AnthonyAmoroseTextChapterNotes

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Contents

CHAPTER ONE NOTES

  • mm = multimedia
  • dmm = digital multimedia

Historical Context

  • digital multimedia can be interactive
  • www became publicly avail outside CERN start if 1992,in form of line based browser, access to handful of servers. line based browser displays text rather than graphics(icons). ex of lined based browser is Lynx
  • 1st films exhibited to public by Lumiere Bros. in Paris 1895

Terminology

  • mixture of media under software control...where display & presentation of the media elements is the sole purpose
  • multimedia production, where media is more intimalely bound up with computation
  • modalities, various perceptions of reading text, listening to sound, looking at pictures in multimedia
  • multiple media requires us to switch between modalities. ex. reading text then looking at a picture
  • digital mulimedia, combo of 2 or more media, represented in a digital form, well intergrated to be presentd via a single interface, or manipulated by a single computer program.

Delivery

  • 1995 industry consortium announced for successor to the CD-ROM using same size and shape platter...DVD (digital versatile disk) capacity up to 17 Gbytes on a double sided disk.
  • generally when mulitimedia is del online the del need not be passive

Non-Linearity

  • 2 models currently in use for combining elements of different media types...PAGE BASED & TIME BASED
  • time based elements are film, audio video. emdedded in a page as if they were images occupying a fixed area
  • page base elements are books and world wide web
  • linked page based multimedia productions are known as hypermedia the best know ex. of this is the world wide web
  • time based multimedia makes time the central organizing principle
  • parallelism, several video clips shown at the same time perhaps overlaid against a static image or a sound track may play during an animation
  • flash, most widely used time based mm (multimedia) technology on the web. jumps between frames controlled in interactive branching and loops
  • powerpoint slideshows provide the most basic sor of mm presentation
  • non linear books...dictionary, phonebook, cookbook, thesaurus

Interactivity

  • interactivity..portrayed as the feature that differs dmm from other forms of comdined media.
  • interactivity empowers the end user of your project by letting them control the content and flow of info to an extent.end users can control only choices that are coded into the program that are allowed
  • ultimate control over "content and flow of info " remains with the producer

User Interfaces

  • user interfaces, extreme one..menus, dialogue boxes, outline buttons and conventions used by most operating systems, mainsteam apps and web forms. Extreme two..interaction with some sort of game is free form w/ any part of the screen liable to cause a response at some time.

Social and Ethical Considerations

  • new technology creates new opportunities for new unethical behavior

Access to MM: Consumption

  • highest level of computer skills are usually acquired through work
  • physical disabilities or learning difficulties may interfere with a persons ability to use a computer
  • examples....arthritis, motor neurone disease, blindness, dyslexia, color blindness
  • available devices to help these issues..voice synthesizers, braille keyboards and monitor color combinations

Control of MM and Content

  • 1999 Apple launched quicktime tv, providing video over the internet
  • platform for internet content selection (pics), the difference between pics & conventional mechanisms, such as banning books or siezure of video tapes is it restricts reception , not distribution
  • internet content rating association(icra) independent org which admins the labelling of web sites, does not do it itself but through a questionaire provided to the web master.
  • icra perceives its mission as protection of children , at the same time it wishes to prserve free speech.

Slide Notes Chapter 1

CHAPTER TWO NOTES

Digital Representation

  • computers are built to only have 2 states, on and off
  • computers store and operate on BITS
  • bits only have 2 values "0 and 1" they can be read as #s to BASE 2
  • bytes are 8 bits and arranged in a linear sequence so that each byte can be identified by its position in the sequence. THIS IS KNOWN AS THE ADDRESS
  • bit patterns can represent INSTRUCTIONS that cause the processor to carry out operations on values stored in memory.
  • instructions = bit patterns therefore sequences of instructions are PROGRAMS that can be stored in memory and executed.
  • STORED PROGRAM MACHINE- the defining characteristic of a computer.
  • Two coding schemes used Hexadecimal & ASCII
    • Hexadecimal: 16 fingers, 16 digits
    • Humans organize 0s and 1s into groups of 4
    • These groups of 4 are can be represented by a single hexadecimal digit
    • 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F
  • Binary Coding
    • Data for a computer... binary
    • zeros and ones,
    • off and on
    • false and true
  • Data for humans... ASCII, Hex... others
    • Coding schemes are used by humans to reduce the volume of binary digits
    • Two coding schemes used
    • Hexadecimal 4 bits => 1 Hex
    • ASCII
    • All end up as 0’s and 1’s
  • ASCII made of two hexadecimal codes
    • One ASCII character - two hex codes
    • ASCII code for R (from text pg 317)
    • hexadecimal: 82
    • binary: 0101 0010
      • ASCII Characters
        • 32 = space, 33=!, 34=", 35=#, 36=$, 37=%, 38=&, 48=0, 49=1, 50=2, 57=9,65=A,thru 90=Z, 97=a, thru 122=z
  • Can you tell by looking at the number 17 if it is (base 10) or (base 16) just by looking at it?
    • no, because the number 1 and the number 7 is valid in both systems,binary and hexidecimal
  • Can you tell by looking at the number 1C if it is (base 10) or (base 16) just by looking at it?
    • yes, its a giveaway because there is no "C" in either binary or hexidecimal. Its ASCII
  • How to count using a different number of fingers
    • 10 fingers: Counting in decimal
    • 0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
    • start over but put a 1 in the higher position
  • 2 fingers: Counting in binary
    • 0, 1
    • start over but put a 1 in the higher position
    • EXAMPLE: 100,101,110,111,1000
  • 16 fingers: Counting in hexadecimal
    • 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F
    • start over but put a 1 in the 1 higher position �
    • EXAMPLE: 01,02,03,04,05,06,07,08,09,0A,0B,0C,0D,0E,0F,10,11,12,13,14,15,16,17,18,19,1A,1B,1C,1D,1E,1F,20,21,22,....

Digitization

  • it is frequently necessary to convert from analogue representation to a digital one, ex. by scanning a picture
  • digitization- converting a signal from analogue to a digital one
  • digitization consist of 2 steps..SAMPLING (measuring the signals value at discrete intervals) and QUANTIZATION (when we restrict the value to a fixed set of levels)
  • analogue to digital converters(ADC's) hardware device
  • sampling rate-# of samples in a fixed amount of time or space
  • quantization levels-the level that a signal is quantized
  • advantage that digital rep have over analogue ones stems from the fact that only certain signal values "those over quantization levels" are valid
  • if a signal is transmitted over a physical medium, such as a magnetic tape, inevitably random NOISE is intro
  • noise will cause a signal value to change.
  • if signal is digital any minor fluctuations caused by noise will make a legal value into an illegal one that lies between quantization levels. restore the original signal by quantizing agian
  • sample and hold-the value of a sample is used for the entire extent between it and the following sample
  • undersamplingresults in inadequate quality from the original "manifestted as distortions and artifacts which are always undesirable
  • harmonics-the # of overtones present in a note played by an instrument that gives each instrument its own TIMBRE
  • timbre -
  • the collection of frequencies and amplitudes is the signals representation in the FREQUENCY DOMAIN
  • frequency domain can be computed using a mathematicl operation known as the FOURIER TRANSFORM
  • DC component is a spike at a frequency of zero
  • higher frequency components are associated w/ abrupt transitions.
  • as higher frequencies are added, the leading & falling edges of the waveform become more nearly vertical
  • filters that remove certain frequencies - sharpening or smoothing an image
  • inverse fourier transform - taking a signal from the frequency domain to the time domain
  • Sampling Theorom - if the highest frequency component of a signal is at Fn, the signal can be properly reconstructed if it has been sampled at a frequency greater than 2Fn. This limiting valua is known as the NYQUIST RATE
  • posterization when a region of an image w/ a continuous gradation of tone is replaced w/ several regions of fewer tones resulting in an abrupt change from one tone to another
  • The most common reason for limiting the number of quantization levels (in any type of signal) is to reduce the amount of memory occupied by the digitized data by restricting the number of bits used to hold each sample value.
  • quantization noise - when sound is quantized to too few amplitude levels, the result is perceived as a form of distortion. *Quantization noise is clearly discernible when sound is sampled to 8 bits (256 levels), but not (except in the opinion of some audiophiles) at the 16 bits (65536 levels) used for audio CDs.
  • Hardware & Software Requirements

Hardware

  • When looking at the hardware requirements of multimedia, there are two distinct cases to consider: requirements for multimedia consumption and the requirements for its production.
  • (MPC) multimedia pc
  • (PDA) personal digital assistant
  • pda's are based on cellular telephone networks which provide LESS bandwiththan a fixed network
  • raw processing power, high speed data buses, large main memeory, & pwerful graphics boards are a necessity for producing mm content; fast high secondary storage is equally important
  • RAID-Redundant Array of Inexpensive Disk. put together out of cheaper and slower disk. improvement is achieved by reading and writing to them in parallel
  • level 0 RAID, the lowest level, specifies a "data striping technique." a data block being written to the array is split into segments which are written to seperate disk.
  • RAID 0 offers no protection against disk failure, if one disk fails the array will fail
  • level 1 RAID, the least sophisticated, mirrors disk which decrease production
  • combine RAID levels 0 an 1 will allow you to gain performance of data striping and the protection of disk mirroring

Software

  • the key to integration is a framework that can accomodate a multiplicity of media and present them to the user. there are 3 approaches....WWW, API, and FLASH
  • WWW uses 2 computer languages...HTML(hypertext markup language) or XML(extended markup language)
  • (API) application programming interface, example QUICKTIME
  • flash, provides mm production in "stand alone" form, no need for additional software to be used

Networks

  • LAN'S are connected together by routers, bridges, and switches to form internets.
  • the internet is a global network of networkscommunicating by a standard set of protocols loosely referred to as TCP/IP
  • TCP/IP- transmission control protocol / internet protocol. internet rules of communication, who speaks first
  • 56kbits per second- the max bandwith avail through a modem
  • broadband - bandwith connectivity 500 kbps or greater. examples.. ADSL, cable modem, satellite
  • ADSL
    • asymmetric digital subscriber line
    • over copper phone wires
    • limited to short distance from phone switch
    • 6.1 mbps (million bps) downstream
    • 640 kbps upstream

Clients and Servers

  • mm distribution over lans or internet based on client/server model of distributed computation
  • server always"listens" and responds
  • client "request"or consumes
  • WWW clients are browsers such as mozilla, firefox, internet explorer
  • protocol - rules governing actions taken by a server/client when it receives a request or response
  • WWW - most popular form of mm online delivery
  • HTTP - simple protocol, for fast transmission of hypertext
  • info in the WWW is described as HYPERMEDIA
  • URL (uniform resource locator) "the familiar web address
  • FTP (file transfer protocol)- one of the TCP/IP family of protocols used for transferring files
  • IP address the name maps to a number

MIME Types

  • MIME (multipurpose internet mail extension)- extension to the internet mail protocols that support the inclusion of data other than plain ASCII text in mail messages
  • MIME allows the transmission of more than just ASCII text (like you’d expect in an email)
  • MIME types are specified in the header
  • Huge variety of MIME types are allowed
    • audio, images, video
    • compressed files
  • IANA (internet assigned numbers authority)

Standards

  • ISO (international organization for standardization)
  • "Standards are documented agreements containing technical **specifications or other precise criteria to be used consistently as rules, guidelines, or definitions of characteristics, to ensure that materials, products, processes and services are fit for their purpose."
  • Multimedia standards are used for: interfaces, file formats, markup languages, network protocols, etc.
  • Three international standard organizations:
    • The ISO
    • The International Electrotechnical Commission (IEC)
    • The ITU (International Telecommunication Union)
    • ISO does every technical field besides electronic engineering (goes to the IEC)
    • ITU is an agency of the UN.
  • ad hocapproach accommodates rapid change

Slide Notes Chapter Two

  • .doc, .jpg,.xls are ex of file extensions
  • file extensions may not be visible, buried in the file itself and computer reads
  • discrete vs continuous
    • Things in the real world can be discrete
    • They either ARE or ARE NOT there
    • These things can be counted
    • Examples:
      • The number of cars in the parking lot
      • The number of beans cin a jar
  • discrete vs continuous
    • Things in the real world can be continuous
    • Continuous can’t be counted, it must be measured
    • Examples:
      • Atmospheric pressure
      • Height of an ocean wave
      • Frequency of a sound wave
  • computers can only count
    • Discrete data is easy for a computer
    • count it and store it as a number
  • Continuous data... not so much
    • music:
      • measure the frequency & amplitude
      • encode as discrete
    • pictures:
      • measure the amount of light and its color
      • encode as discrete

Nyquist Rate and Audio Sampling

  • Continuous phenomenon to digital data:
  • -Do sampling
    • Requires two processes
    • sampling - equally spaced
    • quantization - measuring at each sample
  • Digital data back to continuous phenomenon:
    • Display samples using “sample and hold”
    • Play the sample for the duration
  • How Frequently Should You Sample
  • too few
    • small file size (good)
    • not a faithful representation when replayed
  • too many
    • large file size (bad)
    • excellent representation when replayed
  • The Nyquist rate
    • twice as many samples as the frequency
  • ok file size
    • faithful representation when replayed
  • CD quality is 44,000 samples per second
    • Human hearing response is in the range of 20 to 22,000 cycles per second
  • Nyquist sample rate =
    • highest frequency to be captured = 22,000 CPS
    • 2 x 22,000 = 44,000 samples per second
  • Looking at FieldsOfGold.mp3
    • 4 minutes and 59 seconds long
    • 1,201,173 bytes in length
  • Is this right?
    • CD quality
    • 44,000 samples per second (sample rate)
    • 16 bit samples (quantity stored for each sample) (2**16 = 65,536 individual levels)
  • FieldsOfGold.mp3
    • 4’59 = 299 seconds long
    • 299 x 44,000 samples per second
    • = 13,156,000 samples
    • 13,156,000 x 2 bytes/sample
    • 26,312,000 bytes
    • Should be 26.3 megabytes!

