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Video is the technology of electronically

capturing, recording, processing,

storing, transmitting, and reconstructing

a sequence of still images representingscene in motion.

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Working of video

1. When the light from an object passes througha video camera lens, that light is converted intoan electronic signal by a sensor calledCHARGE-COUPLED DEVICE(CCD).

2. Output of CCD is processed by camera into asignal containing three channels of color andsynchronization pulses.

3. The output of CCD is deal by the differentstandard of video, each dealing with theseparation of signal.

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If each channel of color information is

transmitted as separate signal on its ownconductor then the output is called RGB.

This the preferred method for higher quality

work and professional video work.

Output can be separate into two color

channels ,Cb/Cr and luma component

channel(Y),whish makes the dark and lightpart of video picture.

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In analog system

The video signal from the camera isdelivered to the video in connector of VCR,where it is recorded into magnetic videotape.

One or two sound channel are alsorecorded into the video tape.

The video signal is written into tape by

sppining recording head that changes thelocal magnetic properties of tapes surfacein a series of long diagonal stripes.

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Because the head is tilted at a slight angle

compared with the path of tape, it follows a

helical path, which is called HELICAL SCANrecording.

A single video frame is made up of two

fields that are interlaced and audio isrecorded into separate straight line track at

the top of video tape, sound is recorded

helical between the video tracks.

Audio trac

Video

track

Control track

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In digital systems, video signal from the

camera is first digitized as a single frame

and data is compressed before it is written to

the tape.

Video data

Audio

data

Sub code data

Track information

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Analog display standards

1. NTSC (National Television StandardsCommittee ):-

1. Used in united states, Canada, Mexico, Japan and

many other countries.

2. A system developed by National Television Standards

Committee used for displaying and broadcasting the

video.

3. According to NTSC standard , single frame of video

was made up of 525 horizontal scan lines.

4. scan lines drawn onto the inside face of phosphor-

coated picture tube every 1/30th of a second by a fast-

moving electron beam.

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The electron beam made two passes as

it drew a single video frame:- 1. first it laid down all the odd-numbered lines.

2. second all the even numbered lines.

At a rate of 60 per second .

These passes painted a field and the two fields

were then combined to create a single framesat a rate of 30 frames per second , is known as

INTERLACING.

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2.PAL(Phase AlternateLine)

This system used in united kingdom, westernEurope, Australia, south Africa, china and

south America.

PAL increase the resolution to 625 horizontal

lines.

But slowed the scan rate to 25 frames persecond.

The even and odd lines were interlaced,

each field taking 1/50th of a second to draw.

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3. SECAM (Sequential Colorand Memory) This system was used in France,

eastern Europe, and other countries.

SECAM is 625 line , 50 Hz system.

Different from both the NTSC and PAL

color systems in basic technology and

broadcasting method.

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4. ATSC DTV

Advance television standard committeedigital television

Started as HDTV then changed as ATVand finished as DTV.

It provide TV stations bandwidth topresent four or five standard television

signals or one HDTV signal.

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HDTV

Provide high resolution in a 16:9 aspect ratio. The broadcast industry has an ultra-high-

resolution 1920*1080 interlaced format while

the computer industry would like to settle on

1280*720 progressive-scan system forHDTV.

The 1920*1080 format provides more pixels

than the 1280*720 standard and the refreshrate is also different.

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Digital display standards

1. ATSC:-

Advance television system committee

Is the digital television standard for the

united states , Canada , Mexico, Taiwan

and South Korea.

Supports wide screen aspect ratio of

16:9 with images up to 1920* 1080pixels in size.

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2. DVB(digital video broadcasting):- Used mostly in Europe, where the standard

define the physical layer of a distribution

system.3. ISDB(integrated services digital

broadcasting):- Used in Japan to allow radio and television

stations to convert to digital format.

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Overscan :-

When an image broadcast larger than it fit onstandard TV screen this method is called

overscan.

Underscan:-While in computer screen image displayed in

smaller size and leaving a black border is

called understand.

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Video color

Color reproduction and display is

different between TV and monitors

because monitor uses RGB model.

NTSC TV uses a limited color palette,

restricted luminance and black levels.

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Color Models in Video

YIQ and YUV are the two commonlyused color models in video

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YUV Color Model

Initially, for PAL analog video, it is now also used inCCIR 601 standard for digital video Y (luminance) is the CIE Y primary. Y = 0.299R + 0.587G + 0.114B Chrominance is defined as the difference between a

color and a reference white at the same luminance. Itcan be represented by U and V -- the color differences.

U = B - YV = R - Y

If b/w image, then U = V = 0. --> No chrominance!

** In actual PAL implementation: U = 0.492 (B - Y)

V = 0.877 (R - Y)

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YCbCr Color Model

The YCbCr model is closely related to

the YUV, it is a scaled and shifted YUV.

Cb = ((B - Y)/ 2) + 0.5

Cr = ((R - Y) / 1.6) + 0.5

The chrominance values in YCbCr are

always in the range of 0 to 1.

YCbCr is used in JPEG and MPEG.

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YIQ Color Model

YIQ is used in NTSC color TV

broadcasting, it is downward compatible

with B/W TV where only Y is used.

Although U and V nicely define the colordifferences, they do not align with the

desired human perceptual color

sensitivities. In NTSC, I and Q are usedinstead.

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I is the orange-blue axis, Q is the purple-green

axis.

I and Q axes are scaled and rotated R - Y and B- Y (by 33 degrees clockwise).

I = 0.877(R - Y) cos 33 - 0.492(B - Y) sin 33Q = 0.877(R - Y) sin 33 + 0.492(B - Y) cos 33

I is the orange-blue axis, Q is the purple-green

axis.

I and Q axes are scaled and rotated R - Y and B

- Y (by 33 degrees clockwise).

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Digital video

For making a digital

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