intro_dgital_TV

Universidade de Aveiro

Introduction to Digital Television
Introduction to Digital Television

Prof. António Navarro
Instituto de Telecomunicações
Universidade de Aveiro
3810 Aveiro - PORTUGAL

Tel: +351 234 377900 Fax: +351 234 377901
Email: navarro@av.it.pt
http://www.av.it.pt/colaboradores/Navarro/

1 Instituto de Telecomunicações - Pólo de Aveiro 21-1-2000

Introduction to the Digital Television
Contents
❑ Analog TV
! YUV (YCrCb) Components
! TV Spectrum

❑ Digital TV
! ITU-R BT.601-5 (SDTV-Standard Definition TV)
! ITU-R BT.709-3 (HDTV-High Definition TV)
! DVB Content Plane
! Broadcasting Network Interface
! Satellite Interface


! MPEG-2 Transport Stream - TS packets
➫Adaptation Field
! MPEG-2 Packetised Elementary Streams - PES packets
! MPEG-2 Program Specific Information (PSI) Tables
➫Relation Between PSI Tables : Example
➫Program Association Table (PAT)
➫Program Map Tables (PMT)
➫ Descriptors
➫Conditional Access Table (CAT)
➫CA_Descriptor
! Scrambling and Conditional Access-DVB - ETR 289
! DVB-SI - ETS 300 468 and ETR 162
! References


ANALOG TV -- YUV (YCrCb) Components
ANALOG TV YUV (YCrCb) Components
Y=f_linear (R,G,B) ⇒ (luminance) Black and White TV
Cr=R-Y=f_linear(R,G,B) ⇒ (Color difference or crominance R)
Cb=B-Y=f_linear(R,G,B) ⇒ (Color difference or crominance B)

Y image ⇒

+ + = any color

R G B

(Y+Cr+Cb) image ⇒


TV Spectrum
TV Spectrum
! Compatibility between BW TV and Color TV leads to cross-colour and
cross-luminance interferences.
π θ θ
! Quadrature modulation, C(crominance)=cos(2πfc+θ(t)),θ(t)= f(Cr,Cb).
! NTSC (National Television System Committee)-USA.
! PAL (Phase alternating Line)-Portugal.
! SECAM (Sequentiel Couleur Avec à Mémoire)-France.
! D2-MAC (Multiplexed Analogue Component)-England.
Y (luminance)
C (crominance)
Audio

fc fa

Digital TV -- ITU-R BT.601-5
Digital TV ITU-R BT.601-5
4:4:4 , 4:2:2 and 4:2:0 (not defined in BT.601) Formats

x - Represent luminance samples
0 - Represent chrominance samples


ITU-R BT.601-5
ITU-R BT.601-5

Aspect Ratio 4:3 or 16.9 – 13.5 MHz 16.9 – 18 MHz
System 525-line,60 625-line, 50 525-line, 60 625-line, 50
field/s field/s field/s field/s 720
4:2:2 (4:4:4) 4:2:2 (4:4:4) 4:2:2 (4:4:4) 4:2:2 (4:4:4) 720
540
Number of samples 540
per total line: 858 (858) 864 (864) 1144 (1144) 1152 (1152) 405
-Y (luminance) 429 (858) 432 (864) 572 (1144) 576 (1152)
-Cr, Cb (each color dif.)
Sampling frequency: 13.5 MHz (13.5 MHz) 18 MHz (18 MHz)
-Y (luminance) 6.75 MHz (13.5 MHz) 9 MHz (18 MHz) 960
- Cr, Cb (each color dif.)
Number of samples 4:3- 13.5 MHz
per digital active line: 720 (720) 960 (960) 16:9- 13.5 MHz
- Y (luminance) 720 (720) 480 (960) 16:9- 18 MHz
- Cr, Cb (each color dif.)


