting (ISDB) System integrates all forms of broadcasting System integrates all forms of broadcasting

services into one common data channel which can services into one common data channel which can be passed by satellite, cable or terrestrial delivery be passed by satellite, cable or terrestrial delivery systemssystems

Video servicesVideo services Sound servicesSound services Bulk data servicesBulk data services Interactive data servicesInteractive data services

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ISDB - ConceptISDB - Concept

Proposed to use band segmented transmission - Proposed to use band segmented transmission - orthogonal frequency division multiplex (BST-orthogonal frequency division multiplex (BST-OFDM)OFDM)

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BST-OFDM - JapanBST-OFDM - Japan BST-OFDM is a variant of the European COFDM BST-OFDM is a variant of the European COFDM

system which allows segmenting of the data system which allows segmenting of the data spectrum into 100 kHz blocks.spectrum into 100 kHz blocks.

2 receiver bandwidths proposed.2 receiver bandwidths proposed. 500 kHz portable / mobile for sound and data500 kHz portable / mobile for sound and data 5.6 MHz fixed / mobile for SDTV and LDTV5.6 MHz fixed / mobile for SDTV and LDTV 5.6 MHz fixed for HDTV5.6 MHz fixed for HDTV

Individual band segments can be allocated to Individual band segments can be allocated to separate services which can use different separate services which can use different modulation systemsmodulation systems

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BST-OFDM - JapanBST-OFDM - Japan Allows separate services to be replaced for local Allows separate services to be replaced for local

area broadcastingarea broadcasting Allows for variable ruggedness for fixed / Allows for variable ruggedness for fixed /

mobile / portable receptionmobile / portable reception Could straddle other existing services.Could straddle other existing services. Primarily being developed for japan as a Primarily being developed for japan as a

solution to cluttered broadcasting spectrum.solution to cluttered broadcasting spectrum. In early stages of developmentIn early stages of development No hardware available at this stageNo hardware available at this stage

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8-VSB & COFDM - Spectrum8-VSB & COFDM - Spectrum

8-VSBCOFDM

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Traditional SCPC ModulationTraditional SCPC Modulation

Frequency

MinimumCarrier Spacing

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COFDM - Orthogonal CarriersCOFDM - Orthogonal Carriers

Frequency

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Spectrum of COFDM DTTBSpectrum of COFDM DTTB

6.67 MHz in 7 MHz Channel

AlmostRectangular

Shape

1705 or 6817 Carriers

Carrier Spacing2k Mode 3.91 kHz8k Mode 0.98 kHz

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Digital Modulation - 8-AMDigital Modulation - 8-AM

3 Bits/Symbol

7

1

2

3

4

5

6

0

8-VSB - Coaxial Direct Feed through Tuner on Channel 8 VHF

Before Equaliser After Equaliser

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QPSKQPSK

I

Q

2 Bits/Symbol

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16-QAM16-QAM

I

Q

4 Bits/Symbol

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64-QAM64-QAM

I

Q

6 Bits/Symbol

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64-QAM - Perfect & Failure64-QAM - Perfect & Failure

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64-QAM and QPSK64-QAM and QPSK

I

Q

6 or 2 Bits/Symbol

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Non Uniform 64-QAMNon Uniform 64-QAM

I

Q

2 + 4 Bits/Symbol

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Non Uniform 16-QAMNon Uniform 16-QAM

I

Q

2 + 2 Bits/Symbol

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8-VSB - DTV - Development8-VSB - DTV - Development

1987 FCC inquiry into future TV systems 1987 FCC inquiry into future TV systems andand advisory committee on ATV service was advisory committee on ATV service was established - ACATS established - ACATS

1990 digital TV systems developed1990 digital TV systems developed Competitive testing race undertakenCompetitive testing race undertaken 1993 poor results announced - 1993 poor results announced -

grand alliance (GA) formed by the grand alliance (GA) formed by the contestants. - Extra development contestants. - Extra development

1994 re-testing of GA system1994 re-testing of GA system

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8-VSB - DTV - Development8-VSB - DTV - Development

1996 FCC adopted ATSC standard1996 FCC adopted ATSC standard 1997 each full-power broadcaster loaned a1997 each full-power broadcaster loaned a

second 6 MHz TV channel for second 6 MHz TV channel for simalcasting DTV. simalcasting DTV.

