Multimedia_Chuong123_BKHN doc

4/2/2003 Nguyen Chan Hung– Hanoi University of Technology 1

Multimedia Technology

n Overview

q Introduction

q Chapter 1: Background of compression techniques

q Chapter 2: Multimedia technologies

n JPEG

n MPEG-1/MPEG -2 Audio & Video

n MPEG-4

n MPEG-7 (brief introduction)

n HDTV (brief introduction)

n H261/H263 (brief introduction)

n Model base coding (MBC) (brief introduction)

q Chapter 3: Some real-world systems

n CATV systems

n DVB systems

q Chapter 4: Multimedia Network

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Introduction

n The importance of Multimedia technologies: ‡ Multimedia everywhere !!

q On PCs:

n Real Player, QuickTime, Windows Media.

n Music and Video are free on the INTERNET (mp2, mp3, mp4, asf, mpeg,

mov, ra, ram, mid, DIVX, etc)

n Video/Audio Conferences.

n Webcast / Streaming Applications

n Distance Learning (or Tele-Education)

n Tele-Medicine

n Tele-xxx (Let’s imagine !!)

q On TVs and other home electronic devices:

n DVB-T/DVB-C/DVB-S (Digital Video Broadcasting –

Terrestrial/Cable/Satellite) ‡ shows MPEG-2 superior quality over

traditional analog TV !!

n Interactive TV ‡ Internet applications (Mail, Web, E -commerce) on a TV !!

‡ No need to wait for a PC to startup and shutdown !!

n CD/VCD/DVD/Mp3 players

q Also appearing in Handheld devices (3G Mobile phones, wireless PDA) !!

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Introduction (2)

n Multimedia network

q The Internet was designed in the 60s for low-speed inter￾networks with boring textual applications ‡ High delay,

high jitter.

q ‡ Multimedia applications require drastic modifications

of the INTERNET infrastructure.

q Many frameworks have been being investigated and

deployed to support the next generation multimedia

Internet. (e.g. IntServ, DiffServ)

q In the future, all TVs (and PCs) will be connected to the

Internet and freely tuned to any of millions broadcast

stations all over the World.

q At present, multimedia networks run over ATM (almost

obsolete), IPv4, and in the future IPv6 ‡ should

guarantee QoS (Quality of Service) !!

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Chapter 1: Background of compression

techniques

n Why compression ?

q For communication: reduce bandwidth in multimedia

network applications such as Streaming media, Video-on￾Demand (VOD), Internet Phone

q Digital storage (VCD, DVD, tape, etc) ‡ Reduce size &

cost, increase media capacity & quality.

n Compression factor or compression ratio

q Ratio between the source data and the compressed data.

(e.g. 10:1)

n 2 types of compression:

q Lossless compression

q Lossy compression

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Information content and redundancy

n Information rate

q Entropy is the measure of information content.

n ‡ Expressed in bits/source output unit (such as bits/pixel).

q The more information in the signal, the higher the

entropy.

q Lossy compression reduce entropy while lossless

compression does not.

n Redundancy

q The difference between the information rate and bit

rate.

q Usually the information rate is much less than the bit

rate.

q Compression is to eliminate the redundancy.

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Lossless Compression

n The data from the decoder is identical to the

source data.

q Example: archives resulting from utilities such as

pkzip or Gzip

q Compression factor is around 2:1.

n Can not guarantee a fix compression ratio ‡

The output data rate is variable ‡ problems

for recoding mechanisms or communication

channel.

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Lossy Compression

n The data from the expander is not identical to

the source data but the difference can not be

distinguished auditorily or visually.

q Suitable for audio and video compression.

q Compression factor is much higher than that of

lossless. (up to 100:1)

n Based on the understanding of

psychoacoustic and psychovisual perception.

n Can be forced to operate at a fixed

compression factor.

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Process of Compression

n Communication (reduce the cost of the data

link)

q Data ? Compressor (coder) ? transmission

channel ? Expander (decoder) ? Data'

n Recording (extend playing time: in proportion

to compression factor

q Data ? Compressor (coder) ? Storage device

(tape, disk, RAM, etc.) ? Expander (decoder)

? Data‘