The world of hd
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The World of HD. Dr. Hayden So Department of Electrical and Electronic Engineering 24 Oct, 2008. Area You Ready?. What does HD really mean?. H igh D efinition Full HD 1080p 1920 x 1080 pixels + progressive scan PAL: 768x576 Supposedly higher quality video, TV.

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The World of HD

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The world of hd

The World of HD

Dr. Hayden So

Department of Electrical and Electronic Engineering

24 Oct, 2008


Area you ready

Area You Ready?


What does hd really mean

What does HD really mean?

  • High Definition

  • Full HD 1080p

  • 1920 x 1080 pixels + progressive scan

    • PAL: 768x576

  • Supposedly higher quality video, TV

More Pixels = Higher Quality?


Three characteristics of display

Three Characteristics of Display

  • Panel Size

    • The physical dimension of the panel

    • A 42” panel has a diagonal measurement of 42”

  • Display Resolution

    • The number of picture-elements (pixels) along each X-Y direction

    • In a HD panel: 1920 x 1080 pixels

  • Dot Pitch

    • The distance between two pixel of the screen

Panel Size = Display Resolution * Dot Pitch


More pixel good

More Pixel = Good?

  • Human eye can identify 120 pixels per degree of visual arc

    • i.e. if 2 dots are closer than 1/120 degree, then our eyes cannot tell the difference

  • At a distance of 2m (normal distance to a TV) our eyes cannot differentiate 2 dots 0.4mm apart.

  • Closer to TV => easier to differentiate pixels

  • Far away => cannot tell the difference

screen

Minimum: 2 arc minute


The world of hd

Image courtesy of www.carltonbale.com


Why is hd difficult

Why is HD difficult?

  • One major problem is bandwidth

    • The amount of video data needed to be processed for each frame

  • HD:1920 x 1080 x 50 Hz x 24 bits = 2.48 Gb/s

  • PAL (progressive, digital)768 x 576 x 25 Hz x 24 bits = 133 Mb/s

  • 10x more data needed to be processed, stored


Hdtv transmission

HDTV Transmission

  • Digital Broadcast

    • Vs conventional Analog transmission

  • Over-the-air transmission of HD content

  • Began in Dec 31, 2007


Dtt in hong kong

DTT in Hong Kong

  • DTMB – Digital Terrestrial Multimedia Broadcast

    • (formerly DMB-T/H)

  • Same as mainland China

    • Different from rest of the world

  • Two standards

    • MPEG-2 for Standard Definition TV - Basic

    • H.264 for HDTV – Higher-tier

  • Higher-tier supports full H.264 + interactive


Storing and playing hd movies

Storing and Playing HD Movies

  • DVD was not capable

    • The standard

    • Physically infeasible

  • A double-layer DVD-9 can store around 8 GB of data ~= 4 hours of PAL video compressed using MPEG2

    • 720 x576 @ 25 fps, < 10 Mbps variable video bitrate

  • About 2 hours on a DVD-5

  • Using the same encoding for HD video 1080p24 requires ~5 times the storage

Need new storage + new encoding


Blu ray discs

Blu-ray Discs

  • Next generation DVD

    • Same form factor

  • New Storage

    • Single side: 25 GB

    • Double side: 50 GB

  • New encoding

    • Uses MPEG2 or H.264/AVC

    • Using MPEG2: 2 hours on single side

    • Using H.264/AVC: ~4 hours single side, 8 hours DL


Enabling technology

Enabling Technology

  • Blue-violet laser

  • Blu-ray uses violet 405nm laser

    • DVD: 650nm near infrared

    • CD: 780nm

  • Shorter wavelength allows more information to be stored per unit area

  • Why not use it in DVD?

    • It was very expensive to produce blue laser

    • Until him…


Story of shuji nakamura

Story of Shuji Nakamura

  • A research scientist at Nichia Chemical Industries Ltd. in Tokushima, Japan

  • Graduated with a PhD but decided to stay in Tokushima, instead of Tokyo, to raise his child

  • A research team that shrinks from 3 people in 1979 down to 1 in 1991

  • Invented the world’s first commercially viable blue-violet solid state laser diode

    • Beat all major research universities

    • Beat all big companies: RCA and Hewlett-Packard to Matsushita and Sony


Summary

Summary

  • Given the right condition, HD does give better quality video

  • Over the air broadcast is achieved through digital broadcasting

    • Need new equipments

  • For stored video, Blu-ray is the next standard

  • Blu-ray was only made possible by discovery of ShujiNakamura


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