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COM 205 Multimedia Applications


... film clips with a digital camcorder. convert you own video clips ... Cameras and camcorders that use HI-8 and S-VHS formats are superior to 8 mm and VHS systems ... – PowerPoint PPT presentation

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Title: COM 205 Multimedia Applications

COM 205Multimedia Applications
  • St. Josephs College
  • Fall 2004

Chapter 8
  • Video

  • 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.

  • 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
  • Often requires additional hardware (video
    compression board, audio board, RAID - Redundant
    Array of Independent Disks- for high speed data

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

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

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

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!

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.

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)

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

Video Basics
Broadcast Video Standards
  • NTSC
  • PAL
  • HDTV
  • Six different formats
  • Aspect ratio is 169

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.

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

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.

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.

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

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

Broadcast Video Standards
  • 4 3 Aspect Ratio

Broadcast Video Standards
  • 16 9 Aspect Ratio

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

Analog Video
  • Analog television sets remain the most widely
    installed platforms for delivering and viewing
  • 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.

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.

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.

Video Overlay System
  • Many companies use computer based training (CBT)
  • 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.

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.

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

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.

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

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

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

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

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

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

Digital Video
  • Digital video architecture.
  • Digital video compression.

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

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.

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

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 compress the video for delivery and then
    decode it for playback at rates from 501 to 2001

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)

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

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

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

Video Recording and Tape Formats
  • Composite analog video.
  • Component analog video.
  • Composite digital.
  • Component digital.
  • ATSC digital TV.

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.

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.

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.

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
  • Several other digital component formats are DCT,
    Digital Betacam, DV format, DVCPRO, and DVCAM

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.

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
  • Professional sound and video equipment is very

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
  • Composite Digital most common gt110,000

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

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

Shooting and Editing Video
Shooting and Editing Video
  • Chroma Key or Blue Screen - popular technique for
    making multimedia without the use of expensive
  • 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

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...

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
  • Do not reuse tapes after editing
  • Remove break off tab to avoid overwriting

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

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

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

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

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

  • 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.

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
  • Suitable for QuickTime and AVI file formats as
    well as those produced by Director, etc.

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
  • Limit the size of the video window- the more data
    the slower the playback

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

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