COM 205 Multimedia Applications

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COM 205Multimedia Applications

• St. Josephs College
• Fall 2004

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Chapter 8

• Video

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Overview

• Using video.
• How video works?
• Broadcast video standards.
• Analog video.
• Digital video.
• Video recording and tape formats.
• Shooting and editing video.
• Optimizing video files for CD-ROM.

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Video

• Video is the most recent addition to the elements
  of multimedia
• It places the greatest demands on the computer
  and memory (using about 108 GB per hour for full
  motion)
• Often requires additional hardware (video
  compression board, audio board, RAID - Redundant
  Array of Independent Disks- for high speed data
  transfer)

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Using Video

• Carefully planned video can enhance a
  presentation (eg. film clip of JFK, better than
  an text box of same message)
• Before adding video to a project, it is essential
  to understand the medium, how to integrate it,
  its limitations, and its costs

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Using Digital Video

• Digital video has replaced analog as the method
  of choice for making and delivering video for
  multimedia.
• Digital video device produces excellent finished
  products at a fraction of the cost of analog.

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Using Digital Video

• Digital video eliminates the image-degrading
  analog-to-digital conversion.
• Many digital video sources exist, but getting the
  rights can be difficult, time-consuming, and
  expensive.

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Video Clips

• Ways to obtain video
• shoot new film clips with a digital camcorder
• convert you own video clips to digital format
• acquire video from an archive - often very
  expensive, difficult to obtain permissions or
  licensing rights
• Be sure to obtain permission from anyone you film
  or for any audio you use!

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How Video Works

• Light passes from an object through the video
  camera lens and is converted into an electrical
  signal by a CCD (charge-coupled device).
• High quality cameras have 3 CCD
• Signal contains 3 channels of color information
  (red, green, blue) and a synchronization pulse.

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How Video Works

• If each channel of a color signal is separate it
  is called RGB ( preferred)
• A single composite of the colors and sync signal
  is less precise
• A typical video tape has separate tracks for
  audio, video, and control
• ( See p. 180)

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Video Basics
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How Video Works

• The video signal is magnetically written to tape
  by a spinning recording head following a helical
  path
• Audio is recorded on a separate straight track
• The control track regulates the speed and keeps
  the tracks aligned as the tape plays/records.

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Video Basics
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Broadcast Video Standards

• NTSC
• PAL
• SECAM
• HDTV
• Six different formats
• Aspect ratio is 169

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Broadcast Video Standards

• National Television Standards Committee (NTSC)
• These standards define a method for encoding
  information into electronic signal that creates a
  television picture.
• It has screen resolution of 525 horizontal scan
  lines and a scan rate of 30 frames per second.

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Broadcast Video Standards

• NTSC- National Television Standards Committee -
  1952, (never the same color)
• 1 frame 525 horizontal lines every 1/30 second
• 2 passes - odd/even lines, 60/second
• (60 Hz)
• interlacing - to reduce flicker

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Broadcast Video Standards

• Phase Alternate Line (PAL) and Sequential Color
  and Memory (SECAM)
• PAL has a screen resolution of 625 horizontal
  lines and a scan rate of 25 frames per second.
• SECAM has a screen resolution of 625 horizontal
  lines and is a 50 Hz system.
• SECAM differs from NTSC and PAL color systems in
  its basic technology and broadcast method.

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Broadcast Video Standards

• Advanced Television Systems Committee (ATSC)
  Digital Television (DTV)
• 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.
• This standard allows for transmission of data to
  computers and for new Advanced TV (ATV)
  interactive services.

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Broadcast Video Standards

• Several incompatible standards
• NTSC (US, Japan, many other
• countries)
• PAL - (United Kingdom, parts of
• Europe, Australia, South Africa)
• SECAM - (France Russia, few others)
• HDTV - ( US ) - newest technology

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Broadcast Video Standards

• HDTV- High Definition Television now available,
  allow viewing of Cinemascope and Panavision
  movies with aspect ratio 169 ( wider than high)
  (See p. 184)
• Twice the resolution, interlaced format
• Digitized then compressed for transmission

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Broadcast Video Standards

• 4 3 Aspect Ratio

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Broadcast Video Standards

• 16 9 Aspect Ratio

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Integrating Computers and Television

• Television video is based on analog technology
  and international broadcast standards
• Computer video is based on digital technology and
  other image display standards
• DVD and HDTV merges the two

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Analog Video

• Analog television sets remain the most widely
  installed platforms for delivering and viewing
  video.
• Television sets use composite input. Hence colors
  are less pure and less accurate than computers
  using RGB component.
• NTSC television uses a limited color palette and
  restricted luminance (brightness) levels and
  black levels.

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Analog Video

• Some colors generated by a computer that display
  fine on a RGB monitor may be illegal for display
  on a NTSC TV.
• While producing a multimedia project, consider
  whether it will be played on a RGB monitor or a
  conventional television set.

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Video Overlay System

• 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?)
• A special digitizing video overly board is
  required for the conversion
• Produces excellent quality, full screen, full
  motion video, but costly.

