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Final

CP102 Study Guide - Final Guide: Digital Signature, Software Testing, Unit Testing


Department
Computer Science
Course Code
CP102
Professor
Igor Ivkovic
Study Guide
Final

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Chapter 8 – Digital Media Saniya Kaura / Final Exam 2014
DIGITAL SOUND
Digital Audio Basics Digital audio – music, speech and other sounds rep in binary form for use in digital devices
-analog sound wave is smooth curve  digitized by slicing into vertical segments called samples
sampling rate - # of times per second sound is measured during recording process (Hz)
-higher sampling rate means higher sound quality, and needs more storage space
-voice overs/narrations recorded in 11kHz (11,000 samples/second)
-Music CDs have sampling rate of 44.1 kHz
-radio-quality recordings have sound sample of 8 bit#, high-fidelity recordings have 16 bit#
Audio compression – reduces size of sound file by removing bits of extraneous noise
Sound card – transforms bits stored in audio file into music/sound effects/narrations, a device containing inputs/output jacks, and audio-
processing circuitry
-contains 2 types of circuitry: digital-to-analog converter DAC(transforms digital bits into analog waves) and
analog-to-digital converter ADC(samples live sounds and converts them into digital signals)eg. microphone
Integrated audio – built into comps system board (laptops have it)
Digital Audio File
Formats
Audio Format/Extension Pros Cons
AAC (.aac, .mp4) -good sound quality, compressed format,
used in iTunes
-files are copy-protected, limited to
approved devices
MP3 or MPEG-1 Layer 3 (.mp3) -good sound quality, can be streamed
online
-needs standalone player/browser plug-in
OGG Vorbis (.ogg) -free, open standard, supported by some
browsers
-slow to catch on as a popular standard
WAV (.wav) -good sound quality, supported w/o plugin -raw formats, uncompressed, large files
WMA (.wma) -compressed format, used on several
music download sites
-copy protected, needs Windows Media
Player 9+
-digital audio files supported by <audio> tag: WAV, MP3, OGG
streaming audio – file plays as it is being downloaded
digital audio extraction – technical term for ripping
MIDI Music Digital audio - recording of analog sound signals
Synthesized sound - artificially created, synthetic sound (classified as MIDI music or synthesized speech)
MIDI – musical instrument digital interface; specifies a standard way to store music data for synthesizers, electronic MIDI instruments
and computers; MIDI files contain instructions for individual notes
MIDI sequence – the way MIDI music is encoded; contains instructions specifying pitch of a note, point at which note begins, volume of
note..etc
-special hardware for MIDI Music => MIDI-capable sound card contains a wavetable (aka patchset) – a set of repcorded music
instrument sounds
-Pros of MIDI files – compacter than digital audio files
-Cons of MIDI files – does not produce HQ voals; does not have full resonance of real sound
-Today, MIDI music used for music composition
Speech Recognition
and Synthesis
Speech synthesis – process by which machines produce sound that resembles spoken words (eg. Phone reads email to you)
Speech recognition (software)– refers to ability of a machine to understand spoken word
How speech synthesis works: phoneme (a basic sound unit like “reh” or “gay”) are stringed together to form words
Speech synthesizer is made of text-to-speech software – generates sounds that are played through computer’s sound card
BITMAP GRAPHICS
Bitmap Basics Bitmap graphic – composed of grid of dots/pixels and the colour # for each pixel is stored in binary format
Bitmap graphic formats –
BMP (used for graphic elements like buttons, large files, not used on web);
RAW (photographic images, unprocessed pixel data, large files);
TIFF (desktop publishing, supports True Colour); JPEG (desktop publishing) efficient small file, compressed losing data);
GIF (web graphics, animations);