Download Rate Calculations

  • Example #1
    • 44,100 x 196seconds = 8,643,600
    • 8,643,600 x 2bytes(16bit quantization level)=17,287,200 (file size)
      • 17,287,200MB x 8bits = 138,297,600
      • 138,297,600 / 56kbps(dial up) = 2469.6 seconds download time
  • Example #2
    • 16.52MB(filesize) x 8bits = 132.16
    • 132.16 / 56kbps(dialup) x 10^3 = 2,360seconds download time
  • Example #3
    • 4.13MB (filesize) x 8bits = 33.04
    • 33.04 / 6.1mbps(ADSL) x 10^6 = 5416393.443
    • move decimal 6 places to the left and round to two decimal places
    • final answer = 5.42 seconds
  • Example #4
    • 153.59kb(filesize) x 8bits = 1228.72
    • 1228.72 / 56kbps(dialup) x 10^3 = 21.94142857
    • final answer = 21.94 seconds
      • when dividing a kb size file by 56kbps you do not have to raise it to the power of three
  • Example #5
    • 153.59kb(filesize) x 8bits = 1228.72
    • 1228.72 / 6.1mbps(ADSL) x 10^-3 = .2014
    • you divide by 10^-3 because you are dividing kb10^3 by megabytes 10^6. 3-6 = -3
  • kilobyte = 10^3
  • Megabyte = 10^6
  • Going from:
    • B-> KB-> MB-> GB-> TB-> PB : divide by 1024
    • PB-> TB-> GB-> MB-> KB-> B : multiply by 1024

CHAPTER THREE NOTES

Vector Graphics & Bitmapped Graphics

  • pixels- monitors display pictures as rectangular array pixels. Small, usually square dots of color which merge optically when viewed. pg66
  • low level operations required to set pixel values are performed by a graphic library, which communicates with the display hardware and provides a higher level interface to the application program. pg66
  • a graphics application program must somehow keep an internal model of the image to be displayed. pg66
  • rendering- process of generating a pattern of pixels from a model.pg66
    • Internally an application keeps a numeric model
    • Externally an application must project this internal model onto a bitmapped **display
    • An application must also project this internal model onto a storage model to be able to store and recall it later
    • Moving from logical and physical pixels
    • called rendering
    • may be different size and different resolution
    • will probably require clipping and scaling to move from logical to physical pixels
  • two different approaches to graphic modeling: bitmapped graphics and vector graphics. pg67
  • bitmapped graphics- the image is modeled by an array of pixel values. pg67
    • grandfathered name... more like pixel mapped graphics
  • logical pixels (store values) correspond one to one to physical pixels. pg68
    • images are modeled internally as an array of pixel values... the logical pixels
  • physical pixels- physical dots on the screen. pg68
  • scaling and clipping are the only computations that need to be performed to display a bitmapped image. pg68
  • Scaling and Resize
    • Vector? Simple... change formula
    • Changes can be made BEFORE pixel values are calculated
    • Bitmapped? Complicated...
    • frequently results in artifacts (artifacts-unwanted side effect to data/image)
  • vector graphics- the image is stored as a mathematical description of a collection of individual lines, curves and shapes making up the image. pg68
    • a line is defined by slope, length & position
    • a circle is radius & position
    • a square is length of side & position
  • Rendering is very different w/ vector graphic
    • must translate equations to physical pixels
    • not simply clip or scale
    • must compute the array of physical pixels from the equations
  • a bitmapped image must record the value of every pixel, a vector description can be much more compact. pg68
  • Bitmapped image size is set by
    • size, resolution and color resolution
    • not affected by contents
  • Vector graphics size is set by
    • the contents of the image
    • the more complex, the larger the file gets
    • resolution does not affect the size of the file
  • painting programs operate on bitmaps. pg 70
  • drawing programs work with vector representations; adobe illustrator or freehand, intendend for creating or editing vector graphics, and only provide limited facilities for dealing with bitmaps. pg70
  • photoshop and painter provide extensive support for bitmap manipulation. Either offer little support for vector graphics.pg70
  • Major difference between vector and bitmap is the way the behave when scaled or resized. pg70
  • Bitmap image, if displayed larger than its natural size, each logical pixel must be mapped to more than one physical pixel on the final output device. Acheived by multiplying up the logical pixels or by interpolating new pixels. The effect will usually be loss of quality. pg71
  • vector image, scaling can be performed easily as a simple mathematical operation before the pixel values are calculated. Curves will remain smooth no matter how much a vector image is blown up. pg71
  • bitmap images become jagged or blurred if scaled up. pg71
  • drawing program (vector) lets you build up a vector image out of individual curves lines and shapes. Usually has much of the character of a pen and ink illustration. pg72
  • painting program (bitmap) allows you to make a wide range of different marks and apply color to arbitrary areas of the image. pg72
  • painting programs (bitmap) offer more expressive possiblities but at the expense of high memory requirements and scalablity problems. pg72
  • scanned images, screen shots, photos from digital camera and captured video frames are uaually all bitmaps. pg72
  • charts, diagrams and other data visualizations generated by a program from data usually use vector graphics. pg72

Combining Vectors and Bitmaps

  • vector graphic into a bitmap image easily done pg73
  • rasterizing- the process of intrepreting the vector description. The rasterized image looses all of its vector properties. pg73
  • Rasterized image ceases to be resolution independent. A resolution must be chosen when the rastorization takes place. pg73
  • Converting pixels (bitmap) to vectors is much more difficult. It requires software to identify the boundaries of shapes within the image. Then to approximate those boundaries using available curves and lines and to color them appropriately. pg73
  • Vectorization can be used in a controlled fashion to generate a starting point for a new vector image. Most drawing programs allow you to allow bitmaps without vectorizing them. A bitmap imported in this way is treated as an invisible object. pg74

Layers

  • The arrangement of artwork in layers is an organizational device that is common to both vector and bitmap images. pg75
  • Layers can be duplicated and the duplicates altered separately. pg77
  • A layer is often compared to a digital version of a sheet of clear acetate material, like an overhead projector transparency. pg75
  • used in photoshop heavily
  • Bitmapped and vector graphics use this as an organizational device
  • In bitmapped graphics
    • layers are used like digital tracing paper to isolate objects in the image
    • colors can be separated and manipulated individually

File Formats

  • Lossless compression algorithms have the property that is always possible to reconstruct the original data exactly from its compressed version. pg79
  • Lossy algorithms discard some data, in the case of images data representating visually insignificant details in order to achieve greater compression. pg79
  • GIF, developed by CompuServe, for exchanging bitmapped images between different platforms. Uses a lossless compression technique and restricted to 256 colors. Most suitable for simple images such as cartoon style drawings and synthetic images produced on a computer. pg79
  • JPEG (Joint Photographic Experts Group)- JPEG is a compression technique, images that have been compressed using it maybe stored in any of several file formats.pg80
  • JPEG data can be imbedded in other files.pg80
  • TIFF (Tag Image File Format)- is an elaborate extensible file format that can store full color bitmaps using several compression schemes. pg80
  • BMP- is more properly called the Microsoft Windows Bitmap Format. It only supports a simple form of lossless compression and are usually store uncompressed. pg80-81
  • SVG (Scalable Vector Graphics Format) pg82
  • EPS, SWF, and SVG are not just vector formats. Their main feature is vector capablities however it is possible to incorporate bitmaps into these files as self contained objects.
  • Graphics metafile- a format that accomadates both vector, text and bitmap graphics. pg82

CHAPTER FOUR NOTES: VECTOR GRAPHICS

Vector Graphics

  • The contents of a vector graphic affects its size more than it affects the size of a bitmapped graphic.
  • Provide and elegant way of constructing digital images whose representation is compact, scaleable, resolution-independent, and easy to edit. pg 86
  • Vector Graphics are attractive for networked multimedia because of their compactness.pg 86
  • mandatory for 3-D graphics
  • AKA vectors - vectors have magnitude (length) and direction, (from one point to the other)

Fundamentals

  • In vector graphics, images are built up using shapes that can easily be described mathematically. pg 86
  • When studying vector graphics, it is important to be familiar with the coordinate geometry, which is the field of mathematics underlying the representation of shapes in vector graphics.pg 86

Coordinates and Vectors

  • coordinates-any pixel uniquely identified by the pair (x,y) where 'x' is the column # and 'y' is the row #. example (7,3) 7 is 'x' (the column) and 3 is 'y' (the row) pg 87
  • vector graphics coordinates (real values), A point is defined by its x and y coordinate
    • Can be fractional, Can be negative
  • coordinates of pixels in an image must be integer values (whole numbers) between zero and the horizontal (for x coords) and vertical (for y coords) deminsions in the image pg 87
  • rulers-axes along the edges of your drawings, displayed in vector drawing programs. pg 87
  • coordinate transformation-cooridnates in one system (the user space) are transformed into a different one( the device space). one example would be when an image is rendered in a window on a display.pg 87 & 88
  • pairs of coordinates are used to define points and also used to define displacements pg 88
  • displacements - distance between points or movement from one point to another and can be defined by a pair of points
  • a coordinate system allows us to identify points in space pg 88
  • coordinate geometry comes from using letters to represent 'unknown' values and using equations in those values to specify relationships between coordinates that characterizegeometrical shapes. pg 88
  • pixel coordinates are always whole numbers, you cannot set a value for just part of a pixel.
  • Bounding Box - images can be contained inside a “bounding box” which is the smallest box that contains all the points found in an object, a bounding box is placed by its (0,0) position
  • Absolute coordinates - are coordinates in relation to the entire screen
  • Window coordinates - distance measured inside the window from upper left hand corner. window coordinates are within the window you are looking at

Anti-aliasing

  • When we view a digital photograph, the reconstruction (interpolation) is performed by a display or printer device, and by our eyes and our brain. If the reconstructed image differs from the original image, we are seeing an (ALIAS) i.e. Moire’ patterns
  • Anti-aliasing- the replacement of pixel values at a contrasting edge in an image (especially a diagional edge) with values between the original extremes. This softens the coarse step like appearance (pixellation) often seen in low resolution images. pg 90
  • Scaling a bitmapped graphic sometimes causes the edges of lines to look jagged. A technique that makes those edges appear to be less noticable is called
  • sampling and reconstruction- the process of rendering a vector object to produce an image made up of pixels pg 89
  • jaggies (artifacts) are a form of aliasing caused by undersampling pg 90
  • if an image contains a sharp hard edge boundary, its brightness and color will change directly from one value to another crossing the boundary without any intermediate gradation.pg 90
  • no sampling rate will be adequate to ensure perfect reconstruction, jaggies are always possible no matter how high the resolution that is used for rendering a vector shape. pg. 90

Shapes

  • Bezier Curve - a curve defined by 2 end points with a pair (2 more points called direction points)of direction lines at each end to indicate the directions and rates at which the curve leaves the two end points. a class of smooth curves.
  • Shapes can be filled with color, patterns or gradients. pg 91
  • polyline - a sequence of connected lines, sometimes considered a single object.pg 91
  • closed polylines- first and last points coincide, form regular or irregular polygons, can be used to draw rectangles,(they form a shape)

Curves

  • Bezier Curve break down... a total of 4 points,(P1,P2,P3,P4) 2 end points and 2 points called direction points which usually do not lie on the curve itself. pg 92
  • control points - the end points and direction points on a bezier curve pg 92
  • the length of the lines from each end point to its direction point determine how wide a sweep the curve makes. pg 93
  • direction line - a line, usually when using a pen tool, showing you how far you have pulled the a line from the end point.

Paths

  • path-collection of lines and curves
  • closed path -if the path joins up with itself, there are no end points pg 96
  • open paths have end points pg 96
  • each individual line or curve is called a segment of the path pg 96
  • anchor point - the points where segments join (the original endpoints of the segment) pg 96
  • any collection of curves and lines may be considered as a path, they do not all need to be connected pg 96
  • the usual way to construct a path is by costructing the individual segments with the pen tool which provides great control and permits you to construct accurate curves. pg 96
  • a path is an abstract mathematical entity pg 96

Stroke Fill

  • stroke and fill - making a path visible by either applying a stroke (as with ink or some other medium) to the path or you treat it as the outline shape and fill it (as if with paint or ink)or you can do both. pg 96
  • three line cap options provided by postscript....butt cap, round cap, projecting cap pg 97
  • butt cap - squared off end, may produce an undesirable and ugly effect pg 97
  • round cap - preferred, line filled with a semicircle built across the end pg 97
  • projecting cap - a stroke continued beyond the endpoint of the path by half the width, so that the weight of the stroke relative to the path is the same in all directions. pg 97
  • three styles of line joining provided be Illustrator...mitre, round, bevel pg 97
  • mitre - (picture frame) the outside edges of the lines are extended to meet at a point pg 97
  • round - a circular arc is used to produce a rounded corner
  • bevel - the segments are finished off square where they join, and the resulting notch is filled in with a triangle to produce a flat ended joint. pg 97
  • you can only fill a closed path, however, most drawing programs also allow you to fill an open path...the filling operation implicitly closes the path with a straight line between end pointspg 98
  • a single color is the simplest fill pg 98
  • Gradient fills - are widely used in artwork created in vector drawing programs, and contribute to the characteristic air-brush look of graphic design pg 98
  • linear gradient - colors at each end of a region are specified, and a smooth blend of intermediate colors is generated between pg 98
  • radial gradient - color varying outwards from a center point to the outside of the fill pg 98
  • tiles - a small piece of artwork, made using the facilities provided by your drawing program ( much like piecing together bathroom tile). pg 99
  • pattern fills (such as tiles) are often used as backgrounds pg 99
  • non zero winding rule - used to determine whether a point is inside a path. Greater explanation on how it works pg 100

Transformations and Filters

  • Translation- moving the shape from one place to another pg 101
  • Scaling- changing the shape's size pg 101
  • Rotation- rotating the shape around a point (must identify the rotation point (axis) and what you rotate the object around) ( pg 101
  • Reflection- changing the shape's position so that it mirrors the original one (across a line) pg 101
  • Shearing- changing the angles of the shape pg 101
  • filter -a program in Illustrator and similar programs that add effects to to an object. Examples are.... roughening (produces a rough edge to an object), scribbling (moves anchor points in random fashion),rounding corners (converts corner points into smooth curves) pg 102
  • transformations are simply achieved by altering the coordinates of the defining points of objects. pg 102

3-D Graphics

  • 3-D shapes (objects) are defined by their surfaces
  • Made even more complicated by the fact that a 3-D object inside the computer must be translated into 2-D to be rendered on a computer screen...this results in the need to specify the viewpoint.
  • pictures on a screen are always two-dimensional pg 103
  • 3-D graphics - vector graphics based on three deminsions pg 103
  • 3 dimensions,(x, y and z)..x & y form the ground plane..Z is the height
  • Geometrical shapes of 2-D are replaced by 3-D objects: instead of a circle, 3-D is a sphere, instead of a square, 3-D is a cube pg 103
  • complex objects have a hierarchical structure...sub objects, sub sub objects and so on. pg 105
  • In 2D the axis of rotation is always perpendicular to the X Y axis
  • 3D rotation is more complicated than 2D since you must specify an axis of rotation.
  • 3-D: additional complexity
    • lighting
    • natural
    • artificial
    • surface texture
    • rendering is extremely computationally expensive (demanding)

