Multimedia applications

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Multimedia applications

  1. 1. Multimedia Applications
  2. 2. Video
  3. 3. Overview <ul><li>Using video. </li></ul><ul><li>How video works? </li></ul><ul><li>Broadcast video standards. </li></ul><ul><li>Analog video. </li></ul><ul><li>Digital video. </li></ul><ul><li>Video recording and tape formats. </li></ul><ul><li>Shooting and editing video. </li></ul><ul><li>Optimizing video files for CD-ROM. </li></ul>
  4. 4. Video <ul><li>Video is the most recent addition to the elements of multimedia </li></ul><ul><li>It places the greatest demands on the computer and memory (using about 108 GB per hour for full motion) </li></ul><ul><li>Often requires additional hardware (video compression board, audio board, RAID - Redundant Array of Independent Disks- for high speed data transfer) </li></ul>
  5. 5. Using Video <ul><li>Carefully planned video can enhance a presentation (e.g. film clip of JFK, better than an text box of same message) </li></ul><ul><li>Before adding video to a project, it is essential to understand the medium, how to integrate it, its limitations, and its costs </li></ul>
  6. 6. Using Digital Video <ul><li>Digital video has replaced analog as the method of choice for making and delivering video for multimedia. </li></ul><ul><li>Digital video device produces excellent finished products at a fraction of the cost of analog. </li></ul>
  7. 7. Using Digital Video <ul><li>Digital video eliminates the image-degrading analog-to-digital conversion. </li></ul><ul><li>Many digital video sources exist, but getting the rights can be difficult, time-consuming, and expensive. </li></ul>
  8. 8. Video Clips <ul><li>Ways to obtain video </li></ul><ul><ul><li>shoot new film clips with a digital camcorder </li></ul></ul><ul><ul><li>convert you own video clips to digital format </li></ul></ul><ul><ul><li>acquire video from an archive - often very expensive, difficult to obtain permissions or licensing rights </li></ul></ul><ul><li>Be sure to obtain permission from anyone you film or for any audio you use! </li></ul>
  9. 9. How Video Works <ul><li>Light passes from an object through the video camera lens and is converted into an electrical signal by a CCD (charge-coupled device). </li></ul><ul><li>High quality cameras have 3 CCD </li></ul><ul><li>Signal contains 3 channels of color information (red, green, blue) and a synchronization pulse. </li></ul>
  10. 10. How Video Works <ul><li>If each channel of a color signal is separate it is called RGB ( preferred) </li></ul><ul><li>A single composite of the colors and sync signal is less precise </li></ul><ul><li>A typical video tape has separate tracks for audio, video, and control </li></ul><ul><li>( See p. 192) </li></ul>
  11. 11. How Video Works <ul><li>The video signal is magnetically written to tape by a spinning recording head following a helical path </li></ul><ul><li>Audio is recorded on a separate straight track </li></ul><ul><li>The control track regulates the speed and keeps the tracks aligned as the tape plays/records. </li></ul>
  12. 12. Video Basics
  13. 13. Broadcast Video Standards <ul><li>NTSC </li></ul><ul><li>PAL </li></ul><ul><li>SECAM </li></ul><ul><li>HDTV </li></ul><ul><ul><li>Six different formats </li></ul></ul><ul><ul><li>Aspect ratio is 16:9 </li></ul></ul>
  14. 14. Broadcast Video Standards <ul><li>National Television Standards Committee (NTSC): </li></ul><ul><ul><li>These standards define a method for encoding information into electronic signal that creates a television picture. </li></ul></ul><ul><ul><li>It has screen resolution of 525 horizontal scan lines and a scan rate of 30 frames per second. </li></ul></ul>
  15. 15. Broadcast Video Standards <ul><li>NTSC - National Television Standards Committee - 1952, (“never the same color”) </li></ul><ul><li>1 frame = 525 horizontal lines every 1/30 second </li></ul><ul><li>2 passes - odd/even lines, 60/second </li></ul><ul><li>(60 Hz) </li></ul><ul><li>interlacing - to reduce flicker </li></ul>
