EE442—Multimedia Networking
Jane Dong
California State University, Los Angeles
Part I
Introduction to Multimedia Networking
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Overview
What is Multimedia?
Characteristics of multimedia
Various media types
What is Multimedia networking?
User requirements of multimedia applications on the
network
Technologies associated with multimedia networking
Overall structure of multimedia networking
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What is multimedia?
Definition of multimedia
Hard to find a clear-cut definition
In general, multimedia is an integration of text, graphics, still and
moving images, animation, sounds, and any other medium where
every type of information can be represented, stored, transmitted
and processed digitally
Characteristics of multimedia
Digital – key concept
Integration of multiple media type, usually including video or/and
audio
May be interactive or non-interactive
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Various Media Types
Text, Graphics, image, video, animation, sound, etc.
Classifications of various media types
Captured vs. synthesized media
Captured media (natural) : information captured from the real world
Example: still image, video, audio
Synthesized media (artificial) : information synthesize by the
computer
Example: text, graphics, animation
Discrete vs. continuous media
Discrete media: spaced-based, media involve the space dimension
only (Text, Image, Graphics)
Continuous media: time-based, media involves both the space and the
time dimension (Video, Sound, Animation)
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Classification of Media Type
Sound
Video
Animation
Continuous
Continuous
Text
Image
Discrete
Discrete
Captured
From real world
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Graphics
Synthesized
By computer
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Text
Plain text
Unformatted
Characters coded in binary form
ASCII code
All characters have the same style and font
Rich text
Formatted
Contains format information besides codes for characters
No predominant standards
Characters of various size, shape and style, e.g. bold, colorful
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Plain Text vs. Rich Text
An example of Plain text
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Example of Rich text
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Graphics
Revisable document that retains structural information
Consists of objects such as lines, curves, circles, etc
Usually generated by graphic editor of computer programs
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Example of
graphics (FIG file)
0
-5
-10
4
2
4
2
0
0
-2
-2
-4
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Images
2D matrix consisting of pixels
Pixel—smallest element of resolution of the image
One pixel is represented by a number of bits
Pixel depth– the number of bits available to code the pixel
Have no structural information
Two categories: scanned vs. synthesized still image
Digital still image
Computer
software
Synthesized
image
Capture and
A/D conversion
Scanned
image
Camera
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Images (cont.)
Examples of images
Binary image – pixel depth 1
Gray-scale – pixel depth 8
Color image – pixel depth 24
Gray-scale
colorimage
image
Binary image
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Graphics vs. Image
Graphics
Revisable documents
Document format retains structural information
Semantic content is preserved in presentation
Described as objects
Images
Not revisable
Document format is unaware of any structural information
Semantic content is NOT preserved
Described as bitmaps formed of individual pixels
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Video vs. Animation
Both images and graphics can be displayed as a succession
of view which create an impression of movement
Video – moving images or moving pictures
Captured or Synthesized
Consists of a series of bitmap images
Each image is called a frame
Frame rate: the speed to playback the video (frame per second)
Animation – moving graphics
Generated by computer program (animation authoring tools)
Consists of a set of objects
The movements of the objects are calculated and the view is
updated at playback
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Sound
1-D time-based signal
0. 2
0. 15
0. 1
0. 05
0
-0. 05
-0. 1
-0. 15
-0. 2
0
100
200
300
400
500
600
700
800
900
1000
Speech vs. non-speech sound
Speech – supports spoken language and has a semantic content
Non-speech – does not convey semantics in general
Natural vs. structured sound
Natural sound – Recorded/generated sound wave represented as
digital signal
Example: Audio in CD, WAV files
Structured sound – Synthesize sound in a symbolic way
Example: MIDI file
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Networked Multimedia
Local vs. networked multimedia
Local: storage and presentation of multimedia information in
standalone computers
Sample applications: DVD
Networked: involve transmission and distribution of multimedia
information on the network
Sample applications: videoconferencing, web video broadcasting,
multimedia Email, etc.
A scenario of multimedia networking
Video server
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Image server
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Consideration of Networked Multimedia
Characteristics of multimedia information
Large data volume
Exercise: What is the size of a video clip of 60 minutes if the frame
size is 640*480, the pixel depth is 24, and the frame rate is 24 fps?
Real-time property
Continuous display
Delay requirement of multimedia applications
Properties of current Internet
Limitation of bandwidth
Best effort network, cannot guarantee quality of multimedia
applications
Heterogeneity
Different user requirements
Different user network conditions
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Consideration of Networked Multimedia
Requirements of multimedia applications on the network
Delay requirement
Quality requirement
Satisfactory quality of media presentation
Synchronization requirement
Continuous requirement (no jerky video/audio)
Can tolerant some degree of information loss
Challenges of multimedia networking
Conflict between media size and bandwidth limit of the network
Conflict between the user requirement of multimedia application
and the best-effort network
How to meet different requirements of different users?
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Technologies of Multimedia Networking
Media compression – reduce the data volume
Address the1st challenge
Image compression
Video compression
Audio compression
Multimedia transmission technology
Address the 2nd and 3rd challenges
Protocols for real-time transmission
Rate / congestion control
Error control
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Multimedia Networking Systems
Live media transmission system
Capture, compress, and transmit the media on the fly (example?)
Send stored media across the network
Media is pre-compressed and stored at the server. This system
delivers the stored media to one or multiple receivers. (example?)
Differences between the two systems
For live media delivery:
Real-time media capture, need hardware support
Real-time compression– speed is important
Compression procedure can be adjusted based on network conditions
For stored media delivery
Offline compression – better compression result is important
Compression can not be adjusted during transmission
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Generic Media Streaming System
Input video
Compressed
Streaming
Video
Video
Server
Encoder
Internet
Error control, rate
control can be done
here to improve QoS
Compressed Video
Video Display
Video
Decoder
Receiver
Video Packets
Error control, provide
feedback to the sender
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