3-D Models

  • constructive solid geometry - the simplest approach to 3-D objects, uses a few primitive geometric solids such as the cube, cylinder, sphere, and pyramid to construct more complex objects. pg 106
  • 3-D objects build by squishing and stretching those objects
  • 3-D operations describing the combining of two complex (3-D) objects... union, intersection, and difference pg 106
  • union - is a new object made out of the space occupied by the two together pg 106
  • intersection - the intersection of two objects is the space that the two have in common pg 106
  • difference - the difference of two objects is the space occupied by the the first but not the second pg 106
  • Fractals are a mathematical idea that incorporates an infinite area with a finite perimeter. Example -Draw a triangle. Now draw one on top of it upside down. Keep doing this to infinity rotating a fraction of a degree over and over. pg 108
  • free form modeling - uses a representation of an objects boundary surface as the basis of its model. pg 106
  • free form modeling - Build surfaces from flat polygons or curved patches, results in an object drawn as a “mesh”
  • Extrusion - Draw a 2 dimensional shape through space along a line, the line can be straight or curved
  • procedural modeling-Objects are defined by algorithms or procedures, best known is based on Fractals
  • Fractals- used to model natural objects,exhibit same structure at all levels, AKA "self similar"
  • meatballs-soft objects that you can stick together

Rendering

  • 3-D models only exist in computers
  • Radiosity is an attempt to model the complex reflections that occur between surfaces that are close together pg 114
  • specular reflection- when the light that bounces off the surface of shiny objects.
  • Ray tracing works by tracking the path of a ray of light back from each pixel in the rendered image to a light source. pg 114
    • Ray Tracing made possible
  • The simplest way of shading an object whose surface is made out of polygon is to calculate value for each polygon. pg 113

Slides Notes

  • rectangles and squares
    • rectangles can be described by two corners
    • squares are special cases of the rectangle
  • ellipses and circles
    • ellipses can be described by two points
    • circles (1 point)and the radius; are special cases of the ellipses
  • Structural Hierarchy
    • Things in the real world are compositions of smaller things
    • Things in the 3-D graphics world are also compositions of smaller things
    • Hierarchical structure is an excellent way of coping with complexity
  • see second half chapter 4 power point slide 12, 13, 14 for RENDERING 3-D.

CHAPTER FIVE NOTES: BITMAPPED IMAGES

Resolution

  • RESOLUTION is a measure of how a device approximates continuous images using finite pixels. pg 118
  • resolution is closely related to sampling and some of the ideas about sampling pg 118
  • 2 common ways of specifying resolution
    • dots per inch....printers and scanners
    • pixel dimensions - resolution is normally specified by giving the size of a frame, measured in pixels...example video
  • image quality is dependent on pixel rate.
  • VIDEO DISPLAYS image resolution in the form of pixel dimensions because the same pixel grid is used to display the picture on any monitor(using the same standard) regardless of its size. HOWEVER, monitor resolution is sometimes quoted in dots per inch because of the tendency in computer systems to keep this value fixed and to increase the pixel dimensions of the displayed image when a larger display is used. pg 119
  • color printers complicated - arrange dots in groups using patterns of different colors within each group to produce the required color, SO the size of the color pixel is greater than the size of an individual dot of ink. pg 119
  • LINES PER INCH - resolution of a printer taking account of the way of mixing colors pg 119
  • screen ruling - the numbers of lines per inch will be as few as one fifth of the number of dots per inch pg 119
  • bitmap images are an array of pixel values, they have pixel dimensions and unlike an input and output they have no physical dimensions. pg 120
  • physical dimension = pixel dimension / device resolution ...the device resolution is measured in pixel per unit length. pg 120
  • in order to maintain an images natural size most image formats record a resolution w/ the image data, this resolution is usaually quoted in units of pixels per inch(ppi) to distinguish it from the resolution of physical devices.pg 120
  • an image that requires interpolation of pixels (scaling up) cannot be done w/o loss of image quality. pg 120
  • DOWN SAMPLING - if an images resolution is higher than that of the output device, pixels must be discarded when the image is scaled down pg 121
  • effects of downsampling..(creates a pradox)an image that has bee downsampled for display at a low resolution will often be better than that of an image whose resolution is equal to the display resolution. pg 121
  • OVERSAMPLING - sampling an image (or any other signal) at a higher resolution than that at which it is ultimately displayed. pg 121
  • disadvantage of high resolution is they contain more pixels and take longer to transfer over a network. pg 122

Image Compression

  • RUN LENGTH ENCODING (RLE) - replacing a run of consecutive pixels of the same color by a single copy of the color value and a count of the number of pixels in the run. pg 123
  • RLE has an important property; it is always possible to decompress run length endcoded data and retrieve an exact copy of the original data as it was before it was compressed. pg 123
  • RLE is an example of lossless compression technique. pg 123
  • compression - an operation performed on data to reduce the space required to represent it for reasons of economy or efficiency.Frequently used with bitmap images.
  • lossy compression technique - information is discarded and can never be retrieved during compression. the result is only an approximation of the original and with each compression /decompression the quality will deteriorate. pg 124

Lossless Compression

  • lossless compression can be allpied to any sort of data, its the only sort of compression that can be applied to data such as spreadsheet data,text, or binary executable programs. pg 125
  • variable length codes In coding theory a variable-length code is a code which maps source symbols to a variable number of bits.-Variable-length codes can allow sources to be compressed and decompressed with zero error (lossless data compression) and still be read back symbol by symbol. With the right coding strategy an i.i.d. source may be compressed almost arbitrarily close to its entropy.
  • dictionary based compression - works by constructing a table,or dictionary, into which are entered strings of bytes that are encountered in the input data; all occurences of a string are then replaced by a pointer into the dictionary. pg 124
  • How does dictionary-based compression save space?
    • Ideally entries should be long strings that occur frequently and the effectiveness depends on choosing strings to enter that replace them by their own codes.
  • two techniques of construction a dictionary - (1) LZ77 (2) LZ78. a variation of LZ78 exist know as LZW and is one of the most widely used compression methods. pg 125
  • LZW - basis of Unix compress and GIF. pg 125
  • huffman coding- analyzes information and looks for common sequences of bits and replaces the most common with a smaller respresentation and less common with larger representation. picks out commonly seen sequences.

JPEG Compression

  • image data can tolerate a certain amount of lost data so lossy compression can be used effectively. pg 125
  • JPEG Compression - the most important lossy image compression technique. pg 125
  • JPEG - best suited for for photographs and similar images which are characterized by fine detail. pg 125
  • JPEG works by actually transforming an image into its frequency components. pg 126
  • discrete cosine transform (DCT) takes an array of pixels and produces an array of coefficients, representing the amplitude of the frequency components in the image. pg 126
  • It is impractical to imply DCT to an entire image at once, DCT images are divided into 8x8 pixel squares and each one is transformed separately, it is to computationally expensive to do so. pg 127
  • JPEG compression- the number of quantization levels to be used for each frequency coefficient can be specified separately in a quantization matrix. pg 127
  • JPEG compression- one highly useful feature, it is possible to control the degree of compression and thus the quality of the compressed image bi altering the values in the quantization matrix.
  • compression artifacts - unwanted features in a compressed image, such as sharp edges come out blurred. pg 129
  • What is one artifact of compressing that an image file can exhibit when using JPEG Compression? ANSWER: Since JPEG signs fewer quantization levels to higher frequencies sharp edges like those found in lettering and graphs get blurred.
  • What is it about human vision that JPEG compression takes advantage of in order to compress a file? ANSWER: Humans can not distinguish high frequency changes in an image as well as they can detect low frequency changes. JPEG assigns less importance to the high frequency changes by assigning fewer quantization levels to them.
  • zig zag sequence - the method in which coefficients are processed to maximize the length and runs of zeros

Image Manipulation

  • filters and mask - pre-existing techniques used for altering photographic images. pg 130
  • two broad reasons for manipulating an image - (1) correct deficiencies in an image. example, red eye in a photograph. (2) creating special effects. example, creating a glow around an object. pg 130
  • Photoshop is the industry standard for image manipulation. pg 131
  • bitmapp manipulation is primarily used for preparing images for print and are not relevant to multimedia pg 130
  • multimedia use of bitmap manipulation is the changing of an images resolution or size, often images must be downsampled for a display or monitor. pg 130

Sections, Mask and Alpha Channels

  • alpha channel - a greyscale mask used to specify different degrees of transparency in an image. (glossary)
  • alpha channel - is like a stencil made out of material that can allow varying amounts of paint to pas through it, depending on the transparency value at each point. pg 133
  • What's the Alpha Channel?
    • The Alpha Channel is this nifty storage area in your image's file for non-visible picture elements. Think of it as your picture's own little private utility closet/filing cabinet. The .psp picture file has these extra goodies stored in its Alpha channel that can just travel around with the picture (unseen until you need them) as a part of the file. (fall semester study guide)
  • mask - let you isolate and protect areas of an image as you apply color changes, filters, or other effects to the rest of the image.

Pixel Point Processing

  • image procesing is performed by computing a new value for each pixel in an image pg 136
  • simplest method to compute a new pixels value is solely based on its old value, w/o regard to any other pixel value pg 136
  • how to compute new pixel value... p'=f(p) "f" is called the mapping function. Such functions perform pixel point procesing. pg 136
  • most sophisticated pixel point processing is concerned with color correction and alteration pg 136
  • crudest pixel adjustments made with brightness and contrast sliders pg 136
  • brightness adjust the value of the pixel up or down uniformly and changes the intercept the line and the "Y" axis. pg 136
  • contrast adjust the range of values , either enhancing or reucing the difference between the lightest and darkest areas of the image.adjusting the contrast alters the gradient of the line pg 136
  • levels dialogue - allows you to move the endpoints of a linear mapping function individually, setting the black and white levels in the image. pg 136
  • image histogram - a tool used to help set suitable adjustments (levels) to stretch or shrink the mapping function horizontally and vertically. pg 136

Pixel Group Processing

  • pixel group processing - worksby computing each pixels new value as a fuction not just of its old value, but also of the value of neighboring pixels. pg 139
  • when using a filter the array of weights is called the convolution mask and the set of pixels used in the computation is called the convolution kernel. pg 141
  • Blurring is often used in retouching scans, and mitigating the effects of digial artefacts. pg 143
  • low pass filter - When using a blurring filter, one way to think about the concept is to imagine that the edges have been softened by rubbing together the color value of the pixels (in the same way as you blur edges in a pastel drawing by rubbing them with your finger. An alternative view, based on the concepts of signal processing, is that this operation produces a smoothing effect on the spatial waveform of the image, by filtering out the high frequencies (music production). pg 143

Geometrical Transformations

  • geometrical transformation - It's a process of scaling, translation, reflection, rotation and shearing pg 148
  • applying geometrical transformations to bitmapped images is nt straightforward, every pixel has to be transformed and this will often require that the image be resampled. pg 148
  • interpolation - a method used to reconstruct to an acceptable degree of accuracy. pg 149
  • bilinear interpolation - uses values of four adjacent pixels. pg 150
  • bicubic interpolation - the interpolation is based on cubic splines, that is the intermediate values are assumed ti lie along a Bezier curve connectiong the stored pixels , instead of a straight line, this process takes longer than others. pg 151

Additional Chapter Five Notes

  • A 14-inch monitor provides a 640x480 pixels display.
  • A 17-inch monitor provides 832x624 pixels display.
  • Both 14-inch & 17-inch monitor display at 72 dpi
  • A PAL frame is 768x576 pixels
  • An NTSC frame is 640x480 pixels
  • What is the difference between GIFS and PNGS?
    • pngs can go between transparent and opaque while gifs can only go transparent or opaque
  • red eye in photographs is caused by light reflecting off the eyes RETINAS.

CHAPTER SIX NOTES: COLOUR

Colour and Sceince

  • color is a subjective sensation produced in the brain. pg 157
  • spectral power distribution (SPD) a description of how the intensity of light from some particulsr source varies with wave length. pg 157
  • wavelength of visible light lies roughly between 400nm and 700nm. pg 157
  • A nanoMeter is 1 billionth of a meter...
    • HINT: It’s a very short wave
  • SPD's are to cumbersome to work with when we are secifying colors for use in computer graphics. pg157
  • human eye contains two different sorts of receptor cells
    • rods - which privide night vision and cannot distinguish color (only blk and wht)
    • cones (3 different types) respond to different wavelengths of light(1 for red, 1 for green, 1 for blue)
  • Tristimulus Theory - any color can be specified by just three values, giving the weight of each three values. pg 158
  • Tristimulus Theory - each "CONE" responds to one RED, GREEN or BLUE light. pg 158
  • Additive Primary Colors - Red,Green, Blue pg 158
  • a pixel is made up of "3 dots" RGB, equalling 3 bytes. pg 158
  • optical mixing of light emmited by three component dots of any pixel will make it look like a single pixel of the desired color. pg 158

RBG Colour

  • RBG color model - colors can be constructed out of red green blue given the the proportions of red, green, blue light which must be combined to make up light if the desired color. pg 158
  • there is no real standard for red, green, and blue on computer displays, and the colors produced in response to any particular RGB value can vary between monitors. pg 159
  • A color can be represented by three values, representation is written as (R,G,B) where R,G,B are the amounts of red green and blue light make a color.
    • "AMOUNT" means the proportion of pure (saturated) light for that primary.
    • Example; (100%,0%,0%)= pure saturated primary RED, (0%,100%,0%)=pure saturated primary GREEN, (0%,0%,100%)=pure saturated primary BLUE.
    • (255,255,255)=WHITE, (0,0,0,)=BLACK
    • Different shades of grey can be represented by the mixtures of RBG light with equal values. ex (34,34,34) OR (54,54,54), 2 different shades of grey.

