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© 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