1997 FCC announced DTV service and 1997 FCC announced DTV service and mandated 8 year transition schedule mandated 8 year transition schedule

1997 demonstration, laboratory testing and 1997 demonstration, laboratory testing and field trials of 8-VSB in Australiafield trials of 8-VSB in Australia

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8-VSB - Transition Schedule 8-VSB - Transition Schedule

1/5/991/5/99 coverage of 10 largest marketscoverage of 10 largest markets 1/11/991/11/99 coverage top 30 marketscoverage top 30 markets 1/5/021/5/02 all other commercials on airall other commercials on air 1/5/031/5/03 all non commercial stationsall non commercial stations 20062006 switch off analog service and switch off analog service and

recover 138 MHz of spectrumrecover 138 MHz of spectrum

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8-VSB Equipment8-VSB Equipment

Still at the Still at the prototype prototype stagestage

First chips First chips are being are being tested nowtested now

This year This year domestic domestic receiverreceiver

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European Development - DVBEuropean Development - DVB

1991 European launching group (ELG)1991 European launching group (ELG) 1992 ELG developed MoU for cooperation1992 ELG developed MoU for cooperation 1993 ELG became digital video broadcasting 1993 ELG became digital video broadcasting

(DVB) project - a forum for all interested (DVB) project - a forum for all interested in digital TV to participate in research and in digital TV to participate in research and development as a unified group.development as a unified group.

DVB is a consortium of over 200 network DVB is a consortium of over 200 network operators, broadcasters, manufacturers and operators, broadcasters, manufacturers and regulators in 30 countries working together.regulators in 30 countries working together.

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DVB ProjectDVB Project

The DVB philosophy - The DVB philosophy - open, interoperable, flexible, market-led, global open, interoperable, flexible, market-led, global standards for digital TV standards for digital TV

1980s MAC systems under development gave 1980s MAC systems under development gave way to all digital technology way to all digital technology

Based on common MPEG-2 coding systemBased on common MPEG-2 coding system Integrated set of standards allowing flexible Integrated set of standards allowing flexible

operation across cable, microwave, satellite and operation across cable, microwave, satellite and terrestrial distributionterrestrial distribution

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DVB - COFDM - DevelopmentDVB - COFDM - Development

Easier satellite (DVB-S) & cable (DVB-C) Easier satellite (DVB-S) & cable (DVB-C) systems were developed first.systems were developed first.

DVB-T is the terrestrial member of the DVB DVB-T is the terrestrial member of the DVB family of standards.family of standards.

OFDM transmission originally developed for OFDM transmission originally developed for cable systems, cable systems, adapted to digital radio broadcasting, adapted to digital radio broadcasting, extended by DVB to digital TVextended by DVB to digital TV

DVB-T based on COFDM technologyDVB-T based on COFDM technology

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COFDM - Transition ScheduleCOFDM - Transition Schedule

DTTB test transmission programs are currently DTTB test transmission programs are currently occurring in Denmark, Holland, Finland, occurring in Denmark, Holland, Finland, France, Germany & Italy France, Germany & Italy

1998 Britain & Sweden on air with SDTV 1998 Britain & Sweden on air with SDTV DTTB system using UHF band.DTTB system using UHF band.

2001 Spain plans DTTB to be operational, 2001 Spain plans DTTB to be operational, achieving 100% coverage by 2010.achieving 100% coverage by 2010.

Simulcasting is expected to be around 20 years Simulcasting is expected to be around 20 years in Europe. Focus is SDTV to EDTVin Europe. Focus is SDTV to EDTV

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COFDM - Commercial ReceiverCOFDM - Commercial Receiver News data systems - system 3000News data systems - system 3000

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COFDM DTTB EquipmentCOFDM DTTB Equipment

System 3000 - NDSSystem 3000 - NDS Project mummy bear - NDS zenithProject mummy bear - NDS zenith Dvbird - Thomson SGS PhilipsDvbird - Thomson SGS Philips 3 chip receiver - Philips3 chip receiver - Philips Test receiver - ITIS HarrisTest receiver - ITIS Harris Chip set - Hokia SiemensChip set - Hokia Siemens Over 20 manufacturers showing hardwareOver 20 manufacturers showing hardware

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COFDM - Current HardwareCOFDM - Current Hardware

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Dvbird - Receiver Dvbird - Receiver

