Digital Video

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Digital Video

• COM 112 TV Production
• Skip Sparkman

2
Overview

• Basic Image Formation
• Primary Colors of Video
• What is Digital?
• Why Digital?

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See Key Terms on Text Page 46

• 480p 720p 1080i
• Analog binary digit compression
• Digital DTV field frame
• HDTV interlaced scanning
• Progressive scanning quantizing
• Refresh rate RGB sampling
• Scanning

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Basic Image Formation

• Principle of Image formation
• Picture tube scanning gun generates an
  electronic beam, guided through long neck of
  picture tube to scan thousands of dots on the
  face of the tube

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Basic Image Formation

• Electronic Dots Pixels
• TV Set Interlaced Scanning
• Computer Monitor Progressive Scanning
• TV Set NTSC National Television Standards
  Committee
• TV Set 525 scanning lines in 1/30 second
• Odd lines first 1/60 second 1 field
• Even lines second 1/60 second 1 field

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Basic Image Formation

• Interlaced scanning refers to the odd lines first
  scanned and the even lines scanned second.
• Each scan is a field
• Both scans are a frame

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Basic Image Formation

• Computer Screen is Progressive Scanning
• Each line is scanned in sequence
• It needs a refresh rate of at least 60 frames per
  second

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TV Scanning Rate

• TV is based on 1/30 and 1/60 second
• Scanning rate for camera and TV is 1/30 second
  per frame (1/60 second per field)
• Odd lines in 1/60th and even lines in 1/60th
• Full 525 lines in 1/30th
• Video tape is on same timing 30 frames per
  second.

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High Resolution Digital TV - DTV

• Uses both progressive and interlaced scanning
• Sharper and more easily compressed video

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High Resolution Digital TV - DTV

• 3 DTV systems
• 480p and 720p progressive scanning
• 1080i interlaced scanning

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Primary Video Colors

• RGB Red Green- Blue
• Primary Light colors
• Lens generated images begin with beam splitting
  into primary colors

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What is Digital

• Digital signals are binary code signals.
• on-off
• on 1
• off 0
• Binary digits bits

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Digital Analog Differences

• Analog signals fluctuate
• Digital signals are series of steps

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Digitizing an Analog Signal

• Sampling Checking points along the path from
  which to build a full frame
• High sampling rates more exact pictures

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Digitizing an Analog Signal

• Quantizing Building steps and checking how high
  or low each step is, relative to scale

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Why Digital?

• Quality of picture
• Compression and Signal Transport
• Effects and Picture Manipulation

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Quality

• Higher Resolution
• Better Colors
• Better Black and White Contrast
• No Deterioration in Generation

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Compression and Signal Transport

• Store more material in smaller space with little
  or no loss of quality
• Store material in very small space with some loss
• Speeds up signal transport (streaming)

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Effects and Picture Manipulation

• DVE Digital Video Effects are more flexible
  than analog effects
• Effects can be built and stored for easy recall
• Changes in size, shape, color and contrast are
  more easily accomplished

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Review Points

• NTSC frame is 2 scanning fields
• 30 frames per second (60 fields)
• Interlaced scanning is every other line in 1/60th
  second
• Progressive scanning is every line

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Review Points

• Digital Scanning Systems
• 480p - progressive
• 720p progressive
• 1080i interlaced
• 720p and 1080i are the legitimate High Definition
  TV systems (HDTV)

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Review Points

• Sampling Higher sampling rates mean better
  digital signals

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Review Points

• Compression Reducing digital information to be
  stored or transmitted by packing data into less
  space. High sampling lossless and Low sampling
  rate lossy compression.

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Key Concepts

• A standard television (NTSC) frame is made up of
  two scanning fields
• There are 30 frames (or 60 fields) per second

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Key Concepts

• In progressing scanning, each scanning cycle
  produces a complete frame. It needs a refresh
  rate of at least 60 frames per second.

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Key Concepts

• The established DTV scanning standards are 480p,
  720p, and 1080i

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Key Concepts

• All digital systems are based on the binary
  (on/off, either/or) principle.
• The on state is represented by a 1, and the
  off state by a 0.

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Key Concepts

• A high sampling rate is desirable in digitizing
  an analog signal.

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Key Concepts

• Compression eliminates redundant information to
  increase storage capacity and speed up signal
  transportation.

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