© T.Jaekel, 1/2001 1

The Basics of Digital TV

1. Why do we need Digital TV ?2. How do we make TV digital ?

5. Summary4. How about digital modulation ?

3. What do the different MPEG variants mean?

T. Jaekel, January 2001

© T.Jaekel, 1/2001 2

1. Why do we need Digital TV ?Bandwidth Efficiency

Compatibility Scalability

Quality, Reliability

UHF

more programsper RF channel

signal levelindependentnoise free

HDTV

16:9

SDTV

TV 1

PAL

Ch 24

Ch 24 Ch 25

Ch 32

TV 1

TV 2

TV 4

NTSC

MPEG-2

SECAM

© T.Jaekel, 1/2001 3

2. How do we make TV digital ? - I

PAL:720x75750 fpsinterlaced 4:4:4 MPEG

Scanning

analogue

SDI

4.2 … Mbps5.5 … 8 Mbps(distribution)25 … 50 Mbps(contribution)

4270 Mbps10 bit/pixel

ASI

digital

Compression

(with losses)

© T.Jaekel, 1/2001 4

2. How do we make TV digital ? - II

4:2:0 DCTJPEG

MPEG

VLCround

Scanning Conversion

Motion Estimation Multiplexing

Coefficients

9 8 7 6 38 8 7 5 27 7 7

57

5 26 5 5

2

5 23 2 2

VideoI P B

Audio

Data

2 20 0 0 0 00 0 0 0 0 0

000000 0

0000000

Program

Intra-frame

Inter-frame

D

M-JPEG

Group of Pictures

© T.Jaekel, 1/2001 5

3. What do the different MPEG variants mean?

MPEG-1 < 1,5 Mbps

1 … 100 Mbpsscalable

Audio Visual Objects( s)higher compression ratioAVO

Content ManagementSemantic of Scenes

25, 50, 100 Mbps (HD)

64 … 368 Kbps

0 … 100 Mbps

CDs, Video-CDInternet

DVD

DVBDigital TV( , ATSC)

Internet-TV

archivesretrieval systems(no compression)

Panasonic

videoconferencing

video surveillancespace missionsresearch

Audio: MP2 ( )Audio: (Internet)

MUSICAM, DABMP3

Media PlayerReal Playervirtual studios

Electronic NewsGathering (ENG)

ISDNnx64K mode

JPEG 2000

4:2:2 HP@ML

Meta Data

type parameters used for examples

MPEG-2

MPEG-4

MPEG-7

DVCPro

H.261

Wavelets

DCTbased

nonDCT

© T.Jaekel, 1/2001 6

4. How about digital modulation ?

4QAMQPSK4PSK

16QAM

(C)OFDM

DVB-S

DVB-C

DVB-T

64QAM

Q

Q

Q

I

I

I

m=2

m=42k

1705 carriers1512 for data7.611 MHz

6817 carriers6048 for data7.608 MHz

8k

m=16

lengthcode word

type used forIQ vector diagram

© T.Jaekel, 1/2001

Source: DigiTAG and DVB-Org.

7

Satellite and Cable are already digital.Germany starts 2001, deadline is 2010 forDTT installation and adoption (DVB-T)

5. Summary

© T.Jaekel, 1/2001 8

ASI Asynchronous Serial InterfaceATSC Advanced Television Standard CommitteeAVO Audio Visual ObjectsCD Compact DiscCh ChannelDCT Discrete Cosine TransformationDTT Digital Terrestrial TVDVB Digital Video BroadcastingDVC Digital Video CompressionDVD Digital Versatile DiscENG Electronic News GatheringHDTV High Definition TVHP@ML High Profile at Main LevelISDN Integrated Services Data NetworkJPEG Joint Pictures Expert GroupMbps Megabit per secondsM-JPEG Motion-JPEGMPEG Motion Picture Expert GroupNTSC National Television Standardization Committee(C)OFDM (Coded) Orthogonal Frequency Division MultiplexPAL Phase Alternating LineQAM Quadrature Amplitude ModulationQPSK Quarter Phase Shift KeyingSDI Serial Digital InterfaceSDTV Standard Definition TVSECAM SEquentiel Coleur a MemoireVLC Variable Length Coding

Abbreviations