4 VLSI COFDM 4 VLSI COFDM receiverreceiver

Implements an 8K Implements an 8K FFT (2K/8K mode)FFT (2K/8K mode)

QPSK, 16QAM & QPSK, 16QAM & 64QAM64QAM

1/4,1/8 & 1/32 guard 1/4,1/8 & 1/32 guard intervalsintervals

Onboard tunerOnboard tuner

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Enabling TechnologiesEnabling Technologies

Source digitisation (Rec 601 digital studio)Source digitisation (Rec 601 digital studio) Compression technology (MPEG, AC-3)Compression technology (MPEG, AC-3) Data multiplexing (MPEG)Data multiplexing (MPEG) Transmission technology (modulation)Transmission technology (modulation) Display technology (large wide screens)Display technology (large wide screens)

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Digital Terrestrial TV - LayersDigital Terrestrial TV - Layers . . . provide clean interface points. . . .

PictureLayer

Video Compression

Layer

TransportLayer

TransmissionLayer

MPEG-2packets

MPEG-2 compression

syntax ML@MP

orHL@MP

Multiple Picture Formatsand Frame Rates

Multiple Picture Formatsand Frame Rates

7 MHz

Video packet Video packetAudio packet Aux data

DataHeaders

MotionVectors

Chroma and LumaDCT Coefficients

Variable Length Codes

Packet Headers Flexible delivery of data Flexible delivery of data

1920 x 10801280 x 720

60,30, 24 Hz

COFDM / 8-VSBVHF/UHF TV Channel

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Digital Television Encode LayersDigital Television Encode Layers

Program 1 Multiplexer

Bouquet Multiplexer

Modulator & Transmitter

PictureCoding

AudioCoding

DataCoding

Program 2 Program 3

MPEG TransportStream Mux

ServiceMux

MPEG-2or AC-3MPEG-2

Error Protection

Delivery System

Other Data

Control Data

ControlData

Control Data

Control Data

Video Data Sound

188 byte packetsMPEG Transport Data Stream

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Digital Television Decode LayersDigital Television Decode Layers

MPEG Transport StreamDe-Multiplexer

Demodulator & Receiver

AudioDecoder

DataDecoder

PictureDecoder

MPEG DeMux

MPEGor AC-3MPEG-2

Error Control

Delivery System

DataMonSpeakers

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Transmission TechnologyTransmission Technology

The transmission system is used to transport the The transmission system is used to transport the information to the consumer.information to the consumer.

The system protects the information being The system protects the information being carried from the transmission environmentcarried from the transmission environment

Current Australian analog television uses the Current Australian analog television uses the PAL-B AM modulation systemPAL-B AM modulation system

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Digital TV Transmission Technology

Digital TV Transmission Technology

The transmission The transmission system is asystem is a “data pipe” “data pipe”

Transports data rates Transports data rates of around 20 Mb/sof around 20 Mb/s

Transports data in Transports data in individual containers individual containers called packetscalled packets

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Terrestrial Transmission ProblemsTerrestrial Transmission Problems

Multipath interference - ghostsMultipath interference - ghosts Noise interference - snowNoise interference - snow Variable path attenuation - fadingVariable path attenuation - fading Interference to existing servicesInterference to existing services Interference from other servicesInterference from other services Channel frequency assignment - Channel frequency assignment -

where to place the signalwhere to place the signal

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Digital Modulation - FunctionsDigital Modulation - Functions

Spreads the data evenly across the channelSpreads the data evenly across the channel Distributes the data in timeDistributes the data in time Maintains synchronisation well below data Maintains synchronisation well below data

thresholdthreshold Employs sophisticated error correction.Employs sophisticated error correction. Equalises the channel for best performanceEqualises the channel for best performance

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Digital Has to Fit In With PALDigital Has to Fit In With PAL

We need a digital system that can co-exist with We need a digital system that can co-exist with the existing analog broadcast TV currently in the existing analog broadcast TV currently in use in Australiause in Australia

We use the PAL-B with sound system GWe use the PAL-B with sound system G Australian TV channels are 7 MHz wideAustralian TV channels are 7 MHz wide

on both VHF & UHFon both VHF & UHF Australia uses:Australia uses:

VHF bands I, II & IIIVHF bands I, II & III UHF bands IV & IVUHF bands IV & IV

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Digital Has to Fit In With PALDigital Has to Fit In With PAL World TV channel bandwidths varyWorld TV channel bandwidths vary

