chp 1 - dmm3e-02_pocketpdf_slides

7/30/2019 Chp 1 - DMM3e-02_PocketPDF_slides

1/49

multimedia

Graphics and Colour

Video and Animation

Sound

Text and Typography

Hypermedia

Flash and DOM Scripting

Multimedia and Networks

nigel chapman and jenny chapman

ThirdEdition

ThirdEdition

digita

l 2Fundamentals

Pocket PDF Key Point SlidesDigital Mult imedia 3rd edit ion


2/49

Based on material fromDigital Multimedia, 3rd edition

published by John Wiley & Sons, 2009

2009 Nigel Chapman and Jenny Chapman

These lecture slides 2009Nigel Chapman and Jenny Chapman

All figures MacAvon Media Productions

Pocket PDF Key Point SlidesDigital Mult imedia 3rd edit ion


3/49

Digital Data

2 Pocket PDF Key Point SlidesFundamentals

[email protected]................................................ Ex Libris


4/49

Bits are units of datathat can only have one of

two values.

A byte is eight bits.




5/49

Groups of bits can be interpretedas numbers

to base 2, but can also be treatedas

characters, colours, etc.




6/49

Analogue data must be convertedto digital

form before it can be manipulated by a

computer program.

Digitization comprises two operations:

samplingand quantization.




7/49

Analogue and digital representations




8/49

Sampling and quantizationAn analogue signal




9/49

The sampling rate is the number of samples in

a fixedamount of time or space.



2


10/49

The quantization levels are the set of values to

which a signalis quantized.



2


11/49

Spatialandtemporal signals are made up

of pure sine wave components atdifferent

frequencies.

The Fourier Transform operation can be usedto compute a signals representation in the

frequency domain.



2


12/49

Square wave transformed

into the frequency domain

0 f-f 3f-3f 5f-5f 7f-7f 9f-9f

y = sin(x)

y = sin(x) + sin(3x)/3

y = sin(x) + sin(3x)/3 + sin(5x)/5

y = sin(x) + sin(3x)/3 + sin(5x)/5 + sin(7x)/7

y = sin(x) + sin(3x)/3 + sin(5x)/5 + sin(7x)/7 + sin(9x)/9

y = sin(x) + + sin(101x)/101

Frequency components of a

square wave



2


13/49

Higher-frequency components are associated

with abrupttransitions.



2


14/49

The Sampling Theorem states that, if the

highest-frequency component of a signalis

atfh, the signal can be properly reconstructed

if it has been sampledata frequency greaterthan the Nyquist rate 2 f

h.



2


15/49

Undersamplingleads to aliasing.



2


16/49

?

Sampling and undersampling



2


17/49

Usingtoo few quantization levels leads to

posterization and Moir effects in images, or

quantization noise in sound.



2


18/49

Moir patterns256, 128, , 2 grey levels



2


19/49

Posterization



2


20/49

Compression must often be appliedto media

data.

Compression may be lossless or lossy.



2


21/49

original data

decompressed data

compressed data

compress

decompress

Lossy compression

original data

compress

decompress

compressed data

Lossless compression



2


22/49

Different compression algorithms are

applicable to differenttypes of media

data. Their effectiveness depends on the

characteristics of the dataitself.



2


23/49

Digital Representation

of Media



2


24/49

There are established ways of representing

images, video, animation, soundandtextin

bits.



2


25/49

Mediadata may be representedas atextual

description in a suitable language, or as binary

data with a specific structural form.



2 P k PDF K P i SlidF d l


26/49

Images are displayedas arrays of pixels

and represented usingan internal model.

Generatingthe pixels from the modelis called

rendering.



2 P k t PDF K P i t SlidF d t l


27/49

An image made up of pixels





28/49

Images may be modelledas bitmaps or vector

graphics.





29/49

A bitmap is an array of logical pixels (stored

colour values) that can be mappeddirectly to

the physical pixels on the display.





30/49

9BB5FF B1CFFF B0D2FF A9CFFF 9FCBFF

86B5F9 B0DBFF ADD9FF A9D6FF 9FD3FF

7AACEB A0CCFF A6D3FF A1D0FF A0D0FF

74A8E2 87B7F9 99C4FF A3D0FF A2D0FF

6698D3 6491D5 7AA6EF A1CEFF A5D2FF

logical pixels physical pixels

Simple bitmapped image representation





31/49

In vector graphics, the image is storedas a

mathematicaldescription of a collection of

individuallines, curves and shapes making

up the image, which requires computation torender it.





32/49

A simple vector graphic image





33/49

Vector graphics are often smaller than

bitmaps, are resolution-independentand can

be scaled withoutloss of quality, butthey

are only suitable for certain sorts of syntheticimage, not photographs.





34/49

A vector drawing and a digital photograph

y




35/49

Transforming the vector image and applying effects to the

bitmap

y




36/49

Scaling a vector image (left) and a bitmap (right)




37/49

Moving pictures can be createdas live-action

or animation.




38/49

Live-action must be storedas video.

Animation may be representedin other more

flexible or efficient ways.




39/49

Frames from an animation




40/49

Video frames require alot of storage so video

is invariably compressed for delivery.




41/49

Sound can be representedas a sequence of

samples after digitization.




42/49

CD audio is sampledat 44.1 kHz, higher

sampling rates are sometimes used.

Audio delivered over the Internetis

compressed, often usingthe MP3 codec.




43/49

A character setis a mapping from characters

to character codes.

Unicode is a character set capable of

representingtextin all known languages.




44/49

A fontis a set of character shapes, called

glyphs.




45/49

A B C D E F G H I J K L M N O P

Q R S T U V W X Y Z

a b c d e f g h i j k l m n o p q r

s t u v w x y z

1 2 3 4 5 6 7 8 9 0

A B C D E F G H I J K L M N

O P Q R S T U V W X Y Z

a b c d e f g h i j k l m n o p q

r s t u v w x y z

1 2 3 4 5 6 7 8 9 0

A B C D E F G H I J K L M N

O P Q R S T U V W X Y Z

a b c d e f g h i j k l m n o p q r st u v w x y z

1 2 3 4 5 6 7 8 9 0

A B C D E F G H I J K L M N O P Q R S

T U V W X Y Z

a b c d e f g h i j k l m n o p q r s t

u v w x y z

1 2 3 4 5 6 7 8 9 0

A small selection of fonts




46/49

Many aspects of layout must be controlled

when textis displayed.




47/49

MOLOREET VOLOREET EX-EROSEtum adionse feuis nonhenim ipsusting etumiriure magna feu feummynis augiam, quat.Minit nibh exer aut au-gait wisim autpat. Utirilit pratisci blam-conse min ullaorper ildeliquamet, volorer os-trud te magna at. Upta-tie dolore doluptat nim

velisci psuscidui tat.Lum veniatum vel initlum velit am dolutat,sissequis numsandreetat.

Moloreet Voloreet Exeros

Etum adionse feuis non henim

ipsusting etum iriure magna feu

feummy nis augiam, quat.

Minit nibh exer aut augait wisim

autpat. Ut irilit pratisci blamconse

min ullaorper il deliquamet, volorer

ostrud te magna at. Uptatie dolore

doluptat nim velisci psuscidui tat.

Lum veniatum vel init lum velit am

dolutat, sissequis numsandreet at.

Layout and typography




48/49

Interactivity is produced by executinga

program in response to user input.

In multimedia, programs are often written in

a scriptinglanguage, such as JavaScript orActionScript.




49/49

Metadatais structureddataaboutdata, which

may be attachedto media files to help with

searchingand classifyingthem.


chp 1 - dmm3e-02_pocketpdf_slides

Documents