  16. 16. Broadcast Video Standards <ul><li>Phase Alternate Line (PAL) and Sequential Color and Memory (SECAM): </li></ul><ul><ul><ul><li>PAL has a screen resolution of 625 horizontal lines and a scan rate of 25 frames per second. </li></ul></ul></ul><ul><ul><ul><li>SECAM has a screen resolution of 625 horizontal lines and is a 50 Hz system. </li></ul></ul></ul><ul><ul><ul><li>SECAM differs from NTSC and PAL color systems in its basic technology and broadcast method. </li></ul></ul></ul>
  17. 17. Broadcast Video Standards <ul><li>Advanced Television Systems Committee (ATSC) Digital Television (DTV): </li></ul><ul><ul><ul><li>This digital standard provides TV stations with sufficient bandwidth to present four or five Standard Television (STV) signals or one High Definition TV (HDTV) signal. </li></ul></ul></ul><ul><ul><ul><li>This standard allows for transmission of data to computers and for new Advanced TV (ATV) interactive services. </li></ul></ul></ul>
  18. 18. Broadcast Video Standards <ul><li>Several incompatible standards: </li></ul><ul><li>NTSC (US, Japan, many other countries) </li></ul><ul><li>PAL - (United Kingdom, parts of </li></ul><ul><li>Europe, Australia, South Africa) </li></ul><ul><li>SECAM - (France Russia, few others) </li></ul><ul><li>HDTV - ( US ) - newest technology </li></ul>
  19. 19. Broadcast Video Standards <ul><li>HDTV- High Definition Television now available, allow viewing of Cinemascope and Panavision movies with aspect ratio 16:9 ( wider than high) (See p. 200) </li></ul><ul><li>Twice the resolution, interlaced format </li></ul><ul><li>Digitized then compressed for transmission </li></ul>
  20. 20. Broadcast Video Standards <ul><li>4: 3 Aspect Ratio </li></ul>
  21. 21. Broadcast Video Standards <ul><li>16: 9 Aspect Ratio </li></ul>
  22. 22. Integrating Computers and Television <ul><li>Television video is based on analog technology and international broadcast standards </li></ul><ul><li>Computer video is based on digital technology and other image display standards </li></ul><ul><li>DVD and HDTV merges the two </li></ul>
  23. 23. Analog Video <ul><ul><li>Analog television sets remain the most widely installed platforms for delivering and viewing video. </li></ul></ul><ul><ul><li>Television sets use composite input. Hence colors are less pure and less accurate than computers using RGB component. </li></ul></ul><ul><ul><li>NTSC television uses a limited color palette and restricted luminance (brightness) levels and black levels. </li></ul></ul>
  24. 24. Analog Video <ul><ul><li>Some colors generated by a computer that display fine on a RGB monitor may be illegal for display on a NTSC TV. </li></ul></ul><ul><ul><li>While producing a multimedia project, consider whether it will be played on a RGB monitor or a conventional television set. </li></ul></ul>
  25. 25. Video Overlay System <ul><li>To display analog video (TV) images on a computer monitor, the signal must be converted from analog to digital form ( Where else does this conversion commonly take place?) </li></ul><ul><li>A special digitizing video overly board is required for the conversion </li></ul><ul><li>Produces excellent quality, full screen, full motion video, but costly. </li></ul>
  26. 26. Video Overlay System <ul><li>Many companies use computer based training (CBT) systems </li></ul><ul><li>These require a computer and monitor cabled to a TV and video disc player. </li></ul><ul><li>Overlay boards allow the video disc to be controlled by the computer and display the images on the computer screen. </li></ul>
  27. 27. Video Capture Boards <ul><li>Video overlay boards can capture or digitize video frames and play them back as QuickTime MPEG and AVI movies. </li></ul><ul><li>Some also include audio input and sound management to interleave sound and images </li></ul><ul><li>Some also offer compression and accelerate digitizing, or support NTSC video. </li></ul>
  28. 28. Differences Between Computer and TV Video <ul><li>Computer scan refresh rate = 480 lines/sec </li></ul><ul><li>Computer scan is progressive ( non-interlaced) at 66.67 HZ or higher </li></ul><ul><li>TV scans at 525 (or 625) lines/sec, with interlacing at a frame rate of 60 Hz </li></ul>
  29. 29. Interlacing Effects <ul><li>The TV electron beam actually “draws all the odd line, then all the even lines, interlacing them </li></ul><ul><li>On a computer (RGB) monitor, lines are painted one pixel thick and are not interlaced. Displayed on a TV they “flicker” because they appear in every other field. To avoid this avoid very thin lines and elaborate serifs. </li></ul>