ITU-R BT.709-3
ITU-R BT.709-3
! The Standard recommends that for the new implementations
particularly where interoperability with other applications, including
digital television and computer imagery, is important, the system of an
active image format of 1920 pixels by 1080 lines is preferred.
System 1125/60/ 1250/50/ 1125/60/ 1250/50/
(Aspect ratio 16:9) 2:1(1:1) 2:1(1:1) 2:1 2:1
Number of samples
per total line: 2200 2376 2200 2304
-Y (luminance) 1100 1188 1100 1152
-Cr, Cb (each color dif.)
Sampling frequency:
-Y (luminance) 74.25 MHz (148.5 MHz) 74.25 MHz 72 MHz
- Cr, Cb (each color dif.) 37.125 MHz (74.25 MHz) 37.125 MHz 36 MHz
Number of samples
per digital active line:
- Y (luminance)
1920 1920
- Cr, Cb (each color dif.) 960 960
Numer of active lines per
picture: 1080 (Square pixels) 1035 1152


DVB Content Plane
DVB Content Plane
Private Data (TXT)
DSM-CC
audio video PCR ECM
EMM
MPEG-2
Compression
Private Data
PES PACKER PSI

MPEG-2 Transport Stream (MULT)

Broadcasting Network Interface

PCR- Program Clock Reference
ECM - Entitlement Control Message
EMM - Entitlement Management Message
TXT- Teletext
DSM-CC - Digital Storage Medium Command and Control



! Satellite - DVB-S (ETS 300 421)
➫QPSK
! Cable - DVB-C (ETS 300 429)
➫ 16-QAM, 32-QAM, 64-QAM
! Terrestrial - DVB-T (ETS 300 744)
➫1512 carriers (2k mode), 6048 carriers (8k mode)
➫QPSK, 16-QAM, 64-QAM, Non-uniform 16-QAM, Non-uniform
64-QAM


Satellite Interface -- ETS 300 421
Satellite Interface ETS 300 421

Conv.Punc.(1/2, TS
QPSK 2/3, 3/4,5/6,7/8)
TUNER De-inter. I=12
1 GHz Demod.
RS(204,188,T=8)

EUTELSAT Television POL FEC TS Access Lang.
HOT BIRD Channels (MsY/s)
0
(13 East)
10.722 GHz FKR, MTA, HB4/2OU, H 3/4 29.9 Crytoworks multi
HB4/3OU, 3ABN
10.796 GHz Infosport, Regions, V 2/3 27.5 Viaccess French
Mezzo, Festival,
Histoire,Télétoon,
Odyssée


Transport Stream (TS) Packet
Transport Stream (TS) Packet
! MPEG-2 defines fixed size transport packets with a fixed length of 188
bytes consisting of a 4 byte header information, a variable length
adaptation field and the payload

188 bytes x bytes
transport
packet header payload header
header payload header
header payload
stream

sync transport payload transport transport adaptation continuity adaptation
error unit start PID scrambling field counter field
byte priority
indicator indicator control control
8 1 1 1 13 2 2 4 184-x


TS Packet Header
TS Packet Header

! sync_byte (8 bits) ⇒ The sync_byte is a fixed 8 bit field whose value is '0100
0111' (0x47) and is used to identify the start of a TS packet. Sync_byte
emulation in the choice of values for other regularly occurring fields, such as
PID, should be avoided.
! transport_error_indicator (1 bit) ⇒ When set to ‘1’, it indicates a bit error in
this TS packet.
! payload_unit_start_indicator (1 bit) ⇒ This flag indicates that the first byte
of this TS payload is the start of an unit access (e. g. a PES packet or a PSI
section as explained later).
! transport_priority (1bit) ⇒ when set to 1, it indicates that this TS packet is of
greater priority than other packets having the same PID which do not have this
bit set to ‘1’.


TS Packet Header
TS Packet Header

! PID (13 bits) ⇒ Packet IDentifier is one of the most important field in the TS
header. It identifies TS packets carrying data from the same elementary stream
(e.g. video stream from ‘Sport TV’ programme). Some PID values have special
meaning as described in the following table,

value description
0x0000 Program Association Table
0x0001 Conditional Access Table
0x0002-0x000F reserved
0x00010 Available for PES streams,
… program_map tables, network tables,
0x1FFE or for other purposes.
0x1FFF Null packet


TS Packet Header
TS Packet Header

! transport_scrambling_control (2 bits) ⇒ It indicates the scrambling mode
of this TS packet payload. The Transport Stream packet header, and the
adaptation field when present, shall not be scrambled. It must be set to ‘00’ in
the case of a null packet.

