# Discrete Mathematics Operating Systems Computer Networks

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# INTRODUCTION

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## Goals

– Almost anyone

### Prerequisites:

– Minimum: Have taken “Computer Networks” class

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## Outline of Introduction

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### Today’s Internet Video Traffic

Source: http://www.internetobservatory.net/

Cisco VNI 2011-2016: “Globally, Internet Video traffic will be 55% of all consumer traffic in 2016, up from 51% in

2011” [http://www.cisco.com/go/vni]

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## Various Media Types

### Captured vs. synthesized media

• Captured media (natural) : information captured from the real world (still image, video, audio)

• Synthesized media (artificial) : information synthesize by the computer (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,

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## Classification of Media Type

### Graphics

Captured

From real world

Synthesized

By computer

Discrete Discrete Continuo

us Continuous

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## audio

8

### by bits, e.g., 8 bits

quantized value of analog value

quantization error

sampling rate (N sample/sec)

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## audio

### kbps and up

time

quantized value of analog value

quantization error

sampling rate (N sample/sec)

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• video: sequence of images displayed at constant rate

– e.g. 24 images/sec

• digital image: array of pixels

– each pixel

represented by bits

• coding: use redundancy

within and between

images to decrease # bits used to encode image

– spatial (within image)

## video

………...…

spatial coding example: instead of sending N values of same color (all purple), send only two values: color value (purple) and number of repeated values (N)

………...…

frame i

frame i+1

temporal coding example:

instead of sending complete frame at i+1, send only differences from frame i

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## video

………...…

spatial coding example: instead of sending N values of same color (all purple), send only two values: color value (purple) and number of repeated values (N)

………...…

frame i

frame i+1

temporal coding example:

instead of sending complete frame at i+1, send only differences from frame i

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### audio, video

stored (at server): can transmit faster than audio/video will be rendered (implies

storing/buffering at client)

### voice/video over IP

– interactive nature of human-to-human conversation limits delay tolerance

– e.g., Skype

### audio, video

– e.g., live sporting event (futbol)

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## Networked Multimedia

### computers

• Sample applications: DVD

### the network

• Sample applications: videoconferencing, web video broadcasting, multimedia Email, etc.

Internet

Internet

Video server

Image server

A scenario of multimedia networking

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## Multimedia over Internet

# INTRODUCTION Slide 21

Music

Digital Photos

Intern et

E-mail

Video Clip

Attachment

Video

Conference VoIP

Wireless

Wireless

Browsing

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### Suitable for unexpected burst of data

• no need to establishing an explicit connection

### Limitation of bandwidth

• Bandwidth is shared statistically so data can be sent at any time

• Causing Queuing delay, especially when congested

### network

• IP network is not reliable

• cannot guarantee quality of multimedia applications

### Heterogeneity

• Different user requirements

• Different user network conditions

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## 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

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## System

Video Encoder

Input video Compressed

Video Streaming Server Video Display

Error control, rate control can be done here to improve QoS

Error control, provide feedback to the sender

Compressed Video

Video Packets

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