USA / japan 6 MHzUSA / japan 6 MHz

Australian 7 MHzAustralian 7 MHz

Europeans 8 MHzEuropeans 8 MHz

Affects:-Affects:- tuning, filtering, interference tuning, filtering, interference & system performance& system performance2828

2828

2828

3030

30302929

2929

3131

3131 3232 3333 3434 3535

3535

35353434

34343333

3333

3232

3232

313130302929

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Digital Has to Fit In With PALDigital Has to Fit In With PAL

Digital television system development is Digital television system development is focused in Europe & USAfocused in Europe & USA The systems standards are designed to meet the The systems standards are designed to meet the

needs of the developersneeds of the developers They focus on their countries needs firstThey focus on their countries needs first Australian input is through standards organisations Australian input is through standards organisations

such as the ITU-Rsuch as the ITU-R

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Channel SpacingChannel Spacing

Existing analog TV channels are spaced so they do not interfere Existing analog TV channels are spaced so they do not interfere with each other.with each other.

Gap between PAL TV servicesGap between PAL TV services VHF 1 channelVHF 1 channel UHF 2 channelsUHF 2 channels

Digital TV can make use of these gapsDigital TV can make use of these gaps

Ch 7 Ch 8 Ch 9Ch 6 Ch 9A

VHF Television Spectrum

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Digital ChallengesDigital Challenges Digital TV must co-exist Digital TV must co-exist

with existing PAL serviceswith existing PAL services DTV operates at lower powerDTV operates at lower power DTV copes higher interference levelsDTV copes higher interference levels Share transmission infra-structureShare transmission infra-structure DTV needs different planning methods DTV needs different planning methods

Ch 7 Ch 8 Ch 9Ch 6 Ch 9A

VHF Television Spectrum

8-VSB COFDM

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Digital Service Area PlanningDigital Service Area Planning

Analog TV has a slow gradual failureAnalog TV has a slow gradual failure Existing PAL service was planned for:Existing PAL service was planned for:

50 % availability at 50 % availability at 50 % of locations50 % of locations

Digital TV has a “cliff edge” failureDigital TV has a “cliff edge” failure Digital TV needs planning for:Digital TV needs planning for:

90-99 % availability at 90-99 % availability at 90-99 % of locations90-99 % of locations

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TV System Failure CharacteristicTV System Failure Characteristic

Analog

Digital

Good

RottenClose Far

Distance

Quality

Edgeof

ServiceArea

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TV System Failure CharacteristicTV System Failure Characteristic

Analog

Digital

Good

RottenClose Far

Distance

Quality

Edgeof

ServiceArea

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Digital Provides New ConceptsDigital Provides New Concepts Single frequency networks (SFNs) can help Single frequency networks (SFNs) can help

solve difficult coverage situationssolve difficult coverage situations SFNs allow the reuse of a transmission frequency SFNs allow the reuse of a transmission frequency

many times in the same area so long as many times in the same area so long as exactly the exactly the same program is carriedsame program is carried

Allows lower power operationAllows lower power operation Better shaping of coverageBetter shaping of coverage Improved service availabilityImproved service availability Better spectrum efficiencyBetter spectrum efficiency

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Compression TechnologyCompression Technology

When low bandwidth analog information is When low bandwidth analog information is digitised the result is high amounts of digital digitised the result is high amounts of digital information.information.

5 MHz bandwidth analog TV picture5 MHz bandwidth analog TV picture

170 - 270 Mb/s digital data stream.170 - 270 Mb/s digital data stream. 270 Mb/s would require a bandwidth of 270 Mb/s would require a bandwidth of

at least 140 MHz to transportat least 140 MHz to transport Compression of the information is requiredCompression of the information is required

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Compression - TypesCompression - Types

Two types of compression availableTwo types of compression available

Loss-less compressionLoss-less compression 2 to 5 times 2 to 5 times

Lossy compressionLossy compression 5 to 250 times 5 to 250 times

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Compression - Loss-less TypesCompression - Loss-less Types

Picture differences - temporalPicture differences - temporal Run length data coding - GIFRun length data coding - GIF

101000100010001001101 = 1 + 4x0100 + 1101101000100010001001101 = 1 + 4x0100 + 1101 21 bits source = 12 bits compressed21 bits source = 12 bits compressed

