Introduction to CourseHardik Joshi 3 0 2 4 NA 0.6 Term Paper 0.4 11 0.75 0.25 19-08-2014 5. Special...
Transcript of Introduction to CourseHardik Joshi 3 0 2 4 NA 0.6 Term Paper 0.4 11 0.75 0.25 19-08-2014 5. Special...
-
Introduction to Course 2EC411 Digital Television
Engineering
Dr Usha Mehta
-
Syllabus
Calendar
Lesson Plan
Textbooks:
Modern Television Practice by R. R. Gulati, New
Age International Pub.
Digital Television by Herve Benoit, Third Edition,
Elsevier
Composite Satellite and Cable Television by R.
R. Gulati, New Age International Pub.
19-08-2014 2
-
Course Learning Outcomes
This course is being offered as a complete application/case study for
involving mostly all concepts related to electronics and
communication engineering. Upon completion of this course,
students will be able to:
Understand the concept of real signals like audio and video,
color signal and its effective conversion into electrical signal
Correlate the concept of preparation and processing of signal
required before transmission like amplification, modulation etc.
studied in earlier semesters with real life application.
Understand the concept of transmission and receiver and able
to prepare block level transmitter/receiver for given application.
Analyze various digitization methods/standards and their
effectiveness.
Select the necessary digitization standards for given application
Understand the concept of JPEG, MPEG, HDTV, TV over IP etc.
19-08-2014 3
-
Self Learning
Sr.
No. Topics
1 Recent Developments in Digital Television
Pl. refer: esaki.ee.boun.edu.tr/~morgul/Recent%20TV.pdf
2 Advances in TV/computer motion monitoring
Pl. refer:
http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=96082&url=htt
p%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Farnum
ber%3D96082
3 Pl. learn following topics from net and go through it in detail
Video-On-Demand
Picture-In-Picture Technology
Mirror TV
19-08-2014 4
http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=96082&url=http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber%3D96082http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=96082&url=http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber%3D96082http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=96082&url=http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber%3D96082http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=96082&url=http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber%3D96082http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=96082&url=http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber%3D96082http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=96082&url=http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber%3D96082http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=96082&url=http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber%3D96082http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=96082&url=http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber%3D96082http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=96082&url=http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber%3D96082http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=96082&url=http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber%3D96082http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=96082&url=http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber%3D96082http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=96082&url=http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber%3D96082http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=96082&url=http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber%3D96082http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=96082&url=http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber%3D96082http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=96082&url=http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber%3D96082http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=96082&url=http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber%3D96082http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=96082&url=http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber%3D96082http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=96082&url=http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber%3D96082http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=96082&url=http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber%3D96082http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=96082&url=http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber%3D96082http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=96082&url=http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber%3D96082http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=96082&url=http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber%3D96082http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=96082&url=http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber%3D96082http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=96082&url=http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber%3D96082http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=96082&url=http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber%3D96082http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=96082&url=http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber%3D96082http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=96082&url=http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber%3D96082http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=96082&url=http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber%3D96082http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=96082&url=http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber%3D96082http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=96082&url=http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber%3D96082http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=96082&url=http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber%3D96082http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=96082&url=http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber%3D96082http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=96082&url=http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber%3D96082http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=96082&url=http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber%3D96082http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=96082&url=http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber%3D96082http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=96082&url=http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber%3D96082http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=96082&url=http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber%3D96082http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=96082&url=http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber%3D96082http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=96082&url=http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber%3D96082http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=96082&url=http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber%3D96082http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=96082&url=http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber%3D96082
-
Assessment Methods
Course TERM ASSIGNMENT (TA) LPW
Subject
Code
Subject
Name
Course
Coordinato
rs
Faculty
Involved
L T P C
Assig
nmen
ts
2 class
Tests Special Assignment *
No. of
Practica
l
Conti.
