CEN-318 Multimedia
video
Mohammed Saleem Bhat
m.bhat@mu.edu.sa
Computer Engineering and Networks, College of Engineering , Majmaah University
CEN-318 Multimedia
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.
Computer Engineering and Networks, College of Engineering , Majmaah University
CEN-318 Multimedia
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)
Computer Engineering and Networks, College of Engineering , Majmaah University
CEN-318 Multimedia
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
Computer Engineering and Networks, College of Engineering , Majmaah University
CEN-318 Multimedia
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.
Computer Engineering and Networks, College of Engineering , Majmaah University
CEN-318 Multimedia
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.
Computer Engineering and Networks, College of Engineering , Majmaah University
CEN-318 Multimedia
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!
Computer Engineering and Networks, College of Engineering , Majmaah University
CEN-318 Multimedia
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.
Computer Engineering and Networks, College of Engineering , Majmaah University
CEN-318 Multimedia
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
Computer Engineering and Networks, College of Engineering , Majmaah University
CEN-318 Multimedia
Video Basics
Computer Engineering and Networks, College of Engineering , Majmaah University
CEN-318 Multimedia
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.
Computer Engineering and Networks, College of Engineering , Majmaah University
CEN-318 Multimedia
Video Basics
Computer Engineering and Networks, College of Engineering , Majmaah University
CEN-318 Multimedia
Broadcast Video Standards
• NTSC
• PAL
• SECAM
• HDTV
 Six different formats
 Aspect ratio is 16:9
Computer Engineering and Networks, College of Engineering , Majmaah University
CEN-318 Multimedia
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.
Computer Engineering and Networks, College of Engineering , Majmaah University
CEN-318 Multimedia
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
Computer Engineering and Networks, College of Engineering , Majmaah University
CEN-318 Multimedia
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.
Computer Engineering and Networks, College of Engineering , Majmaah University
CEN-318 Multimedia
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.
Computer Engineering and Networks, College of Engineering , Majmaah University
CEN-318 Multimedia
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
Computer Engineering and Networks, College of Engineering , Majmaah University
CEN-318 Multimedia
Broadcast Video Standards
• HDTV- High Definition Television now
available, allow viewing of Cinemascope
and Panavision movies with aspect ratio
16:9 ( wider than high) (See p. 184)
• Twice the resolution, interlaced format
• Digitized then compressed for transmission
Computer Engineering and Networks, College of Engineering , Majmaah University
CEN-318 Multimedia
Broadcast Video Standards
• 4: 3 Aspect Ratio
Computer Engineering and Networks, College of Engineering , Majmaah University
CEN-318 Multimedia
Broadcast Video Standards
• 16: 9 Aspect Ratio
Computer Engineering and Networks, College of Engineering , Majmaah University
CEN-318 Multimedia
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
Computer Engineering and Networks, College of Engineering , Majmaah University
CEN-318 Multimedia
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.
Computer Engineering and Networks, College of Engineering , Majmaah University
CEN-318 Multimedia
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.
Computer Engineering and Networks, College of Engineering , Majmaah University
CEN-318 Multimedia
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.
Computer Engineering and Networks, College of Engineering , Majmaah University
CEN-318 Multimedia
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.
Computer Engineering and Networks, College of Engineering , Majmaah University
CEN-318 Multimedia
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.
Computer Engineering and Networks, College of Engineering , Majmaah University
CEN-318 Multimedia
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
Computer Engineering and Networks, College of Engineering , Majmaah University
CEN-318 Multimedia
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.
Computer Engineering and Networks, College of Engineering , Majmaah University
CEN-318 Multimedia
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
Computer Engineering and Networks, College of Engineering , Majmaah University
CEN-318 Multimedia
Computers and Video
Computer Engineering and Networks, College of Engineering , Majmaah University
CEN-318 Multimedia
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)
Computer Engineering and Networks, College of Engineering , Majmaah University
CEN-318 Multimedia
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
Computer Engineering and Networks, College of Engineering , Majmaah University
CEN-318 Multimedia
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
Computer Engineering and Networks, College of Engineering , Majmaah University
CEN-318 Multimedia
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
Computer Engineering and Networks, College of Engineering , Majmaah University
CEN-318 Multimedia
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
Computer Engineering and Networks, College of Engineering , Majmaah University
CEN-318 Multimedia
Digital Video
• Digital video architecture.
• Digital video compression.
Computer Engineering and Networks, College of Engineering , Majmaah University
CEN-318 Multimedia
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.
