chapter 11 multimedia

7/31/2019 Chapter 11 Multimedia

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C H A P T E R 1 1


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What is multimedia?

u me a can ave a many e n ons ese

include: Mu t me a means t at computer n ormat on can e

represented through audio, video, and animation in

a t on to tra t ona me a .e., text,graphics/drawings, images).


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General definition

goo genera wor ng e n on or s mo u e s:

M u lt im e d ia is t h e fie ld c o n ce r n e d w it h t h eco m p u t e r co n t r o lle d in t e gr a t io n o f t e xt ,

gr a p h ics , d r a w in gs , s t ill a n d m o vin g images

v eo , an mat on, au o, an any ot er me awhere every type of information can be represented,s ore , ransm e an processe g a y.


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Multimedia A lication Definition

u me a pp ca on s an app ca on w c

uses a collection of multiple media sources e.g. text,grap c , mage , oun au o, an ma on an orvideo.


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What is H erText and H erMedia?

yper ex s a ex w c con a ns n s o o er

texts. T e term was nvente y Te Ne son aroun 19 5.


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H erText Navi ation

usually non-linear (as indicated below).

This has implications in layout and organisation ofma er a an epen s a o on e app ca on ahand.


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H ermedia

yper e a s no cons ra ne o e ex - ase .

can include other media, e.g., graphics, images, ande pec a y e con nuou me a oun an v eo.


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Exam le H ermedia A lications?

e or e e s e es examp e o

ahypermedia application. Powerpo nt

Adobe Acrobat

Many Others?


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Multimedia A lications

xamp es o u me a pp ca ons nc u e:

World Wide Web u me a u or ng, e.g. o e acrome a rec or

Hypermedia courseware

- -

Interactive TV

Virtual reality

Di ital video editin and roduction s stems

Multimedia Database systems


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Multimedia S stems

u me a ys em s a sys em capa e o

processing multimedia data and applications. A Mu t me a System s c aracter se y t e

processing, storage, generation, manipulation and

ren t on o u t me a n ormat on.


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Characteristics of a Multimedia S stem

u me a sys em as our as c c arac er s cs:

Multimedia systems must be computer controlled. u me a sys ems are n egra e .

The information they handle must be represented digitally.

interactive.


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Challen es for Multimedia S stems

s r u e e wor s

Temporal relationship between data Render different data at same time continuously.

Sequencing within the media

p ay ng rames n correct or er t me rame n v eo

Synchronisation inter-media scheduling

. .for humans to watch playback of video and audio and even

animation and audio. Ever tried watching an out of (lip) sync film for a long time?


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Ke Issues for Multimedia S stems

e ey ssues mu me a sys ems nee o ea w

here are: ow o represen an s ore empora n orma on. How to strictly maintain the temporal relationships on play

What process are involved in the above.

Data has to re resented di itall nalo Di ital

Conversion, Sampling etc.

Large Data Requirements bandwidth, storage,

D a ta co m p r e s sio n is u s u a lly m a n d a t o r y


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Desirable Features for a Multimedia S stem

desirable (if n o t a p r e r e q u is it e ) fo r a

Ver y H igh P r o ces s in g P o w er n eed ed t o d ea l w it hla r ge d a t a processing and real time delivery of media.

Special hardware commonplace. Mu lt im ed ia Cap a b le F i le Sys t em n eed ed to d e live r

r ea l - t i me media e. . Video Audio Streamin .

Sp e cia l H a r d w a r e / So ft w a r e n e e d e d e .g. R AI D

technology . D a ta R e p r e s e n t a t io n s F ile Fo r m a t s th a t s u p p o r t

m u l t i m e d i a should be easy to handle yet allow forco m p r e s sio n / d e co m p r e s sio n in r e a l-t im e .


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Desirable Features for a Multimedia S stem

s u b s y s t e m needs to be efficient and fast. Needs to allow for real-time recording as well as playback of data. e.g. Direct to Diskrecordin s stems.

Spec ia l Ope r a t in g Sys tem to a llow a ccess to fi le s ys tema n d process data efficiently and quickly. Needs to support directtransfers to disk, real-time scheduling, fast interrupt processing,

I/O streaming etc. St o r a ge a n d M e m o r y la r ge s t o r a ge u n it s (o f t h e o r d e r o f hundreds of Tb if not more) and large memory (several Gb ormore . arge ac es a so requ re an g spee uses or e c entmanagement.