Asset
Term
End
Exam
No. WT
Type of
Assignme
nt WT
WT WT
2EC41
1
Digital
television
Dr. Usha
Mehta
Prof.
Hardik
Joshi
3 0 2 4
NA 0.6
Term
Paper 0.4 11 0.75 0.25
19-08-2014 5
-
Special Assignment
Term Paper Topics 3D Television
Ambilight
Broadcast Flag
CableCARD
Digital Light Processing
Digital Right Managements
Digital Video Recorder
Direct Broadcast Satellite
DVD and HD-DVD
Blue Ray Disc
Flat Panel Display
High Definition Multimedia Interface
IP TV
Laser TV Display Technology
LCD Display
Morror TV
OLED TV
P2P TV
Pay-Per-View
Personal Video Recorder
Pixelplus: Digital Filter Image
processing technology
Picture-In-Picture
Plasma Display
Remote Control
Surface Conduction Electron Emitter
Display
Video On Demand
Ultra High Definition TV
Sling Box
Time Shifting
Web TV
Evaluation in Display Technology
History of television
Audiography
Audio Restoration
History of Sound Recording
Audio Engineering
19-08-2014 6
-
Introduction to Television
Dr Usha Mehta
-
Acknowledgement
This presentation has been summarized from
various books, papers, websites and
presentations on Television Engineering all
over the world. I couldn’t remember where
these large pull of hints and work come from.
However, I’d like to thank all professors and
scientists who created such a good work on
this emerging field. Without those efforts in
this very emerging technology, these notes
and slides can’t be finished
19-08-2014 8
-
What is Television?
Tele: Distance, a Greek prefix
Telegraph, telephone, teletex, telescope, telecast,
telecommunication……
Vision: to see, Latin word
From early days, mankind has a desire to
see the things of far away…
In Mahabharat, Dhutrashtra….
In real world, motion picture and then came
television
19-08-2014 9
-
What is Television…
It contains…..
Images - Black and White Shades of Grey
Colour - Hue & Saturation
Sound - Audio Information
Data - Teletext & Other Data
Synchronisation - Specifies the Timing
Transport System - Gets all above items to
your TV
19-08-2014 10
-
Let’s build our own TV Transmission-
Receiver System
19-08-2014 11
-
19-08-2014 12
-
Was it happened in History the same way
you think?
19-08-2014 13
-
History - Ferdinand Braun - CRT 1890 Ferdinand Braun developed the
Cathode Ray Tube.
1897 developed the Cathode Ray
Oscillograph, the precursor to the radar
screen and the television tube
1907 First use of cathode ray tube to
produce the rudiments of television images.
He shared the Nobel Prize for physics in
1909 with Guglielmo Marconi for his
contributions to the development of wireless
telegraphy
19-08-2014 14
-
John Logie Baird - Basic TV Oct 1923 John Logie Baird was the first
person anywhere in the world to
demonstrate true television in the form
of recognisable images, instantaneous
movement and correct gradations in light
and shade. Scanning was done mechanically with a Nipkow
disc. The first 30 line picture transmitted was a Maltese
cross.
1927 he also demonstrated video recording
1928 transatlantic television
1937 the broadcast of high definition colour pictures
1941 stereoscopic television in colour
1944 the multi-gun colour television tube, the forerunner of
the type used in most homes today 19-08-2014 15
-
Early Mechanical Approach to TV Mechanical Nipkow discs were used to scan the
image and reconstitute the image at the receiver.
PE cells were used to capture the image. The
problem was synchronising the disks
19-08-2014 16
-
30 Line Mechanical TV
19-08-2014 17
-
Electronic Television - Farnsworth
In 1922 at Age 14 Philo Farnsworth
had the idea of how to make Electronic
Television possible.
Sept. 7, 1927, Farnsworth painted a
square of glass black and scratched a
straight line on the centre. The slide
was dropped between the Image
Dissector (the camera tube that
Farnsworth had invented earlier that
year) and a hot, bright, carbon arc
lamp.