  30. 30. Differences Between Computer and TV Video <ul><li>TV broadcasts an image larger than the screen so that the “edge” of the image is against the edge of the screen. This is called overscan </li></ul><ul><li>Computer images are smaller than the screen area (called underscan ) and there is a border around the image </li></ul>
  31. 31. Computers and Video
  32. 32. Differences Between Computer and TV Video <ul><li>When a computer screen is converted to video the outer edges do not fit on the TV screen only about 360-480 lines of the computer image are visible. </li></ul><ul><li>Avoid using the outer 15% of the screen for graphics, or titles for use on TV </li></ul><ul><li>Use the safe title area </li></ul>
  33. 33. Video Color <ul><li>Color reproduction and display are also different in TV and computers monitors </li></ul><ul><li>Computers use RBG component video and produce more pure color </li></ul><ul><li>NTSC TV uses a limited color palette and restricted luminance (brightness) and black levels </li></ul>
  34. 34. Working with Text and Titles for Video Productions <ul><li>Use plain, bold, easily read fonts </li></ul><ul><li>Use light color text on a dark background </li></ul><ul><li>Avoid color combinations like yellow/violet, blue/orange which “vibrate” </li></ul><ul><li>Avoid black or colored text on white background </li></ul>
  35. 35. Working with Text and Titles for Video Productions <ul><li>Make lines and graphics at least two pixels wide </li></ul><ul><li>Use parallel lines and boxes sparingly and draw them with thick lines </li></ul><ul><li>Avoid “hot” colors </li></ul><ul><li>Keep graphics and titles in the safe screen area </li></ul>
  36. 36. Working with Text and Titles for Video Productions <ul><li>Bring titles on slowly and let them remain on the screen sufficiently long, fade out </li></ul><ul><li>Avoid “busy” screens- use additional pages instead </li></ul>
  37. 37. Digital Video <ul><li>Digital video architecture. </li></ul><ul><li>Digital video compression. </li></ul>
  38. 38. Digital Video Architecture <ul><li>Digital video architecture consists of a format for encoding and playing back video files by a computer. </li></ul><ul><li>Architecture includes a player that can recognize and play files created for that format. </li></ul>
  39. 39. Digital Video Compression <ul><li>Digital video compression schemes or “ codec's ” ( co der/ dec oder) is the algorithm used to compress (code) a video for delivery. </li></ul><ul><li>The codec then decodes the compressed video in real-time for fast playback. </li></ul><ul><li>Streaming audio and video starts playback as soon as enough data has transferred to the user’s computer to sustain this playback. </li></ul>
  40. 40. Video Compression <ul><li>To store even a 10 second movie clip requires the transfer of an enormous amount of data in a very short time </li></ul><ul><li>30 seconds of video will fill a 1 GB hard drive </li></ul><ul><li>Typical hard drives transfer about 1MB/second and CD- ROMs about 600K/second </li></ul>
  41. 41. Video Compression <ul><li>Full motion video requires the computer to deliver the data at 30 MB/second more than today’s PCs and MACs can handle </li></ul><ul><li>Solution- use video compression algorithms or codec's </li></ul><ul><li>Codec's compress the video for delivery and then decode it for playback at rates from 50:1 to 200:1 </li></ul>
  42. 42. Video Compression & Streaming <ul><li>Codecs ( such as MPEG, JPEG) use lossy compression schemes </li></ul><ul><li>Streaming technologies are also used to provide reasonable quality , low-bandwidth on the WEB </li></ul><ul><li>Playback starts as soon as enough data have been transferred to the user’s computer instead of waiting for the whole file to download </li></ul><ul><li>( RealAudio and RealVideo software) </li></ul>
  43. 43. MPEG <ul><li>Standard developed by the Moving Pictures Experts Group for digital representation of moving pictures and associated audio </li></ul><ul><li>http://mpeg.org </li></ul>