value description
00 not scrambled
01 user defined
10 user defined
11 user defined


TS Packet Header
TS Packet Header
! adaptation_field_control (2 bits) ⇒ This field indicates whether this TS
packet header is followed by an adaptation field and/or payload.
value description
00 reserved for future use by ISO/IEC
01 no adaptation_field, payload only
10 adaptation_field only, no payload
11 adaptation_field followed by payload
! continuity_counter (4 bits) ⇒ The continuity_counter is a 4 bit field
incrementing with each Transport Stream packet with the same PID. The
continuity_counter wraps to 0 after its maximum value. It shall not be
incremented when the adaptation_field_control of the packet equals '00' or '10'.
It can be used to find packet loss.
! Adaptation_field ⇒ This field (see its description in the next slide) is
followed by N contiguous bytes of data (payload) from the access units (PES
packets, PSI sections, etc). The number of data_bytes, N, is equal to 184
minus the number of bytes in this adaptation_field.


Adaptation Field
Adaptation Field

adaptation discontinuity random elementary
optional stuffing
field stream
indicator access 5 flags fields bytes
priority
length indicator
indicator
8 1 1 1 5

transport transport adaptation optional
splice private field
PCR OPCR private 3 flags fields
countdown data extension
data
length length
42 42 8 8 8 3

ltw_valid ltw piecewise splice
DTS_next_au
flag offset rate type

1 15 2 22 4 33

! adaptation_field_length (8 bits) ⇒ This field specifies the number of bytes in
the adaptation_field immediately following the adaptation_field_length.


Packetised Elementary Streams: PES Packets
Packetised Elementary Streams: PES Packets
Elementary Stream (ES):
I- Picture P- Picture
Access Units, e.g. Pictures
variable variable
Packetised ES:
PES Packets variable variable

PES I- Picture PES P-Picture
Header data Header data
Adaptation Field-
Transport Stream: Stuffing bytes
TS Packets
TS PES TS PES TS PES
Header Packet data Header Packet data Header Packet data

fixed fixed fixed

❍ The PES packet headers are additional information directly related
to the elementary stream, e.g. the type of the stream, audio or video.

PES Packet Header
PES Packet Header
0x 00 00 01

stream_id Description
1011 1101 Private_stream_1
Packet PES optional
start stream 1011 1111 Private_stream_2
packet PES
code id
length Header 110x xxxx MPEG-2 or MPEG-1 audio
prefix stream number x xxxx
24 8 16 1110 xxxx MPEG-2 or MPEG-1 video
stream number xxxx
1111 0000 ECM_stream
1011 1100
1111 0001 EMM_stream
1111 0010 DSM-CC_stream
1111 1111
The number of bytes in this PES packet
following the last byte of this field


Program Specific Information (PSI) tables
Program Specific Information (PSI) tables

! Four tables defined by MPEG-2 Systems,

" Program Association Table (PAT)
" Program MAP Table (PMT)
" Network Information Table (NIT)
" Conditional Access Table (CAT)


Relation Between PSI Tables :: Example
Relation Between PSI Tables Example
Program Association Table
Network Information Table
(in TS Packets with PID=0)
(syntax not defined in MPEG-2 Systems)
Program Transport
Delivery Network
Number Packet PID
0 122 Information
1 60
…. …. Program Map Table for Program #20
…. …. (in TS Packets with PID=200)

20 200 PES Streams PID
Video 500
Conditional Access Table PCR 500
(in TS Packets with PID=1) Audio 1 510
Audio 2 520
Scrambling Management
ECM 530
Information Private Stream (TXT) 540


Program Association Table (PAT) -- PID=0
Program Association Table (PAT) PID=0
! The overall table is to be split into one or more sections with the
following syntax (section number),

table section section transport version current section last N CRC
id syntax length stream number next number section loop 32
'0'
indicator id indicator number

8 1 1 2 12 16 2 5 1 8 8 32

program Network
network program program
number 0 (NIT)
PID ... number i map ...
PID PID_i

16 3 13 16 3 13

! Program number 0 => NIT PID


! table_id (8 bits) ⇒ This field identifies the content of a TS PSI section,
value description
0x00 program association section
0x01 conditional access section
0x02 TS_program_map_section
0x03-0x3F ITU-T Rec. H.222.0 | ISO/IEC 13818
reserved
0x03-0x3F user private
0xFF forbidden

and according to the above Table_id assignments, is set to 0x00.
! section_syntax_indicator (1 bit) ⇒ Set to ‘1’.
! section_length (12 bit) ⇒ It specifies the number of bytes of this section,
starting immediately following this field and including the CRC. The value in
this field shall not exceed 1021.