On the receiver they saw the straight-
line image and then, as the slide was
turned 90 degrees, they saw it move.
This was the first all-electronic
television picture ever transmitted.
19-08-2014 18
-
Vladimir Zworykin - Iconoscope
In 1923 Vladimir Zworykin of RCA made a patent application for a
camera device, and by 1933 had developed a camera tube he called
an Iconoscope. Although Zworykin submitted his patent application
first after many years of legal battle Farnsworth was acknowledged
as the inventor of electronic television.
By the end of 1923 he had also produced a picture display tube, the
"Kinescope“
19-08-2014 19
-
Significant Television Inventions
These inventions were the underlying basis of the
development of Television as we know it today
19-08-2014 20
-
Evolution 1857: Isolation of selenium by Bergelius
1873: Discovery of light sensitive property of Selenium
1884:Nipko’s Disk
1908: All Electronic TV system by A.A. Campbell
1923: Iconoscope by V. Zworykin
1926:TV transmission for members of Royal Institution
1928: Color Transmission
1930: Similar idea by Fransworth
After years of patent battles, Fransworth won but RCA (Radio
Corporation of America) bought ideas from both
1936: Britain strarted TV Program
1939: USA
1959:India
1982:Color TV in India 19-08-2014 21
-
Picture Transmission Picture info is optical and broken in “Pixels”
Ideally infinite pixels
Simultaneous pick-up of info is not possible so
scanning
With scanning, the problem of “Image Storage”
Energy conversion from optical to electrical form by
camera using scanning process
Photoelectric Effects
Photoemission
Photo conductivity
19-08-2014 22
-
Photoemission
Light is in the forms of bundles of energy
called photons
When these photons of light are bomarded
on certain metals, the electrons are
dislodged from the surface
Caesium Silver, Bismuth, Lithium etc
Photons are proportion to intensity of light
Iconoscope, Image Orthicone etc use this
principal
19-08-2014 23
-
Photoconductivity
The resistance of semiconductor material is
proportional to light incidenting on it.
Selenium, Antimony Trisulphide, Lead
oxide etc.
Vidicon, Plumbicon etc. use this effect
19-08-2014 24
-
Charge Coupled Device
A charge-coupled device (CCD) is a light-
sensitive integrated circuit that stores and
displays the data for an image in such a
way that each pixel (picture element) in the
image is converted into an electical charge,
the intensity of which is related to a color in
the color spectrum. CCDs are now
commonly included in digital still and video
cameras.
19-08-2014 25
-
In the absence of an external electric field the photo
generated hole and electron will quickly re-combine and be
lost. In a CCD an electric field is introduced to sweep these
charge carriers apart and prevent recombination.
19-08-2014 26
-
19-08-2014 27
-
Four Primary Functions
Charge Generation
Collection & storage
Charge transfer
Charge measurements
19-08-2014 28
-
19-08-2014 29
-
19-08-2014 30
-
19-08-2014 31
-
CMOS Sensor/Active Pixel Sensor
19-08-2014 32
photodiode
-
CCD
High quality
Low noise images
More matured devices
because of mass
production
CMOS
Because of large
number of transistors,
some of photons lost
and light sensitivity is
low
Lower quality,
resolution, sensitivity
Lower cost and longer
battery life
19-08-2014 33
-
Vidicon Camera Tube
19-08-2014 34
-
Colour Camera
19-08-2014 35
Partially silvered
-
Basic Monochrome
Television Transmitter
19-08-2014 36
-
Basic Monochrome
Television Receiver
19-08-2014 37
-
Elements of Picture Tube
19-08-2014 38
-
Elements of Color Picture Tube
19-08-2014 39
-
Display Technologies
Cathode Ray Tube (CRT)
Vacuum Florescent Display (VFD)
Field Emission Display (FED)
Flat Panel Display
Light Crystal Display (LCD)
Plasma Display Panel (PDP)
Rear projection/ front projection
Digital Light Processing DLPs
Organic Light Emitting Diode (OLED)
19-08-2014 40
-
19-08-2014 41
-
DLP
19-08-2014 42
-
How LCD Works
LCD Monitor Technique Animation.mp4
19-08-2014 43
LCD Monitor Technique Animation.mp4
-
19-08-2014 44
-
Geometric Form
Frame adopted is rectangle with Aspect
Ratio (Width/Height) = 4/3
Reasons: 1.Most of the motion occurs in horizontal plane
2.Eyes can view more easily and comfortably
3.For enabling direct television transmission of film programs
without wastage of any film area - Motion pictures use a
rectangular frame with width/height ratio of 4/3 – so
adopted this aspect ratio in TV
19-08-2014 45
-
Aspect Ratio
Not the actual size but aspect ratio of the
size of the picture produced on the receiver
screen and the picture being televised must
be the same.
