Radio, TV, HDTV

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

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Modulation

• Amplitude modulation
• Frequency modulation
• Phase modulation

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TV in the US

• NTSC
• National Television Standards Committee
• Never Twice the Same Color
• 1930s standard for black and white TV
• 1950s standard for color TV

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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

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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 TVs
• 200 dots for VCRs

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Horizontal line

• Painted at the rate of
• 15,734 Hz
• 63.6 µSec

From Kelin Kuhns NTSC course slides
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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
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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

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What about those old buttons?

• Brightness
• Old monochrome signal
• Saturation
• Amplitude of the color signal
• Hue
• Phase of the color signals
• My old applet

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Line 21

• Dont waste the VBI!
• Use line 21 for
• Closed captioning
• V-chip
• XDS
• Time
• Station call letters
• Network

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Grand Alliance

• Prestigious list of members
• ATT, General Instrument, MIT, Philips, Sarnoff,
  Thomson, and Zenith
• Started in the late 80s
• Well behind the Japanese effort
• But digital won out over analog
• Grand Alliance HDTV Systems Specs

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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)

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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 its not same quality

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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

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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

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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?