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Video Overlay System

• Many companies use computer based training (CBT)
  systems
• These require a computer and monitor cabled to a
  TV and video disc player.
• Overlay boards allow the video disc to be
  controlled by the computer and display the images
  on the computer screen.

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Video Capture Boards

• Video overlay boards can capture or digitize
  video frames and play them back as QuickTime MPEG
  and AVI movies.
• Some also include audio input and sound
  management to interleave sound and images
• Some also offer compression and accelerate
  digitizing, or support NTSC video.

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Differences Between Computer and TV Video

• Computer scan refresh rate 480 lines/sec
• Computer scan is progressive ( non-interlaced) at
  66.67 HZ or higher
• TV scans at 525 (or 625) lines/sec, with
  interlacing at a frame rate of 60 Hz

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Interlacing Effects

• The TV electron beam actually draws all the odd
  line, then all the even lines, interlacing them
• 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.

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Differences Between Computer and TV Video

• 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
• Computer images are smaller than the screen area
  (called underscan) and there is a border around
  the image

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Computers and Video
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Differences Between Computer and TV Video

• 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.
• Avoid using the outer 15 of the screen for
  graphics, or titles for use on TV
• Use the safe title area ( See p. 184)

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Video Color

• Color reproduction and display are also different
  in TV and computers monitors
• Computers use RBG component video and produce
  more pure color
• NTSC TV uses a limited color palette and
  restricted luminance (brightness) and black levels

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Working with Text and Titles for Video Productions

• Use plain, bold, easily read fonts
• Use light color text on a dark background
• Avoid color combinations like yellow/violet,
  blue/orange which vibrate
• Avoid black or colored text on white background

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Working with Text and Titles for Video Productions

• Make lines and graphics at least two pixels wide
• Use parallel lines and boxes sparingly and draw
  them with thick lines
• Avoid hot colors
• Keep graphics and titles in the safe screen area

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Working with Text and Titles for Video Productions

• Bring titles on slowly and let them remain on the
  screen sufficiently long, fade out
• Avoid busy screens- use additional pages
  instead

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Digital Video

• Digital video architecture.
• Digital video compression.

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Digital Video Architecture

• Digital video architecture consists of a format
  for encoding and playing back video files by a
  computer.
• Architecture includes a player that can recognize
  and play files created for that format.

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Digital Video Compression

• Digital video compression schemes or codecs (
  coder/decoder) is the algorithm used to compress
  (code) a video for delivery.
• The codec then decodes the compressed video in
  real-time for fast playback.
• Streaming audio and video starts playback as soon
  as enough data has transferred to the users
  computer to sustain this playback.

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Video Compression

• To store even a 10 second movie clip requires the
  transfer of an enormous amount of data in a very
  short time
• 30 seconds of video will fill a 1 GB hard drive
• Typical hard drives transfer about 1MB/second and
  CD- ROMs about 600K/second

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Video Compression

• Full motion video requires the computer to
  deliver the data at 30 MB/second more than
  todays PCs and MACs can handle
• Solution- use video compression algorithms or
  codecs
• Codecs compress the video for delivery and then
  decode it for playback at rates from 501 to 2001

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Video Compression Streaming

• Codecs ( such as MPEG, JPEG) use lossy
  compression schemes
• Streaming technologies are also used to provide
  reasonable quality , low-bandwidth on the WEB
• Playback starts as soon as enough data have been
  transferred to the users computer instead of
  waiting for the whole file to download
• ( RealAudio and RealVideo software)

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MPEG

• Standard developed by the Moving PIcturesExperts
  Group for digital representation of moving
  pictures and associated audio
• http//mpeg.org

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Digital Video Compression

• MPEG is a real-time video compression algorithm.
  (Moving Picture Experts Group)
• MPEG-4 (1998-1999) includes numerous multimedia
  capabilities and is a preferred standard.
• MPEG-7 (2002) (or Multimedia Content Description
  Interface) integrates information about motion
  video elements with their use.
• MPEG 21 under development

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Digital Video

• Video clips can be shot or converted to digital
  format and stored on the hard drive.
• They can be played back without overlay boards,
  second monitors or videodiscs using QuickTime or
  Active Movie for Windows
• Analog video can be converted to digital or now
  created in digital form

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Video Recording and Tape Formats

• Composite analog video.
• Component analog video.
• Composite digital.
• Component digital.
• ATSC digital TV.

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Composite Analog Video

• Composite video combines the luminance and chroma
  information from the video signal.
• Composite video produces lowest quality video and
  is most susceptible to generation loss.
• Generation loss is the loss of quality that
  occurs while moving from original footage to
  editing master to copy.

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Component Analog Video

• Component video separates the luminance and
  chroma information.
• It improves the quality of the video and
  decreases generation loss.
• In S-video, color and luminance information are
  kept on two separate tracks (Y/C) to improve the
  picture quality.
• Betacam is a new portable professional video
  format which lays the signal on the tape in three
  component channels.