achieved by setting the magnitude of the current
in the deflection coils to correct values both at
the TV camera and the receiving picture tube
19-08-2014 46
-
Various Aspect Ratio
4:3 => old TV and Computer Monitor
3:2=>classic 35mm movie in silent era
8:5=>credit card
5:3=>European wide screen
1.85:1=>US wide screen
2.39:1=>current wide screen
16:9=>HD video
19-08-2014 47
-
Aspect Ratio Comparison
19-08-2014 48
-
Why 16:9? Dr. Powers cut out rectangles with
equal areas, shaped to match each of
the popular aspect ratios. When
overlapped with their center points
aligned, he found that all of those
aspect ratio rectangles fit within an
outer rectangle with an aspect ratio of
1.77:1 and all of them also covered a
smaller common inner rectangle with
the same aspect ratio 1.77:1. The
value found by Powers is exactly
the geometric mean of the extreme
aspect ratios, 4:3 (1.33:1) and 2.35:1,
which is coincidentally close to 16:9
(1.77:1). Applying the same geometric
mean technique to 16:9 and 4:3 yields
the 14:9 aspect ratio, which is likewise
used as a compromise between these
ratios.
19-08-2014 49
http://en.wikipedia.org/wiki/Geometric_meanhttp://en.wikipedia.org/wiki/Geometric_meanhttp://en.wikipedia.org/wiki/Geometric_meanhttp://en.wikipedia.org/wiki/14:9http://en.wikipedia.org/wiki/14:9http://en.wikipedia.org/wiki/14:9
-
Synchronization
Same coordinated should be scanned at
any instant both by the camera tube beam
and the picture tube beam
achieved by transmitting synchronizing pulses
along with the picture information
19-08-2014 50
-
Image Continuity
Persistence of vision : sensation produced when
nerves of the eye’s retina are stimulated by incident
light does not cease immediately after the light is
removed but persists for about 1/16th of a second
Scanning rate is made greater than 16 per second
i.e. number of pictures shown per second is more
than 16 – hence our eye can able to integrate the
changing levels of brightness in the scene
Present day motion pictures – 24 still pictures of
the scene are taken per second and projected on
the screen at the same rate
19-08-2014 51
-
Scanning
19-08-2014 52
-
Horizontal Scanning
19-08-2014 53
Linear rise of current in the deflection coils deflects the beam across
the screen with a continuous uniform motion for the trace from left
to right .
