ohm module 1 introduction and overview mms 2011

8/3/2019 Ohm Module 1 Introduction and Overview MMS 2011

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Dr.B.Yogameena


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D6GB Multimedia Systems

Faculty: Dr.B.Yogameena ([email protected])

Outline for today

Highlevel introduction to multimedia

systems


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To discuss

Course Introduction

MultimediaDefinitions

Multimedia - Applications Multimedia Data

Hypermedia

Digital Technology
http://../Ohm_D6BG_Multimedia%20Systems%20course%20plan_2011.dochttp://../Ohm_D6BG_Multimedia%20Systems%20course%20plan_2011.doc


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Text Books:

1. Ze-Nian Li and Mark S. Drew, Fundamentals ofMultimedia, Pearson Prentice Hall, October 2003.

2. K. Rammohanarao, Z. S. Bolzkovic and D. A. Milanovic,Multimedia Communication Systems, Prentice Hall, May2002.

3. Yao Wang, Joern Ostermann, and Ya-Qin Zhang, Video

Processing and Communications, Prentice Hall, 2002. 4. Fred Halsall, Multimedia Communications:Applications, Networks, Protocols and Standards,Addison-Wesley, 2001.


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Multimedia- ApplicationsMultimedia plays major role in following areas

Instruction

Business

Advertisements

Training materials

Presentations

Customer support services

Entertainment Interactive Games


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Multimedia- Applications

Enabling Technology

Accessibility to web based materials

Teaching-learning disabled children & adults

Fine Arts & Humanities

Museum tours

Art exhibitions Presentations of literature


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In Medicine

Source:

Cardiac Imaging,

YALE centre for

advanced cardiacimaging


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In training


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Public awareness

campaign

SourceInteractive Multimedia Project

Department of food science&

nutrition, Colorado State Univ


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Example Multimedia Applications Video teleconferencing, distributed lectures, telemedicine,

tele symphony White board, collaborative document editing

Augmented reality DVDs, digital movies, VOIP telephony (Vonage, Skype) Networked games Video on demand (from cable TV, satellite etc.), IPTV

(AT&T U-verse)

Can you think of more applications?

YouTube.com, founded in Feb 2005 Every minute, 10 hours of video is uploaded


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Definition: Multimedia Multimedia means the computer information/data

being transferred over the network which is composedof one or more modality where every type ofinformation/data can be represented, stored,transmitted and processed digitally to enrich itscontent and enhance communication.

Systems operating on multiple modalities: text, audio,images, drawings, animation, video etc.

Sychronizing multiple modalities is important and hard


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Multimedia Information System


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Data Types in MM system

Text Data

ASCII stands for American Standard Code for InformationInterchange. Computers can only understand numbers, so an

ASCII code is the numerical representation of a character.


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Text DataThis included both unformatted text, comprisingstrings of characters from a limited character

set, and formatted text strings as used for the

structuring, access and presentation ofelectronic documents.


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Text Data

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

T D


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Text Data

ASCII uses 7 bits to represent a character. As a result only 127characters are defined as standard ASCII characters. Characters 128-

255 are called extended ASCII characters.

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


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Text Data

EBCDIC

EBCDIC (Extended Binary Coded Decimal InterchangeCode) 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 to represent 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 16 bit,44.1 kHz audio that is uncompressedabout 650 megabytes.

S d D t


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Sound Data

Table shows how the size of a file is affected by the sampling rate 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 11 kHz 16 bit Stereo 2.59 MB


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

I D t


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Image Data

Image Data

Images, or pictures, are two-dimensional arrays of datacalled bitmaps, with each element is called pixel.


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Image Data

UnitsDpi - Dots Per Inch

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

called color depth and pixel depth, the bit depth determines

the number of colors that can be displayed at one time.

Color Depth Number of Colors4 bits 168 bits 25616 bits 65,53624 bits 16,777,216

Table 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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Video Data


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MultimediaHardware Peripherals Input devices

Output devices

Storage devices

Communication devices

_Modems

_Network Interfaces


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Input Devices

Keyboards And Mice Scanners And Digital cameras

MIDI Keyboards

Touch screens Trackballs Tablets


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Continue

Voice recognition systems

Infrared remotes


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Continue

Magnetic Card Encoders And Readers

Video cameras


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Output Devices

Monitors Speakers

VR helmet and VR immersive display

Video Devices


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Storage Device

Syquest drives


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Continue

CD-ROM Drives

Magneto-optical drives Laserdisc Player


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To discuss

Course Introduction

MultimediaDefinitions

Multimedia - Applications

Multimedia Data

Hypermedia

Digital Technology
http://../Ohm_D6BG_Multimedia%20Systems%20course%20plan_2011.dochttp://../Ohm_D6BG_Multimedia%20Systems%20course%20plan_2011.doc


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Hypermedia and MultimediaAhypertext system: meant to be read nonlinearly, by

following links that point to other parts of thedocument, or to other documents

HyperMedia: not constrained to be text-based, caninclude other media, e.g., graphics, images, andespecially the continuous media sound and video.

