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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

The World of HD

Dr. Hayden So

Department of Electrical and Electronic Engineering

24 Oct, 2008

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

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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