! transport_stream_id (16 bits) ⇒ It serves as a label to identify this TS from any
other multiplex within a network. Its value is defined by the user.
! version_number (5 bits) ⇒ This field indicates the version number of the whole
Program Association Table. The version number shall be incremented by 1
whenever the definition of the Program Association Table changes. Upon reaching
the value 31, it wraps around to 0.
! current_next_indicator (1 bit) ⇒ When set to '1' indicates that the Program
Association Table sent is currently applicable. When the bit is set to '0', it indicates
that the table sent is not yet applicable and shall be the next table to become valid.
! section_number (8 bits) ⇒ It gives the number of this section. The section_number
of the first section in the Program Association Table shall be 0x00. It shall be
incremented by 1 with each additional section in the Program Association Table.
! last_section_number (8 bits) ⇒ It specifies the number of the last section (that is,
the section with the highest section_number) of the complete Program Association
Table.


Program MAP Tables -- PID=selected by PAT (encoder)
Program MAP Tables PID=selected by PAT (encoder)
! Each table provides the mappings between the program number and the program
elements that comprise it. Each table has only one section, identified by the
program_number field, with the following syntax.
table section section program version current section last PCR
id syntax length number number next number section PID
'0'
indicator indicator number

8 1 1 2 12 16 2 5 1 8 8 3 13 4

program N N
info loop loop CRC_32
length descriptors

32

stream elementary ES info N
type PID length loop
descriptors

8 3 13 4 12


! table_id (8 bit) ⇒ Set to 0x02 since it is a TS_program_map_section (see the
table in a previous slide)
! section_syntax_indicator (1 bit) ⇒ Set to '1'.
! section_length ⇒ It specifies the number of bytes of the section starting
immediately following the section_length field, and including the CRC. The
value in this field shall not exceed 1021.
! program_number (16 bit) ⇒ It specifies the program number which should be
equal to program_number_I (see in PAT). One program definition shall be
carried within only one TS_program_map_section. This implies that a program
definition is never longer than 1016 bytes.
! version_number (5 bit) ⇒ This field is the version number of this
TS_program_map_section. The version number shall be incremented by 1
modulo 32 when a change in the information carried within the section occurs.


! current_next_indicator ⇒ When set to '1' indicates that the
TS_program_map_section sent is currently applicable. When the bit is set to '0',
it indicates that the TS_program_map_section sent is not yet applicable.

! section_number (8 bits) and last_section_number (8bits) ⇒ Each, set to 0x00.

! PCR_PID (13 bit) ⇒ It indicates the PID of the Transport Stream packets
which shall contain the PCR fields valid for the program specified by
program_number.

! program_info_length (12 bit) ⇒ The first two bits shall be '00'. It specifies the
number of bytes of the descriptors immediately following the
program_info_length field.


! stream_type (8 bit) ⇒ It specifies the type of program element carried within the
packets with the PID whose value is specified by the elementary_PID.
stream_type Description
0x00 Reserved
0x01 MPEG-1 video
0x02 MPEG-2 video
0x03 MPEG-1 audio
0x04 MPEG-2 audio
0x05 Private_sections
0x06 PES packets containing private data
0x07-0x7F …….
0x80-0xFF User Private
! Elementary_PID (13 bit) ⇒ It specifies the PID of the TS packets which carry the
associated program element.
! ES_info_length (12 bit) ⇒ It specifies the number of bytes of the descriptors of the
associated program element immediately following the ES_info_length field

Descriptors
Descriptors
! Descriptors are structures used to carry specific information about the program
or program elements (e.g. elementary stream). A particular descriptor is
identified by the descriptor_tag field. Its followed by the descriptor_length.
Some descriptor_tag values (2-18) have normative meaning,

