Motion Perception and Visual Effects Quiz
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Questions and Answers

What is the key biological phenomenon that contributes to the visual effect of motion?

  • Persistence of vision (correct)
  • Afterimage effect
  • Optical illusion
  • Color mixing

    • How long does an image remain on the retina according to the persistence of vision phenomenon?

  • 25 ms (correct)
  • 75 ms
  • 10 ms
  • 50 ms

    • What is the purpose of the critical fusion frequency in motion perception?

  • To determine image brightness
  • To create a static image
  • To achieve smooth motion transition (correct)
  • To enhance color perception

    • What must be guaranteed for the visual reality to be represented smoothly?

    <p>High rate of image repetition</p> Signup and view all the answers

    What type of display device is commonly associated with motion viewing?

    <p>Cathode Ray Tube (CRT)</p> Signup and view all the answers

    What occurs when two light sources are illuminated in quick succession, according to the phi phenomenon?

    <p>A single light appears to move between two points</p> Signup and view all the answers

    What aspect affects the critical fusion frequency?

    <p>The brightness of the light source</p> Signup and view all the answers

    Which of the following is NOT an aspect of the motion video described?

    <p>It reflects static images</p> Signup and view all the answers

    What does the filament in the electron gun do?

    <p>Emits a stream of electrons when heated</p> Signup and view all the answers

    What is the function of phosphorescence in CRTs?

    <p>Light emitted after the electron beam is removed</p> Signup and view all the answers

    How often must the screen be refreshed to eliminate flicker?

    <p>60 times/sec</p> Signup and view all the answers

    What defines a pixel in a raster display?

    <p>One individual dot or picture element</p> Signup and view all the answers

    Which type of light emission occurs while the phosphor is being struck by electrons?

    <p>Fluorescence</p> Signup and view all the answers

    What contributes to the critical fusion frequency in CRT displays?

    <p>The intensity of the ambient lighting</p> Signup and view all the answers

    What arrangement is primarily used in color CRTs for electron guns?

    <p>Delta electron gun arrangement</p> Signup and view all the answers

    What does persistence refer to in relation to CRT phosphors?

    <p>Time until phosphorescence decays to 10% of initial light output</p> Signup and view all the answers

    What is the minimum frame rate required for perceiving continuous motion?

    <p>15 frames per second</p> Signup and view all the answers

    What technology is used in Color CRTs to differentiate electron beams?

    <p>Shadow mask</p> Signup and view all the answers

    What can cause flickering on a CRT monitor?

    <p>Low refresh rate</p> Signup and view all the answers

    In field-based video systems, how are frames displayed?

    <p>Alternating scan lines in two fields</p> Signup and view all the answers

    What is a consequence of using interlacing in video capture?

    <p>Missing lines lead to tearing</p> Signup and view all the answers

    Which of the following correctly distinguishes progressive scan from interlacing?

    <p>Progressive scan shows a sequence of complete images</p> Signup and view all the answers

    How does a display using interlacing enhance the viewing experience?

    <p>By displaying fields at twice the frame rate</p> Signup and view all the answers

    Why do software programs typically choose two adjacent fields for still frame display?

    <p>To complete the missing set of lines</p> Signup and view all the answers

    What is the main characteristic of the NTSC television system?

    <p>It has a frame rate of 30Hz and consists of 525 lines.</p> Signup and view all the answers

    How is the aspect ratio for conventional TV defined?

    <p>4:3</p> Signup and view all the answers

    What is a consequence of conventional video systems having low resolution?

    <p>They are usually played in a small window on computer screens.</p> Signup and view all the answers

    What is the traditional frame rate and line count for the PAL system?

    <p>25Hz and 625 lines.</p> Signup and view all the answers

    How is pixel detail affected by scanning lines in video resolution?

    <p>Two lines are required for certain picture elements.</p> Signup and view all the answers

    Which statement best describes interlacing in video playback?

    <p>It results in the entire video image lighting up and fading out uniformly.</p> Signup and view all the answers

    How does resolution in conventional video systems compare to computer screens?

    <p>Computer screens often have resolutions up to 1024×768 or higher.</p> Signup and view all the answers

    What does SECAM stand for?