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Composite Digital

• Composite digital recording formats combine the
  luminance and chroma information.
• They sample the incoming waveforms and encode the
  information in binary (0/1) digital code.
• It improves color and image resolution and
  eliminates generation loss.

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Component Digital

• Component digital formats add the advantages of
  component signals to digital recording.
• D-1 component digital format is an uncompressed
  format which has a very high quality image.
• It uses a 19 mm (3/4-inch) tape in order to save
  data.
• Several other digital component formats are DCT,
  Digital Betacam, DV format, DVCPRO, and DVCAM
  formats.

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ATSC Digital TV

• These standards provide for digital STV and HDTV
  recordings that can be broadcast by digital TV
  transmitters to digital TV receivers.
• ATSC standards also provide for enhanced TV
  bringing the interactivity of multimedia and the
  Web to broadcast television.

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Vaughns Law of Multimedia Minimums

• Your goal is to produce multimedia that is
  adequate and does its job but doesnt throw you
  into bankruptcy.
• Experiment with various levels of consumer grade
  equipment
• Professional sound and video equipment is very
  expensive

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Recording Formats

• S-VHS and Hi-8 consumer quality
• Component (YUV) - Sony BetacamSP the professional
  standard for broadcast quality
• Component Digital- a digital version of the
  Betacam- best format for
• graphics gt 900,000 and produces 15 minutes of
  video
• Composite Digital most common gt110,000

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Shooting and Editing Video

• Shooting platform
• use a steady tripod
• or a camera with an electronic image
  stabilization feature to avoid shaky hand
  effect
• or use camera moves and moving subjects to
  disguise your lack of steadiness

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Shooting and Editing Video

• Lighting performance is the main difference
  between professional and consumer camcorders
• Use a simple floodlight kit or natural daylight
  to improve the image
• Onboard flood lights can be used as fill light to
  illumine faces

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Shooting and Editing Video
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Shooting and Editing Video

• Chroma Key or Blue Screen - popular technique for
  making multimedia without the use of expensive
  backgrounds
• 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

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Shooting and Editing Video

• Composition
• Avoid wide panoramic shots
• Use close-ups, head and shoulders
• Remember the more a scene changes the slower the
  playback will be
• Keep the camera still, let the subject add the
  motion by walking, turning...

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Using Video Tapes

• Fast forward new tapes and rewind them so that
  the tension is even (called packing)
• Black-stripe the tape by running it through the
  recorder with the lens cap on -eliminates snowy
  noise
• Do not reuse tapes after editing
• Remove break off tab to avoid overwriting

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Video Hardware Resolution

• Horizontal resolution -the number of lines of
  detail the camera can reproduce
• Different from the vertical scan lines on TV
• The lens, and number, size and quality of the
  CCDs determine the resolution
• Poor resolution poor image

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Consumer Grade Equipment

• Mass production at low cost easier to use
• Cameras and camcorders that use HI-8 and S-VHS
  formats are superior to 8 mm and VHS systems
• HI-8 is most widely available tape format and
  best consumer grade

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Making Tape Copies

• For demo or promo tapes use at least Super VHS (
  HI-8 is best and allow unlimited copies to be
  made without degradation)
• Copying ( dubbing) depends on the tape format and
  the quality of the equipment being used
• Copy in SP mode- faster writing produces better
  images

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Video Window Size

• Shrinking a digitized image improves it perceived
  sharpness
• ( Also happens when you switch from 19 to 13
  TV)
• The image is crisper because the scan lines are
  closer together

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Editing with Consumer VCRs

• Editing with 2 VCRs causes problems because the
  two machines are not in sync
• Editing software, such as Premier, or After
  Effects, has become more commonly used in
  multimedia

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P64

• Video telephone conferencing standard for
  compressing audio and motion video images
• Encodes audio and video for transmission over
  copper or fiber optic lines
• Other compression systems are currently being
  developed by Kodak, Sony, etc.

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Optimizing Video files for CD-ROMs

• CD- ROMs are an excellent distribution media for
  multimedia inexpensive, store great quantities
  of information, with adequate video transfer
  rates
• Suitable for QuickTime and AVI file formats as
  well as those produced by Director, etc.

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Optimizing Video files for CD-ROMs

• Limit the synchronization between video and audio
• AVI interleaves them
• QuickTime files must be flattened - to
  interleave the audio and video
• Use regularly spaced key frames (10 to 15 frames
  apart)
• Limit the size of the video window- the more data
  the slower the playback

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Optimizing Video files for CD-ROMs

• Choose the software compression algorithm
  carefully
• Sorenson codec is optimized for CD-ROM playback
• Cinepack algorithm, available with AVI and
  QuickTime, is also optimized for CD-ROM
  playback
• Use Norton speed Disk to defragment your files
  before burning the master

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Summary

• Various video standards are NTSC, PAL, SECAM, and
  ATSC DTV.
• Categories of video standards are composite
  analog, component analog, composite digital, and
  component digital.