Additive mixing -three values (#%,#%,#%) of amount of light of three primary colors which must be mixed to produce a specific color. pg 160

  • the three #'s of RGB are not absolute values, it is only their relative values that matter. pg 160
  • each value of RGB is 256 different values. 0 thru 255 = 8 bits each = 1 byte = 24 bits or 3 bytes total. pg 161
  • 16.8 million different color combinations using 256 values each. pg160

Colour Depth

  • color depth - the number of bits used to hold a color value. pg 161
  • 24 bit color - when 3 bytes are used, shorthand for 24 bit color depth. pg 161
  • A SINGLE BIT ALLOWS US TO REPRESENT 2 DIFFERENT COLORS,(usually black and white) pg 161
  • 4 bit color depth allows 16 different colors. pg 161
  • Color Depth
  • Usually expressed in bits
    • One byte for each of the RGB => 24 bits
    • Back to binary...
    • 1 bit => 2^1 => 2 choices
    • 2 bits => 2^2 => 4 choices
    • 4 bits => 2^4 => 16 choices
    • 8 bits => 2^8 => 256 choices
  • greyscale images - represented by (RBG) color values r=g=b (34,34,34) pg 161
    • RGB (25, 25, 25) is dark grey
    • RGB (200, 200, 200) is light grey
    • there can be a max of 256 different shades of gray
  • some computer systems use 16 bits to hold color values
    • 16 is not divisible by 3 (rgb)
    • therefore one bit is unused or different # of bit are assigned to the three vaues.
    • in this case red and blue use 5 bits and green is allocated 6 bits
    • the human eye is more sensitive to green light than the other two primary colors this is the reason for the 6 bit allocation to green pg 162
  • color depth terms - millions of colors (24bit), thousands of colors(16bit) 256 colors(8 bit) pg 162
  • True color refers to 24 bit color pg 163
  • Hi color refers to 16 bit color pg 163
  • COLOR DEPTH IS A CRUCIAL FACTOR IN DETERMINING THE SIZE OF A BITMAPPED IMAGE. pg 163
    • Any reduction in color depth has a 3-fold effect on the final image size
    • A 100X100 RGB image
    • at 24 bit color => 30,000 bytes uncompressed
    • at 16 bit color => 20,000 bytes uncompressed
    • 1 byte => 1/3 reduction of size
  • Posterization- is when colors are distorted and details are lost. two similar colours are replaced by the same one, and banding and other visible artefacts may appear where gradations of color are replaced by sharp boundaries.

Index Colour

  • two constraints on monitor colour depth
    • an image file of 24 bit color may be considered too large for available disc space or it may take too long to transmit over a network.
    • or that the video ram (vram) provided in the monitor is not sufficient to hold a full screen image at 3 bytes per pixel.
  • palette- an index of 256 specific colors with each image.
    • one way of thinking about index color is as a digital equivilant of painting by numbers.
  • logical colors stored for logical pixels
  • physical colors displayed as pysical pixels
  • GIF supports 8 bit index color images
  • JPEG images stored in 24 bit color must be reduced to 8 bit if necessary at the time of display
  • dithering- done by grouping together pixels in an area to be colored and applying color to individual pixels in each group in a suitable pattern.
    • this process is an extension of the use of half toning.
  • dithering, at low resolutions may produce poor results it is better suited for high resolution work.
  • web safe palette- a restricted set of 216 colors, the only palette you can rely on to be reproduced by web browsers on any system using 8 bit color.

Other Colour Models

  • RBG color model is the most important means of representing color used in images for multimedia because it corresponds to the way in which color is produced on computer monitors and also how color is detected by scanners.

CMYK

  • C= cyan
  • M= magenta
  • Y= yellow
  • K= black
  • Complimentary Colors
    • C= G+B=W-R
    • M= R+B=W-G
    • Y= R+G=W-B
  • The color on the left is called complimentary color of the one on the extreme right.
    • Example: Magenta is a complimentary color of green
  • Examples of CMYK materials would be ink, paper and paint.
  • CMYK is an Additive model (like RGB) and appropriate for use with light
  • CMYK also provides the Subtractive model that is appropriate for use with ink and paint... things that absorb light'
  • important point to grasp is that the light that is reflected from a color surface is not changed in color by the process of reflection.
  • process colors -the four colors cyan, yellow, magenta and black in printing.
  • CMYK colors are hard to manufacture because some unwanted colors are absorbed at the same time.

HSV

  • Hue- the wavelength at which most of the energy of the light is concentrated (the dominate wavelength)
  • there are 4 hues in the color spectrum, red, yellow, green, blue
    • Isaac Newton identified seven hues, red, orange, yellow, green, blue, indigo, & violet of the rainbow.
  • a pure hue can be more or less diluted by mixing it with white; the dominate hue remains the same but the presence of other hues make the color paler.
  • a color's appearance will be modified by the intensity of light
    • less light makes it appear darker
    • the brightness of a color is a measure of how light or dark it is
  • in terms of paint, a hue is a pure color
    • adding white decreases its saturation producing a tint
    • adding black decreases its brightness producing a tone
  • a color saturation is measured by its purity
  • HSV, HSB, HSL
    • Hue, is the dominant frequency,expressed as degrees from red
    • Saturation, how pale the hue is; adding white to paint reduces the saturation
    • value. brightness, lightness. The color’s value, brightness or lightness;(adding black to paint reduces the brightness)
  • You probably relate to Cyan to other blues you know (hue), how pale it is (saturation) and its brightness (intensity-V)

Colour Spaces based on colour differences

  • to produce a measure of brightness from an RGB value, you must weigh the three componets separately
    • Y= .2125R + .7154G + .0721B
    • the quantity Y defined here is called luminance

Device-independent colour spaces

  • RGB and CMYK are the most commonly used color models but they are both device dependent.
  • device dependent means
    • different monitors provide different red green and blue primaries
    • different source of ink and paper produce different CMYK

Channels and Colour Correction

  • channel- each of three gray scale images making up a color image
  • the blue screen technique is commonly used in video and film making as well as constructing face images.
    • listen to lecture for more discription

Consistant Colour

  • Different devices use different phosphors
  • 'Physical devices are not usually linear, they curve
    • Red, Green and Blue phosphors each react differently and
    • They do not react linearly... this means
      • 10 times as much excitation will not produce 10 times as much emitted light
      • In the end, it is all a compromise
  • Phosphors and excitation circuitry age

CHAPTER SEVEN NOTES: VIDEO

Introduction

  • Persistence of Vision - an image that you see will stay on the retina for a certain period of time. pg 190
  • Fusion frequency how fast you have to show images for people perceive it to be contiuous motion as oppose to a fast flickering slide show.pg 190
    • Fusion Frequency is not fixed
    • depends on the individual persons eyes
    • depends on surrounding light
    • depends on the brightness of the image relative to the viewing environment
    • ~ 40 frames per second, will start to look as if were flickering (appoximate not fixed, some people can see up to 75 frames per second)
    • Less than 40 frames per second
      • flickering occurs
      • individual images appear losing the illusion of motion (will look like a really fast slide show)
  • Video - capture of frames and then playback
  • Animation - create frames individually and then playback
  • Video is Computationally demanding
    • Capture - must be fast enough to achieve a convincing representation of real time (illusion) of motion. pg190
    • Transport - (if across the web) must be fast enough to carry those captured frames at a rate fast enough to produce the illusion of motion
    • Playback-must be fast enough to play those captured frames at a rate fast enough to produce the illusion of motion.
      • If video is not played back fast enough you will experience dropped frames
  • Graceful Degrade - in transport, as bandwith degrades while playing a video the frame rate will drop and continue to drop as the bandwith degrades,possibly as far as just showing a still frame. The audio portion will continue to play smoothly because audio is not nearly as large as video. Quicktimes method

Digitizing Video

  • Video Standards
  • NTSC (National Television Systems Committee)
    • North America and Japan
    • Started out as analogue starndard for television
    • 24 frames per second
    • 640 pixels wide by 480 pixels high pg 192
    • If you use 24bit color 640 X 480 X 3bytes = 900kilobytes pg 192
    • 1 second of uncompressed NTSC video comprises almost 30 frames pg 192
  • PAL(Phase Alternating Line)
    • Western Europe and Australia
    • 25 frames per second pg 192
    • 768 pixels wide X 576 pixels high (different frame size standard than NTSC)pg 192
    • 31 megabytes per second or 1.85 gigabyted for each minute. pg 192
  • Both standards were derived from old analogue television standards and modified as technology has gotten better.
  • NTSC & PAL
    • Define different screen sizes
    • Define different frame rates
    • Both have the same aspect ratio of 4:3
    • BUT... they each are digitized (through sampling) to the same screen size
  • The result?
    • The pixels are not square
    • PAL is taller than it is wide
    • NTSC is wider than it is tall
  • NTSC and PAL video standards present different pixel shapes, neither of which is square. This happens because even though they have different frame sizes, they both enforce the same 4:3 ratio. This ratio is referred to as the __ASPECT__ ratio.
  • The size of Video (From Dr.Rowan's Slides)
    • At a 640 X 480 framesize
    • Using 3 byte color (24 bits, one byte per color) each frame ~ 2 megabytes
    • One second of video (uncompresssed) is 26 Megabytes
    • One minute is 1.85 gigabytes
  • The size of video above exceeds home computers interface standards and what can be carried by the internet.
  • Video Compression
    • Capture
      • compression and digitization will happen in the camera as the images are being captured.
      • you never have access to the original version because it has aleady been compressed therefore artifacts and aliasing has occurred.
      • Also occurs in the computer with the isight cam
  • Video Compression in the Computer (using isight camera)
    • Analog is presented to the computer through a video capture card
    • Compression is done (usually) in the video capture card, also digitization
    • Allows for a really small camera because the work is done elsewhere
  • Analogue v. Digital
    • analogue signal is susceptible to noise corruption and digital is not
    • analogue signal possibly corrupted (with noise) through the cable running to the computer
    • Analog noise will cause small fluctuations from pixel to pixel
    • RLE can’t compress it because each pixel is a bit different
    • REMEMBER - the story of the blue wall.
      • Captured w/ a digital camera and compression happens inside the camera the video is "pure" in that no noise is introduced therefore the signal can be RLE incoded.
        • 640 x 480 = 307,200
        • 307,200 can be represented by < 24 bits, call it 3 bytes
        • RLE: 307,200 (3bytes) + RGB (3 bytes) = 6 bytes
      • Captured w/ an isight camera with a outside wire running to the computer noise can be introduced causing possibly changes to each pixel. The end result could be different shades of blue and makes RLE compression more difficult or invalid
        • 640 x 480 = 307,200 bytes
        • Noise makes each pixel a little different
        • RLE: 307,200 bytes x RGB (3bytes) = 921600 bytes
  • Hardware v. Software Compression
    • hardware compression happen inside the camera or video card, its circuitry, you have no control over it.
    • software compression you have some control over it through some parameters.
      • CODEC - a piece of software that is a coder / decoder. It is the softerware that takes a raw image and compresses it and then also the software that takes that same image and expands it back. Many different formats of CODEC exist.

Streamed Video

  • Video is transported across the web and played as it arrives
  • Similar to broadcast TV, its real time and does not store on your computer.
  • Can be part of video conferencing, listening to a radio station on the web, etc.
  • Network bandwidth is the enemy
  • Three metods of delivery (true streaming,embedded video,progressive download)
    • True Streaming video
      • never stored on a disk
      • example would be...watching a television show on the internet.
        • you can watch the show, stop it, start it, and go back but you never get a copy of it.
        • a hybrid form of television
        • a good way for TV networks and advitisers to know how many viewers there are, unltimately knowing how much $$ to charge for advertising.
      • on some, you can advance ahead of where the download is complete and the play will start again at the new spot
  • Embedded Video
    • entire file is transferred before play begins(basically a download)
    • stored on disk (must have enough space)
  • Progressive download or HTTP streaming
    • will start to play but won't play (you see the bar moving)
      • sending data to you then sees how long it take for you to receive the data
      • predicts when the download will complete and starts playing when there is enough downloaded to safely play without interruption
    • unlike true streaming YOU GET A COPY to play later, but you need to have enough disk space
    • on some, you can advance ahead of where the download is complete and the download will start again at the new spot

Analogue Broadcast Standards

  • The TV legacy
    • Raster scan (a television legacy about how things are captured)- 525 lines in US and Japan
    • when television was initially fromed there was not enough bandwidth to..
      • transmit 525 lines at a rate of 40+ frames per second, they could not send that much info.
    • so you are being tricked with INTERLACED FIELDS
      • Interlacing Fields is transmitting half of the Raster Scan 262 lines (or every other line) at 20 frames per second, then at the next transmission sending the other half (every other line) of the Raster scan at 20 frames per second.
        • There was enough bandwidth to send half but not all at the same time.
      • when broadcasting each Raster scan at 20 times a second they come together to 40 times a second. Your brain does the fusion so there is perceived motion.
  • MORE INTERLACING FIELDS (THE PROBLEM)
  • Interlacing works fine for television but causes problems when going digital
    • fields (interlacing fields) are sent at different times and are CAPTURED at different times.
    • there is a 1/20th sec delay in showing the 1st line and then showing the 1st line again. remember interlace fields show every other line, 2 fields
    • cameras work in the same way, capturing an image using interlacing fields.
      • this means that when capturing a really fast moving object the object will have moved during that 1/20th sec delay or inbetween those 2 captures.
      • this causes the artifact known as the COMB EFFECT
  • COMB EFFECT- looks as if someone racked a comb across the image because every other line is little bit further than it should be.
  • COMB EFFECT is the artifact that is created when going from broadcast television (analogue raster scan) to digital.
  • How to solve Comb Effect problem
    • You can average the two frames and construct a single frame
    • You can toss out one of the fields and interpolate between them
    • Neither is very good...
  • Film to Video
    • The Problem
      • video is 30 frames per second
      • film is 24 frames per second
      • This is a 5 to 4 ratio
    • How do you make 30 frames from 24?
      • The 3-2 pull down
        • 3 film frames occupy the first 3 fields
        • 2 film frames occupy the next 2 fields
  • 3/2 PULLDOWN from Wikipedia
  • The process of converting 24 frame/s material to 29.97 frame/s is known as 2:3 pulldown (sometimes also called 3:2 pulldown). The term “pulldown” comes from the mechanical process of “pulling” the film down to advance it from one frame to the next at a repetitive rate (nominally 24 fps). This is accomplished in two steps. The first step is to slow down the film motion by 1/1,000. This speed change is unnoticeable to the viewer, and makes the film travel at 23.976 frame/s (or 7.2 seconds longer in a 2-hour movie).
  • The second step of the 2:3 pulldown is distributing cinema frames into video fields. At 23.976 frame/s, there are four frames of film for every five frames of NTSC video:
  • These four frames are “stretched” into five by exploiting the interlaced nature of NTSC video. For every NTSC frame, there are actually two complete images or fields, one for the odd-numbered lines of the image, and one for the even-numbered lines. There are, therefore, ten fields for every 4 film frames, and the telecine alternately places one film frame across two fields, the next across three, the next across two, and so on. The cycle repeats itself completely after four film frames have been exposed, and in the telecine cycle these are called the A, B, C, and D frames, thus:
  • A 3:2 pattern is identical to this except that it is shifted by one frame. For instance, starting with film frame B, followed by frame C, yields a 3:2 pattern (B-B-B-C-C). In other words, there is no difference between the two — it is only a matter of reference. In fact, the "3:2 pulldown" notation is misleading because according to SMPTE standards the first frame of every four-frame film sequence (the A-frame) is associated with the first and second fields of one video frame, and is scanned twice, not three times.
  • Watching a movie in a theater
    • movie is captured at 24 frames per second, which is not fast enough to fuse(create motion)
    • The solution
      • An INTERRUPTER is on the projector that shows the same frame twice which increases the frame rate to 48 frames per second