    <p>Sequential Couleur Avec Memoire</p> Signup and view all the answers

    What is the maximum data rate of mpeg-1?

    <p>1.5 Megabit/sec</p> Signup and view all the answers

    What significant improvement does mpeg-2 have over mpeg-1?

    <p>It interleaves audio and video.</p> Signup and view all the answers

    What is the first step in producing computer animation?

    <p>Input process with key frames.</p> Signup and view all the answers

    What technique is used to create intermediate positions in animation?

    <p>In-betweening through interpolation.</p> Signup and view all the answers

    What is the calculated raw video size for PAL TV at 25 frames per second with 425x290 resolution and 16 bits per pixel?

    <p>5.9 Mbytes/s</p> Signup and view all the answers

    Which interpolation technique allows for smoother movement in animations?

    <p>Spline interpolation</p> Signup and view all the answers

    What does morphing achieve in animation?

    <p>It transforms one image into another.</p> Signup and view all the answers

    What is the minimum required sampling rate for capturing video in the PAL system?

    <p>7 MHz</p> Signup and view all the answers

    Which video format was defined by Microsoft for its Video for Windows systems?

    <p>AVI</p> Signup and view all the answers

    What event happens during the composition stage of animation?

    <p>Foreground and background figures are combined.</p> Signup and view all the answers

    How does a color lookup table (CLUT) change object colors in animation?

    <p>By mapping input colors to output colors.</p> Signup and view all the answers

    How many scan lines are there in each frame of PAL TV?

    <p>625</p> Signup and view all the answers

    What is the approximate time it takes to sample each pixel in the PAL system?

    <p>0.15 μs</p> Signup and view all the answers

    What feature is common to both AVI and QuickTime video formats?

    <p>They are software-only systems.</p> Signup and view all the answers

    What is the frame rate at which video playback is supported by both AVI and QuickTime formats?

    <p>30 fps</p> Signup and view all the answers

    Which type of storage is necessary for capturing video data?

    <p>A large hard disk</p> Signup and view all the answers

    What is the typical color depth supported by both AVI and QuickTime formats?

    <p>16 bit</p> Signup and view all the answers

    What is the significance of the 40 ms frame duration for the PAL system?

    <p>It indicates the time allocated for each frame.</p> Signup and view all the answers

    Study Notes

    Multimedia Systems and Applications - Lecture 6 - Video and Animation

    • Video and animation both create a sense of motion.
    • They exploit properties of the human eye's ability to view pictures.
    • Motion video is a crucial multimedia element for capturing viewer interest.
    • Motion's visual effect is due to persistence of vision.
    • Persistence of vision: An object remains on the eye's retina for a short time after viewing (approximately 25 milliseconds).
    • Phi phenomenon: When two close light sources are shown in quick succession, it appears as a single light moving between the points.
    • Discrete images are perceived as continuous because of these phenomena.
    • Temporal aspect of illumination: Smooth motion needs a high enough repetition rate of images per frame.
    • The persistence of vision should cover the interval between the flashes.
    • Critical Fusion Frequency (CFF): The rate at which stimuli are presented and are still perceived separately.
    • Stimuli presented faster than the CFF are perceived as continuous.
    • Motion in video pictures relies on frames being presented faster than the CFF, depending on light source brightness.
    • Brighter light sources result in higher fusion frequencies.

    Display Technologies - Cathode Ray Tubes (CRTs)

    • CRTs are the most common display devices.
    • CRTs are evacuated glass bottles.
    • CRTs use extremely high voltage.

    Display Technologies - Raster Displays

    • Raster: A rectangular array of points or dots.
    • Pixel: A single dot or picture element in a raster.
    • Scan line: A row of pixels in a raster.

    Display Technologies - Phosphors

    • Fluorescence: Light emitted from a phosphor while being struck by electrons.
    • Phosphorescence: Light emitted after the electron beam is removed.
    • Persistence: The time between excitation removal and when phosphorescence drops to 10% of initial light output.