0-1 Reserved
2 video_stream_descriptor
3 audio_stream_descriptor
…. ….
9 video_window_descriptor
10 CA_descriptor
…. ….
19-63 Reserved
64-255 User_Private


video_stream_descriptor
video_stream_descriptor
Fields in any descriptor
video_stream_descriptor(){
descriptor_tag (8 bits)
descriptor_length (8 bits)
multiple_frame_rate_flag (1 bit)
frame_rate_code (4 bits)
MPEG_1_only_flag (1 bit)
constrained_parameter_flag (1 bit)
still_picture_flag (1 bit)
if(MPEG_1_only_flag= =1){
profile_and_level_indication (8 bits)
chroma_format (2 bits)
frame_rate_extension_flag (1 bit)
reserved (5 bits)
}
}


Conditional Access Table (CAT) -- PID=1
Conditional Access Table (CAT) PID=1

PAT sections
PMT sections
PIDs - Audio,
Prog 4 PID M Video, ECM, PCR
Prog 4

TS PID 0 Video 4 PID M Audio 4 PID 1 EMM 1 Video 4 ECM 4 EMM 2

CA-
CAT sections system 1 EMM-1 reference
CA-
system 2 EMM-2 reference


Conditional Access Table (CAT) -- PID=1
Conditional Access Table (CAT) PID=1
! This table provides the association between one or more CA systems, their
EMM streams (CMT table-ETR 289) and any special parameters associated
with them. The table may be segmented into one or more sections, before
insertion into TS packets with the following syntax,

table section section version current section last N CRC
id syntax length number next number section loop 32
'0'
indicator indicator number descriptors

8 1 1 2 12 18 5 1 8 8 32

! CA fields have the same meaning as those of PAT sections.


Conditional Access Descriptor
Conditional Access Descriptor
! This descriptor is used to indicate the PIDs of TS packets (CA_PID) which shall
contain ECM or EMM information (CMT-see ETR 289). If this descriptor
appears in a CAT section then a system-wide conditional access management
information (EMM) exists.
If this descriptor is present in a PMT section then, the CA_PID points to packets
containing program related access control information (ECM). Its presence within
loop N indicates applicability to the entire program and within loop N2 indicates
applicability to the associated program element (e.g. video stream).
CA_descriptor() {
Type of CA system
descriptor_tag (8 bits)
for ECMs or EMMs. descriptor_length (8 bits)
Not specified in MPEG-2, CA_system_ID (16 bit)
only specified in DVB (ETR 162) reserved (3 bits)
CA_PID (13 bits)
for(i=0;i<N;i++){ private_data_byte}(8 bits)
}


Scrambling and Conditional Access DVB -ETR 289
Scrambling and Conditional Access DVB -ETR 289
! The Common Scrambling Algorithm (CSA) is designed to minimize the
amount of memory in the de-scrambler circuit at the expense of the
complexity in the scrambler.
! The CSA operates on the payload of either a TS packet or a PES packet.
Scrambling shall only occur at one level (TS or PES). The scrambling of
Sections are at TS level. Clear and scrambled sections cannot be combined in
a single TS packet. Adaptation_Field stuffing bytes (0xFF) are used to create
TS packets with only clear or scrambled Sections.
! ETR 289 specifies the scrambling_control_field in TS packets and PES
packets,
Bit values Description
00 No scrambling of TS/PES packet payload
01 Reserved for future DVB use
10 TS/PES packet scrambled with Even Key
11 TS/PES packet scrambled with Odd Key


ETR 289, CA Message Table (CMT) --EMM or ECM
ETR 289, CA Message Table (CMT) EMM or ECM

! ETR 289 specifies a Section for the transport of conditional Access (CA)
information such as ECMs and EMMs. The structure of this CA information is
specific to each CA System Specifier (see a list of CA_system_id in ETR 162).
The header of CA_message section() may be used for filtering. CA_message
section() is actually a Private section as defined in MPEG-2.

