course 1 television and video systems fundamentals

8/19/2019 Course 1 Television and Video Systems Fundamentals

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Television & Video Systemand Technologies

Course 1: Television and Video Systems Fundame


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Objectives

Identify the basic human needs satisfied by TV and video system

Understand why and how TV and video systems came to being

Define the basic structure of a TV and video system

Enumerate the limitations of the human vision systems

Understand the sampling algorithm used by electronic vision sys


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Presentation Outline

The evolution of TV and video systems and technologies

The basic structure of a TV system

The exploitation of the human being’s limited vision system

Sampling for “vision” – frames, fields, lines, image rezolutio


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The evolution of TV & video systems

Why television ?


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Why television ?

SATISFIED NEED -> provides accessto relevant visual and audioinformation (e.g. people, animals,

places, objects, etc.) f rom one welldefined location in space and timeto another, different, well definedlocation in space and time (at mostin the “same” time)


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The [his]story

www.tvhistory

http://www.tvhistory.tv/http://www.tvhistory.tv/


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Data Aquisition Storage /

transmission Rendering

Video

sensor Encoding Decoding D


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The limits of human vision (I)

Visual acuity (in eng. also “acuteness” or “clearness” of vision

“measures the capacity of the

human eye to distinguish spatial details at a given distance”

e.g. different objects and shapes of same light intensity


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The limits of human vision (I)

Visual acuity (in eng. also “acuteness” or “clearness” of vision

α – whole screen viewing angle

β – separation angle

D – visualisation angleH – image/video height

i+1

i

1

2

H

n

β

more on this late

FROM EXPERIMENTAL CONCLUSIONS

-> D/H = 4 … 5

-> β ~ 1’ (1/60 of a degree)


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The limits of human vision (II)

Contrast sensitivity

“measures the capacity of the humaneye to distinguish details of differentobjects from their background based

on their difference in luminanceand/or colour ”

Y 0

Y Y+dY


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The limits of human vision (III)

Persistance of vision

“measures the capacity of thehuman eye to retain the“impression” made by the image

even after the image is gone”

-> linked to the perc

motion and image f


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Sampling for “vision”

continuous in time (t)the “seen” world

continuous in space (2D/3D)


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sampled in time (Δt)the “perceived” world

based on the persistence of

property of the human eye


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1 sample in time at (t) = 1 image (2D or 3D)

!!! 1 sample in time at (t) = 1 frame (in TV&video engi


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frames in time (Δt)the “perceived” world

sampled in space once (2D ->1D)

based on the acuity of vision

property of the human eye


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!!! 1 sample in 2D space at (y) = 1 line (in TV&video eng

the line is still continuous in

space along 1 dimension this is ANALO


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frames in time (Δt)the “perceived” world

sampled in space twice (2D ->1D -> …)

still based on the acu

property of the huma


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! 1 sample in 2D space at (y and x) = 1 pixel (in TV&video

this is DIGITA

and video


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Sampling for “vision” -> Ana

How many Frames ? -> from perception of vision

Frame rate = number of frames per se

Frame rate a.k.a. “vertical frequency ”

It is a frequency -> it is measured in H

Frame rate ~ 25 Hz (minimum)


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How many Lines (n) ? -> from the acuity of vision

Di+1

i

1

2

H

n

β

α/2

FROM EXPERIMENTAL CONCLUSIONS

-> D/H = 4 … 5

-> β ~ 1’ (1/60 of a degree)

=2 ∙

2 ∙

≈ 440 ÷ 660


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How are the lines ordered ? -> from technical availab

scanning = methods of “exploring the screen” and sepa

into lines (it is a process)


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progressive scanning = one line after the other

Start

Horizontal scanning

Horizontal blanking(Cursa inversă

pe orizontală)

Vertical blanking(Cursa inversă

pe verticală)

1

2

3

n


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interlaced scanning = 1 frame divided into 2 fields


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interlaced scanning

Even numbered lines go i

Odd numbered lines go in

-> number of lines shou


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interlaced scanning -> number of lines should

Start

Linia 1

câmp 1

Linia 2

câmp 1

Linia 312

câmp 1Prima jumătate

din Linia 313

câmp 1

A doua jumătate

din Linia 313

câmp 2

Linia 314

câmp 2

Linia 315

câmp 2

Linia 625

câmp 2


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Line issues (conclusions … first half XX century)

-> number of lines should be ODD!(depending on how much bandwidth is available)

-> number of lines should be more than ~ 440(depending on what is considered “optimal” for the D/H rati


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Conclusions

Identify the basic human needs satisfied by TV and video system

Understand why and how TV and video systems came to being

Define the basic structure of a TV and video system

Enumerate the limitations of the human vision systems

Understand the sampling algorithm used by electronic vision sys

course 1 television and video systems fundamentals

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