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Dr.B.Yogameena
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D6GB Multimedia Systems
Faculty: Dr.B.Yogameena (ymece@tce.edu)
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.doc8/3/2019 Ohm Module 1 Introduction and Overview MMS 2011
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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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Multimedia- Applications
In Medicine
Source:
Cardiac Imaging,
YALE centre for
advanced cardiacimaging
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Multimedia- Applications
In training
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Multimedia- Applications
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
22 kHz 8 bit Stereo 2.59 MB
AM Radio 11 kHz 16 bit Stereo 2.59 MB
11 kHz 8 bit Stereo 1.29 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.doc8/3/2019 Ohm Module 1 Introduction and Overview MMS 2011
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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
Quantized to 3 bits ,
8 gray levels
Quantized to 1 bits ,
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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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