Lecture 1: Introduction
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Learning Objectives
In this lecture, you will learn;
• The computer terms common to digital media
• The difference between analog and digital data
• What the binary system means
• The basic steps of digitization: sampling and quantization
• The general strategies for reducing digital media file sizes
• The reason for file compression and types of file
compression
• What cloud computing means and various types
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Analog Information
• Continuous information
• An infinite number of divisions exist between any two
measurements
• Examples;
–Time
–Weight
–Sound loudness
–Light brightness
• Digital data
– discrete
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Analog vs. Digital
• Sight and sound we perceive in our natural world are
analog information continuous and infinite number of
points between any two points.
• Computers handle discrete digital data. In addition, the
amount of data has to be finite.
• Sight and sound must be converted into finite discrete
digital data in order for the computer to handle.
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Digitization
• To convert analog information into digital data that
computers can handle
• 2-step process:
1.Sampling
o Sampling rate: how often you take a data
2.Quantization
o refers to the number of allowable levels you map
(or round) the values
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Suppose this is the timeline of the puppy’s
first-year growth
True timeling Once a month sampling Interpolate the points
Once a week sampling
Interpolate the points
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Quantization
For 10 discrete levels, you may have the 10 allowable
values as
• 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, and 2.9
• 0, 5, 10, 15, 20, 25, 30, 35, 40, 45
• 2, 4, 6, 8, 10, 12, 14, 16, 18, 20
• 1, 2, 3, 4, 5, 6, 7, 8, 9, 10
• ... and so forth
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Suppose you choose 2.0, 2.1,...,44.9, 45.0
• You have increased the number of levels from 10 to 431.
• Pros:
– Increase precision compared to using
0, 5, 10, 15, 20, 25, 30, 35, 40, 45
– Increase range compared to using
2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9
• Cons:
– Increasing the number of allowable levels (i.e.
increasing bit depth) will increase the file size.
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Sampling and Quantization
Digitizing media involves sampling and quantization
regardless of the type of media:
– images
– video
– audio
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Overview of how sampling rate and bit
depth affect digital media file quality
Sampling rate is Bit depth is related to:
related to:
digital images image resolution, or number of allowable
number of pixels colors in an image
digital video number of pixels in the number of allowable
video, frame rate colors
digital audio sampling rate of the number of allowable
audio (it limits how high levels of amplitude
the pitch of the audio can
be captured)
Details will be covered in lectures for each media type.
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Bits (1 of 2)
• In computer systems, data is stored and represented in binary digits,
called bits.
• A bit has two possible values, 0 or 1. Eight bits is called a byte
• More bits can encode more information.
• More bits require more computer storage.
• Number of possible values equal to two power of number of bits N
(2𝑁 )
• The number of bits to encode information especially for digital media
are very large.
• We use prefixes, such as mega and giga, to better conceive the
number of bits and bytes of computer storage.
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Prefixes
• Note the size is computed by the exponential of 2.
• The exponent is increased in a step of 10,
• i.e. 210 , 220 , 230 , 240 , 250 ,...
• It is Not 103 , 106 , 109 , 1012 , 1015 ,...
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Using Bits to Represent Numeric Values (1 of 2)
• Base-10: Commonly used in our daily life
5 8 7 2
= 5 103 + 8 10 2 + 7 101 + 2 10 0
= 5 1000 + 8 100 + 7 10 + 2 1
= 5000 + 800 + 70 +2
= 5872
• Base-2 : Used in machine language (language that
computers understand)
1 0 1 1
= 1 23 + 0 2 2 + 1 21 + 1 20
= 1 8 + 0 4 + 1 2 + 11
=8 +0 +2 +1
= 11( Eleven in decimal notation)
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Base-10 to Base-2 Example (1 of 2)
To convert 1910 to binary notation : Decimal Binary
19/2 = 9 remainder 1 0 0
9/2 = 4 remainder 1 1 1
4/2 = 2 remainder 0 2 10
2/2 = 2 remainder 0 3 11
1/2 = 2 remainder 1 4 100
5 101
6 110
7 111
1910 = 100112
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Using Bits to Represent Text (2 of 2)
ASCII: Stands for American Standard Code for
Information Interchange
Each character
uses 8 bits
For example, the character
A is represented by 65.
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Unicode
• Another standard for encoding text character
• Can represent a large collection of multilingual characters
• Uses 16 bits to encode a text character because
multilingual character sets are larger than the ASCII set
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Using Bits to Represent Images
• Bitmap images, such as digital photos
– color value of each pixel encoded into bits
• Vector graphics, such as graphics created in Flash
– coordinates of anchor points encoded into bits
– tangent of each anchor points encoded into bits
• Bitmap images, vector graphics, and pixels will be
explained in the digital images lecture
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Using bits to Represent Sound
• Sampled audio
– amplitude for each sample encoded into bits
For CD quality audio, it has 44,100 samples per
second of the audio
• MIDI music (Musical Instrument Digital Interface)
– each musical instrument has an ID which can be
encoded into bits
– each musical note has an ID which can be encoded
into bits
• Sampled audio and MIDI will be explained in the audio
lecture
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Compression
• File compression means techniques to reduce file size
• Two categories in terms of whether the data get lost
during the compression:
– lossy compression: Some data will be lost and cannot
be recovered. Examples: JPEG, MP3, MP4
– lossless compression: Every bit of data originally in a
file remains after it is uncompressed, and all the
information is restored. Example PNG
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Trade-offs of Reducing File Size
Data will be lost or altered when you apply these strategies:
• Reduce sampling rate
• Reduce bit depth
• Apply file compression
When data is lost or altered, you sacrifice the exactness of
the media original information. This affects the quality of
the media.
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Cloud Computing
• Cloud:
– a large group of interconnected computers accessible
via the Internet
• Cloud computing:
– a computing model in which software applications and
files are hosted on a cloud
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Cloud Computing vs. Traditional Desktop
Computing Model
Cloud Computing Model Traditional Desktop Computing
Model
Software applications and files are You install and run copies of
hosted on the cloud via the software programs on your
Internet. personal computer.
Your documents are stored on the Your documents are stored on
cloud and you can access them your personal computer
via Internet anywhere regardless
of which device you use.
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Three Service Models of Cloud Computing
• Software as a Service (SaaS)
• Platform as a Service (PaaS)
• Infrastructure as a Service (IaaS)
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Software as a Service (SaaS)
• Allows users to run software applications on the cloud via
their devices
• Examples:
– Web-based email
– Google Calendar
– mobile apps that access the services
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Platform as a Service (PaaS)
• Allows users (usually software developers) to deploy onto
the cloud their applications, which may be created or
acquired by them, using programming languages,
libraries, and tools that are supported by the cloud
provider
• Examples:
– Oracle Database Cloud Service
– Google Play Store
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Infrastructure as a Service (IaaS)
• Provides computing resources, such as computing
processing, storage, and networks, for users (typically
businesses) to deploy and run arbitrary software
applications
• Examples:
– Amazon EC2
– Google Compute Engine
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