This document provides an overview of digital television (DTV) standards and technologies. It discusses: 1. The DVB standard architecture and key components like MPEG transport streams. 2. Video and audio coding standards used in DTV like MPEG-1, MPEG-2, MPEG-4, and H.264. 3. The ATSC digital television standard developed in the United States, including its use of 8-VSB modulation, forward error correction techniques, and the "cliff effect" in reception.

1. DTV INTRODUCTION
Mrs. M. P. Atre
PVG

4. DIGITAL VIDEO DATA SIGNAL

5. DIGITAL AUDIO DATA SIGNAL

6. DVB-SNG:
standard for
news gathering
Multiprotocol
Encapsulation, or
MPE for short, is a
Data link layer
protocol defined
by DVB which has
been published as
part of ETSI EN
301 192.
It provides means
to carry packet
oriented protocols
(like for instance
IP) on top
of MPEG transport
stream (TS).

7. STANDARDS FOR BROADCASTING
Country: USA India Japan Brazil,Phillipines China
Integrated Services Digital Broadcasting (ISDB)
SCM(single carrier modulation), MCM(multicarrier modulation) (MCM
example: OFDM)

9. DVB STANDARD ARCHITECTURE
**Highlighted blocks represent DVB
architecture

10. TERMINOLOGY
 Multimedia Home Platform, or MHP in short
 MHEG (the Multimedia and Hypermedia
Information Coding Experts Group) running over
DVB-T in the UK

11. @ MHP
 The Multimedia Home Platform has been provided
in DVB as supplementary service for MHP-enabled
receivers
 Two versions which are MHP 1.1. and MHP 1.2.
 MHP used for transmitting HTML (Hypertext
Multimedia Language) files familiar from the
Internet, and Java applications.
Continued…

12. @ MHP
 Starting the HTML and Java applications requires
special software (or middleware) in the receiver.
 MHP-capable receivers are more expensive and
not available in great numbers on the market.
 MHP applications are broadcast in many countries
but are currently really successful only in Italy

13. CONTENTS BROADCAST BY MHP ARE:
• Games
• Electronic programme guides
• News
• Interactive program-associated services
• "Modern" teletext

14. DVB STANDARD SCHEME
Encoding Stage Transport Stage Transmission Stage
For Encoding and Transport stage, both stages use
MPEG-2

15. MMDS
MMDS stands for Multichannel Multipoint Distribution Service. It is
used as replacement of cable TV service provider. MMDS is used to
cover rural areas where it is not possible to reach by broadcast
and cable TV operators.

16. LMDS
LMDS stands for Local Multipoint distribution service. It is used for
providing TV and 2-way internet service similar to MMDS.
NOC: Network
Operation Centre

17. MULTIPLEXED MPEG-2 TRANSPORT STREAM
PACKETS

18. MPEG-2 TRANSPORT STREAM PACKET

19. SPECIAL TRANSPORT STREAM PACKETS:
PMT & PAT

20. PAT

21. PMT

22. DESCRAMBLING IN THE DVB RECEIVER

23. CAT-CONDITIONAL ACCESS TABLE

24. DESCRAMBLING

25. VIDEO ENCODING STANDARDS
 MPEG-1 standard
 MPEG-2 standard
 MPEG-4 standard
 H.264 standard

26. INTRODUCTION TO VIDEO ENCODING
STANDARDS
 Motion Picture Experts Group (MPEG) was
established in January 1988 as a work group to
create international standards of audio and video
encoders/decoders (codec)
 MPEG-1 standard was published in 1989 and
approved as the international standard in 1992
 MPEG-2 approved in 1994
 New improvements, which would have lead to the
MPEG-3 standard, were later incorporated in the
MPEG-2. This caused the acronym MPEG-3 not to
be used

27. INTRODUCTION….. CONTINUED..
 Structure of the MPEG-4 standard was set out in 1993
and the standard was approved in 1998
 Work on MPEG-7, which covered audio and video
content, began in 1997 and the standard was approved
in 2002
 The group is developing the MPEG-21 standard, which is
called the multimedia framework
 This group is also working with other standards related to
the use of audio and video standards mentioned, such as
the Intellectual Property Management Protection
(IPMP)
 MPEG is a member of the International Standards
Organization (ISO)

