What is multimedia

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What is multimedia?

• Combining materials in many media- text, graphic
  art, sound, video and animation -,and delivering
  it via digital computer or other electronic
  means.
• 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.

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• Multimedia is media that utilizes a combination
  of different content forms. The term can be used
  as a noun (a medium with multiple content forms)
  or as an adjective describing a medium as having
  multiple content forms. The term is used in
  contrast to media which only utilize traditional
  forms of printed or hand-produced text and still
  graphics.In general, multimedia includes a
  combination of text, audio, still images,
  animation, video, and interactivity content forms.

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Extended multimedia

• Interactive multimedia Giving an end user some
  control over what elements to present and when.
• Hypermedia providing a linked structure through
  which a user can navigate through elements.

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Classifications of various media types I.

• 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

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Classifications of various media types II.

• Discrete vs. continuous media
• Discrete media spaced-based, media involve the
  space dimension only
• Continuous media time-based, media involves both
  the space and the time dimension

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Classification of Media Type
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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
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

Example of graphics (FIG file)
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Images

• 2D matrix consisting of pixels
• Pixelsmallest 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

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

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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

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Sound

• 1-D time-based signal

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Sound

• 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.

Image server
A scenario of multimedia networking
Internet
Video 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 640480, the
  pixel depth is 24, and the frame rate is 24 fps?
• Real-time property
• Continuous display
• 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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Technologies of Multimedia Networking

• Media compression reduce the data volume
• Image compression
• Video compression
• Audio compression
• Multimedia transmission technology
• Protocols for real-time transmission
• Rate and error control

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Multimedia Networking Systems

• Live media transmission system
• Capture, compress, and transmit the media on the
  fly
• 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

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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
Compressed Video
Streaming Server
Video Encoder
Internet
Compressed Video
Video Packets
Receiver
Video Decoder