Transcript Introduction

Introduction
MUMD-290 Multimedia
Development
Concepts >> Practical Stuff
• Digital media studies rely on both conceptual
and practical knowledge.
• Simply learning a particular version of a
particular program restricts your creativity
• Instead, focus on the concepts
• New programs are constantly being developed
Popular Programs
Image/Photo Editing
• Adobe Photoshop
• Paint Shop Pro
• Aperture
Drawing
• Adobe/Macromedia
Fireworks
• Adobe Illustrator
Popular Programs
Video Editing
• Apple iMovie
• Apple Final Cut
• Adobe Preimere
Audio Editing
• Apple Garage Band
• Apple Logic Studio
• Adobe Audition
• Sony Sound Forge
KEY CONCEPTS
• Analog information versus digital data
• Converting analog to digital data:
– sampling and
– quantizing
• File size calculation
• File compression
KEY CONCEPTS
• Bits and bytes
• Base-10 versus base-2
Why study these?
File size and prefixes
• Digital files—image, sound, and especially
video files—can be very large.
• Prefixes (such as kilo, mega, and giga) should
mean something to you.
Bits
• By learning binary notation and decimal to
binary conversion, you will see how digital
multimedia can be stored and handled on a
computer as bits.
Bit depth
• Understanding binary systems helps you
comprehend the connection between bit
depth or color depth of an image and the
number of colors; for example,
• 8-bit refers to 256 colors and
• 24-bit refers to millions of colors.
Bit rate
• In working with digital video, you will often
encounter the term bit rate.
• The bit rate of a video affects the smoothness
of its playback.
• Understanding bits helps you understand how
you can calculate your video’s average bit rate
to predict its playback.
hexadecimal
• In Web graphic creation, hexadecimal notation
is used to designate color
• For example, #FF0000 represents red.
• conversion of decimal to binary notations
helps you learn how the hexadecimal notation
of a color is obtained.
Analog Versus Digital Representations
• Pencil is between 7¼ and 7½
• But as you zoom in, the precision is infinite.
Analog Versus Digital
Analog is continuous
• infinite number of
divisions exist between
two points
• Real numbers
• 1/3 =
1.33333333….forever
Digital is Discrete
• Finite number of
divisions exist between
two points
• Integer numbers
• 1, 2, 3, 4, ….,
• Only 9 divisions exist
between 0 and 10.
Digital Data
• Digital images, video, or audio are ALL
represented using binary numbers
• Digital  Binary (1,0)
• CD, DVD – Laser Etch (1) or no etch (0)
• Hard drive – Magnetized (1) or not (0)
Analog vs. Digital
Old fashioned records…
• Etching device is
mechanical and analog
• Etch depth is
continuous
• Infinite depths are
possible
Music CDs
• Laser etching device is
digital
• Etch or no etch
• There is NO half etch,
quarter etch, etc.
Analog vs. Digital
• Mixing paint is an
analog way to make
colors
• You can add an
infinitesimal amount of
paint to achieve infinite
colors.
• Digitally, you have to
encode colors using
binary numbers
•
•
•
•
00 – Black
01 – Red
10 – Blue
11 – Pink
Binary Numbers  Colors
3 bits can encode 8 colors
• 000 Black
• 001 Red
• 010 Blue
• 011 Green
• 100 Purple
• 101 Yellow
• 110 Pink
• 111 White
• In general N bits can
encode 2N colors
• 1 bits = 21 = 2
• 2 bits = 22 = 4
• 3 bits = 23 = 8
• 4 bits = 24 = 16
• …
• 8 bits = 28 = 256
8 Bits = 1 Byte
• Aside from a bit (1 or 0), a byte is the base
unit of measurement.
• Why?
• The answer is complicated…
Byte Prefixes
Kilo
K
210 = 1,024
Mega
M
220 = 1,048,576
Giga
G
230 = 1,073,741,824
Tera
T
240 = 1,099,511,627,776
Peta
P
250 = thousand trillion
Exa
E
260 = million trillion
Zetta
Z
270 = billion trillion
Yotta
Y
280 = trillion trillion
DOES A KILO EQUAL 1000 OR 1024?
• Although in science one kilo equals 1000 (e.g.,
one kilogram equals 1000 grams),
• a kilobyte (KB) is 1024 bytes,
• a megabyte (MB) is 1,048,576 bytes
• Nerd test: How many KB is 1500 bytes?
How many KB is 1500 bytes?
• 1500 bytes/1024 = 1.4648KB (NOT 1.5KB)
• How many bytes are in 4.7 Gigabytes?
How many bytes is 4.7 Gigabytes?
• 4.7 billion bytes
= 4,700,000,000 bytes?
Or
• 4.7 * 1,073,741,824  Gigabyte 230
= 5,046,586,572 bytes?
How many bytes is 4.7 Gigabytes?
DVD makers label DVD-R’s as 4.7GB
even though they contain exactly
4,700,372,992 bytes.
Note that 4,700,372,992 bytes divided by
a Gigabyte 230 is actually 4.3 GB
4,700,372,992 /1,073,741,824 = 4.3 GB
How can they do that?
• How can Sony label a DVD with 4.7 GB when it
really only stores 4.3 GB?
• Answer: In 1998 the International
Electrotechnical Commission (IEC) approved new
prefixes (see the book).