Huffman coding - PKZIPHuffman coding - PKZIP Short codes for common blocksShort codes for common blocks Longer codes for uncommon blocksLonger codes for uncommon blocks

Lookup tablesLookup tables

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Compression - Lossy TypesCompression - Lossy Types

Quantisation - roundingQuantisation - rounding Motion vectorsMotion vectors Prediction & interpolationPrediction & interpolation Fractal codingFractal coding Discrete cosine transform (DCT)Discrete cosine transform (DCT)

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Compression - DCTCompression - DCT

8x8 Pixels

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MPEG-2 - I, P & B FramesMPEG-2 - I, P & B FramesUncompressed SDTV Digital Video Stream - 170 Mb/s

Picture 830kBytesPicture 830kBytes Picture 830kBytesPicture 830kBytesPicture 830kBytesPicture 830kBytesPicture 830kBytesPicture 830kBytes

I Frame B Frame P FrameB Frame

100 kBytes 12 kBytes 33 kBytes12 kBytes

II - - intra picture coded without reference to other intra picture coded without reference to other pictures. pictures. Compressed using spatial redundancy onlyCompressed using spatial redundancy only

PP - - predictive picture coded using motion compensated predictive picture coded using motion compensated prediction from past I or P framesprediction from past I or P frames

BB - - bidirectionally-predictive picture using both past and bidirectionally-predictive picture using both past and future I or future I or P framesP frames

MPEG-2 Compressed SDTV Digital Video Stream - 3.9 Mb/s

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MPEG-2MPEG-2

Compresses source video, audio & dataCompresses source video, audio & data Segments video into I, P & B framesSegments video into I, P & B frames Generates system control dataGenerates system control data Packetises elements into data streamPacketises elements into data stream Multiplexes program elements - servicesMultiplexes program elements - services Multiplexes services - transport streamMultiplexes services - transport stream Organises transport stream data Organises transport stream data

into 188 byte packetsinto 188 byte packets

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MPEG-2 - Formats ML & HLMPEG-2 - Formats ML & HL

MPEG-2 defines profiles & levelsMPEG-2 defines profiles & levels They describe sets of compression toolsThey describe sets of compression tools

DTTB uses main profile.DTTB uses main profile. Choice of levelsChoice of levels Higher levels include lower levelsHigher levels include lower levels

LevelLevel resolution resolutionLow level (LL)Low level (LL) 360 by 288 360 by 288 SIFSIFMain level (ML)Main level (ML) 720 by 576 720 by 576 SDTV SDTV High level (HL)High level (HL) 1920 by 11521920 by 1152 HDTVHDTV

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Common Image Format CIFCommon Image Format CIF

1920 pixels x 1080 lines progressive scan is 1920 pixels x 1080 lines progressive scan is now being promoted as the world CIF.now being promoted as the world CIF.

All HDTV systems will need to support this All HDTV systems will need to support this image format and then allow conversion to any image format and then allow conversion to any other display formats that are supported by the other display formats that are supported by the equipment.equipment.

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DTTB - Content & ServicesDTTB - Content & Services

DTTB was designed to carry video, audio and DTTB was designed to carry video, audio and program data for televisionprogram data for television

DTTB can carry much more than just TVDTTB can carry much more than just TV Electronic program guide, teletextElectronic program guide, teletext Best of internet serviceBest of internet service Broadband multimedia data, news, weatherBroadband multimedia data, news, weather Interactive servicesInteractive services Software updates, gamesSoftware updates, games

Services can be dynamically reconfiguredServices can be dynamically reconfigured

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Video Program CapacityVideo Program Capacity

1 HDTV service - sport & high action1 HDTV service - sport & high action 2 HDTV services - both film material2 HDTV services - both film material 1 HDTV + 1 or 2 SDTV non action/sport1 HDTV + 1 or 2 SDTV non action/sport 3 SDTV for high action & sport video3 SDTV for high action & sport video 6 SDTV for film, news & soap operas6 SDTV for film, news & soap operas

However you do not get more for nothing.However you do not get more for nothing. More services means less qualityMore services means less quality

For a payload of around 19 Mb/sFor a payload of around 19 Mb/s

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Spare Data CapacitySpare Data Capacity

Spare data capacity is Spare data capacity is available even on a fully available even on a fully loaded channel.loaded channel.