28. 1. MPEG 1 STANDARD
 Aims at the compression of audio and video images
previously digitized
 USES : Short video clips made available on the
Internet, video compact disks (VCDs), and videos
distributed on disks of the CD-ROM type use this
standard
 MP3 audio compression is layer 3 of the MPEG-1,
thus the acronym MP3
 Compression rate is variable and it’s possible to
reach a compression rate of 200:1

29. MPEG1 CONTINUED..
 With the maximum rate the images become
distorted, because the compression introduces
artifacts in the image
 It depends on the quality of the compression
algorithm and the compression rate used.
 Thus, most of the videos compressed with the
MPEG-1 use a compression rate lower than 50:1
 Even at this rate, the horizontal resolution obtained
after the compression is low, circa 320 lines, and
similar to the VHS format.
 The compression used is the multi frame type

30. MPEG-2 STANDARD
 MPEG-2 was developed in conjunction with the Video
Coding Experts group from the International
Telecommunications Union (ITU-T)
 Also known in the ITU-T community as H.262
 USES :DVDs and digital TV broadcasting use this standard,
which is more advanced than MPEG-1
 Produces better quality images
 The compression rate, just like in the MPEG-1, is variable
but normally values of around 40:1 are used

31. MPEG-2 ..CONTINUED..
 More efficient at compressing, without apparent quality loss,
than MPEG-1
 Demands higher computational effort in the process,
requiring more powerful hardware than that needed for
MPEG-1
 The horizontal resolution obtained after the compression is
superior to that of the VHS format
 Compression used is the multi frame type
 Assembling process of the group of pictures (GOP) used by
the multi frame technique, it is more complex to compress
MPEG-2 content than to retrieve it

32. 3. MPEG-4 STANDARD
 Standard created by the MPEG group for the
compression of audio and video images previously
digitized
 Used on videos transmitted by the Internet, as well
as on cell phones that use images
 Common on several standards of digital TV
broadcasting, especially HDTV in its advanced
video coding (AVC) version
 MPEG-4 accepts different profiles
 HDTV broadcasting systems use it as the encoding
standard, as an alternative to MPEG-2

33. Video
Quality
Compression
Ratio
Bandwidth
(bits/sec)
Motion JPEG
Broadcast 7–27 : 1 10 – 26 Mbps
MPEG-2 Broadcast/HDTV 30–100 : 1 3 – 16 Mbps
MPEG-1 VCR/Business 25–100 : 1 .5 – 4 Mbps
H.261/H.263 Video Conf 24–200 : 1 128 K – 1 Mbps
MPEG-4 Video Phone 50–1000 : 1 4.8 K – 64
Kbps

34. Spatial arrangement for mono, stereo,
Dolby surround, and surround 5.1 audio

35. ATSC DTV
Advanced Television Systems Committee, USA

36. INTRODUCTION
 ATSC stands for the Advanced Television Systems Committee,
which developed the standards for DTV used in the United
States (as well as in Canada, Mexico, and Korea)
 The principal standards comprise ATSC documents A/53 for
digital television and A/52 for AC-3 audio compression
 ATSC DTV signals are not compatible with NTSC
 One fundamental difference between digital ATSC and analog
NTSC television is that NTSC transmits complete pictures,
but the ATSC system effectively sends the pictures
broken down into many small parts, with a set of
instructions to put them back together again
 So, what is produced and seen in the studio may or may not
be exactly what all receivers produce, depending on how they
interpret the instructions
 This is the base for video compression

37. FEATURES
 8-VSB Modulation
 Transmitted bit rate
 FEC
 Cliff effect

38. 8-VSB MODULATION
 Type of Digital Modulation
 8-VSB is a special form of AM modulation using a
single carrier modulated to eight different amplitude
levels
 The carrier is modulated with a compressed
bitstream signal carrying all the information needed
for the channel
 This modulation occurs at the transmitter in a piece
of equipment called an exciter

39. 8-VSB MAIN SERVICE FUNCTIONAL BLOCK
DIAGRAM

40.  The compressed bitstream input to the DTV exciter
is processed and converted into digital symbols
 The output of the exciter is a series of pulses of
carrier wave, each with one of eight different
amplitude levels that are assigned to eight symbols
 These symbols are output at a rate of 10.76 million
every second.

