Matakuliah
Tahun
Versi
: T0553/Sistem Multimedia
: 2005
:5
Pertemuan 07
Video
1
Learning Outcomes
Pada akhir pertemuan ini, diharapkan mahasiswa
akan mampu :
• Menunjukkan Penggunaan Video pada Aplikasi
Multimedia
2
Outline Materi
•
•
•
•
•
•
•
Different Kind of Movies
Analogue Video
Digital Video
Compression Technique
Broadcast Video Standards
Digital Video Format
Using Digital Video
3
Different Kind of Movies
Movies from Film
Analog Video
Digital Video
4
Movie From Film
• Sequential image frames are recorded on film
using a light sensitive technology similar to still
photography.
• Film must be chemically developed
• Editing requires physically cutting and splicing
the film
5
Analogue video
• Video information that is stored using television video signals, film,
videotape or other non-computer media
• Each frame is represented by a fluctuating voltage signal known as
an analogue wave form or composite video.
• Composite analogue video has all the video components:
brightness, colour and synchronization
• Then, combined into one signal for delivery
• Usage : television
• Problems: colour blending, low clarity, high generation lost, difficult
to edit
6
Digital Video
• Digital video is the digitisation of analogue video signals
into numerical format
• It creates the illusion of full motion by displaying a rapid
sequence of changing images on a display device.
• Conversion from analogue to digital format requires the
use on an ADC (Analogue to Digital Converter)
• A Digital to Analogue Converter (DAC) can be used to
output digital video on analogue equipment
7
File Size Considerations
• Several elements determine the file size, in additional to the length
of the video. These including:
– Frame rate
• Number of images displayed within a specified amount of time to convey a
sense of motion
• Usually measured in frames per second
• Standard video movie  30 fps, movie film  24 fps
• Video digital  at least 15 fps
– Frame or Image size
• The width and height of each individual frame or image
• Determines the quality of the image displayed and the processing involved
to display that image
• Standard full screen resolution is 640x480 pixels
• Video screen display is one fourth the size of the full window screen
(320x240)
– Color depth/Resolution
• Number of colors displayed on the screen at one time
• Ranging from 1 bit to 8 bit, 16 or 24 bit per pixel
8
File Size Considerations
• Quality directly related to frame size, image size and color depth.
• Quality also depends on content. Motion picture needs higher frame
rate
File size = Frame Size x Frame Rate x Color Depth x Time
• Where:
–
–
–
–
Frame size = image size ( width x height in pixels)
Frame rate = frames per second
Color depth = measured in bytes
Time = time in seconds
This does not include any sound data !
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Compression techniques
• Since the size of raw digital video is so prohibitively large we need
some means to compress the information
• Video compression and decompression program, known as Codecs
• Lossy compression techniques cause some information to be lost
from the original image
– Redundant information
– Example: Image and video
• JPEG and MPEG
• Intraframe and Interframe
• Lossless compression techniques do not lose information
throughout the compression and decompression process
– Example use in text images
• Exactly same before and after compression
• Technique is identify repeating words and assign them a code.
• Decompression, the code would be changed back to the actual word.
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Digital video editing
• Analogue tape editing is a linear process
– To find the section you want, you may have to forward
or rewind the video tape
– To move a section to another place in the sequence
you have to either re-record the section onto another
tape or physically cut and splice the video tape
• Digital video editing can be non-linear process
– You can move sections around inside the computer
and play those sections back in any order
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Broadcast Video Standards
• NTSC
– North America, South
America, Japan
– 525 interlaced resolution
lines
– 30 frames per second (fps)
• PAL (Phase Alternate
Line)
• SECAM
– France, Russia
– 625 interlaced resolution
lines
– 25 frames per second (fps)
• HDTV
– Six different formats
– Aspect ratio is 16:9
– Australia, South Africa,
Europe
– 625 interlaced resolution
lines
– 25 frames per second (fps)
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Overscan
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Digital Video File Formats
• .MOV signifies Quicktime, an Apple standard. It is
playable on Macintosh and Windows machines.
• .AVI is a Microsoft standard that is playable on Windows
and Macintosh machines.
• .MPEG (.MPG) is playable on Unix and Windows
machines. Macintoshes can play MPEG, but may have
trouble with the audio track.
• .RM files are used by RealNetworks streaming. They are
playable on Windows, MacOS, and Unix computers.
• .ASF files are a Microsoft streaming format, and play on
Windows, MacOS, and Solaris.
• .WMV files are a Microsoft format used in Microsoft
MovieMaker
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MPEG video
• Named after the Moving Picture Experts Group
who devised the compression and file formats
• There are a number of MPEG formats:
– MPEG-2 is used for digital TV broadcasts and DVDs
– MPEG-1 is a format used for low quality video
(generally displayed on computers)
• MPEG-1 Layer 3 is the popular encoding mechanism for
MP3 audio files (more on this later in this course)
– MPEG-4 is a new format for multimedia presentations
• Can require separate hardware to decode higher
quality MPEG video data
15
MPEG compression example
A simple scene showing a car moving
across a desert landscape
Only the difference
between the current
and next frame needs
to be stored
This is called intraframe coding
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QuickTime
• Developed by Apple, Inc.
• Primarily for playback without
any hardware assistance
• Can achieve compression
ratios of 25 to 200:1
• The QuickTime format can
also store audio, graphics,
3D and text making it more
much versatile for multimedia
applications
17
Microsoft AVI
• Audio Video Interleave format
• Interleaving is a technique used to embed two or
more things into the same stream of information
• In every chunk of information you will find some
video data and some audio data
8, 16
or 24
bits
001001010010010101010011110101...
001001010010010101010011110101...
...
001001010010010101010011110101...
001001010010010101010011110101...
Video
information
Audio
information
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Consumer desktop video
• Typified by the Apple iMac DV computer
• IEEE 1394 or FireWire interface
• Digital camcorders
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How Video can be used effectively
• Showing physical procedures. Some uses are:
– Installing a board in a PC
– Adjusting engine timing
• Attracting and holding attention. Some uses are:
– Advertising products and services
– Teaching new skills to busy employees
• Presenting scenarios. Some uses are:
– Training technicians to respond to equipment malfunctions
– Demonstrating possible uses for a product
• Analyzing motion . Some uses are:
– Body motion to improve athletic performance
– Traffic patterns for transportation planning
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Advantages and Disadvantages
of using video
• Carefully planned, well-executed video clips can make a dramatic
difference in a multimedia project
• Use video only when all other methods (text, still images) are not
enough; don’t use it just because it’s possible
• Video adds visual impact to multimedia applications:
– Advantages
•
•
•
•
Captures interest
Increase retention
Clarifies complex physical actions and relationships
Can incorporate other media
– Disadvantages
•
•
•
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Is expensive to produce
Requires extensive memory and storage
Requires special equipment
Does not effectively illustrate abstract concepts and static situations
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