CA_section
table_id '0' N CA_data_bytes
length

8 1 3 12


ETR 289, CA Message Table (CMT) --EMM or ECM
ETR 289, CA Message Table (CMT) EMM or ECM
! ETR 289 specifies a range of 14 table_id values (0x82-0x8F) for
CA_message_sections carrying different types of Conditional Access
information (EMM). Two values of the table_id values (0x80 and 0x81) signals
that a change of ECM contents has occurred. This change condition can be used
for filtering of Conditional Access information.
Table_id Description
value
0x00-0x02 MPEG-2 (PAT, CAT, PMT)
0x03-0x3F MPEG-2 Reserved
0x40-0x73 DVB-SI – ETS 300 468
0x74-0x7F DVB reserved for future use
0x80 CA_message_section (ECM)
0x81 CA_message_section (ECM)
0x82-0x8F CA_message_section (CA_system private-
EMM)
0x90-0xFE Private (user defined)

Scrambling and Conditional Access
Scrambling and Conditional Access

TS_scrambled Descrambler clear stream
stream DEMULT
(CSA)
Control_words
(CWs)
µC

Decryption
CMT-ECM CW
(CW encrypted)
Service_key

Decryption
CMT-EMM Service_key
(Service_key encrypted and
Conditional Access)
EMM
User_key
(Conditional Access)
Smart
PCMCIA Card
EN 50221 Standard
Card


DVB-SI (Specific Information)
DVB-SI (Specific Information)
DVB-ETS 300 468 and ETR 162
DVB-ETS 300 468 and ETR 162

! PAT, CAT and PMT of PSI give information only for the
multiplex in which they are contained (the actual TS). ETS 300
468 provides additional tables with appropriate descriptors for
identification of services, information on services and events
carried by different multiplexers and even on other networks.
The syntax and semantics of these additional tables and the NIT
are defined in this ETS.
! All tables are split into sections before insertion in TS packets.


ETS 300 468
ETS 300 468
! Network Information Table (NIT) - It provides information about the physical
network.
! Bouquet (a collection of services marketed as a single entity) Association Table
(BAT) - It provides a list of services and other information for each bouquet.
! Service Description Table (SDT) - It contains data describing the services in the
system, e.g. names de services, the service provider, etc.
! Event Information Table (EIT) - It contains data concerning events or
programmes such as event name, start time, duration, etc.
! Running Status Table (RST) - It gives the status of an event (running/not
running).
! Stuffing Table (ST)- It invalidates existing sections
! Time and Date Tables (TDT) - It provides information about the present time
and date.
! Time Offset Table (TOT) - It provides information about the local time offset.


ETS 300 468
ETS 300 468
MPEG-2 defined ETS 300 468 defined
PID=0 PID=0x0010 PID=0x0010 PID=0x0011
NIT NIT BAT
PAT Actual Other
delivery delivery
System system
PID=0x0013
RST
PID=1 PID=0x0011 PID=0x0011
SDT SDT PID=0x0014
CAT Actual Other TDT
Transport Transport
Stream Stream
PID=0x0014
PID=P PID=0x0012 PID=0x0012 TOT
EIT EIT
PMT Actual Other PID=0x0010 to 0x0014
Transport Transport
Stream Stream ST
Present/following Present/following
Schedule Schedule

Table_id distinguishes tables with the same PID (e.g. BAT and SDT)


References
References
❑ Recommendation ITU-R BT.601.5, Studio encoding parameters of digital television for
standard 4:3 and wide-screen 16:9 aspect ratios.
❑ Recommendation ITU-R BT. 709-3, Parameter values for the HDTV standards for
production and international programme exchange.
❑ ITU-T Rec. H222.0 |ISO/IEC 13818-1:1994, Information technology-Generic coding of
moving pictures and associated audio-Part 1:systems.
❑ H. Benoit, 1998, Televisión Digital, Paraninfo, Madrid.
❑ ETS 300 421, 1994, Digital broadcasting systems for television, sound and data services;
Framing structure, channel coding and modulation for 11/12 GHz satellite services.
❑ ETS 300 468, 1997, Specification for Service Information (SI) in DVB systems.
❑ ETR 162, 1995, Allocation of services information (SI) codes for DVB systems.
❑ ETR 289, 1996, Support for use of scrambling and Conditional Access (CA) within
digital broadcasting systems.


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