The World of HD Dr. Hayden So Department of Electrical and Electronic Engineering 24 Oct, 2008

Area You Ready?

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

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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  Digital Broadcast 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 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 x 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  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 Shuji Nakamura