Digital Video Standards

  • In the begining TV signals were analogue and needed to be converted to digital format
  • Digital from NTSC and PAL are ANALOG standards
  • What do you do when you have a continuous analogue signal and want to make it digital?
    • SAMPLE AND QUANTIZE IT
    • But directly sampling for each pixel results in a data stream of 20 Mbytes/ second
  • Coping with Video Size (With Human Vision or Compression)
    • One way to deal with video size (making it smaller) is to adjust scrren size and frame rate. However there are NTSC an PAL standards for this already set.
    • Consider human vision limitations
      • Human eyes can see intensity stronger that they can see color, so color information is dropped.
      • fewer samples are taken for color than luminance when sampling
      • Without dropping any information (sub-sampling)...
        • for each pixel on the screen 4 pieces of info will have to be encoded
        • The luminance, red, blue, and green
  • Designers realized that Green contributes the most to intensity, Red is next and Blue hardly contributes anything to luminance
    • Based on this, it was decided to use a formula for luminance; Y = 0.2125R+0.7154G+0.0721B (there is a use for algebra)
    • Designers are playing on the fact that, 2 things, humans cannot see color changes as well as they can see intesity changes and that these things are interrelated in a way that it can be expressed by the formula so that they only have to send 3 variables and calculate the fourth on the fly.
      • results in a 25% data reduction
      • -Y (luminance) -Cb (blue chrominance) -Cr (red chrominance
      • you would send the Y, Blue, an Red and the pixels in the screen will compute wat the green is suppose to be, you are only having to send 3 pieces of info rather than 4
  • Chrominance Sub-Sampling
    • not sampling the color as frequently as you are sampling the intensity
    • Of every 4 frames store the luminance
    • only store a proportion of the color info
      • Examples
        • I:R:B 4:4:4, there are 4 parts to each frame, you do nothing to them. IRGB > IRGB > IRGB > IRGB
        • 4:2:2 CCIR 601 video sampling,reduces 4 pieces of data for the 4 frames, used with professional video devices. IRB > Intensity > IRB > Intensity (The Green is Calculated)
        • 4:1:1 NTSC DV,one out of every 4 frames has color info. reduces 6 pieces of info over 4 frames. IRB > Intensity > Intensity > Intensity (The Green is Calculated)
        • 4:2:0 PAL DV, PAL uses 8 frames rather than 4. IR > I >IR > I then IB > I > IB >I (The Green is Calculated) - notice the inconsistency? Should be called 8:4:2

DV and MPEG

  • DV and its different forms:
    • MiniDV, DVCAM & DVPRO
  • DVCAM & DVPRO
    • use the same compression algorithm (5:1)
    • use the same data stream (25Mbits)
    • use 4:2:2 (professional)sampling where DV uses 4:1:1(amature)
  • MPEG-1 originally meant for Video CD
    • never got very popular
    • developed into a family of standards
  • MPEG-4 rose from the ashes
    • used for iTunes video

Intro to Video Compression

  • A Computational Irony
    • Digital has been touted as a way to create exact copies while analog (VCR) cannot...
      • Analog VCR suffers from generational loss (suffers from noise)
      • Digital doesn’t suffer from generational loss
    • BUT only if you use video compression that is... LOSSLESS
    • lossless video compression technique is not used because the lossless ones don’t compress enough
  • Lossless compression
    • original > compression routine > compressed original > decompress routine > original = exact duplicate
  • Lossy compression (what is used for video)
    • Original > compression routine > compressed original > decompress routine > Changed Original 2 > Changed Original
  • Compression - two versions
    • Spatial
      • Individual images can be compressed using the techniques discussed in the bitmapped section
        • video is a bunch of individual frames (pictures)
        • each picture can be compressed.
      • Doesn’t result in very much compression for video
      • Doesn’t take into consideration the other frames that come before or after it
        • Simply put - compress each one of the frames and don't do anything about the one before or after it.
        • Truth is that when your watching a scene, a scene does not change every frame, it moves a little bit (slight changes) but it does not completely change
    • Temporal Compression 1
      • Based on the time sequence of things
      • Use the Difference in two frames
      • naive approach can result in good compression
      • Uses subtraction and saving the difference in the movement of an object.
      • works well for a small amount of movement
      • A Tarantino film? not so much (to much movement, action)
    • Temporal Compression 2
      • When an object moves
      • compute its trajectory
      • fill in the resulting exposed background
      • BUT there’s a problem...
      • why isn’t this an easy thing to do?
      • Video is bitmap
        • Bitmapped images do not have defined objects (we do not know where the objects are)... that’s Vector graphics...
      • What to do?
        • Define blocks of 16 x 16 pixels
        • called a macroblock
        • Compute all possible movements of the block within a short range
        • Compute a vector to define that movement
        • Store the movement vectors
        • Compress the vectors
  • More on Temporal Compression
    • Need some place to start from (Keyframe)
    • KeyFrames-
      • a quick way to find a keyframe is to go through a film and find when the most difference happens.
        • a scene change - it goes from one scene to the next on one frame everything is going to be dofferent between the 2 frames.
    • Can be forward or backward prediction
    • Called KeyFrames
      • pick a keyframe
      • compute next image from that
      • compute next image from that
    • What happens when the scene completely changes?
      • Pick a new key frame...
      • But HOW?
      • Requires powerful AI
  • Video Compression What does this?
    • Coder/Decoder - Codec
    • encodes and decodes video
    • can be symmetric
      • it takes as long to compress as decompress
    • can be asymmetric
      • it takes longer to compress or decompress than it does to decompress to compress

MPEG-4

  • MPEG 4 is a codec
  • Designed for streams that contain video, still images, animation, textures 3-D models
    • allows all kinds of stuff in it
  • Contains methods to divide scenes into arbitrarily shaped video objects
    • Example: the 16 x 16 blocks of pixels used in temporal 2 compression
  • The idea is that each object has an optimal compression technique
    • The idea is that allowing all these different kinds of things in the stream, is that each one of them has a perferred way of compression. So for example video is different than sill images and still is different than animation and all those things can have their own independent and optimize compression routines if you identify them as different objects. Which is why MPEG 4 allows that.
  • BUT...
  • Dividing a scene into arbitrarily shaped video objects is non-trivial
    • so they drop back to the rectangular object position (the 16 x 16 pixel block)
  • Quicktime and DivX use the rectangular video object idea
    • they don't try to find arbitrarily shaped objects they just declare rectangular object.
  • Uses forward interframe compression
    • takes the Keyframe and the next frame subtract and save the difference for compression.
  • Using the simpler technique reduces the computational complexity allowing it to be implemented on small devices like portable video players.
    • playback is really easy because all the work has already been done. All you have to do is add the things together.

Other Codecs for Multimedia

  • Cinepak, Intel Indeo & Sorenson
  • All use “vector” quantization
    • divides frame into rectangular blocks
    • these frames are called “vectors” but they don’t represent movement or direction. Meaning not vectors matematically.
  • Codec uses a collection of these “vectors”
    • uses the table idea much like JPEG uses a table of color for the bitmap to reference to find the right color. These codecs do the same w/ video, they look for a 16 x 16 square and look through the whole video for that one square. Every time they find it instead of sending that square every time it used they send it once and then refer to it in the rest of the video.
    • This builds up a CODE BOOK which a book of the 16 x 16 squares that occur frequently in the video.
  • This is a LOSSY technique.
    • contains typical patterns seen in the frames
      • textures, patterns, sharp and soft edges
    • compares the “vectors” to the ones in the code book
    • if it is close, it uses the code book entry
      • meaning if the compression finds a pattern that is close but not exactly like one listed in the Code Book it can substitute the pattern with one already listed in ths code book, this why it is a lossy technique.
    • (does this explain the patchwork painting of the screen when the digital signal goes bad?)

“Vector” quantization

  • a frame contains indices into the code book
    • for example - a frame for a 16 x 16 block has a reference to code book page 5
    • the code book is transmitted 1st
    • then the vectors are transmitted
    • then the blocks not in the code book
  • reconstructs the image from “vectors” in the code book
    • makes decompression very straight forward and efficient
    • this makes the implementation of a player very easy
  • What about the compression?
  • this is an asymmetric codec
  • compression takes ~150 times longer than decompression
  • Cinepak and Intel Indeo use temporal compression and simple differencing
  • Sorenson uses motion compensation similar to the MPEG-4 standard
    • Summary: All the work is done up front, searching through the video, building the code book, getting the vectors and so on. This is why compression takes so long. However, decompression is quick because all the work is done on the front end. You can decompress with inexpensive hardware. Example would be producing videos for sale, you want it to be cheap for the customer to be able to play your videos.

So... How do codecs vary?

  • compression and decompression complexity
    • affects the artifacts that are created
      • the codec that you choose will results in different artifacts
    • affects the time required to carry them out
    • affects the volume of the data stream created
    • affects the type and expense of the equipment used on both ends
    • affects whether or not it can be implemented in hardware of software

Comparison 4 Different Codecs

  • Bear in mind that this comparison is not absolute and will vary from frame to frame but in general...
    • MPEG-4
      • detail is good (at the sacrifice of speed)
    • DV
      • detail is good but the biggest
    • Sorenson
      • loss of detail (see pg 218-219)
    • Cinepak
      • loss of detail
      • smallest file

A word about QuickTime

  • All standards so far have defined the data stream... not the file format
  • QT is the defacto standard design of a component-base architectural framework
    • allows plugins (components) to be developed by others
  • Every QT movie has a “time base”
    • records playback speed and current position relative to a time coordinate system to allow them to be replayed at the right speed on any system
    • If the playback speed of the device is not fast enough, QT drops frames keeping audio synchronization

More about QuickTime

  • Plugins make it flexible so that it can accommodate new file formats
  • comes with a standard set of plugins (components)
    • compressor components include
      • MPEG-4, Sorenson and Cinepak
    • movie controller interface provides uniformity
    • transcoder components to convert to other formats
  • supports true streaming and progressive download


CHAPTER EIGHT NOTES: ANIMATION

Intro

  • Two ways to create moving images
    • capture using a camera
    • create using animation techniques
  • Using iMovie
    • Capture images using miniDV camera, manipulate using iMovie
  • Animation is a creation of moving pictures one frame at a time. pg 242
  • Animate means "to bring to life" using still images to create frames pg 242
  • Animation Techniques
    • draw each frame individually (flipbook)
    • paint on (or otherwise modify) existing video or film
      • rotoscope changes frames of an existing film (see Capture Animation and Image Sequence)
        • "adding scenery into film that does not exist" Dr. Rowan
        • Trace some portion of a frame and delete it
        • Add something drawn-in later
  • Cut out Manipulation or (Felt Board Animation)
  • ClayMation or modeling clay manipulation
  • hybrid animation - mixed cell and film
  • Cel Animation - a sheet of transparent acetate on which images for animation are drawn and painted, allowing layering of images to build up a scene. Example- Homer Simpson is drawn on a cel and laid over a backgound such as the living room which is drawn seperatley.In producing a sequence, only moving elements on the cel need to be redrawn for each frame, the fixed parts of the scene (sofa or a lamp for example) only need to be drawn once. pg 243
    • Cel Animation done layers (think of gimp/inkscape project) really exspensive to do.
    • A background can be drawn on a long sheet extending beyond the bounds of a single frame and move between shots behind the cell, this produces an effect of traveling through a scene. pg 243
  • DISNEY(CELL)
    • Disney, Snow White 1937(cell)
    • Use paintings on clear plastic,hand painted cells
    • Disney had an army of excellent painters
  • SIMPSONS(CELL)
    • Cell animation
    • First 14 episodes were hand painted
    • Subsequent episodes used digital-ink-and-paint to mimic hand-painted cells
  • Cut out Manipulation or (Felt Board Animation) -taking an actual piece of the image move it and take a picture and repeat. Example:In SouthPark they lift the head creating a gap (take a picture) then lower the head closing the gap (take a picture). When played this will give the illusion that the characters mouth is talking.
    • The story line is more important than the artistic value.
    • Cutout animation is much cheaper to produce vs. cel animation
  • SOUTHPARK(CUTOUT)
    • Pilot was cut-out animation in the style of Terry Gilliam of Monty Python fame (197-)
    • Subsequent episodes used computer animation that mimicked cut-outs
    • Added some live film in later episodes
    • Late added some shadowing effects
  • Simpsons takes 6-8 Months per episode
  • South Park takes 6 weeks
  • ANIMATION PROCESS
    • All animaton requires that you create a individual drawing by some means
    • 2-D model to 2-D frame
      • hand drawn
      • cell
      • cutout
      • Examples- SouthPark(cutout), Simpsons(cel)
        • Both are hand drawn or hand built.
    • 3-D model to 2-D frame
      • physical model manipulation
      • stop motion clay-mation
      • 3-D computer modeling (blender)
        • Positives of a 3D model to a 2D frame (physical)
          • you do not need to create shadows, just move the light where you want it
          • easy to move the camera to film what you want to see
          • Examples - Gumby & Wallace and Gromit & Gumby
      • 3-D computer modeling
        • Examples - Toy Story and Jimmy Neutron
  • 2-D model producing 2-D images- really simple after the drawings are created
    • create the image
    • store the image as a frame
    • create another image
  • 3-D model producing 2-D images
    • There are two ways of creating this, but both approaches share the following elements
      • produce the model
        • In claymation you have to produce a "Gumby" model
        • In Blender you have to create a 3D model inside the computer.
      • manipulate the model
        • In claymation you pysically move your character as much as you want it to move in 1/24th of a second then you take a picture of it. More direct
        • Problem with claymation is knowing how much to move an object to make it look like, for example, if it is running slow or fast. How much do you move the leg?
        • In Blender you have to tell the objects where you want them to go and how fast you want them to get there. More complicated because you have to tell the computer how you want the object to move.
        • Creating accelaration or different speeds in Blender is easier, all done by formulas
      • define light source
      • define camera position and angle
  • 3-D model producing 2-D images
    • Using a physical 3-D model
      • Wallace and Gromit(30 frames per day,5 years to produce)
      • Move the model
      • Capture the frame
      • Very time-consuming!
    • Using a computer-based 3-D model
      • Toy Story, A Bug’s Life, Monsters
      • Build the model (takes a lot of time for the human)
      • Move the model (not too bad for the human)
      • Render frame (time consuming for the computer but not the human)
  • As film is projected at 24 frames per second, drawn animation in traditional media technically requires 24 drawings for each second of film, a total of 1,440 drawings for every minute.pg 242
  • Animation does not require seamlessly smooth movement and can be shot on 2's which means two frames of each drawing are captured rather than just one. pg 243
  • Shot on the 2's gives an effective frame rate of 12 frames per second for film or 15 for NTSC video. pg 243
  • Animation made soley from drawings or paintings on paper...every aspect of the image must be repeated for every single frame that is shot. pg 243
  • STOP MOTION - traditional animation technique where objects or characters are photographed one frame at a time, being moved or altered a small amount btween each frame so that the illusion of motion is created when the frames are played back in a sequence.
  • STOP MOTION - also known as 3-D animation, techniques used are using miniature 3-D sets like stage sets on which objects are carefully moved on between shots.
  • CLAY ANIMATION - figures and objects are made out of a malleable modeling material such as Plasticine. Figures can be manipulated between shots to produce natural movement and otherwise impossilbe changes and transformations. Example - Wallace and Gromit films pg 244
  • Hybrid forms of animation...mixing cel and 3-D animation. Most celebrated example is Who Framed Roger Rabbit, mixing live action and animation. pg 244
  • Three forms of animation...2-D, 3-D, and hybrid.
  • Digital technology affords new opportunities for using animation and techniques from it in new contexts. pg 244

