Unit 1 Lesson 01
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Unit 1 Lesson 01 Unit 1 Lesson 01 Presentation Transcript

  • Lesson 1 Video and Digital Video Basics Digital Video BASICS Schaefermeyer
  • Objectives
    • Explain persistence of vision
    • Explain scanning
    • Describe a cathode ray tube
    • Describe the difference between interlaced and progressive scanning
    • Explain the use of fields and frames
    Schaefermeyer Digital Video BASICS
  • Objectives (continued)
    • Explain time code and how it is used
    • Explain the analog video signal
    • Describe digital video sampling
    • Understand the concept of video formats
    • Explain the differences between DV and other digital formats
    • Understand the concepts of compression and color sampling
    Schaefermeyer Digital Video BASICS
  • Vocabulary
    • Analog
    • Bandwidth
    • Capture card
    • Cathode ray tube (CRT)
    • Chrominance
    • Codec
    • Color sampling
    • Compressed
    • Field
    • FireWire
    • Frame
    • Frame accurate editing
    • Frequency
    • High definition (HD)
    Schaefermeyer Digital Video BASICS
  • Vocabulary (continued)
    • Hue
    • Interlaced video
    • Linear
    • Luminance
    • National Television System Committee (NTSC)
    • Noise
    • Nonlinear
    • Persistence of vision
    • Pixels
    • Progressive scanning
    • Red, green, blue (RGB)
    • Resolution
    • Sampling
    Schaefermeyer Digital Video BASICS
  • Introduction to Video Persistence of Vision
    • The persistence of vision theory states that the human eye holds a still image for a fraction of a second, remaining on the retina long enough to blend with the next image.
    • Film displays 24 still images each second (frames per second or fps).
    Schaefermeyer Digital Video BASICS
  • Introduction to Video Scanning
    • A cathode ray technology (CRT) has two basic parts—an electron gun in back and a screen in front.
    • The inside of the screen is covered with thousands of tiny phosphorus dots called pixels.
    • The back of a color CRT holds three electron guns: red, green, and blue (RGB).
    • The electron gun receives the input signal and shoots an electron beam at the screen, lighting up the pixels.
    Schaefermeyer Digital Video BASICS
  • Scanning (continued)
    • National Television System Committee (NTSC) video is made up of 525 lines of pixels across the screen, called scan lines.
    • The electron beam scans odd scan lines first, to display half a frame called a field.
    • Then the beam scans even lines. Using two fields to create a complete image is called interlaced video.
    • NTSC video runs at 30 frames per second.
    Schaefermeyer Digital Video BASICS
  • Scanning (continued)
    • The delivery methods for video signals have limited bandwidth (size of the “pipe” that information travels through).
    • Progressive scanning creates each frame by scanning the scan lines in order.
    • High definition (HD) uses more scan lines.
    Schaefermeyer Digital Video BASICS
  • Introduction to Video Time Code
    • Each video frame has a unique identifying number called a time code.
    • In the time code 14:54:32:12, 14 represents hours, 54 means minutes, 32 means seconds, and 12 is the frame number.
    • The type of editing made possible by time code is called frame accurate editing.
    Schaefermeyer Digital Video BASICS
  • Introduction to Video Aspect Ratio and Resolution
    • The width of a visible picture is determined by the aspect ratio.
    • The aspect ratio for standard definition television is 4:3, meaning for every four pixels across, there are three pixels up.
    • HD uses a 16:9 aspect ratio and digital video uses a 3:2 aspect ratio.
    Schaefermeyer Digital Video BASICS
  • Aspect Ratio and Resolution (continued)
  • Introduction to Video Analog Versus Digital Signals
    • Audio and video signals that replicate sound or light waves are called analog.
    • Drawbacks to an analog signal:
      • Little glitches called noise, which get worse with each copy (“generational loss”)
      • Linear nature...you can’t jump back and forth
      • Bandwidth issues because it is hard to make smaller
    Schaefermeyer Digital Video BASICS
  • Analog Versus Digital Signals (continued)
    • Digital video solves the problems with analog:
      • Uses a process called sampling so it does not pick up noise in the signal
      • Nonlinear editing system means you do not have to go through the middle to get to the end
      • Can be compressed to get better video quality using the same bandwidth
    Schaefermeyer Digital Video BASICS
  • Introduction to Digital Video DV Format
    • Each digital format has its own language called a codec (short for compression/ decompression”)
    • One way digital video formats compress video is through color sampling—the amount of information used to describe the color in the video image.
    Schaefermeyer Digital Video BASICS
  • DV Format (continued)
    • Light=luminance
    • Hue=specific color such as red, blue, or green
    • Chrominance=amount of saturation
    • Digital video stores all the luminance information and keeps only part of the color information.
    Schaefermeyer Digital Video BASICS
  • Introduction to Digital Video FireWire
    • A capture card converts video into digital information for the computer.
    • DV uses a FireWire capture card, allowing users to capture video through a standard port.
    • A great advantage of DV is that the video comes in as a digital signal and stays that way.
    Schaefermeyer Digital Video BASICS
  • Summary
    • A television contains a cathode ray rube (CRT) with two basic parts. The electron gun in back shoots a beam that lights up pixels, which are organized in scan lines, on the screen in front.
    • One interlaced video frame consists of two fields—the first created by scanning odd numbered lines; the second created by scanning even numbered lines. Video is displayed at 30 fps, or 60 fields per second.
    • A progressive scanned frame of video is scanned in a single pass, with each line scanned in order. Progressive scanned video can be displayed at 24, 30, or 60 fps.
    Schaefermeyer Digital Video BASICS
  • Summary (continued)
    • Analog video copies light waves. Digital video captures points along those waves; the number of points is determined by the sampling frequency.
    • Analog video is linear and cannot be compressed, or made smaller. Digital video is nonlinear and can be compressed.
    • DV captures the video at 3.6 Mb, uses 4:1:1 color space, and is displayed in a 3:2 aspect ratio with a display resolution of 720 x 480.
    • The DV format includes miniDV, DVCPRO, and DVCAM.
    • DV connects to editing stations through FireWire, eliminating the need for expensive capture hardware.
    Schaefermeyer Digital Video BASICS