Transcript prezentacija 16.6.2010-MilenaJocic

Conference: Digitization of
National Heritage,
June 16th 2010.
Analog to Digital TV
Transition in the Republic
of Serbia
M.Sc.E.E. Milena Jocić
Adviser, Department for
Telecommunications
Ministry of Telecommunications and
Information Society, Republic of Serbia
Television
• Commercially available since the late 1930s
• Television is more than popular in Serbia:
The average Serbian citizen spends
approximately six hours a day watching TV!
• Analog to digital TV transition we are
discussing about: only for terrestrial
platform!
Amazing thing about human
brain that makes television
possible:
If a still image is divided into small dots,
the brain will reassemble the dots into a
meaningful image
Pixel
On a TV screen, the small dots are
called pixels (picture element)
Resolution (number of pixels)
The most common resolutions of TV screen:
• 768x576 pixels (SD), generally signal is
broadcasted in 4:3 aspect ratio
• 1920x1080 pixels (HD), broadcasted in
16:9 aspect ratio
Another amazing thing about
human brain that makes
television possible:
If a moving scene is divided into a
sequence of still pictures and if the still
images are shown in rapid succession, the
brain will reassemble the still images into a
single, moving scene
It is possible because of HVS and HAS
Human Visual System (HVS) – characteristics of the
human visual system are not perfect and its
disadvantages are used in video compression:
Persistence of vision is a characteristic of the human
eye - light that reaches the eye remains in our
consciousness about a tenth of a second more
Human Auditory System (HAS) - characteristics of
the human auditory system are not perfect and its
disadvantages are used in audio compression
Why going digital?
•
•
•
•
better picture and sound quality
variety of contents
more radio and television programs
new services for users with disabilities and
for senior citizens
• enhanced additional services
• portable and mobile program reception
• convergence of services
Optical to analogue image conversion
Optical image
Electrical signal
Output voltage
Sky
Tree
Sky
Smoke
Branch
Scanned line
By scanning optical image, electrical signal is
formed, as an exact replica of an optical image
Optical to digital image conversion
Optical image
Line
Electrical signal
Output
voltage
Scanned line
Signal processing in digital technology consists of :
• Digitization (sampling, quantization)
• Compression
• Coding
Why compression?
Broadcasting of big amount of information
requires a large bandwidth:
• For analog TV - 5-6 MHz
• For digital TV - minimum 10 times of the
bandwidth for analog is needed
• That is why data compression is used
• Compression methods used in digital TV:
MPEG-2 and MPEG-4
• Serbia has chosen MPEG-4
Multiplexing
DVB
package
NP 1
NP 7
RP 1
MUX
maximum 14
programs
Distribution
RP ≤7
• In one DVB-T2 MUX, maximum 14 SD programs
• Distribution: primary and secondary
DVB package
•Box in which the data is stored
SI Service Information
PSI Program Specific Information
Video
Audio 1
Audio
Data
Audio 2
Teletext
Data
Why modulation?
• Modulated signal requires less power to
transmit and a smaller antenna due to the
higher frequency of the carrier wave
• In digital TV, digital modulations are used
• Digital modulation: an analog carrier
signal is modulated by a digital bit stream
Popular scheme for digital TV:
COFDM
• A large number of closely-spaced sub-carriers
are used to carry data
• Each sub-carrier is modulated with a
conventional modulation scheme (such as QAM
or PSK) at a low symbol rate, maintaining total
data rates similar to conventional single-carrier
modulation schemes in the same bandwidth
COFDM
time
RF channel
bandwidth
frequency
subband
frequency
time
segment
time
OFDM
symbol
frequency
Transmission standards in Europe:
DVB-T and DVB-T2
• DVB-T is used all around Europe, but DVB-T2 is spreading fast
Serbia has chosen DVB-T2. Why?
• DVB-T2 provides higher bit-rate within the same TV channel band,
comparing to DVB-T
• The owners of broadcasting equipment that use DVB-T2 standard
will benefit: DVB-T2 supports many programs content within one
multiplex
• DVB-T2 is compatible with IPTV
• Investments in the digitalization process in the Republic of Serbia
demand a great deal of financial means. Switch to a different
standard (from DVB-T to DVB-T2) would demand new investments
• DVB-T2 secures sufficient bit-rate for the needs of many HDTV
programs
• The application of DVB-T2 standard significantly increases digital
dividend
Switchover from analog to
digital TV broadcasting
• Serbia must switch-off the analog TV
signal before 17th June 2015
• Recommendation of the EC to the EU
member states: ASO until 2012
• Serbian decision: April 4th 2012!
Distribution network architecture
National headend
RHE
DVB-T2
NHE
IP/MPLS network
Regional headend
DVB-T2
RHE
SDTV
RHE
[email protected]