Opportunistic use of Opportunistic use of spare data capacity when spare data capacity when available can provide available can provide other non real time data other non real time data services.services.

Example: 51 secondExample: 51 secondBMW commercialBMW commercial

The Commercial wasThe Commercial wasshown using 1080 Linesshown using 1080 Lines

Interlaced. 60 Mb of data Interlaced. 60 Mb of data was transferred during it. was transferred during it. In the Final 3 seconds theIn the Final 3 seconds the

BMW Logo was displayed BMW Logo was displayed allowing 3 Phone Booksallowing 3 Phone Booksof data to be transmitted.of data to be transmitted.

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Navigation SystemsNavigation Systems

The concept of channel numbers for networks The concept of channel numbers for networks may disappear with DTVmay disappear with DTV

Television becomes one of a number of services Television becomes one of a number of services carried within the data pipe.carried within the data pipe.

Users will select what service or program they Users will select what service or program they wish to decode. The box then finds it.wish to decode. The box then finds it.

Each digital transmission can carry program Each digital transmission can carry program directories for all service providersdirectories for all service providers

This area is still under heavy developmentThis area is still under heavy development

84

Australian ActivityAustralian Activity

ABA report on digital television in Australia ABA report on digital television in Australia recommended using HDTVrecommended using HDTV

FACTS have set up a specialists group to advise FACTS have set up a specialists group to advise and direct commercial advanced television and direct commercial advanced television developmentdevelopment Represents commercial television (7,9,10)Represents commercial television (7,9,10) ABA and communications lab have been assisting this ABA and communications lab have been assisting this

groupgroup NTA, ABC and SBS are not representedNTA, ABC and SBS are not represented

NTA commenced own trialsNTA commenced own trials

85

Laboratory TestsLaboratory Tests

Tested both COFDM & 8-VSB systemsTested both COFDM & 8-VSB systems Investigated operation within the existing Investigated operation within the existing

Australian broadcasting infrastructureAustralian broadcasting infrastructure Systems evaluated as data pipesSystems evaluated as data pipes Both systems operate satisfactorily with only Both systems operate satisfactorily with only

small operational differences evidentsmall operational differences evident Report on measurements was produced for the Report on measurements was produced for the

FACTS specialists groupFACTS specialists group

86

Laboratory Tests - Test RigLaboratory Tests - Test RigEUTC/N Set & Attenuators PAL & CW

Spectrum AnalysersControlComputer

DomesticTelevisionReceiver

ModulatorControl

Computers

Plot &Printing

87

Laboratory Tests - Test RigLaboratory Tests - Test Rig

COFDMModulator

MPEG Mux

MPEG Encoder

MPEG Encoder

MPEG Mux

8-VSBModulator

RF LO

Power Meter PAL & CWInterferenceGenerators

88

Field TestsField Tests

Field tests conducted in Sydney on VHF Field tests conducted in Sydney on VHF channel 8 during oct-nov 1997channel 8 during oct-nov 1997

Both COFDM & 8-VSB systems evaluated at Both COFDM & 8-VSB systems evaluated at over 150 sites using an ABA field vehicleover 150 sites using an ABA field vehicle

Comparison of the digital and existing PAL Comparison of the digital and existing PAL systems performance at each sitesystems performance at each site

Concentrating on difficult reception sitesConcentrating on difficult reception sites Report on field trials was produced for theReport on field trials was produced for the

FACTS specialists group FACTS specialists group

89

A Future Digital System ConceptA Future Digital System Concept

HypermediaIntegrated Receiver

Decoder (IRD)

MMDS

Satellite

Terrestrial

Cable

B-ISDNXDSL CD, DVD

DVC

Broadcast Interactivity

90

Future - Things to Be DoneFuture - Things to Be Done

Decide on digital transmission standardDecide on digital transmission standard Policy HDTV vs multiple SDTVPolicy HDTV vs multiple SDTV Minimum data rates / quality ?Minimum data rates / quality ? Multiplex / content provider relationshipsMultiplex / content provider relationships Pay vs free to airPay vs free to air Sort out service provider issuesSort out service provider issues Conditional access systemsConditional access systems Ancillary dataAncillary data

91

The EndThe End

Thankyou for your attentionThankyou for your attention

Any questions?Any questions?