Computer Engineering and Networks, College of Engineering , Majmaah University
CEN-318 Multimedia
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 realtime for fast playback.
• Streaming audio and video starts playback as soon as
enough data has transferred to the user’s computer to
sustain this playback.
Computer Engineering and Networks, College of Engineering , Majmaah University
CEN-318 Multimedia
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
Computer Engineering and Networks, College of Engineering , Majmaah University
CEN-318 Multimedia
Video Compression
• Full motion video requires the computer to
deliver the data at 30 MB/second more than
today’s 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 50:1
to 200:1
Computer Engineering and Networks, College of Engineering , Majmaah University
CEN-318 Multimedia
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 user’s computer
instead of waiting for the whole file to
download
• ( RealAudio and RealVideo software)
Computer Engineering and Networks, College of Engineering , Majmaah University
CEN-318 Multimedia
MPEG
• Standard developed by the Moving
PIcturesExperts Group for digital
representation of moving pictures and
associated audio
• http://mpeg.org
Computer Engineering and Networks, College of Engineering , Majmaah University
CEN-318 Multimedia
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
Computer Engineering and Networks, College of Engineering , Majmaah University
CEN-318 Multimedia
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
Computer Engineering and Networks, College of Engineering , Majmaah University
CEN-318 Multimedia
Video Recording and Tape
Formats
•
•
•
•
•
Composite analog video.
Component analog video.
Composite digital.
Component digital.
ATSC digital TV.
Computer Engineering and Networks, College of Engineering , Majmaah University
CEN-318 Multimedia
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.
Computer Engineering and Networks, College of Engineering , Majmaah University
CEN-318 Multimedia
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.
Computer Engineering and Networks, College of Engineering , Majmaah University
CEN-318 Multimedia
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.
Computer Engineering and Networks, College of Engineering , Majmaah University
CEN-318 Multimedia
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.
Computer Engineering and Networks, College of Engineering , Majmaah University
CEN-318 Multimedia
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.
Computer Engineering and Networks, College of Engineering , Majmaah University
CEN-318 Multimedia
Vaughn’s Law of Multimedia
Minimums
• Your goal is to produce multimedia that is
adequate and does it’s job but doesn’t throw
you into bankruptcy.
• Experiment with various levels of consumer
grade equipment
• Professional sound and video equipment is
very expensive
Computer Engineering and Networks, College of Engineering , Majmaah University
CEN-318 Multimedia
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 > $900,000 and produces 15 minutes of
video
• Composite Digital most common >$110,000
Computer Engineering and Networks, College of Engineering , Majmaah University
CEN-318 Multimedia
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
Computer Engineering and Networks, College of Engineering , Majmaah University
CEN-318 Multimedia
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
Computer Engineering and Networks, College of Engineering , Majmaah University
CEN-318 Multimedia
Shooting and Editing Video
Computer Engineering and Networks, College of Engineering , Majmaah University
CEN-318 Multimedia
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
Computer Engineering and Networks, College of Engineering , Majmaah University
CEN-318 Multimedia
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...
Computer Engineering and Networks, College of Engineering , Majmaah University
CEN-318 Multimedia
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
Computer Engineering and Networks, College of Engineering , Majmaah University
CEN-318 Multimedia
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
Computer Engineering and Networks, College of Engineering , Majmaah University
CEN-318 Multimedia
Consumer Grade Equipment
• Mass production at low cost; easier to use
• Cameras and camcorders that use HI-8 and SVHS formats are superior to 8 mm and VHS
systems
• HI-8 is most widely available tape format and
best consumer grade
Computer Engineering and Networks, College of Engineering , Majmaah University
CEN-318 Multimedia
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
Computer Engineering and Networks, College of Engineering , Majmaah University
CEN-318 Multimedia
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
Computer Engineering and Networks, College of Engineering , Majmaah University
CEN-318 Multimedia
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
Computer Engineering and Networks, College of Engineering , Majmaah University
CEN-318 Multimedia
P*64
• 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.
Computer Engineering and Networks, College of Engineering , Majmaah University
CEN-318 Multimedia
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.
Computer Engineering and Networks, College of Engineering , Majmaah University
CEN-318 Multimedia
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
Computer Engineering and Networks, College of Engineering , Majmaah University
CEN-318 Multimedia
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
Computer Engineering and Networks, College of Engineering , Majmaah University
CEN-318 Multimedia
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.
Computer Engineering and Networks, College of Engineering , Majmaah University