    Displaying Animation

    • Refreshing: Frames need to be refreshed to display new images.
    • Deciding: As new pixels are hit, older ones decay.
    • Frequency: Electron beams must frequently hit all pixels to avoid flicker.
    • Synchronization: The Critical Fusion Frequency(CFF) is necessary to prevent flicker.
    • CFF typically occurs at 60 times per sec, but varies with intensity, individual perception, and lighting conditions.

    Display Technology: Color CRTs

    • Color CRTs are more complicated than monochrome CRTs, requiring precise manufacturing geometry.
    • Color CRTs use a pattern of color phosphors (red, green, blue).
    • Three electron guns and a metal shadow mask differentiate the beams to create different colors.

    Frame-Based Video

    • Continuous motion is perceived when frames are shown at a rate faster than 15 frames per second.
    • PAL systems have a 25-frames-per-second rate.
    • Lower rates make the image appear poor.
    • Playback displays images successively.

    Flicker/Field-Based Video

    • CRT flicker can occur with low refresh rates.
    • Screen phosphors lose excitation and create afterglow between sweeps.
    • Interleaving/interlacing divides a frame into two fields.
    • Two fields display each frame using alternative scan lines and twice the frame rate.

    Progressive vs. Interlacing

    • Progressive displays all scan lines of a frame at once.
    • Interlaced displays a frame in two separate field, showing every other scan line.

    Interlacing

    • Film cameras capture images at high rates.
    • Video capturing methods use interleaving.
    • Odd-numbered frames contain one set of lines, even numbered frames contain another set.
    • The lines of separate fields are displayed at different times.
    • Still image display often involves combining two interleaved fields to address missing scan lines.

    Playback

    • Video playback displays frames successively to create the illusion of smooth motion.

    Broadcast Television

    • Three main systems: NTSC (525 lines, 30Hz), SECAM (625 lines, 25Hz), PAL (625 lines, 25Hz).

    Video Resolution

    • Pixels are the smallest detail.
    • Pixels may be displayed between scan lines, requiring two lines.
    • Vertical resolution is only about 70% of total lines.
    • 4:3 Aspect Ratio is common for standard television.

    Video Sampling Rate

    • Capturing video requires a lot of samples per frame.
    • PAL systems' sampling data rate is impacted by frame rate, scan lines, and horizontal pixels for sampling each pixel.
    • Required hardware depends upon video sample rate and resolution.

    Video Formats

    • AVI (Audio Video Interleaved)
    • QuickTime
    • MPEG

    Animation

    • Animation brings something to life by showing changes with visual impact.
    • Two main kinds of effect are: motion dynamic—time-varying positions, and update dynamic—time-varying shape, color, or texture.
    • Animation is based on visual effects that exploit the persistence of vision and the phi phenomenon.
    • Computer animations involve input, in-between, and output.

    Input Process

    • Animation starts with inputting key frames.
    • Key frames must be digitized.
    • Combined figures form frames.
    • Often done by using traditional artistic techniques before digitization.

    In-between Process

    • In-between frames are calculated between key frames and fill in the gaps in movement.
    • The process of generating frames between key frames is called interpolation.
    • Interpolation gives the system a starting and end point in movement, thereby calculating intermediate positions.
    • Linear or spline interpolation methods are often used for different animation movements/shapes.

    In-between Calculations

    • Linear interpolation is simple, but objects don't move smoothly.
    • Spline interpolation is more complex but can produce smoother movements and more natural animation.
    • Color look-up tables are used to change the color of objects in animation.

    Displaying Animation

    • Video rules govern animation display.
    • Frame rates of 15-20 fps are preferable for smoothness.
    • Animation can be generated as a digital video clip or displayed directly within the animation tool.

    Animation Tools

    • Different software tools are used for various animation styles (e.g. Macromedia, Poser, or 3D animations).
    • VRML (Virtual Reality Modeling Language) is an animation language.

    Report

    • .asf, .avi, .qt, .wmv are video formats.

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    Multimedia Systems and Applications Lecture 6 - Video and Animation PDF

    Description

    Test your knowledge on the biological phenomena contributing to motion perception, including persistence of vision and critical fusion frequency. This quiz covers essential concepts related to visual displays and the mechanics of motion viewing. Challenge yourself with questions about light sources, CRT components, and the principles of motion in visual reality.

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