W#5B Multimedia Processing

7/28/2019 W#5B Multimedia Processing

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Text Processing ke

Multimedia Processing

Zainal A. Hasibuan


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Acknowledgment

This slide is mainly taken from Multimedia

System Tutorial at Hong Kong University by

Romeo CK YIP email:

[email protected]
mailto:[email protected]:[email protected]


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Fundamentals of Multimedia

What is a Multimedia System?Data types in multimedia system

Quality of Service (QoS)

Lossless and Lossy Compression

Covered Topics


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Multimedia System

There is no clear definition of the term

"Multimedia System".

Multimedia versus Multi Media

Common characteristics of a Multimedia System

Digital

Interactive

Networking Integration of text, graphics, sound, image, and video


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What is Multimedia?

media that uses multiple forms of information

content and information processing to inform or

entertain the (user) audience.[Wikipedia]

Text Audio Image Animation Video Interactivity


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What is multimedia?

any combination of two or more media,

represented in a digital form, sufficiently

well integrated to be presented via a singleinterface, or manipulated by a single

computer program. [Chapman]


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What is Multimedia?

Key properties of multimedia [Steinmetz] :

Discrete and continuous media

Independent media

Computer-controlled systems

Integration


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Discrete and Continuous Media

Discrete media composed of time-

independent information items.

Example: text, graphics, or images.

Continuous media consist of time-

dependent information items.Example: sound or video.


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Discrete and Continuous Media

Continous

Discrete

Captured

(from real world)

Synthesized

(by computer)

Natural

SoundVideo

Still

Images

Synthetic

Sound

Animation

Text Graphics


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Software

Applications for different media types

Images: image editing, painting and

drawing

Text: editor, layout programs

Video: editing and post production

Animation: drawing

Sound: editing and effects


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Digital Media

Analog Data

The signals, which we send each other tocommunicate, are data. Our daily datahave many forms: sound, letters, numbers,and other characters (handwritten orprinted), photos, graphics, film. All this

data is in its nature analog, which meansthat it varies in type.


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Digital Data

A digital system is an electronic unit. Therefore,

it can only deal with data, which are associated

with electricity. That is accomplished using

electric switches, which are either off or on. It

can be illustrated with regular household

switches. If the switch is off, it reads numeral 0.If it is on, it is read as numeral 1.


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Bits

Each 0 or 1 is called a bit. Bit is an abbreviation of the

expression BInary digit, which is derived from the binary

number system.

Digital Media

0 1 bit

1 1 bit

0110 4 bit

01101011 8 bit

Table 1.1 Example of Bits


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Binary Number System

The binary number system is made up of digits.

Compare with decimal system (10 digit system),

decimal system uses digits 0 through 9, the binarysystem only uses digits 0 and 1.

Digital Media

Table 1.2 Decimal System and Binary System

Number in Decimal System Representation in Binary Number System

0 0

2 10

3 11

8 1000


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Units

1 byte = 8 bits

1 kilobytes(kB) = 1024 bytes

1 megabytes(MB) = 1000 kB = 1024000 bytes

Digital Media


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Digital Media

Examples of storage media

Hard disk, MO, Compact Disc

Pros and Cons of Digital Data

Pros: Digital can reproduce, transmit, or copy

without introducing loss in quality.

Cons: Consume a lot more bandwidth during

transmission than analog signal.


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Data Types in MM system

Text Data

ASCII stands for American Standard Code forInformation Interchange. Computers can only

understand numbers, so an ASCII code is the

numerical representation of a character.


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Text Data

Figure 2.1 ASCII table and description (copyright: www.asciitable.com)


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Text Data

ASCII uses 7 bits to represent a character. As a result only 127

characters are defined as standard ASCII characters. Characters

128-255 are called extended ASCII characters (Figure 2.2).

Figure 2.2 Extended ASCII codes (copyright: www.asciitable.com)


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Text Data

EBCDIC

EBCDIC (Extended Binary Coded DecimalInterchange Code) is a character set used on early

IBM computers. EBCDIC was first introduced in 1965,

it was the new character-coding scheme came with

IBM System 360 series. EBCDIC uses 8 bits torepresent a character.


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Text Data

UNICODE

The Unicode character uses 16 bits to represent acharacter, thus more than 65000 characters can be

represented. While 65000 characters are sufficient for

encoding most of the many thousands of characters

used in major languages of the world.


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Sound Data

Sound Data

A typical compact disc can hold up to 74 minutes of 16bit, 44.1 kHz audio that is uncompressed about 650

megabytes.


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Sound Data

Table 2.1 shows how the size of a file is affected by the samplingrate and bit length. The file is a one-minute sound clip, recorded

and saved in various forms in the Microsoft Windows WAV file

format.Quality Sampling Rate Resolution File Size

CD 44 kHz 16 bit Stereo 10.3 MB

44 kHz 8 bit Stereo 5.18 MB

FM Radio 22 kHz 16 bit Stereo 5.18 MB


AM Radio



Table 2.1 Variation of file size and sampling rate (60 seconds audio clip in MS WAV format)


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Image Data

Image Data

Images, or pictures, are two-dimensional arrays ofdata called bitmaps, with each element is calledpixel.


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Image Data

Units

Dpi - Dots Per Inch

Bit Depth - The number of bits used to hold a pixel.

Also called color depth andpixel depth, the bit depth

determines the number of colors that can be displayed

at one time.Color Depth Number of Colors

4 bits 168 bits 25616 bits 65,53624 bits 16,777,216

Table 2.2 Color Depths


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Video Data

Video Data

Video, or moving images, is a sequence of images.

To create a sense of continuity, video must be

played at a rate of at least 25 frames per second (fps).


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Nature of Digital Document

Text (.doc, .txt, .pdf, etc),

Image (.jpg, .png, .gif, .bmp, etc),

Audio (.wav, .au, .mp3, etc), Video (.avi, .asf, .mov, etc)


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Why compression?

Keep more stuff in memory (increasesspeed)

Increase data transfer from disk to

memory

[read compressed data and decompress] is

faster than [read uncompressed data]

Premise: Decompression algorithms are

fast

True of the decompression algorithms we

use


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Lossless & Lossy Compression

Lossless Compression

The original data obtained from lossless compression

can be recovered from its compressed data

e.g. Huffman Coding

Lossy Compression

Compressed data of lossy compression cannot berecovered to the original data.

e.g. JPEG, MPEG


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Sample Word Frequency Data(from B. Croft, UMass)


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Zipf and Term Weighting Luhn (1958) suggested that both extremely common and extremely

uncommon words were not very useful for indexing.


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Summary

Common characteristics of multimedia systems:

digital, interactive, distributed, and involving a wide

range of data types, such as video and audio.

QoS as an alternative to best effort approach in

networking.

Documents

W#5B Multimedia Processing