Analog to DigitalAnalog to Digital TV TV Transition Transition in the Republic in the Republic
of Serbiaof Serbia
Conference: Digitization of Conference: Digitization of National Heritage, National Heritage,
June 16June 16thth 20201010..
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
By scanning optical image, electrical signal is formed, as an exact replica of an optical image
Optical image
Output voltage
Scanned line
SkyTree
Sky Smoke
Branch
Electrical signal
Optical image
LineOutput voltage
Scanned line
Signal processing in digital technology consists of :
• Digitization (sampling, quantization) • Compression• Coding
Optical to digital image conversion
Electrical signal
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
NP 1
NP 7
RP 1
RP ≤7
MUXmaximum 14
programs
Distribution
• In one DVB-T2 MUX, maximum 14 SD programs
• Distribution: primary and secondary
DVB package
DVB package
Data
Audio 1
Audio 2
Video
Audio
Data
Teletext
Data
Data
Radio
Radio
TV
TV
SI Service Information
PSI Program Specific Information
•Box in which the data is stored
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
frequency
OFDMOFDMsymbol
time
frequency
RF channel bandwidth
frequencysubband
timesegment
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
IP/MPLS networkIP/MPLS network
NHE
DVB-T2
DVB-T2
SDTV
RHE
Regional headend
RHE
RHE
NationalNational headend headend
[email protected]@mtid.gov.rs