1 revision. 2 multimedia systems 2 lecture 1 - introduction to multimedia lecture 2 - perception...

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RevisionRevision

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Multimedia Systems 2Multimedia Systems 2 Lecture 1 - Introduction to Multimedia Lecture 2 - Perception (Light and colour, true and palette colour) Lecture 7 - Image Formats (vector/bitmap, GIFF, JPEG etc.) Lecture 3/4 - The Internet & Networked Multimedia Lecture 5 - The World Wide Web Lecture 6 - Web Pages Lecture 8 - Digital Video (MPEG) Lecture 9 - Streaming Video Lecture 10 - Multimedia Design Lecture 11 - Video Displays Lecture 12 - Display Adapters Lecture 13 - Graphics Lecture 14 - 3D Graphics Accelerator Cards & APIs Lecture 15 - Communications Theory

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PerceptionPerception

Electromagnetic spectrum

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Colour Sources/DisplaysColour Sources/Displays

TypesActive sources - monitorsPassive sources - printed documents

Primary Colours (RGB,CMY)

Principle of Operation

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Colour Models Colour Models

Colour GamutHuman Colour SensitivityOther Colour Models

HLSHSV

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True Colour Image Data Model

True Colour Image Data Model

Y

X

Pixel

Image

R G B

Colour

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Palette Colour Image Data Model

Palette Colour Image Data Model

Y

X

Pixel

Image

Index

R G B

Palette

R G B

Colour

165 16 49

R G B

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True colour Vs. Palette colour

True colour Vs. Palette colour

True Colour:High qualityExpensive hardwareRequire more memory (normally 3 times)

Palette ColourLimited number of coloursCheap hardwareEnables easier implementation of certain

techniques

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Image FormatsImage Formats

Two principle methods of representing graphical dataVectorsBitmaps (raster or pixel maps)

• Lossless Compression

• Lossy Compresion

Advantages/Disadvantages

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Graphics Interchange Format (GIF)

Graphics Interchange Format (GIF)

Advantages/DisadvantagesFile FormatFunction of each sectionAnimatedTransparent

GIF Signature

Screen Descriptor

Image Descriptor

Global Colour Map

Local Colour Map

Image Data

GIF Terminator

Repeated 1 to n times

Identifies GIF and format

GIF87A or GIF89A

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Joint Photographic Experts Group

Joint Photographic Experts Group

JPEGAdvantages/DisadvantagesJPEG stagesApproximate compressionProblems of over-compression

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The Internet & Networked Multimedia

The Internet & Networked Multimedia

Interconnected set of networks Design principles

Interoperability Uniform naming and addressing Layering SimplicityEnd-to-end protocols

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Uniform naming and addressing

Uniform naming and addressing

The IP 32-bit addressing structure139.184.14.13

Domain Name Servers (DNS)PurposeFunctionDNS process

Domain Names IP addresses

Classes

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LayeringLayering

Reason for using layered systemFunction of each layer

Application Layer (e.g. HTTP, SMTP)

Transport Layer (TCP, UPD)

Physical Layer (e.g.Ethernet)

Network Layer (IP)

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Internet ProtocolInternet Protocol

The main functions of IP IP Datagrams and packets in general

Datagram structureIP SecurityRouters

M

Version Header Length Type of service

Total Length

Identification

Fragment OffsetD

Time-to-live Protocol

Source IP Address

Header checksum

Data (<=64kB)

Options

Destination IP Address

Header

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Transmission Control Protocol (TCP)

Transmission Control Protocol (TCP)

What does it provide that IP doesn’t?PurposeOperation

TCP connection set-up

Source port

Destination port

Sequence Number

Acknowledgement Number

Data

Urgent Pointer

Data offset

Reserved Flags

Window

Checksum

Header

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Web PagesWeb Pages

StaticHTMLSHTML

DynamicNSFASPPHPCGI

Server side and Client side scripting

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Digital VideoDigital Video

Moving Picture Experts Group MPEG2OperationCompression

I B B P B B P B B I

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Video DisplaysVideo Displays

Display technologyCathode Ray TubeFlat panel displays

• Liquid Crystal (LCD)

OperationAdvantages/Disadvantages

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General operation Function of:

Electron gunsPhosphors Raster scanShadow mask /

Aperture grill

Colour CRT DisplaysColour CRT Displays

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CRT DisplaysCRT Displays

Dot pitchResolutionScanning

InterlacedNon-interlacedFrame/ Refresh rateScan rateDot clock

Screen sizesScreen Curvature

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Colour Liquid Crystal Displays

Colour Liquid Crystal Displays

Light source ReflectedGenerated

• backlit• edgelit

Operation of a Colour LCDNematic TechnologyPassiveActive

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GraphicsGraphics

2D GraphicsVectorBitmap

3D GraphicsCoordinate system X,Y,Z Geometry dataTexture dataDefining 3D objectsGraphics Pipeline

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Defining 3D ObjectsDefining 3D Objects

Objects in the 3D scene and the scene itself are transformed through five spaces when proceeding through the 3D pipelineModel SpaceWorld SpaceView SpaceClip SpaceScreen Space

Function of each

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View Frustrum and ClippingView Frustrum and Clipping

View frustrumPurposeOperation

ClippingPurposeOperation

Perspective divide

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Graphics PipelineGraphics Pipeline

Purpose and OperationStages

Application/SceneGeometry

• Translation

• Rotation

• Scaling

• Skewing

Triangle Set-upRasterization / Rendering

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FinFin

Fin