PNG (web graphics, compressed w/o data loss)
-Bitmap graphics are in games, smartphone pics, cameras, scanners, photos in email attachments, web page graphcis
-Created using PAINT software – Photoshop, Corel, Paint
Scanners and cameras scanner – used to convert printed image into bitmap graphic
digital camera – creates digital images of real objects
CCD – charged-coupled device/ an image sensor made up of grid of tiny light-sensitive diodes called photosites in a digital cam
-CCD’s photoshites correspond to pixels (large CCD = more pixes = better quality)
How to get images out of the camera? Using card readers, direct cable transfer, infrared port, media transfer, docking station,
email
Image resolution Resolution – dimensions of a grid that forms a bitmap graphic (expressed as horizontal and vertical pixels eg. 150 x 100 pixels)
Megapixel 1 million pixels (eg. Camera with resol of 1600x1200 => produces 1.9 mega pixels when multiplied
-pixels in bitmap graphic are stored as bits, so more pixels = more bits needed to store file
-size at which bitmap is displayed or printed depends density and resolution (dimensions) of image grid (when you shrink or
stretch the resolution always stays same, only density changes)
-printer / scanner expresses image grid as dpi (dots per inch) or ppi (pixels per inch)
-zooming on your computer only changes size of image grid, not size of graphic
-experts recommend web graphics not to exceed 100 KB, email attachments not to exceed 1 MB
Cropping – process of selecting part of an image
Resolution dependent – bitmap graphics are resolution dependent; the quality of the image depends on its resolution
Pixel interpolation – process of creating new pixels by average the colors of nearby pixels (used when you enlarge pic)
-one problem is enlarged pic is pixelated – jagged appearance, file size increases but quality falls
Color depth and palettes Color depth - # of colors available for use in an image
Monochrome bitmap – the computer divides image into a matrix; white cell ON pixel is coded “1”, black cell OFF is coded “0”
-“on” or “off” patterns
-math note: resolution/8 bits = #bytes of pic (because 8 bits in a byte!)
-black and white photos are actually grayscale images where each pixel is represented by intensity of light, usually 8 bits/pixel
grayscale pallete – includes many intensities or “shades” of gray (256 shades of gray)
color pallete – used by digital artists to define selection of colors for an on-screen image
system pallete – collection of colors used for interface elements in OS like windows 8
web paellete – collection of colors that display without distortion
RGB color model – color displayed for a pixel based on intensity of red, green, blue signals
-each RGB color signal assigned a value from 0 to 255 (0 = absence of color, 255 = highest intensity level for that color)

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-pixel is white when RGB signals are set to max intensity
-pixel is gray shade when RGB signals are equal but at lower intensity
-pixel is purple when RB signals are on
-256x256x256 = 16.7 million possible colors
true color bitmap – (24-bit bitmap) is a graphic that uses this full range of colors
-produce HQ pics, but too large files to post, attach etc.
-in HTML source docs, some colors have names while others have hexadecimal (base 15) triplet like #FFCO57 (#RRGGBB)
Image compression Image compression – technique that recodes data in an image file so it contains fewer bits
Lossless compression – means to compress a file and then reconstitute all the data into its original state (offered by TIFF,
PNG, GIF)
-type of lossless compression is Run-length encoding (RLE) – replaces a series of similarly coded pixels with a binary
code that indicates the # of pixels and their colors
Lossy compression – throws away some of the original data during compression process (offered by JPEG)
-GIF, JEPG, PNG, TIFF include compression options!
-BMP and RAW do not include compression options!
