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Unit 1 Lesson 01


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Unit 1 Lesson 01

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