DIGITAL TV

3. Introduction to Digital Television
Analog television systems are severely limited by
the bandwidth they have available.
Simply put, additional subscription service require
additional bandwidth and if it is not available,
revenue growth is limited.
Digital Station
Analog Station
Ch. 6 Ch. 7 Ch. 8 Ch. 9 Ch. 10 Ch. 11 Ch. 12
6 Mhz 6 Mhz 6 Mhz 6 Mhz 6 Mhz 6 Mhz 6 Mhz

4. Why Digital Television?

5.  Crystal Clear Picture and Sound
Degradation of analog
Signal
ANALOG ANALOG
SIGNAL SIGNAL
Multi path distortion

6. Multicasting
 Instead of transmitting
a single program,
broadcasters can use
this digital signal to
transmit – on one
channel- at least four
programs in resolution
of today’s standard-
definition TV.
 This is known as the
Multicasting

7. Data Casting
 Digital Television also
has the ability to
broadcast data
simultaneously.
 This is called data
casting. It means you
will be able to use an
on-screen menu to
access additional
information about the
running program

8. Other Services
 Local channels, news and information about area,
Whether report, travel report, national news, home
shopping, games….
 Sports service-the latest results, interviews with
personalities, special offer
 Home banking, checking your balance, E-mail,
paying bill….etc
 In fact in the new world of Digital Television the
only limit on the range of available service will be
the imagination of the service providers.

9. Technical Background

10.  Y-Signal
 R-G-B- Camera output
 R-Y & B-Y Selection
 Weighting Factors
 R-Y V & B-YU
 U +V  QAM  C
 Y + C  Frequency
Interleaving
 Composite Colour
Video Signal

11. Digitization of Composite Colour Signal
 Video Signal Quantization  It has been practically verified
 Compression that sampling of the analog
video signal at 256 levels is
sufficient to allow the
reproduced signal to be almost
undetectable form the original
analog signal.
 An 8 bits code word is
necessary due to 256 levels.
 In the proposed coding scheme
for television signals, black level
corresponds to 64 (code
01000000) and peak white to
level 204 (code 11001100) as
labeled in the figure.

12. Compression
 Composite Video signal can be thought of
as an analog compression technique as it
allows colour in the same bandwidth as
monochrome.
 Whilst digital compression schemes do exist
for composite video, these effectively put
two compressors in series which is not a
good idea.
 So solution MPEG

13. Basic of Video Compression

14. MPEG and Video Compression

15.  The MPEG is the current standard used for
digital video. In this system, only the
difference between the current frame, and
the next frame is considered.
 Block matching algorithms are employed to
detect if an object has move in the scene.
 mathematical process called Discrete
Cosine Transform (DCT) is used to
compress the data.

16. Why MPEG?
 Two adjacent frames in a motion picture
sequence are usually very identical. Often the
only difference is that some parts of the picture
have shifted slightly between the frames.

17.  If the content of the current frame was mostly sent
in the previous frame, why send it again?
 Just send the instructions for shifting pieces of the
previous frame to their new position in the current
frame.
 If the pixel points in the same area are all very
nearly the same colour why send the same colour
over and over?
 Just send the colour for the whole area ones.

18. Video Compression Technique

20. Set-Top Box With conditional Access
System

22. Conclusion
 Digital television has several advantages over traditional TV, the most
significant being use of a smaller channel bandwidth. This frees up
space for more digital channels, other non-television services such as
pay-multimedia services and the generation of revenue from the sales
of frequency spectrum taken by analog TV. As digital becomes more
popular it is likely that the existing analogue services will be removed.
 The digital terrestrial set-top-box has been demonstrated at
Doordarshan Delhi by receiving the 5 TV programs and 2 Radio
channels on 516MHz channel frequency using Yagi antenna.
 In most 'digitalised' country, the switch-off of all analogue
terrestrial TV broadcasts is scheduled to begin in 2009.

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24. Thank You