The World of HD

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# The World of HD - PowerPoint PPT Presentation

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

Dr. Hayden So

Department of Electrical and Electronic Engineering

24 Oct, 2008

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
• 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?
• 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?
• 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
• Vs conventional Analog transmission
• Over-the-air transmission of HD content
• Began in Dec 31, 2007
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
• 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
• 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
• 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
• 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
• Given the right condition, HD does give better quality video