– Gibi = 230 = 1,073,741,824
– Mebi = 220
– Kibi = 210
• So, sony thinks its OK to interpret Giga as a billion
• Microsoft, Apple, and other stick to the base-2
intepretation of Kilo, Mega, Giga, etc.
What should I follow?
• Does a Kilobyte equal 1000 bytes or 1024 bytes?
• Does a Megabyte equal 1 million or 210?
• The new prefixes are meant to make it crystal
clear if you are not measuring digital storage, i.e.,
– A kilogram is 1000 grams
– A kibigram is 1024 grams
• If you are talking about Bytes, the base-2
interpretation is still the practical standard.
– Sony is just misleading people.
Binary Notation
Math and CS Majors:
Sorry, I know you know this…
Everyone else:
Sorry, I know
this is not what
you wanted to
learn….
Base 10
Base 10 Base 10Base 10Base 10
•
•
•
•
•
3872
3 × 103 + 8 × 102 + 7 × 101 + 2 × 100 =
3 × 1000 + 8 × 100 + 7 × 10 + 2 × 1 =
3000 + 800 + 70 + 2 =
3872
Base 2
Base 2Base 2 Base 2 Base 2
•
•
•
•
•
1101
1 × 23 + 1 × 22 + 0 × 21 + 1 × 20 =
1×8 +1×4 +0×2 +1×1=
8
+ 4
+0
+1=
13 (in decimal notation)
Convert 19 to binary
•
•
•
•
•
•
Division of Number
19/2 = 9
9/2 = 4
4/2 = 2
2/2 = 1
1/2 = 0
• Answer 11001
Remainder
1
1
0
0
1
Simple but Ground-breaking
• Every base-10 number can be represented
using binary notation.
Nerd Clock - BCD clock
binary coded decimal
Digital Progression
•
•
•
•
•
•
Text
Numbers and math
Images
Sound
Video
What’s next (smell?)
•
•
•
•
•
Francis Bacon 1605
Claude Shannon 1937
1957
1970’s
1990’s
Digitizing Text - ASCII Codes
Digitizing Images
Digitizing Sound
Time-based
Sample many
times per second
For each sample,
encode the
volume, pitch,
tone, etc.
Channelbased
For each
sound/instrument,
encode the time,
duration, etc.
In both cases, you need a device
that can read the encoding and
“recreate” the sound.
Digitizing video
Sample analog video
signal X times per
second, convert each
frame to digital image.
Include Meta
information, i.e., frame
rate
Analog  Digital
Conversion
No matter what your converting,
two concepts are always important
Sampling rate
Quantization level
Sampling Rate
• How often do you measure?
• How often do you capture the signal?
• Example:
– In Video  Frames per second
• Determines motion realism and smoothness
Quantizing
• When you sample, how precise is your
measurement.
• How detailed is your sample.
• Example:
– In Images  Bit Depth of each pixel
• Determines the number of colors in the image
• True color  8-bit  black & white
Limits of Digital Representations
• Our eyes and ears naturally perceive the world in
analog.
• In Digital images, audio, and video, humans can
notice
– Low sampling – Choppy video, distorted sound
– Low quantization level – Unrealistic color, dull sound
• Digital representations can never be exactly the
same as the natural/analog equivalents
– This would require infinite bits.
Goal: Indistinguishable
• By sampling enough data and by measuring it
very precisely (quantization), you can…
• Create digital media that is indistinguishable
from the analog equivalent
– Human eye can NOT distinguish an image with 16
million colors from one that has 4 billion colors
– Similarly can NOT tell 120 FPS video from 600 FPS.
Data/File Sizes
• To store quality digital media requires
– High sample rate
• 44,000 times per second for CD quality audio
– Deep bit-depth
• 24-bit for true color images
• Lots of data
• File sizes can be enormous!
File Size – First Road block
• In the 1970’s, 80’s, and 90’s, the concepts and
technology existed to support digital media.
• Initially the files where too big to fit on
“portable” storage devices.
• Compact Disks (CDs) brought digital music to
the masses.
– But, CD’s still didn’t have the capacity to bring
digital video to the masses.
Bandwidth – Second Road block
• Today: DVD, Blu-ray and Flash Memory
provide adequate storage and portability for
digital video.
• But, the Internet/WWW is still not suitable for
disseminating (sharing) high quality digital
video.
• However, this is already changing.
Compression
• File compression techniques helped overcome
serious problems caused by limitations on
portable storage and network bandwidth.
• The compression in MP3 digital audio files
brought a single song from 200MB to 5MB,
– which single-handedly led to the birth of digital
music piracy.
Nature of Compression
Lossy
• Loss of quality
– Reduce bit-depth
– Reduce sampling rate
Lossless
• No loss of quality
– Via clever tricks
– Exploits patterns and
repetition in the binary
data.
Summary
• Digital really means “represented with only 0’s
and 1’s.”
– N bits can represent 2N different things…
– Those things could be
• Colors
• Volume levels
• Etc.
• Representing images, audio, and video digitally
requires lots of bits  big files
• Digital media compression is still very important
when transmitting over the Internet.
What the book doesn’t say
• Digital media can be easier
– To edit
– To combine (Multimedia)
– To interact with
• Digital media does NOT
– Degrade in quality (etches wear down)
• But it’s much easier to lose/erase.