At the peak of the rise, the saw tooth wave reverses its direction and
decreases rapidly to its initial value, producing the retrace or flyback
-
Vertical Scanning
19-08-2014 54
-
Because of the motion in the scene being televised, the
information or brightness at the top of the target plate or
picture tube screen normally changes by the time the beam
returns to the top to recommence the whole process. This
information is picked up during the next scanning cycle and
the whole process is repeated 25 times to cause an illusion of
continuity
During the horizontal and vertical retrace intervals, the
scanning beams at the camera tube and the picture tube are
blanked and no picture information is either picked up or
reproduced
Synchronizing pulses are transmitted during this period –
resulting in distortionless reproduction of the picture details
19-08-2014 55
-
No. of Scanning Lines Most scenes have brightness gradations in
the vertical directions
The ability of the scanning beam to allow
reproduction of electrical signals according
to these variations and the capability of the
human eye to resolve these distinctly (while
viewing) depends on the total number of
lines employed for scanning
Number of scanning lines is judged by
considering the bar pattern as shown
where alternate lines are black and white
19-08-2014 56
-
No. of Scanning Lines….. If the thickness of the scanning beam is equal to the width of
each black and white bar and the number of scanning
lines is chosen equal to the number of bars, then the
electrical information corresponding to the brightness of each
bar will be correctly produced during the scanning
process
Greater the number of lines, better will be the resolution
19-08-2014 57
-
Critical Viewing Distance
The total number of lines is limited by the resolving capability
of the human eye at the minimum viewing distance
19-08-2014 58
-
With reasonable brightness variation and
a minimum viewing distance of 4 times
the picture height (D/H = 4), the angle
that any two adjacent elements must
subtend at the eye for distinct resolution
is approximately one minute (1/60
degree)
19-08-2014 59
-
In practice, the picture elements are not arranged as equally
spaced elements but have random distribution of black, grey
and white depending on the nature of the picture details.
Analysis and tests suggests that about 70% of the total line
get separately scanned in the vertical direction and the
remaining 30% get merged with other elements due to the
beam spot falling equally on two consecutive lines (as shown
in figure)
Thus the effective number of lines distinctly resolved Nr = Nv × K
where K is the resolution factor whose value lies between 0.65 & 0.75
Assuming the value of k = 0.7; Nr = 860 × 0.7 = 602
19-08-2014 60
-
Other factors affecting choice of
No. of Scanning Lines
Improvement in resolution is not very significant with line
numbers > 500
Channel bandwidth increases with the increase in number of
lines
- cost of the system increases
- reduces the number of channels in a given VHF/UHF
transmission band
As a compromise between quality and cost, the total number of
lines (inclusive of those lost during vertical retrace) has been
chosen to be 625 in the 625-B monochrome TV system.
19-08-2014 61
-
Flicker
25 frames per second in television picture is not
rapid enough to allow the brightness of one picture
or frame to blend smoothly into the next during the
time when the screen is blanked between
successive frames
Produces flicker
Eliminated in motion pictures by showing each
picture twice – ie 48 views of the scene per second –
still the same 24 picture frames per second
ie each picture frame twice
It means more data to transfer with rapid speed
means more bandwidth may require……. 19-08-2014 62
-
Scanning
Progressive Interlaced
19-08-2014 63
-
Interlaced Scanning
19-08-2014 64
-
Pixel Aspect Ratio and Scanning
Progressive VS Interlaced Video Modes and
Pixel Aspect Ratio.mp4
19-08-2014 65
Progressive VS Interlaced Video Modes and Pixel Aspect Ratio.mp4Progressive VS Interlaced Video Modes and Pixel Aspect Ratio.mp4
-
Resolution
The ability of the image reproducing system
to represent the fine structure of an object
is known as its resolving power or
resolution.
19-08-2014 66
-
Vertical Resolution The extent to which the scanning system is
capable of resolving picture details in the
vertical direction is referred to as its vertical
resolution.
Vr = Na x K Na = No. of effective lines =625-40 (during retrace) =585
K=Kell’s factor, ratio between the number of lines of
resolution perceived and the number of pixels or TV scan
lines being used (across the same distance) taking into
account degradation that might occur in any or all steps
of the image reproduction process = 0.69 approx.