The World Wide Web (WWW) the best example of apopular hypermedia application.


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Digital Image Formation

f(x,y) = reflectance(x,y) * illumination(x,y)Reflectance in [0,1], illumination in [0,inf]


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Sampling and Quantization


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Sampling and Quantization


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Same Pixel Size, different Sizes


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Same Size, Different Pixel Sizes


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Quantization False Contouring


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Original 8-bit image,

256 gray levels

Quantized to 6 bits ,

64 gray levels


8 gray levels


2 gray levels

Quantization-False Contouring


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Varying Gray Level Resolution


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Problem: Limited bandwidth

Need for compressionAudio

CD quality: 44100 samples per seconds with 16 bits persample, stereo sound

44100*16*2 = 1.411 Mbps For a 3-minute song: 1.441 * 180 = 254 Mb = 31.75 MB

Video For 320*240 images with 24-bit colors

320*240*24 = 230KB/image 15 frames/sec: 15*230KB = 3.456MB

3 minutes of video: 3.456*180 = 622MB

Di t C i T f


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Discrete Cosine Transform

DCT converts the information from spatialdomain tofrequency domain

Consider an unsorted list of 12 numbers

between 0 and 3 -> (2, 3, 1, 2, 2, 0, 1, 1, 0, 1, 0,0). Consider a transformation of the listinvolving two steps

sort the list

Count the frequency of occurrence of each of thenumbers

(4,4,3,1 ) spatial info lost, captured freq. info

Discrete Cosine Transform (DCT)


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Discrete Cosine Transform (DCT)

This is DCT

DCT is an orthogonal transformm so its inverse


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g f

kernel is the same as forward kernel

This is inverse

DCT


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Properties of DCT: real,


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001

bygiven,matrixaltridiagonsymmetricthe

oforseigen vecttheareDCTtheofvectorsbasis3.The

2-MEPG1,-MPEGJPEG,

codingtransformcompactionenergyexcellent.2

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Properties of DCT: real,orthogonal, energy-

compacting,eigenvector-based

The 64 (8 X 8) DCT Basis


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The 64 (8 X 8) DCT Basis

Functions

Each 8x8 block can

be looked at as a

weighted sum of

these basis functions.

The process of 2D

DCT is also theprocess of finding

those weights.


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DCT: Why does it do this? DCT takes advantage of redundancies in the data bygrouping pixels with similar frequencies together Higher frequencies = lower number

Lower frequencies = higher number If lossy compression is acceptable, then each data unit

can then be divided by quantization coefficient (QC)

Zig Zag Scan


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Zig Zag Scan

..

8X8

1X64

To group low frequency coefficients intop of the vector

Maps 8 x 8 to a 1 x 64 vector.

DCT ( )


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DCT (cont)

DPCM on DC Components


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DPCM on DC Components

The DC component value in each 8x8 block is largeand varies across blocks, but is often close to that inthe previous block.

Differential Pulse Code Modulation (DPCM): Encodethe difference between the current and previous 8x8block.


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RLE on AC Components

The 1x64 vectors have a lot of zeros in them, moreso towards the end of the vector

Encode a series of 0s as a (skip,value) pair, where

skip is the number of zeros and value is the nextnon-zero component Send (0,0) as end-of-block value

8X8 block of pixel values takenfrom original image


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using 415 (the DC coefficient)

and rounding to the nearest

DCT

Subtracting -128

quantization

(16 is the value of the firstpixel from quantization


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263 0 3 2 6 2 4 1 4 1 1 5 1 2 1 1 1 2 0 0 0 0 0

1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

0 0 0 0 0 0 0 0 0

Zig-zag scan

26 3 0 3 2 6 2 4 1 4 1 1 5 1 2 1 1 1 2 0 0 0 0

0 1 1 EOB

Huffman

coding

ohm module 1 introduction and overview mms 2011

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