-use file compression utility for these – manual, uses lossless compression to shrink file size
-zipping is another term for compressing
-unzipping/extracting term for reversing compression procesEE
VECTOR and 3D Graphics
Vector Graphics Basics Vector graphic – set of instructions for re-creating a picture in terms of shape, size, position, colour for each object in image
-have file extensions like .WMF .AI .DXF .EPS .SWF .SVG
-Bitmap VS Vectors: vector graphics resize better than bitmaps w/o being pixelated or blurry, require less storage space
than bitmaps, not usually as realistic as bitmap images, easier to edit object in vector graphic than in bitmap graphic as
layerable
digitizing tablet – device that provides a flat surface for a paper-based drawing and mouse to click points/lines/vectors
-vector graphic software: corel, illustrator, libreoffice, inkscape
Gradient – smooth blending of shades (3d effect)
Metafile – graphic containing both bitmap and vector data
Vector-to-Bitmap Conversion Rasterization – superimposing a grid over a vector image and determining colour for each pixel
-Mac: command shift 3 to rasterize
-PC: screenshot to rasterize
-once vector graphic converted to bitmap, loses all its qualities, so no longer layerable, movable
-converting bitmap graphic into vector graphic more difficult than vice versa
-can be done using tracing software – locates edges of objects in bitmap then, converts to vector objects
Vector Graphics on the Web Vector graphics that can be used on web:
-SVG (scalable vector graphics) – supported by most modern browsers w/o plugin (eg. On cell phones)
-Flash
-Pros of using vector graphics on Web:
-consistent quality, searchable, compact file size
HTML5 <canvas> tag – container for graphics that are drawn and animated using scripting language like JavaScript
3-D Graphics 3D Graphics – stored as a set of instructions (like vector graphics) but instructions contain locations and lengths of lines
that form a wireframe for a 3D object
3D wireframe – covered with surface texture and color to create graphic
rendering – process of converting wireframe with surface colour and texture
ray tracing – technique of adding light/shadows to give 3D effect using light source
software to create 3D: Autodesk AutoCad, or Caligari trueSpace
-60 frames/second look smoothest for game animations
DIGITAL VIDEO
Digital Video Basics Digital video – series of still frames projected at fast rate to fool human eye onto perceiving continuous motion, and uses bits to
store colour and brightness data for each frame
Desktop video – video created on personal computer
-steps for making video: produce, transfer, edit, output (explained below)
Producing Video Footage -digital video camera: capture footage as series of bits
-analog video camera: footage stored on tape as continuous tracks of magnetic patterns (analog footage needs to be
converted to digital format to be edited)
-webcams: cheap, built in computer, or peripheral; captures series of still photos; designed for “talking head” apps
Video Transfer Video capture – process of converting analog video signals into digital format
Video Editing Linear editing – old method, recording segments from one videotape onto another; required minimum of 2 VCRs
Nonlinear editing – new method, requires computer hard disk and video editing software
-pro: can use random-access device to easily edit
Video Output Aspect ratio – relative W and H of video frame: wide screen 16:9, full screen 4:3
Codec – compresses video stream when video is stored, decompresses file when video is played
-popular codec: MPEG, DivX, H.264
Compression ratio – ratio of compressed data to uncompressed data (eg. 35:1, has more compression, smaller file size, lower
image quality than file with 5:1)
Bitrate – amount of data transferred per second as video plays (higher bitrate = better quality)
Container formats – another name for video file formats, hold compressed video and audio data streams that form a video
-AVI, MOV, MPEG, WEBM, ASF, WMV, FLV, VOB, OGG
transcoding – proves of converting digital video from one format to another
Web Video Streaming video – site sends small segment of video to your computer, plays it, and sends next part after, and so on
-HTML5 <video> tag supports several video formats, but does not designate a common video format for all HTML5 complaint
browsers
DVD-Video DVD image – prototype of your DVD that is stored on computer’s hard disk
-Computer can only burn data on DVD-R, DVD+R, DVD-RW (lease compatible in dvd players)
DIGITAL RIGHTS MANAGEMENT
Content Basics Media content – tv shows, movies, music, books
Digital content – term for movies and other content stored digitally
-content is accessed by player (hardware or software players)
Time shifting – process of recording a broadcast
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Place shifting – allows media that originates in one place to be access at another
-often used on computer networks with WIFI
Formal shifting – process of converting media files to different formats (eg. Ripping CD)