Capture Animation and Image Sequence

  • FRAME GRABBING - instead of storing an entire data stream arriving from a camera, you only store the digital version of a single frame each time you have set up a shot correctly. pg 245
  • RETROSCOPING - the process of tracing frame by frame on a layer, selected elements from a live action video clip, which is subsequently deleted.The process can be achieved digitally or by older means. pg 247
  • GIF - Graphics Interchange Format- an 8 bit bitmapped Web graphic file format using index color, which can permit one arbitrary color to be defined as transparent.
  • ANIMATED GIF - a GIF file that contains more than one image. Web browsers and other programs will display each image in a turn, which make GIF suitable for animation. Animated GIF is the only file format for animated sequences which does not require a browser plug-in for play back on Web pages.
  • Build an animated GIF
    • Allows for sequences of images to be placed in one “image” that, when displayed, shows movement
    • animated GIF DOES NOT provide a very reliable way of ADDING animated features to Web pages. pg 248
    • GIF can be used to store any form of animation. pg 248
    • GIF CANNOT
      • add sound
      • you are restricted to a 256 color palette
      • images are lossless compressed which conserve quality but does not offer much compression.
  • Each frame of animated GIF is displayed by the browser as it arrivespg 248
    • however, network speeds mean that there maybe exessive, and irregular, delays between frames. Making any frame rate that maybe specified in the file irrelevant. pg 248
    • in general, there is little chance of an animated GIF consistently playing back at a high frame rate to give smooth animation unless it is small.pg 248
      • Web page advertising is what animated GIF's are most often used for. pg 249
  • Video format will provide the best results for capturing animation of any duration especially if it contains sound. pg 249
  • QuickTime's Animation - compression is RLE and when codec is at its highest setting it is lossless. There is also a lossy mode setting for higher compression ratios. Because it is RLE compression it works well with flat colors which makes it suitable for animation. pg 249

Digital Cell and Sprite Animation

  • SPRITE ANIMATION - animation based on moving objects. Example: a moving body in a walk cycle. pg 250
  • SPRITE - what the objects are refered to as in an animation. pg 250
  • FACES - a still image representing one single state of sprite (the object). Example: one position of a body during a walk cycle. pg 250
  • More SPRITE
    • Works on the idea of layers that are automated
      • a sprite can be thought of as an automated layer
      • it’s motion is driven by a program
    • One layer is the background
    • Sprites are over that
    • Sprites can have faces
    • Sprites can move and show different faces as they move...
  • Digital Cell
    • 2-D model
    • Works on the idea of layers
    • like bitmapped image layers
    • One layer is the background
    • Other layers are of the different parts that will move
    • By moving each part a little bit you create frames of an animation

Key Frame Animation

  • KEYFRAMES - in animation and film making it is a drawing that which defines the strarting point and ending points of any smooth transition. pg 251
    • Came from Disney following Ford’s ideas
    • Break production into simpler tasks
    • Assign tasks to less skilled labor
    • At Disney, Key Frames, the important frames,
      • done by skilled animators
      • came at important portions of the action
      • came at scene changes
    • Less skilled labor connected the action
      • key-frame to key frame (in-betweeners)
    • Process is similar to interpolation
      • remember Blender IPO? InterPOlation
  • INTERPOLATION - the calculation of values of a function lying between two known points. pg 252
    • the simplest form of interpolation is LINEAR. this means the object moves an equal distance between each frame, the distance moved per frame being the total distance between the objects positions in the starting and ending keyframes, divided by the number of frames in the sequence.
  • LINEAR INTERPOLATION means the object moves at a constant velocity causing 2 problems....
  • Forms of interpolation
    • linear... motion follows a straight line
    • velocity is constant
    • moves same distance for each unit of time
    • not natural... instantly starts, instantly stops
      • Applebees apple story, the apple jumps up and down at the same speed (doesn't look right) they are using linear interpolation
  • quadratic... motion follows a curve
    • acceleration (deceleration) is constant
    • “easing in” and “easing out”
    • smooth motion can be achieved by using the Bezier curves instead of straight lines to interpolate between key frames.pg 253

Web Animation and Flash

  • SHOCKWAVE FLASH (SWF)-most popular web animation format.pg 254
  • SWF is a vector format which makes it suitable for Web animation. pg 254
  • SWF formats can have lower bandwidth requiremets than video of any bitmap format. pg 254
  • Vector animations do not offer the full range of visual possibilities available in bitmaps. pg 254
  • An SWF file consist of items which are divided into two broad classes.. pg 260
    • definitions - used to store definitions of the symbols used in animation into a dictionary pg 260
    • control items - instructions to place, remove, or move a symbol(identified by its name in the dictionary) pg 260
  • SWF data is encoded in a binary form and compressed, resulting in very small files. pg 260
  • Flash
    • Has a stage & characters
    • Follows a timeline
    • Supports their form of interpolation called “tweening”
    • Action is driven by scripts

The Timeline and Stage

  • Timeline - a graphical representation of a sequence of frames, similar to the timeline in video editing applications. pg 255
  • FLASH'S STAGE- is a sub window in which frames are created by drawing objects. Objects can be created on the stage using some built in drawing tools. pg 255
  • ONION SKINNING - in Flash animation onion skinning allows preceding frames (up to 5) to be displayed semi transparently under the current frame. This makes it easier to see the changes between frames and to align objects correctly. pd 256
  • Supports their form of interpolation called “tweening”

Symbols and Tweening

  • SYMBOL - graphical objects stored in a library in a special form that allows them to be reused. pg 256
    • Three types of Symbols
      • graphic symbols - reusable vector objects
      • button symbols - specialized type symbols used for adding interactivity to Flash
      • movie clip - self contained animations with their own timelines that play within the movie.
  • TWEENING - the interpolation of additional frames between key frames to compltete the illusion of motion or action. pg 256/257
    • motion tweening - the interpolation of motion in animation between key frames.
    • shape tweening/morphing- a form of interpolation where the shapes of graphical objects are transformed between key frames. Example: a square can be turned into a circle.

Motion Graphics

  • Interpolation between key frames can be applied to bitmap images. Since bitmaps do not contain identifiable objects, the use of layers to isolate different elements of an animation is essential. pg 261
  • The simplest animations are made by repositioning layers, either by dragging them or by entering coordinates and interpolating motion between key frames. pg 261
  • Interpolation can be applied to other properties of a layer, its angles can be varied so that it appears to rotate. pg 262
  • Linear interpolation leads to abrupt changes in direction.pg 263
  • Bezier interpolation changes in direction are smooth. pg 263
  • Motion Graphics (AfterEffects)
    • 2D model to 2D image
    • Takes the photoshop image with all its layers
    • Provides a means of manipulating the images to make motion
  • Achieving natural human motion
    • This is REALLY hard to do unless you use MOTION CAPTURE
    • points mapped on a dancer, moves are captured by cameras around the stage.
    • amimated character created and those points put on the character and the dance scene is created
    • The dancing elephant story.

3-D Animation

  • 3-D animation timelines are used as a convient way of organizing the animation and motion paths and generally used to desribe movement.
  • KINEMATICS - the study of the motion of bodies without references to mass or force. It is only concerned with how things can move rather than what makes them move. pg 268
  • INVERSE KINEMATICS - works backwards from effect to cause. pg 268

Virtual Reality

  • phrase was originally used to describe an immersive sensory experience of a synthetic world.
  • Total immersive VR (YOU ARE IN IT, maybe as a participant)
    • Stereo head mounted display
    • sensors to detect your position
      • on your head
      • on your hands (or any other part that will be in the scene

VRML

  • Virtual Reality Modeling Language - was created on a wave of enthusiasm for VR and the WWW IN 1994. PG 269
  • VRML - allows the specification of objects, in terms of their geometry (whether they are a cube, cylinder, sphere, and so on) and the material that they are composed. pg 270
  • VRML provides a mechanism for distributiing VR and 3-D over the internet.
  • In order to create an illusion of a 3-D image moving through space VRML must be rendered in real time.
  • not immersive (you aren’t in them directly)
  • not stereo vision
  • viewed on a screen
  • you can navigate through them

Quicktime VR

  • Two types of QuikTime movies
    • panoramic movie - presents a 360 degree view of a scene
    • object movie - allow a user to examine an object from different angles as if by walking around it.
  • not immersive (you aren’t in them directly)
  • not stereo vision
  • viewed on a screen
  • you can navigate through them


WRAP UP LECTURE

How Internet Works Slides 2 thru 5

  • The important part to DHCP
    • the Browser is a client
    • use data name server (DNS) to assign a domain name to an IP address
    • stuff you specify beyond the domain name tells the remote server what files you want.
  • How it Works
    • Hook up over you ISP
    • the DNS (Data Name System) assigns you an IP # (135.10.34.443)
    • now you have an IP that is in your client (browser, Safari)
    • browser is now working , you can enter in a URL. Ex. www.Yahoo.com (send)
    • connects from your machine through the ISP to the ISP data name server (DNS) which equates to yahoo .com to an IP address.
    • client now knows who it (yahoo .com )is through DHCP
    • internet knows the DHCP client wants to connect to the particular web server. EX. (www.yahoo.com)
    • internet now knows the IP for the client (DHCP: 135.10.34.443) & IP for the server (http://www.yahoo.com = 235.01.30.564).
    • now you connect
    • Once connected, (the internet knows IP's for both ends) what you specify beyond the domain name tells the server what pages to send your browser. EX. www.yahoo.com /vehicles/2008/suvs.html
    • if you enter in only yahoo.com the assumption by the internet is that you want the home page only. The /index.html

How to start a website

  • You have to buy a Domain Name
    • register.com
    • godaddy.com
  • The Domain Name supplier
    • pay by the year
      • exclusive rights to use that domain name for however long you pay for it.
    • may provide some storage space for your web pages using their IP
    • probably get email accounts with it
    • will allow you to configure your site
    • set up domain-name-to-IP mapping

Let’s look at LINKS

  • notice that the links are distinguished from regular text (underlined and color)
  • also... once used, they turn a different color
  • here the nodes connected by links are only 1 level deep...
    • 4-5 is usually the deepest that is recommended
    • ENTER PICTURE
  • you can have links...
    • between pages
    • into pages
    • within pages
      • all are set up so you can do links in html

Disorientation..

  • Where am I?
    • URL is SOMETIMES useful... Example:
    • Why just sometimes?
      • dynamically generated content like PHP, Perl, CGI (scripted language)
        • Wep page is Dynamic...its created on the fly.
        • Example would be a weather page or an almanac
      • webpage can be different each time you visit it
        • all your browser receives from a server is a bunch of text. Your browser makes the web page look or appear the way it does on the screen.
    • Where was I?
      • browsers have “back” buttons
      • pages can have embedded links that take you back
      • browser history works without user interaction
      • browser bookmarks work with user interaction
      • use search engine and remember search strings
        • Google

Finding your way around...

  • Bookmarks User-built
    • indices and links can be built by hand
    • people search the web and keep useful indexes making them part of the site
    • may rely on the user to search and rate sites
  • Indices Machine-built
    • indices and links are built using spiders, robots or WebCrawlers
    • these are programs that search the web looking for content
      • another way to build bookmarks is by having programs go out and look for things. Ex. spiders, robots, webcrawlers. They look at content on the Web that looks for things.
        • example of how they work...send out a spider, webcrawler, or robot to search through web pages looking for e-mail addresses. It would indentify an e-mail address by finding the @ or mail to ;. It would then save all the e-mail adresses found and build a list. People then could sell the list of e-mail addresses. This is originally how SPAM was generated

WebCrawlers

  • Once looked and collected email addresses to sell to spammers
  • Simple to do
    • request a page
    • look through the text of the page for something @ something.something
  • Can be defeated by using unfriendly-to-robot-code like: jrowan (at) GGC (dot) USG (dot) EDU
    • humans can read this just fine!

