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Understanding HDTV: The Evolution of Electromagnetic Waves and Television Standards

This detailed overview explores the complexities of electromagnetic waves and television standards, focusing on HDTV development from NTSC to modern formats. It highlights frequency allocation, modulation techniques, picture frame rates, and resolution. The discussion includes advancements in color television, closed captioning, and the role of the Grand Alliance in promoting digital over analog systems. Learn how video compression methods such as MPEG-2 and the telecommunications act of 1996 shaped current broadcasting landscapes, paving the way for new channels and enhanced viewing experiences.

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Understanding HDTV: The Evolution of Electromagnetic Waves and Television Standards

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  1. Radio, TV, HDTV CSCI 107 19-?? March, 2003

  2. Electromagnetic waves • Disturbance in the electric force field • Characterized by either or • Frequency • Wave length

  3. The Spectrum

  4. Allocationsphysical and political • US frequency allocation • TV frequencies • Visible light • The whole thing

  5. Modulation • Amplitude modulation • Frequency modulation • Phase modulation

  6. 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

  7. “Frames” • New picture at 29.97 Hz • Divided into two frames • Avoid flicker • but with serrations • Frame rate is 59.94 Hz • Picture size • 480 lines • with several “vertical blanking lines”

  8. “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

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

  10. 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

  11. Adding color to the transmission • Three signals • Y: the old monochrome signal • 0.299 R + 0.587 G + .114 B • I: orange-cyan signal • 0.596 R - 0.275 G - .321 B • 3.579545 Mhz in-phase • Q: purple-green signal • 0.212 R - 0.523 G + .311 B • 3.579545 Mhz 90° out-of phase

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

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

  14. 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

  15. 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)

  16. Channels and sub-channels • Channels are 19.39 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

  17. 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

  18. 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

  19. 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?

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