Problem: pirating music, illegal downloads
Analog hole – allows pirates to capture content using mic to record songs/videos in theatres
DRM Technologies DRM (Digitial rights management) – collection of techniques used by copyright holders to limit access to and use of digital content
-eg. FairPlay, Windows Media DRM
DRM technologies include:
Authentication – simple form of DRM, content can be accessed only by authorized individuals (eg. Log in with password), provides
weak protection alone
Proprietary media formats – copy protected music CDs, DVDs (copy protected CDs contain a software program that strips out
intentionally corrupted data)
Encryption – gold standard of DRM, need encryption key to access that can be handled by software/hardware (eg. Itunes)
-software-based DRM encryption routes content to a recording device as it is decrypted during playback
-hardware-based DRM encryption t-ecnos: CSS, AACS, HDCP  protect content from unauthorized playback, recording,
transmission
digital watermark – pattern of bits, inserted at places in an image or content stream to track, identify, verify, and control content use,
can only be read by compliant devices
-some watermarks are called “broadcast flag” – set of bits inserted into data stream that specifies how stream can/cannot be
used -broadcast flags limit resolution/sound quality of playback, prevent fast forwarding during commercials, limit content use to
specific regions, prohibit copying or limit # of copies that can be made
Music DRM -Music CDs adhere to standardized Red Book format which implements DRM with a data bit that can be set to “no copy” (but Red
Book no-copy bit is easy to defeat)
-downloaded content are stored locally on computer, so can be accessed multiple times, easily copied to other devices, don’t need
internet
-streaming live music easier to protect with authentication DRM (log in when you want to access)
Movie DRM -CSS (content scramble system) – DRM technology designed to encrypt and control use of content stored on DVDs
-renders DVD copties non functional, and enforces restrictions like region coding, uses an authentication key that allows a DVD
disc and player to prove to each other they are legit
AACS (advanced access content system) – DRM technology for Blu-ray discs depends on authentication and revocation, works
with encrypted content stream but much stronger encryption key than CSS, also AACS compliant devices contain their own unique
set of keys that can be revoked if a player if found to be compromised while CSS devices all have same key
-when you stream movie eg on Netflix it buffers, buffering opens potential hole for pirating so streaming movies are protected by
HDCP (High-bandwith digital content protection) – hardware based DRM technology that requires compliant devices for content
playback
Ebook DRM -Kindle, and Nook are devices designed to decrypt ebook files
Enforcement -by law, copyright holder only entity that can copy work and distribute, but also, can have license agreements and usage policies
Chapter 9 – The Computer Industry: History, Careers and Ethics
COMPUTER HISTORY
Manual Calculators Manual calculator – device that helps in the process of numeric calculations, but requires human operator to keep track of algorithm
Abacus – type of manual calculator used in ancient Rome, Greece, India, China, Japan now replaced by digital calculators; consists
of beads mounted on a rods
-Other calculators include Napier’s Bones and slide rule
Napier’s bones – invented by John Napier; a device made of several rods divided into 10 squares, each labeled with 2 numbers
Slide rule – invented by William Oughtred using Napier’s logarithms (1621)
Mechanical Calculators Mechanical calculator – implements algorithms autonomously, operator simply enter numbers and pulls lever/turns wheel to carry
out calculation (developed as early as 1621)
Shickard’s calculator – has a series of interlocking gears, each of the ten spokes represent a digit (when wheel turned full, it carried
over 1 to left)
Pascaline – (1642) invented by Blaise Pascal, a mechanical device to perform addition, subtraction, multiplication, dvision
Leibniz calculator (1673) – invented by Gottfried Wilhelm
Arithometer – first mass-produced mechanical calculator
Difference engine – (1822) invented by Charles Babbage; device operating using steam power to do calculations for
astronomical/engineering applications
-1833 => failed to fabricate gears to make working version of this complex device
-1834 => Analytical Engine – new general purpose calculating device; designed to process programs and data stored on
punch cards
Computer Prototypes
Generations of
Computers
Personal Computers
THE COMPUTER AND IT INDUSTRY
Industry Overview
Economic Factors
Product Life Cycles
Market Share
Marketing Channels
Industry Regulation
CAREERS FOR COMPUTER PROFESSIONALS
Jobs and Salaries
Education and
Certification
Job Hunting Basics
Resumes and Web
Portfolios
Professional Networking
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