  44. 44. Digital Video Compression <ul><li>MPEG is a real-time video compression algorithm. ( M oving P icture E xperts G roup) </li></ul><ul><li>MPEG-4 (1998-1999) includes numerous multimedia capabilities and is a preferred standard. </li></ul><ul><li>MPEG-7 (2002) (or Multimedia Content Description Interface) integrates information about motion video elements with their use. </li></ul><ul><li>MPEG –21 under development </li></ul>
  45. 45. Digital Video <ul><li>Video clips can be shot or converted to digital format and stored on the hard drive. </li></ul><ul><li>They can be played back without overlay boards, second monitors or videodiscs using QuickTime or Active Movie for Windows </li></ul><ul><li>Analog video can be converted to digital or now created in digital form </li></ul>
  46. 46. Video Recording and Tape Formats <ul><li>Composite analog video. </li></ul><ul><li>Component analog video. </li></ul><ul><li>Composite digital. </li></ul><ul><li>Component digital. </li></ul><ul><li>ATSC digital TV. </li></ul>
  47. 47. Composite Analog Video <ul><li>Composite video combines the luminance and chroma information from the video signal. </li></ul><ul><li>Composite video produces lowest quality video and is most susceptible to generation loss. </li></ul><ul><li>Generation loss is the loss of quality that occurs while moving from original footage to editing master to copy. </li></ul>
  48. 48. Component Analog Video <ul><li>Component video separates the luminance and chroma information. </li></ul><ul><li>It improves the quality of the video and decreases generation loss. </li></ul><ul><li>In S-video, color and luminance information are kept on two separate tracks (Y/C) to improve the picture quality. </li></ul><ul><li>Betacam is a new portable professional video format which lays the signal on the tape in three component channels. </li></ul>
  49. 49. Composite Digital <ul><li>Composite digital recording formats combine the luminance and chroma information. </li></ul><ul><li>They sample the incoming waveforms and encode the information in binary (0/1) digital code. </li></ul><ul><li>It improves color and image resolution and eliminates generation loss. </li></ul>
  50. 50. Component Digital <ul><li>Component digital formats add the advantages of component signals to digital recording. </li></ul><ul><li>D-1 component digital format is an uncompressed format which has a very high quality image. </li></ul><ul><li>It uses a 19 mm (3/4-inch) tape in order to save data. </li></ul><ul><li>Several other digital component formats are DCT, Digital Betacam, DV format, DVCPRO, and DVCAM formats. </li></ul>
  51. 51. ATSC Digital TV <ul><li>These standards provide for digital STV and HDTV recordings that can be broadcast by digital TV transmitters to digital TV receivers. </li></ul><ul><li>ATSC standards also provide for enhanced TV bringing the interactivity of multimedia and the Web to broadcast television. </li></ul>
  52. 52. Vaughn’s Law of Multimedia Minimums <ul><li>Your goal is to produce multimedia that is adequate and does it’s job but doesn’t throw you into bankruptcy. </li></ul><ul><li>Experiment with various levels of consumer grade equipment </li></ul><ul><li>Professional sound and video equipment is very expensive </li></ul>
  53. 53. Recording Formats <ul><li>S-VHS and Hi-8 consumer quality </li></ul><ul><li>Component (YUV) - Sony BetacamSP the professional standard for broadcast quality </li></ul><ul><li>Component Digital- a digital version of the Betacam- best format for graphics > $900,000 and produces 15 minutes of video </li></ul><ul><li>Composite Digital most common >$110,000 </li></ul>
  54. 54. Shooting & Editing Video <ul><li>Shooting platform </li></ul><ul><ul><li>use a steady tripod </li></ul></ul><ul><ul><li>or a camera with an electronic image stabilization feature to avoid “shaky hand effect” </li></ul></ul><ul><ul><li>or use camera moves and moving subjects to disguise your lack of steadiness </li></ul></ul>
  55. 55. Shooting & Editing Video <ul><li>Lighting performance is the main difference between professional and consumer camcorders </li></ul><ul><li>Use a simple floodlight kit or natural daylight to improve the image </li></ul><ul><li>Onboard flood lights can be used as fill light to illumine faces </li></ul>
  56. 56. Shooting & Editing Video