Search Engines

  • Search web pages looking for keywords
  • Then they build a catalog of keywords
    • You enter a keyword in the engine
    • It looks at its table
    • It sends you the URLs associated with the keyword
  • GOOGLE extends this by including the number of links that point to that particular page
    • it will display the wepage with the most links pointed to it first.
    • uses a rating system of importance

Web Protocols

  • Protocols define the rules to be followed in a conversation
    • who talks first
    • what is acceptable to request
    • what are acceptable responses to a request
    • syntax is the actual form of each interaction
  • HTTP - Hyper Text Transfer Protocol
    • identifies it as a web page request
      • client always talks 1st
  • FTP - File Transfer Protocol
    • identifies it as a file that needs to be downloaded
    • not seen as much anymore
    • was originally designed just to download files
  • SMTP - Simple Mail Transport Protocol
    • identifies it as pertaining to email

Parts of the URL

  • Has three parts:
    • (1)Specifies the protocol to use
      • HTTP
      • FTP
      • SMTP
        • if you do not specify protocol when entering a URL, todays browsers automatically assumes and adds the http:// to it because it is required by the internet
  • (2)The Domain Name
    • www.ggc.usg.edu
  • (3)Other defining stuff
    • directory info and pages (fixed content)
    • data to be handed to a program (dynamic content)

Other defining stuff... directory info and pages

  • HTTP://www.jimrowan.com
    • assumes HTTP://www.jimrowan.com/index.html yielding web page (the very 1st page)
  • www.jimrowan.com/about/
  • -can have two responses
  • -assumes index.html yielding web page
  • -assumes you want a directory list yielding a list of the contents of the directory:
    • CV.html
    • index.html
    • publications.html
  • www.jimrowan.com/about/index.html
  • www.jimrowan.com/about/research.html
  • www.jimrowan.com/about/before1990/index.html
  • www.jimrowan.com/about/after1990/index.html

Other defining stuff...data to be handed to a program

  • http://cgi.ebay.com/
  • ebaymotors/ws/eBayISAPI.dll
  • ?ViewItem&item=260182066605&
  • ssPageName=ADME:X:AAQ:MOTORS:1123

A brief history

  • Tim Berners-Lee (not al gore)
    • invented the internet
    • 1980 built the first web server
    • mid 1980s worked with hypertext
    • 1988- “I just had to take the hypertext idea and connect it to the TCP and DNS ideas and ta-da! the World Wide Web!”
    • wrote the first web browser (the client)

Command driven computer interface

  • Example
    • Last Login: Tues Nov 27 16:52:18 on console
    • Welcome to Darwin!
    • host 112-26:~jrowan$

GUI

  • Alan Kay worked for XEROX PARC 1970’s
    • created first GUI in 1976
    • Dynabook 1968 (prototype lap top design)
    • "The way to predict the future is to invent it yourself"
  • Steven Jobs Macintosh 1984

Outside Reading

Questions

  • When using the internet you are directing a conversation that occurs between two computers. One of these computers is the one that you are running a browser on, the other is the one that the website is hosted on. By clicking a hyperlink on the webpage, the user is telling the browser, which is the CLIENT, to send a request for the webpage (specified by the URL) from the SERVER
  • The domain name in a URL is in human readable form. For the internet to work that domain name must be translated into an IP address. What is the part that is responsible translating the domain name into the IP address? DHCP
  • "In this URL:
  • In a traditional, html-based website what is the filename of the home page? URL
  • Al Gore claims to have invented the internet. Who is actually credited with its invention? Tim Berners Lee
  • There are programs that automatically search through the web to collect and aggregate information. There are a variety of names for these programs. Give one of the names that were mentioned in class.

Web Crawlers, Spiders, Robots

  • One way to defeat these web-searching programs is to present information in a form that is human-friendly but not program-friendly. Give one example of how this might be done. tamorose(at)GGC(dot)USG(dot)EDU
  • There are times when a web designer would want to help these automated web-searching programs in their quest for information about your web pages. One way to do this is to embed LINKS (what’s it called?) in the html. In this way the web designer could provide appropriate keywords, page names and content descriptions.
  • Web protocols specify the rules that must be followed in a conversation between computers. Name two different things that web protocols specify. 1.who talks first 2.what is an acceptable response to a request
  • In class we discussed three different web protocols. HTTP is the most familiar of these. Name the other two giving their acronym and the acronym’s meaning. FTP-File Transfer Protocol & SMTP - Simple Mail Transport Protocol
  • If the URL you enter into your browser is:

http://www.jimrowan.com/about/before1990/research.html Write the number 14 next to the name of the file that is going to be sent to your browser and circle the name and number. research.html is the file that will be sent

  • If the URL you enter into your browser is:

http://www.jimrowan.com/about/after1990 Write the number 15 next to the name of the file that is going to be sent to your browser and circle the name and number. (If the name happens to be the same as in question 14, you will have two circles drawn around the file name) you will receive the index.html file in the after 1990 file. The reason is that there is no file listed following /after 1990 in the URL. So, index.html is the automatic default file when there is not a specific file listed. If index.html is not in the file the you will get a return of PAGE NOT FOUND.

Copyright,Fairuse,MillenniumCopyrightAct

Copyright

  • What is copyright?
    • It is a legal concept, enacted by most governments, giving the creator of an original work exclusive rights to it, usually for a limited time.
  • Name two rights that the copyright holder is given
    • The right to be credited for the work and to determine who may adapt the work to other forms.
  • Copyright covers ideas and information themselves. True or False?
    • False; Only the form or manner in which they are expressed.
  • Two authors may own copyright on two substantially identical works, if it is determined that the duplication was coincidental, and neither was copied from the other. True or False?
    • True
  • A widely circulated strategy to avoid the cost of copyright registration is referred to as the "poor man's copyright." It proposes that the creator send the work to himself in a sealed envelope by registered mail, using the postmark to establish the date.The United States Copyright Office accepts this technique as substitute for actual registration. True or False?
    • False
  • What was copyright originally used for?
    • It was used as a way for the government to restrict printing
  • How long does a copyright last?
    • It lasts anywhere form 50-100 years after the creators death
  • True or False: A work that that does not have a copyright symbol is public domain?
    • False: A law passed in 1989 made it assumed to be copyrighted unless the author opts out
  • How are copyrights enforced?
    • They are enforced by civil matter or in some cases by criminal sanctions.
  • What is the name of the law that changed the length of a copyright in the United States in 1998?
    • Copyright Term Extension Act
  • What is the symbol for a sound recording copyright?
    • A small circle with the letter “P” inside.
  • What are 2 of several international conventions that standardized the copyright law?
    • Berne Convention and Universal Copyright Convention
  • What are 2 fundamental justifications of copyright laws established by the legislative acts?
    • 1. To benefit society by promoting the creation of new works. 2. To protect the moral rights the creators of the works.
  • Few of several exclusive rights attached to the holder of a copyright are...
    • To import or export work; to perform or display work publicly; to sell or assign their rights to others; to transmit or display by radio or video.
  • What does "exclusive right" mean?
    • Only the copyright holder is free to exercise those rights, and others are prohibited from using the work without his permission.
  • When are Exemptions granted?
    • Exemptions are granted when it is shown that access-control technology has had a substantial adverse effect on the ability of the people to make noninfringing uses of copyrighted works.
  • When do exemptions expire?
    • Exemptions expire after three years.
  • What are derivative works?
    • Works that adapt the original works
  • What is the symbol that indicates something has been copyrighted?
    • A "c" enclosed in a circle.
  • What stems from the U.S. first amendment?
    • The United States Trademark law
  • What year was the Universal Copyright Convention drafted?
    • 1952
  • What is another reason the Copyright act was designed?
    • To implement the treaties signed in December 1996 at the World Intellectual Property Organization Geneva Conference
  • Who opposed the Copyright Act?
    • scientists, librarians, and academics
  • What United States Senator introduced the Copyright Act of 1976?
    • John Little McClellan
  • How many myths are associated with the Copyright Act?
    • ten

Fairuse

  • What does Fair use allow?
    • Allows limited use of copyrighted material without requiring permission from the rights holders, such as use for scholarship or review
  • To justify the use of information fair, what does one have to demonstrate?
    • One must demonstrate how it either advances knowledge or the progress of the arts through the addition of something new.
  • In determining whether the use made of a work in any particular case is a fair use how many different factors are there to consider?
    • Four
  • The four factors of analysis for fair use set forth are?
    • 1.Purpose and character 2.Nature of the copied work 3.Amount and substantiality 4.Effect upon work's value
  • The purpose and character of the use, including whether such use is of a commercial nature or is for nonprofit educational purposes, is a factor in determining what?
    • Whether something is fair use or not
  • The fair use doctrine stems from which constitutional amendment?
    • The first amendment
  • What is a fair use doctrine?
    • A doctrine in the US copyright law that allows limited use of copyrighted material without requiring permission from the right holder.
  • True or False: Any use that seems fair is fair use
    • False
  • True or False: If it is copyrighted, it is NOT fair use
    • False

Millenniun Copyright Act

  • What does DCMA stand for?
    • Digital Millennium Copyright Act
  • When was Digital Millennium Copyright Act (DMCA) passed?
    • October 28,1998
  • DMCA Title IV contains an assortment of provisions,name two of those
    • Clarified and added to the duties of the Copyright Office and it added provisions to facilitate distance education.
  • DMCA Title III modified section 117 of the copyright title states that those repairing computers can make certain temporary, limited copies while working on a computer. True or False
    • True
  • What is the DMCA Title V?
    • Vessel Hull Design Protection Act
  • What does Title III: Computer Maintenance Competition Assurance Act from the DMCA say?
    • It modified section 117 of the copyright title so that those repairing computers could make certain temporary, limited copies while working on a computer
  • Which president signed the DMCA into a law?
    • President Bill Clinton.
  • What does it mean that DMCA is anti-competitive?
    • It gives copyright holders--and the technology companies that distribute their content-- the legal power to create closed technology platforms and exclude competitors from interoperating with them.
  • What does OCILLA stand for?
    • Online Copyright Infringement Liability Limitation Act
  • What does OCILLA do?
    • It protects online service providers against copyright liability if they follow certain rules.
  • What does DMCRA stand for?
    • Digital Media Consumer’s Rights Act
  • What does SSSCA stand for?
    • Security Systems and Standards Certification Act
  • Is linking to infringing content illegal?
    • yes
  • The DCMA amended which title to the U.S. code
    • 17
  • Which Act of the Congress was amended by the Digital Millenium Copyright Act?
    • Copyright Act of 1976
  • DMCA Title IV added all of the following provisions EXCEPT:
    • changed the remedies for the circumvention of copy prevention systems
  • Who is Dmitry Sklyarov and why was he arrested in 2001 for?
    • For alleged infringement of the DMCA
  • What is The Advanced eBook Processor
    • It is a software application which allows users to strip usage restriction information from restricted e-books
  • What is title II of the DMCA?
    • It limits the liability of Internet Service Providers for certain infringements

Test One

  • at home your connection to the internet will most likely be made using DHCP while most servers have fixed IPs. What does the use of DHCP mean in terms of the IP address?
    • It is DYNAMIC, your IP address is always changing
  • Name an affordance found in a bound book that is not found in an electronic pdf version of that same book.
    • In a bound book you can take notes in the margins
  • Many bound books are intended to be read from front to back in a linear manner. What is one mechanism that allows you to read that same book in a non linear manner?
    • Index / page numbers
  • Media that we have discussed in class have two predominant organizing schemes. An audio file (like an mp3 for example) is a form of media that is....
    • time based
    • frequency based
    • page based
    • sample based
  • Would it be possible for the code 38 to be a hexadecimal (base 16) code?
    • yes
  • Would it be possible for the code 38 to be an octal (base 8) code?
    • no
  • Are the number of beans in a 1 quart jar an example of a discrete of continuous real world phenomenon?
    • discrete because it can be counted
  • To model a discrete phenomenon that is found in the real world should the phenomenon be counted or measured?
    • counted
  • You have taken over a research project after the retirement of a colleague. One of the things you inherited is a library of audio files that were sampled at 20,000 samples per second with a 2 byte sample size. As it turns out, your research requires that you be able to identify sounds that have a frequency of 12,000 cycles per second. Will you be able to use the audio library for your research?
    • No
      • why???
      • the audio files were sampled at 20,000 samples per second which means that the actually fidelity is 10,000 cycles per second which is 2,000 samples short of the needed 12,0000 cycles per second.
      • 12000 cyc/sec = 24,000 samples/sec at 2 bytes
  • CD quality audio recordings are sampled at 44,000 samples per second. Each one of these samples is two bytes (stereo has two tracks so a stereo recording has 4 bytes, two per track). How many bytes of data would you have to capture if you record in stereo for 3 seconds
    • 44,100 X 3sec=132,300
    • 132,300 X 4bytes=529,200bytes
    • 529,300 bytes of data
  • Referring to the previous question - if instead of 2 byte samples, you took 1 byte samples the resulting file would be
    • a little smaller
    • half as big
    • twice as big
  • Referring to the previous question, if instead of a 2 byte samples you took a one byte sample how many different values could the individual samples take on?
    • 2^8=256
  • You have taken over a research project after the retirement of a colleague. One of the things you inherited is a library of audio files that were sampled at 20,000 samples per second with a 2 byte sample size in order to capture frequencies that humans can hear. Your new research involves identifying sounds made by elephants that are below normal human hearing at 20 cycles per second. Can you use these audios for your research?
    • yes
      • why??
  • On film (or in video) the frame sampling is fixed. Sometimes that sampling rate causes things in the scene to exhibit retrograde motion. What appears to be happening when watching this film or video?
    • objects can be moving forward as their parts appear to be moving backwards. Ex. car is driving forward as the wheels appear to be spinning backwards.
  • For the sake of argument, assume that a gradient shown is a bitmap image that displays 256 shades of gray. How many bits must be stored for each pixel to store 256 shades of gray?
    • 8 bits, because 2^8 = 256
  • How big would a file be if you waned to to store only half as many (128) shades of gray?
    • same size
    • a little bit smaller
    • half as big
    • less than half as big
  • If a diagram (fragmented disk) represented the disk drive of a computer where the black rectangles represent occupied memory locations and the white rectangles represent available memory locations, we would say the that the memory is fragmented. Why would you want to defragment it?
    • so that when you store more info on it , it is not scattered all over the disk. If the info is scattered all over the disk it will take the computer longer to access the info, if the disk is defragmented then access will be faster.
  • Using an asymmetric connection to the internet it will take less time for you to post your YouTube video than it will take your friend to download the video
    • No, it will take longer for me to post and less time or them to download
  • Using the internet involves client programs and server programs. Your browser is an example of of a server program
    • false, the browser is the client
  • The IP address, a sequence of numbers, is used by the internet to route traffic from one end to the other yet when we use a browser to access the internet we are not required to enter the IP address. Instead we enter a (BLANK) which gets translated by the DNS to an IP address
    • domain name
  • Bitmap graphics and vector graphics have very different internal models. This affords them very different advantages and different disadvantages. Which would be best suited for the use in an animation
    • vector graphics.
  • What affects the size of a vector graphic?
    • contents of the image
  • What affects the filesize of a bitmap graphic?
    • both height and width
    • contents of the image
    • height alone
    • width alone
  • The process of converting the internal model of a vector graphic to a bitmapped external model is....
    • Rendering
  • Converting a bitmapped graphic into a vector graphic is more difficult than converting a vector graphic to a bitmapped graphic
    • true

