Transcript Multimedia Communication

Multimedia Communication
Video Terminology
CP586 © Peter Lo 2003
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Summary
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Examine analog video
Define terminology used in digital video.
Discuss digital video characteristics.
Compare two types of digital video compression
and define the term “key frame”.
List a variety of video standards.
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Analog Video
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Each frame of video is represented by a
fluctuating voltage known as an analog wave form.
A composite signal has brightness, colour and
synchronisation elements combined in the one
signal.
NTSC, PAL and SEACAM are the three most
widely used composite video signals.
CP586 © Peter Lo 2003
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Analog to Digital Video
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NTSC, PAL and SEACAM signals are analog
(wave based).
Computers store video in a digital format.
The process of digitising video is known as
capturing or sampling.
CP586 © Peter Lo 2003
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Terminology
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High Definition Television (HDTV)
Component video stores colour, brightness and sync
information as separate signals.
Generational loss occurs because the signal
deteriorates from one generation to the next.
Digital video is not subject to generational loss
because each copy is identical to the parent or
original.
CP586 © Peter Lo 2003
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Digital Video Characteristics
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Digital video consists of several frames displayed
in quick succession.
A frame has similar characteristics to that of a
digital image
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Frame Rate.
Frame size.
Colour depth or resolution.
CP586 © Peter Lo 2003
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Compression
Inter-frame compression
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This method of compression uses redundancy techniques to
remove repetition between frames.
This involves the use of a key frame.
Intra-frame compression
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This method of compression stores each individual frame
as a discrete image.
Each of these images are then compressed individually.
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Key Frame
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Inter-frame compression is perfect when there is a
limited amount of background action, for example
a video conference.
Video capturing software allows you to set the
number of Key frames.
Each subsequent frame of the digital video is
compared to the key frame and only the changes
are stored which reduces file size.
CP586 © Peter Lo 2003
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Computer Animation
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3DFX can be used to generate animation.
3DFX can create video file (.AVI) for your
assignment.
3DFX is based on an object orientated model. The
wire frame objects can be given properties, paths
and behaviours.
2D or Path animation can be created in ToolBook.
CP586 © Peter Lo 2003
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JPEG
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JPEG stands for Joint Picture Experts Group.
This standard was developed for still images and
has a compression rate of 20:1.
It can be used for intra-frame compression.
Files in this format have a .JPG or .JPEG
extension.
What type of compression (ie. Lossy or lossless)
does JPEG use?
CP586 © Peter Lo 2003
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MPEG
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Short for Moving Picture Experts Group, and
pronounced m-peg, a working group of ISO.
The term also refers to the family of digital video
compression standards and file formats developed
by the group.
Files in this format have a .MPG or .DAT
extension.
MPEG provides a 50:1 compression rate.
CP586 © Peter Lo 2003
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Video for Windows
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A format developed by Microsoft Corporation for
storing video and audio information.
Files in this format have a .AVI extension.
AVI files are limited to a 320 x 240 resolution, and
30 frames per second, neither of which is adequate
for full-screen, full-motion video.
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QuickTime
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The QuickTime video and animation system
developed by Apple Computer.
QuickTime is built into the Macintosh
operating system and is used by most Mac
applications that include video or animation.
Files in this format have a .MOV extension.
CP586 © Peter Lo 2003
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Real Video
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A streaming technology developed by Real
Networks for transmitting live video over the
Internet.
Real Video uses a variety of data compression
techniques.
Files in this format have a .RAM extension.
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ActiveMovie
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A new multimedia streaming technology
developed by Microsoft.
ActiveMovie is already built into the Internet
Explorer browser will be part of future versions of
the Windows operating system.
Supporting most multimedia formats, including
MPEG, ActiveMovie enables users to view
multimedia content distributed over the Internet,
an intranet, or CD-ROM.
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