  57. 57. Shooting & Editing Video <ul><li>Chroma Key or Blue Screen - popular technique for making multimedia without the use of expensive backgrounds </li></ul><ul><li>In shooting against a blue screen, be sure that the lighting is perfectly even and that actors are not too close to the screen so that color “spills” over on them </li></ul>
  58. 58. Shooting & Editing Video <ul><li>Composition </li></ul><ul><ul><li>Avoid wide panoramic shots </li></ul></ul><ul><ul><li>Use close-ups, head and shoulders </li></ul></ul><ul><ul><li>Remember the more a scene changes the slower the playback will be </li></ul></ul><ul><ul><li>Keep the camera still, let the subject add the motion by walking, turning... </li></ul></ul>
  59. 59. Using Video Tapes <ul><li>Fast forward new tapes and rewind them so that the tension is even (called “packing”) </li></ul><ul><li>Black-stripe the tape by running it through the recorder with the lens cap on -eliminates “snowy noise” </li></ul><ul><li>Do not reuse tapes after editing </li></ul><ul><li>Remove break off tab to avoid overwriting </li></ul>
  60. 60. Video Hardware Resolution <ul><li>Horizontal resolution -the number of lines of detail the camera can reproduce </li></ul><ul><li>Different from the vertical scan lines on TV </li></ul><ul><li>The lens, and number, size and quality of the CCDs determine the resolution </li></ul><ul><li>Poor resolution = poor image </li></ul>
  61. 61. Consumer Grade Equipment <ul><li>Mass production at low cost; easier to use </li></ul><ul><li>Cameras and camcorders that use HI-8 and S-VHS formats are superior to 8 mm and VHS systems </li></ul><ul><li>HI-8 is most widely available tape format and best consumer grade </li></ul>
  62. 62. Making Tape Copies <ul><li>For demo or promo tapes use at least Super VHS ( HI-8 is best and allow unlimited copies to be made without degradation) </li></ul><ul><li>Copying ( dubbing) depends on the tape format and the quality of the equipment being used </li></ul><ul><li>Copy in SP mode- faster writing produces better images </li></ul>
  63. 63. Video Window Size <ul><li>Shrinking a digitized image improves it perceived sharpness </li></ul><ul><li>( Also happens when you switch from 19” to 13” TV) </li></ul><ul><li>The image is crisper because the scan lines are closer together </li></ul>
  64. 64. Editing with Consumer VCRs <ul><li>Editing with 2 VCRs causes problems because the two machines are not in sync </li></ul><ul><li>Editing software, such as Premier, or After Effects, has become more commonly used in multimedia </li></ul>
  65. 65. Video Conferencing <ul><li>Video telephone conferencing standard for compressing audio and motion video images </li></ul><ul><li>Encodes audio and video for transmission over copper or fiber optic lines </li></ul><ul><li>Other compression systems are currently being developed by Kodak, Sony, etc. </li></ul>
  66. 66. Optimizing Video files for CD-ROMs <ul><li>CD- ROMs are an excellent distribution media for multimedia: inexpensive, store great quantities of information, with adequate video transfer rates </li></ul><ul><li>Suitable for QuickTime and AVI file formats as well as those produced by Director, etc. </li></ul>
  67. 67. Optimizing Video files for CD-ROMs <ul><li>Limit the synchronization between video and audio </li></ul><ul><ul><li>AVI interleaves them </li></ul></ul><ul><ul><li>QuickTime files must be “flattened” - to interleave the audio and video </li></ul></ul><ul><li>Use regularly spaced key frames (10 to 15 frames apart) </li></ul><ul><li>Limit the size of the video window- the more data the slower the playback </li></ul>
  68. 68. Optimizing Video files for CD-ROMs <ul><li>Choose the software compression algorithm carefully </li></ul><ul><ul><li>Sorenson codec is optimized for CD-ROM playback </li></ul></ul><ul><ul><li>Cinepack algorithm, available with AVI and QuickTime, is also optimized for CD-ROM playback </li></ul></ul><ul><ul><li>Use Norton speed Disk to defragment your files before burning the master </li></ul></ul>
  69. 69. Summary <ul><li>Various video standards are NTSC, PAL, SECAM, and ATSC DTV. </li></ul><ul><li>Categories of video standards are composite analog, component analog, composite digital, and component digital. </li></ul>

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