Digital and High Definition Television

7/24/2019 Digital and High Definition Television

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Digital and HighDefnition

Television


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NTSC television system defcienci

Luminance resolutionis inadequate or large screen

Chromaresolutionis insucient in horizontal direct

!ider as"ect ratio !ould #e more suita#le or maty"es o "rogramming.

The interleaving o luminance and color signalsconserves #and!idth #ut causes intererence #et!t!o signals.


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NTSC television system defcienci

$nterlacing a""ears to lo!er the resolution or motionma&es the scanning'line structure more o#vious.


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$m"roved (erormance !ith theCurrent System

(ea&ing Circuit em"hasizes the high requencies inluminance signal !hich gives the illusion o greaterhorizontal resolution.

To achieve higher as"ect ratio !ith the system% e!scan lines can #e reduced. This is called letterboxin


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$m"roved (erormance !ith theCurrent System

Com# )iltering reduce intererence #et!een the lumand chroma signals.

$ncrease color resolution requires luma and chromasignals to #e se"arated.

*+. Connectio

monitor


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Digital and High'Defnition ,ideo

Digital television can #e transmitted !ith almost anresolution and as"ect ratio and !ith either interlacenoninterlaced scan.

*+. D,D uses a resolution o -/ #y 01/ "i+els%"rogressive scan !ith a rame rate o 0 or 2/ ram"er second.

Digital Television Transmission Standards


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(rogressive Scanning


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$nterlaced Scanning


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(i+el or "icture element is the smallest "ortion o a "icture thcan #e dis"layed.

(i+el as"ect ratio 3(45

Dis"lay resolution

Num#er o distinct "i+els in each dimension that can #e dis"

*+. 61/ + -/

Num#er o "i+els in one rame7 86%9// "i+els


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s"ect ratio is the ratio o the num#er o the horizo"i+els to the num#er o the vertical "i+els.

:itrate amount o data that are #eing used everysecond.

High #it rate high resolution

Lo! #it rate lo! resolution


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Frame rate% also &no!n as frame frequency% is the reqat !hich an imaging device dis"lays consecutive images c)rame rate is e+"ressed in rames "er second 3)(S5
https://en.wikipedia.org/wiki/Frequencyhttps://en.wikipedia.org/wiki/Frequency


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Digital *ncoding and Com"ression

)actors that needs to #e considered !hen creating divideos

4esolution

)rame 4ate

Num#er o #itsThe relative amount o color inormation com"ared

the luminance


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The num#er o luminance sam"les "er rame is equal the num#er o "i+els.

NPL=NVNH

!here NPL7 num#er o luminance "i+els "er rame

NV7 vertical resolution in "i+els

NH7 Horizontal resolution in "i+els

;$ each o the t!o color signal is one'ourth as theluminance signal% NPT76.


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4a! Data 4ate

fb= NPTmRf

Where fb= number of bit rate per second

NPT= number of pixels per frame, including both chroma and lpixels

m= number of bits per sample

Rf= frame rate in frames per second

01/ "i+els !ith a 2/ hertz rame rate and "rogressive


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01/ "i+els% !ith a 2/ hertz rame rate and "rogressiveluminance is sam"led using 1 #its "er sam"le. The tchannels also uses 1 #its "er sam"le% #ut the color rone'ourth that used or luminance. )ind the a""ro+imor this signal% neglecting synchronization% error corr

com"ression.

7 01/ + 90/ 7 "i+els

Since each o the color signals has one ourth the num#er o luma "i+e

7 09/.1>"i+els

7 09/.1+ > 1 > 2/ 7 110.6 Mb/s ans.


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@(*A ,ideo Com"ression3@otion (ictures *+"erts Arou"5

Standard #it rate or Terrestrial :roadcasting is 68.2@#Bs

ty"es o com"ression

6.5 Losslesscom"ression' reduces num#er o #its!ithout losing any data.

.5 @(*A com"ression 3losscom"ression5' !or&slargely #y discarding data that% !hile not entirelyredundant% is less im"ortant than the data retained.


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@(*A ,ideo Com"ression

@(*A com"ression #egins #y reducing the num#er#its required to transmit a reerence rame #y usingalgorithm called Discrete cosine transorm 3DCT5

@(*A is sometimes reerred to as motion (*A

(*A 3oint (hotogra"hic *+"erts Arou"%5

)urther com"ression can #e made #y ta&ing advano the act that not everything !ithin a ty"ical scenechanges rom rame to rame. *+. Ne!s re"ort


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Scenes !ith a great deal o motion does not really nto #e encoded !ith high resolution. *+. S"orts even


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Terrestrial Digital TelevisionTransmission

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Digital and High Definition Television