Vr = 585 X 0.69 = 400lines
19-08-2014 67
-
Horizontal Resolution
Aiming at equal vertical and horizontal
resolution and as such the number of
alternate black and white bars that should
be considered is equal to Na × aspect ratio =
585 × 4/3 = 780
But effective number of alternate black and
white segment = N = Na × aspect ratio × k =
585 × 4/3 × 0.69 = 533
19-08-2014 68
-
Bandwidth for Monochrome Signal To resolve the 533 squares or picture elements the scanning spot must
develop a video signal of square wave nature switching continuously along
the line between voltage levels corresponding to black and peak white.
Since along one line there are 533/2 ≈ 267 complete cyclic changes, 267
complete square wave cycles get generated during the time the beam takes to
travel along the width of the pattern.
Thus the time duration th of one square wave cycle is equal to
19-08-2014 69
-
Let’s try…..
The relevant data for a closed circuit TV system is given
below. Calculate the highest modulating frequency that will
be generated while scanning the most stringent case of
alternate black and white dots for equal vertical and
horizontal resolution.
No. of lines = 250
Interlace ratio = 1 : 1
Picture repetition rate = 50/sec
Aspect ratio = 4/3
Vertical retrace time = 10% of the picture frame time
Horizontal retrace time = 20% of the total line time
Assume resolution factor = 0.8
19-08-2014 70
-
Influence of number of lines on
bandwidth…
Effect of interlaced scanning on bandwidth
Effect of field frequency on bandwidth
Bandwidth requirement of transmitting
synchronization pulses…
19-08-2014 71
-
1080p (aka Full HD/ FHD and BT.709) is a
set of HDTV high-definition video modes
characterized by 1080 horizontal lines of
vertical resolution[1] and progressive scan,
as opposed to interlaced, as is the case with
the 1080idisplay standard. The term
usually assumes a widescreen aspect
ratio of 16:9, implying a resolution of
1920x1080 (2.1 megapixel) often marketed
as Full HD.
19-08-2014 72
http://en.wikipedia.org/wiki/Graphics_display_resolution#FHDhttp://en.wikipedia.org/wiki/BT.709http://en.wikipedia.org/wiki/High-definition_televisionhttp://en.wikipedia.org/wiki/High-definition_videohttp://en.wikipedia.org/wiki/High-definition_videohttp://en.wikipedia.org/wiki/High-definition_videohttp://en.wikipedia.org/wiki/Display_resolutionhttp://en.wikipedia.org/wiki/1080p#cite_note-1http://en.wikipedia.org/wiki/Progressive_scanhttp://en.wikipedia.org/wiki/Interlaced_videohttp://en.wikipedia.org/wiki/1080ihttp://en.wikipedia.org/wiki/Widescreenhttp://en.wikipedia.org/wiki/Aspect_ratio_(image)http://en.wikipedia.org/wiki/Aspect_ratio_(image)http://en.wikipedia.org/wiki/16:9http://en.wikipedia.org/wiki/Megapixel
-
Why odd no. of lines in interlaced
scanning?
Interlaced error
19-08-2014 73
-
Bandwidth for Colour signal
For a very small colour details, the eye can
perceive only its brightness, not its hue, so
large bandwidth is not required for colour
signal
Perception of colours by the eye is limited to
objects which result in a video frequency
output up to about 1.5 MHz.
19-08-2014 74
-
Brightness and Contrast
19-08-2014 75
-
Brightness: by adding/subtracting equal dc
value to each pixel
Contrast: by increasing/decreasing the
peak-to-peak amplitude or differences
between white and black level
19-08-2014 76
-
Luminance, Hue and Saturation Luminance/Brightness
Amount of light intensity as perceived by the eye
regardless of the color
Hue/tint
Predominant spectral colour of the received
light.
Different hue has different wavelengths of
spectral radiation
Saturation
The spectral purity of the colour light
An indication of how little the color is diluted by
white
19-08-2014 77
-
Hue, Saturation and Luminance
19-08-2014 78
-
Questions!!!!!
19-08-2014 79
Were you waiting for this slide to come???
-
Thanks!
19-08-2014 80