Test Two

  • 1st question was identifying a cell in a table that has an x and y axis
    • (x,y) or (2,3)
  • Displacement question
    • if the line (arrow) goes backwards (right to left) on the vector table and up (or increases) the diplacement is -x (x = the number placements it goes back) and y (y = the number it increases). Test answer was x = -6 and y = 1
    • if the line (arrow) goes backwards (right to left) on the vector table and down (or decreases) the diplacement is -x (x = the number placements it goes back) and -y (y = the number it decreases). Test answer would have been x = -6 and y = -1
    • if the line (arrow) goes forward (left to right) on the vector table and down (or decreases) the diplacement is x (x = the number placements it goes forward) and -y (y = the number it decreases). Test answer would have been x = 6 and y = -1
    • if the line (arrow) goes forward (left to right) on the vector table and up (or increases) the diplacement is x (x = the number placements it goes forward) and y (y = the number it increases). Test answer would have been x = 6 and y = 1
  • In the diagram above a comouter screen is shown with an open application window whose upper left hand corner is located at (340,200). In that window application there is a black square. The black square's upper left hand corner is located at (75,90) relative to the application window. What are the absolute coordinates of the black square?
    • add the "x" coordinates, 340 + 75 = 415
    • ad the "y" coordinates, 200 + 90 = 290
    • answer (415,290)*
  • The diagram above (not shown) is a number 8 shaped object (at an angle) that is displayed on a computer screen. Give the TWO points that define the bouding box that contains the object
    • A bounding boxes location is defined by 2 points, the top left hand corner and the bottom right hand corner.
    • The answer to the test question was (503,210) & (835,410)
  • You apply a chemical compound to an object that makes the object appear to be cyan in color.What color is the chemical compound absorbing?
    • red
      • how? (cyan= green + blue)(cyan= white - red)
  • Assume you print most of your documents exclusively in red. Which two colors of ink will be used the most (assume the ink cartridge has cyan, magenta, yellow and black)
    • yellow and magenta
      • look at the circle chart
  • Questions 7,8,& 9 are about rotated, translation and reflected.
    • which diagram (4 of them) could be desribed as showing an object (labeled A) that was first rotated around the center of the bounding box and then translated to the position labeled B?
      • ALL 4 DIAGRAMS
    • which diagram (4 of them) could be desribed as showing an object (labeled A) that was translated to a different position labeled B?
      • 1st diagram, it was translated ONLY. no rotation or reflection took place. That is key in picking the correct answer.
    • which diagram (4 of them) could be desribed as showing an object (labeled A) that was reflected across a line that is parallel to the Y axis to the position labeled B?
      • 2nd diagram, they match up when you fold the diagram in half on the Y axis
  • Name one piece of software used to edit vector graphic images?
    • Inkscape
  • Constructive Solid geometry questions with pictures of objects
    • Intersection - only defines those points that are "touching each other when the 2 objects are combined. All the surrounding "left overs" drop off.
    • Union - combining two (or more) objects to create one new object. Example - two rectangular cubes combine to create a cross.
    • Difference - after combining two objects (A & B) the object is what remains after you subtract out (A - B) all of object "B" including the intersection.
      • This will more than likely create 2 seperate objects
  • In class we discussed the three forms of 3-D modeling; Procedural Modeling, Free Form Modeling, and Construtive Solid Geometry
  • Extrusion is a version of one of these forms, which one?
    • Free Form
  • Blender, the software we will be working with, gives the user a selection of basic shapes that can be used as basic building blocks to be assembled and manipulated to make more complex forms. This makes blender which form of 3-D modeling?
    • Constuctive Solid Geometry
  • If a copression technique is described as "lossy" what does that mean?
    • It loses some of it data during compression, when sent the receiving party will not get the original version.
  • Lighting a 3-D object realistically is complex. Ray tracing is one way to light a scene that produces photo realistic results even when there are multiple objects in the scene. What does ray tracing take into account that allows it to produce these photorealistic results?
    • reflection of the light off one object effects lighting of other objects. It is repeated for each pixel in the image
  • Diagram: The below image measuers 3 pixels by 3 pixels and has 2 different colors. The 24 bit RGB encoding of the two colors are; green (0,255,10) and red (255,0,5)
    • |G | G | G |
    • |G | R | R |
    • |R | R | G |
  • Without data compression, how many bytes would be required to represent this image?
    • 3 bytes per pixel X 9 pixels = 27 bytes
  • If that same image were compressed using RLE data compression, write uot the string of bytes that this compression would produce
    • 4RGB, 4RGD, 1RGB = 12 bytes
  • If that same image were represented using a color table , write out the color table and the minimal bit map required to represent this image.
    • color table
      • [00000000][11111111] 1st 3 sets represent green
      • [00000000][11111111]
      • [00000000][00000000] last 3 sets repesent red
    • minimal bitmap
      • [000]
      • [011]
      • [110]
        • or is it [00001111][0]
        • Total number of bytes = 9 bytes
  • What is it about human vision that JPEG image compression takes advantage of in order to compress a file?
    • humans do not see high frequency changes as well as low frequency changes. JPEG does not code high frequencies with as many quantization levels as it does low frequencies.
  • What is one artifact of compression that an image file can exhibit when using JPEG compression?
    • blurring of hard edges - jaggies
  • How many levels of transparency can a 8 bit mask provide?
    • base 2^8 = 256 levels
  • Convolution mask questions

Test Three

  • Interlaced fields are the vestigial parts of analog television broadcasting. When converting these images to video one approach is to put both interlaced fields in a single buffer and then display that at a high enough frame rate to make motion to appear. Under what conditions does this process cause an artifact known as the "comb effect."
    • when there is a fast moving object captured in the scene. 1/20th of a second delay between the 1st frame and the 1st frame shown again.
  • The speed at which images must be presented in order for humans to perceive motion is about 40 images per second. This is known as the __________________ frequency.
    • fusion frequency
  • Several different conditions can cause this frequency to vary somewhat. Name one.
    • backgroung lighting
    • a persons eyes, everybodys are different
  • Video players, like Quicktime for instance, can be built to gracefully degrade under certain conditions. What does the expression "gracefully degrade" mean?
    • as the bandwith starts to narrow or "degrade" the video will start to look like a fast moving slide show. Eventually the video will degrade to a still image, however the audio will still play because it is much smaller and does not need nearly as much bandwith. Video degrades 1st because of its size.
  • The ratio of the width to height on a video screen is called the __________________ ratio.
    • ASPECT
  • NTSC and PAL video standards enforce the same 4:3 ratio even though they have different frame sizes. How do they do this? (hint: think pixels...)
    • the pixels are not square, one standards pixels are wider than tall and the other standard s are taller than wide.
  • Video can be compressed using two different approaches. One way simply compresses each frame as if it were an individual image. This intra-frame compression technique is referred to as __________________ compression.
    • spatial
  • Video can be compressed using two different approaches. One way compresses the frames using information from previous or subsequent frames. This inter-frame compression technique is referred to as __________________ compression.
    • temporal
  • Inter-frame compression mentioned in 8 relies on key frames. What of the original non-key frames is stored between these key frames?
    • the difference
  • ( yes / no ) If there is a great deal of motion in a video, the inter-frame compression technique mentioned in 9 above will result in a much larger file than if the video doesn't have as much motion.
    • yes
  • Much like the use of a color table to reduce the file size of still images, Intel Indeo, MPEG-4 and Cinepak use "code books" to reduce video file size. What is stored in these "code books" that is used to recreate the original frames of that video?
    • 16 x 16 pixel blocks or patches of color
  • Building this "code book" requires searching all frames of the video before building it. This causes the building of the compressed video to take much longer than the playing of the video. For this reason, this kind of codec is known as a/an...
    • a) symmetric codec
    • b) asymmetric codec
  • (true / false) In our NTSC DV cameras (the ones that can be checked out from the library) the video is compressed before it is written on the video tape.
    • true
  • Blender is a form of 3-D animation software that is of what type?
    • a) Free Form
    • b) Procedural
    • c) Extrusion
    • d) Constructive Solid Geometry
  • Cell animation is a form of animation that Walt Disney perfected in the 1930's. Which popular animated show uses a computer-based form of cell animation?
    • a) South Park
    • b) The Simpsons
    • c) Wallace and Gromit
    • d) Toy Story
  • Felt board animation (aka cut-out animation) is a form of animation. Which popular animated show uses a computer-based form of felt board animation?
    • a) South Park
    • b) The Simpsons
    • c) Wallace and Gromit
    • d) Toy Story
  • Physical model manipulation (aka clay-mation) is a form of animation. Which popular animated show uses a computer-based form of claymation?
    • a) South Park
    • b) The Simpsons
    • c) Wallace and Gromit
    • d) Toy Story
  • Animation created from 3-D models built inside a computer using software that is much like Blender is another animation technique. Which popular animated show uses a computer-based form of felt board animation?
    • a) South Park
    • b) The Simpsons
    • c) Wallace and Gromit
    • d) Toy Story
  • The process of taking a 3-D model built inside a computer, lighting it and producing the frames of an animated movie is called _______________________ .
    • rendering
  • The process of generating the frames that fall between the key frames of an animated movie is called _______________________ . (in this question you can either give me the name of the process or the title given to the people who carry it out)
    • inbetween or interpolation
  • What is the 3-2 pulldown?
    • converting film (24 frames per second) into video (30 frames per second)
    • 3 film frames - first 3 fields
    • 2 film frames - next 2 fields
  • To create an animated film in which the motion of the animated characters is to appear to be natural human motion you would first hire an actor to make the motions wearing a special suit and then map the animated character to those motions. What is this process called? _______________________
    • motion capture
  • An immersive VR environment requires the use of stereo headset to produce different images for each eye. What else must be kept track of in order to make the immersive VR function properly?
    • hands, head or any other part of your body that might be in the scene
  • If you were more interested in the rapid production of an animated movie than you were in the final artistic quality of that movie which form of animation might you choose?
    • a) cell animation
    • b) clay-mation animation
    • c) felt-board animation
    • d) 3-D modeling
  • Which form of animation would you choose if you wanted shadows and reflections generated automatically?
    • a) cell animation
    • b) clay-mation animation
    • c) felt-board animation
    • d) 3-D modeling

Test Four

  • When using the Internet you are directing a conversation that occurs between two computers, the CLIENT and the SERVER. The browser runs on the __________________ while the website is hosted on the __________________.
    • clien and server
  • The domain name in a URL is in human readable form. For the Internet to work that domain name must be translated into an IP address. What part is responsible translating the domain name into the IP address? __________________
    • DNS - Data Name System
  • What are two parts of the three distinct parts of a URL?
    • protocol and domain name
  • There are programs that automatically search through the web to collect and aggregate information. There are a variety of names for these programs. Give one of the names that were mentioned in class. __________________
    • spiders, robots, and web crawlers
  • Whose pioneering work at XEROX PARC resulted in the creation of the desktop metaphor in 1978 and presented on the XEROX Alto III? __________________
    • Alan Kay
  • In a traditional, html-based website what is the filename of the home page?

__________________

    • index.html
  • Al Gore claims to have invented the Internet. Who is actually credited with its invention? __________________
    • Tim Berners Lee
  • Looking at the visual found at:

http://wiki.ggc.usg.edu/mediawiki/images/6/6d/JrowanWebRootDIrectoryExample.tiff This is a screen grab of the web root directory for the www.jimrowan.com website

  • What is the file number of the file that would be sent to the browser if the user entered the URL: http://www.jimrowan.com/academicLife/after1990/research.html?
    • the file that would be sent is - research.html
  • What is the file number of the file that would be sent to the browser if the user entered the URL: http://www.jimrowan.com/academicLife/before1990/  ?
    • The file that would be sent is the "index.html file that is in the before 1990 file.
  • ( TRUE / FALSE ) A widely circulated strategy to avoid the cost of copyright registration is referred to as the "poor man's copyright." It proposes that the creator send the work to himself in a sealed envelope by registered mail, using the postmark to establish the date. The United States Copyright Office accepts this technique as substitute for actual registration.
    • false
  • Name one of the two rights that the copyright holder is given.
    • The right to be credited for the work
  • ( TRUE / FALSE ) Fair Use allows the limited use of copyrighted material but permission must be obtained in writing before the use.
    • False
  • ( TRUE / FALSE ) Even though the name implies that it was enacted after the year 2000 (Millennium is 1000 years), the Digital Millennium Copyright Act was actually passed in 1998.
    • True
  • Give two of the 4 factors that determine whether the work was used with Fair Use.
    • purpose and character
    • nature of the copied work
  • ( TRUE / FALSE ) If there is not a copyright notice, then that means the work is public domain.
    • false
  • DMCA Title IV added all of the following provisions EXCEPT:
    • A. facilitate distance education
    • B. changed the remedies for the circumvention of copy prevention systems
    • C. collective bargaining and the transfer of movie rights

    • D. assist libraries with keeping copies of sound recordings
  • ( TRUE / FALSE ) If it is copyrighted, it is NOT fair use.
    • false
  • ( TRUE / FALSE ) Is linking to infringing content illegal?
    • true
  • __________________ protects online service providers against copyright liability if they follow certain rules.
    • OCILLA
  • The fair use doctrine stems from which constitutional amendment?
    • First Admendment
  • Musical recordings that make it out into the public domain but have not been officially released by the artist or their associated management or their production companies are called what? __________________
    • Bootleg Recordings
  • Classical music is an example of a musical work that is in the __________________ and therefore are not controlled or owned by anyone.
    • public domain
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