Radio, TV, HDTV CSCI ?? March, 2003

Electromagnetic waves Disturbance in the electric force field Characterized by either or –Frequency –Wave length

The Spectrum Radio/TV.5 to 220 Mhz Microwave~2.5 Ghz Infrared10 Thz Visible light10 15 hz X-ray10 15 hz Gamma rays

Allocations physical and political US frequency allocation TV frequencies Visible light The whole thing

Modulation Amplitude modulation Frequency modulation Phase modulation

TV in the US NTSC –National Television Standards Committee –“Never Twice the Same Color” 1930’s standard for black and white TV 1950’s standard for color TV

“Frames” New picture at Hz Divided into two frames –Avoid flicker but with serrations –Frame rate is Hz Picture size –480 lines –with several “vertical blanking lines”

“Resolution” Vertical resolution fixed by the frame size Horizontal resolution not so precise –In theory 425 horizontal dots per line –In practice 300 dots for older TV’s 200 dots for VCR’s

Horizontal line Painted at the rate of –15,734 Hz –63.6 μSec From Kelin Kuhn’s NTSC course slides

Color TV “One of the great electrical engineering triumphs was the development of color television in such a way that it remained compatible with black and white television.” Kelin Kuhn NBC Peacock

Adding color to the transmission Three signals –Y: the old monochrome signal R G B –I: orange-cyan signal R G B Mhz in-phase –Q: purple-green signal R G B Mhz 90° out-of phase

What about those old buttons? Brightness –Old monochrome signal Saturation –Amplitude of the color signal Hue –Phase of the color signals My old applet

Line 21 Don’t waste the VBI! Use line 21 for –Closed captioning –V-chip –XDS Time Station call letters Network

Grand Alliance Prestigious list of members –AT&T;, General Instrument, MIT, Philips, Sarnoff, Thomson, and Zenith Started in the late 80’s –Well behind the Japanese effort But digital won out over analog Grand Alliance HDTV Systems Specs

Scanning formats Interlaced –480i (704 by 480) –1080i (1920 by 1080 Choice of broadcasters? Progressive –480p (704 by 480) –720p (1280 by 720) Choice of cable? –1080p (1920 by 1080)

Channels and sub-channels Channels are Mbps Sub-channels allow several streams –Perhaps the same old channels But now the broadcasters have more channels! –Perhaps totally new programs –But it’s not same quality

Video Compression MPEG-2 –The faster the image changes, The fuzzier the picture can be –Types of frames I – Intra –Fairly complete image P – predicted –Differences from previous image B – backward prediction –Differences between past and future images

Macrocells 16x16 arrays of luminance –Not as much chrominance This can be varied to be “good enough” –Uses a Discrete Cosine Transform Just like JPEG Transmitted with Run-length coding –Reduces bits needed for repeated colors Simon Frasier CMPT 386 Multimedia Systems

Format of choice by 2006 Telecommunications Act of 1996 –Current TV license holders get new channels PBS field test, Charlotte 1994 WRAL – first experimental HDTV Current stations Will rabbit ears return?