41. TRANSMITTED BIT RATE
 Each symbol is able to carry 3 bits of digital data
 Therefore, the 10.76 million symbol per second output of
a DTV exciter can represent 10.76 * 3 = 32.28 Mbps
(megabits per second) of digital data
 It is important to understand that the “data” being
transmitted may represent video, audio, or other types
of ancillary data information
 Once in the bitstream, it is all referred to as data
 Information bit rate for an ATSC bitstream is 19.39 Mbps
but data rate coming out of a DTV exciter so much higher
than the actual data rate of the video, audio, and ancillary
information being broadcasted
 This is because of additional bits needed for forward
error correction ( FEC )

42. FEC-FORWARD ERROR CORRECTION
 Forward error correction (FEC) is used to make the signal more
robust and able to withstand distortions in the transmission path
 Multipath distortion is a common problem with over-the-air
television signals, caused when multiple signals from the same
transmitter arrive at the receiver at slightly different times
 There may also be various forms of interference such as lightning
strikes that create large RF noise pulses, which can affect
reception at great distances from the strike.
 Smaller RF pulses are created by electric motors, car ignition
systems, and many other things. All of these conditions can cause
data to be lost.
 The special error correction codes added to the DTV signal helps
receivers to fix problems with the received signal.
 In addition, DTV receivers have special circuitry called
adaptive equalizers to help cancel out the effects of unwanted
signals

43. CLIFF EFFECT
 With analog television, the received picture can be excellent
(in areas of strong signal reception), mediocre, exhibiting
“ghosting” and “snow” (in areas of marginal reception), or
unwatchable (in areas of poor reception)
 ATSC DTV pictures never display ghosts because, so long as
the receiver can decode the digital data that describes the
picture, it can reconstruct a nearly perfect picture
 However, under extreme conditions, with low received signal
strength and/or strong multipath interference echoes, the DTV
receiver may no longer be able to correctly decode the picture
(and/or the sound)
 In that case, the picture and/or sound disappear completely.
They go from perfect to nothing, with almost no intermediate
stage. This is known as the “cliff effect,” which is common to
many digital transmission technologies

44. ATSC COMPRESSED BITSTREAM
ATSC Data Stream

45. DESCRIPTION OF ATSC BITSTREAM
 The ATSC compressed bitstream, comprising digital
video, digital audio, and ancillary data, is known as
a transport stream
 This is created by the ATSC encoders and
multiplexer and delivered to the television station’s
transmitter at a rate of 19.39 Mbps
 The transport stream is made up of blocks of
compressed digital data, known as packets, which
carry video, audio, and ancillary data
 This is in contrast to the continuous stream of
analog information for an NTSC signal

46.  The ATSC packets contain 188 bytes of data, but the first
byte of each packet is used for synchronization, and an
additional three packets are used for management of the
bitstream, so 184 bytes are actually available for audio,
video, data, and PSIP (Program and System Information
Protocol Standard)
 For comparison with the 19.39 Mbps data rate of the
ATSC bitstream, the fastest broadband cable Internet
connection available for the home can download data at
about 5Mbps, whereas a dial-up 56kbps modem for a
personal computer has a data rate of only 0.056Mbps

47. ATSC VIDEO FORMATS

48. OTHER COMPRESSION SYSTEMS
 Although AC-3 (Audio Coding-3) is widely used for DTV, it
is by no means the only compression system for audio
encoding.
 Several other systems are widely used in radio and
elsewhere. These include an earlier Dolby system called
AC-2, also MPEG-1 layer 1, MPEG-1/2 layer 3 (usually
known as MP3), and the more recent MPEG AAC
(Advanced Audio Coding).
 The recent systems provide much higher audio quality at
lower bit rates. There are continuing developments, and
a technique called Spectral Band Replication (SBR)
further improves high-frequency audio response in low-
bit-rate applications

49. ADVANCED COMPRESSION SYSTEMS
 Recent developments in compression technology allow high
quality encoding with much greater efficiency than MPEG-2
 The AVC/H.264 system (developed in conjunction with MPEG)
and the VC-1 system (based on Microsoft Windows Media 9)
provide equivalent picture quality at about half the bit rate or
less.
 Such systems allow more programs to be transmitted in
less bandwidth.
 However, because of the necessity not to make existing DTV
receivers obsolete overnight, broadcasters must continue to
use the MPEG-2 standard for many years to come.
 Various proposals are under consideration to allow the new,
more efficient codecs to be used in some circumstances

50. THANK YOU