N et w o r k Su p p o r t Clie n t -s e r ve r s ys t em s co m m o n a ss r u e sys ems common. So ft w a r e To o ls u s e r fr ie n d ly t o o ls n e e d e d t o h a n d le

m e d i a , design and develop applications, deliver media.


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Com onents of a Multimedia S stem

ow e us cons er e omponen s ar ware anSoftware) required for a multimedia system:

, ,

Microphone, Keyboards, mice, graphics tablets, 3D input devices,tactile sensors, VR devices. Digitising Hardware

Stor a ge Devices H a r d d isks , CD-ROMs, DVD-ROM, e tc

Co m m u n ica t io n N e t w o r k s Lo ca l N e t w o r k s , I n t r a n e t s ,

Internet Multimedia or other s ecial hi h s eed networks.

Co m p u t e r S ys t em s M u lt im e d ia D es k to p m a c h in e s ,

Workstations, MPEG/VIDEO/DSP Hardware Disp la y Devices CD-q u a li ty sp ea ke r s , H DTV,SVGA, H i-

Re s monitors, Colour printers etc.


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A lications

xamp es o u me a pp ca ons nc u e:

World Wide Web yperme a courseware

Video conferencing

- -

Interactive TV

Home shopping

Games Virtual reality

Digital video editing and production systems


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A Brief Look at Multimedia Data:Input andFormat

e x a n a c a a

Source: keyboard, speech input, optical character recognition, datastored on disk.

Stored and input character by character:

Sto r age o f t ex t is 1 byt e pe r ch a r ac t e r ( t ext o r fo r m a t

c a r a cte r .

F o r o t h e r fo r m s o f d a t a ( e .g. S p r e a d s h e e t file s ) . M a y s to r e

format as text (with formatting) others may use binary encoding.

Format: Raw text or formatted text e.g HTML, Rich Text Format(RTF), Word or a program language source (C, Pascal, etc..

. .HTML format sequence, Sequence of C program statements.

Size Not significant w.r.t. other Multimedia data.


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r a p cs Format: constructed by the composition of primitive objects

such as lines ol ons circles curves and arcs.

Input: Graphics are usually generated by a graphics editorprogram (e.g. Illustrator) or automatically by a program (e.g.

.

Graphics are usually editable or revisable (unlike Images).

Gra hics in ut devices: ke board (for text and cursor control),mouse, trackball or graphics tablet. graphics standards :OpenGL, PHIGS, GKS

Do not take up a very high storage overhead.


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Still pictures which (uncompressed) are represented as a bitmap (a

grid of pixels). Input: digitally scanned photographs/pictures or direct from a

digital camera.

In ut: Ma also be enerated b ro rams similar to ra hics or

animation programs. Stored at 1 bit per pixel (Black and White), 8 Bits per pixel (Grey

Scale Colour Ma or 2 Bits er ixel True Colour

Size: a 512x512 Grey scale image takes up 1/4 Mb, a 512x512 24 bitimage takes 3/4 Mb with no compression.

camera 10+ Megapixels 29Mb uncompressed!

Co m p r e s s io n i s co m m o n ly a p p lie d .


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u o

Audio signals are continuous analog signals. npu : m crop ones an en g se an s ore

CD Quality Audio requires 16-bit sampling at 44.1 KHz

. . - ,

1 Minute of Mono CD quality (uncompressed) audio requires 5Mb.

1 Minute of Stereo CD quality (uncompressed) audio requires

10 Mb. Usuallycom p r ess ed (E .g. MP 3, AAC, F la c , Ogg Vor b i s ) .


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Input: Analog Video is usually captured by a video camera and then

digitised. There are a variety of video (analog and digital) formats

Raw video can be regarded as being a series of single images. Thereare t icall 2 0 or 0 frames er second.

E.g. A 512 512 size monochrome video images take 25 x 0.25 =6.25Mb for a minute to store uncompressed.

.25 = 30Mb for a minute to store uncompressed.

High Definition DVD (14401080 = 1.5 Megapixels per frame) ~ 4.5 x. .

possible frame rates!)

Digital video cle a r ly n e e d s t o b e co m p r e s s e d fo r m o s t t im e s .


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chapter 11 multimedia

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