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Chapter 6
Video
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Overview
Using video.
How video works?
Broadcast video standards. Analog video.
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Overview
Digital video.
Video recording and tape formats.
Shooting and editing video. Optimizing video files for CD-ROM.
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Using Video
Video is an excellent tool for delivering
multimedia.
Video places the highest performance
demand on computer and its memory
and storage.
Digital video has replaced analog as the
method of choice for making and
delivering video for multimedia.
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Using Video
Digital video device produces excellent
finished products at a fraction of the
cost of analog.
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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How Video Works
Light reflected from an object through
the cameras lens is converted into
electronic signal by charge-coupled
device (CCD).
This electronic signal contains three
channels of color information and
synchronization pulses (sync). Several video standards exist that deal
with the amount of separation between
the components of the signal.
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How Video Works
Analog video transfer methods
Componentvideo separates color andbrightness over three cables.
S-videoseparates color and brightness overtwo wires.
Compositevideo transmits the whole videosignal in a single cable.
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Broadcast Video Standards
National Television Standards Committee
(NTSC):
These standards define a method for
encoding information into electronic signalthat creates a television picture.
It has screen resolution of 525 horizontal
scan lines and a scan rate of 30 frames persecond.
United states, Canada, Mexico and Japan
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Broadcast Video Standards
Phase Alternate Line (PAL)
PAL has a screen resolution of 625 horizontal lines and a scan rate of
25 frames per second.
Used in United Kingdom, Western Europe, Australia, South Africa,
China and South America.
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Broadcast Video Standards
Sequential Color and Memory (SECAM):
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.
Used in France, Eastern Europe and few other countries
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Broadcast Video Standards
Advanced Television Systems
Committee (ATSC) Digital Television
(DTV):
This digital standard provides TV stations withsufficient bandwidth to present four or five
Standard Television (STV) signals or one High
Definition TV (HDTV) signal.
This standard allows for transmission of data tocomputers and for new Advanced TV (ATV)
interactive services.
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Analog Video
Overscan and the safe title area:
Analog television sets remain the most
widely installed platforms for delivering and
viewing video. Overscanoccurs when an image is larger
than the standard TV screen.
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Analog Video
Overscan and the safe title area
(continued):
Underscan occurs when computer
monitors display a smaller image onpicture tube.
The safe title area is where the image will
not be affected by overscanning, even inthe worst conditions.
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.
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Analog Video
Video color:
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
Video color (continued):
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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Analog Video
Interlacingeffects:
In television, the electron beam makes two
passes on the screen while drawing a
single video frame. It first lays down all the odd-numbered
lines, and then all the even-numbered
lines, hence they are interlaced.
While capturing images from a video
signal, they can be filtered through a de-
interlacing filter provided by image-editing
applications.
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Analog Video
Text and titles for television and taking
care of analog tapes:
Titles for video productions can be created
with an analog character generator.
Computers can create titles digitally using
video and image-editing software.
New tapes should always be fast-forwarded to the end and then rewound, to
ensure even tape tension.
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Analog Video
Text and titles for television and taking
care of analog tapes:
Font for titles should be plain,san serif and
bold enough to be easily understood.
Do not kern tightly
When dealing with dark background, use
white or light color for text.
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Digital Video
Video clip stored on any mass-storagedevice can be played back on a
computers monitor without special
hardware.
Setting up a production environment for
making digital video, requires some
hardware specifications.
Some specifications include computer
with FireWire connection and cables,
fast processor, plenty of RAM, fast and
big hard disk.
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Digital Video Compression
Digital video compression schemes or
codecs 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 startsplayback as soon as enough data has
transferred to the users computer to
sustain this playback.
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Digital Video Compression
MPEG is a real-time video compression
algorithm.
MPEG-4 includes numerous multimedia
capabilities and is a preferred standard.
MPEG-7 (or Multimedia Content
Description Interface) integrates
information about motion videoelements with their use.
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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 qualitythat occurs while moving from original
footage to editing master to copy.
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Component Analog Video
Component video separates the luminanceand 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 waveformsand encode the information in binary
(0/1) digital code.
It improves color and image resolutionand eliminates generation loss.
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Component Digital
Component digital formats add theadvantages 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 broadcasttelevision.
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Shooting and Editing Video
Import video and sound at the highest
resolution and with the least amount of
compression possible.
Resolution should be reduced andfootage must be compressed later
according to the requirements.
A steady shooting platform shouldalways be used.
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Shooting and Editing Video
Good and even lighting is extremely
important.
Blue screen in digital video editing
applications is a popular technique formaking multimedia.
Wide panoramic shots and camera
motion should be avoided whenshooting for a small computer window
on CD-ROM or the Web.
O ti i i Vid Fil f CD
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Optimizing Video Files for CD-
ROM
CD-ROMs provide an excellent distribution
medium for computer-based video.
When preparing video for CD-ROM
distribution, interleave the audio track(s)with the video track. (flattening)
Key frames should be used every 10 to 15
frames and the size of the video windowmust be kept small.
The Sorenson codec is optimized for CD-
ROM playback.
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Summary
Digital video method is used for making
and delivering video for multimedia.
Charge-coupled device (CCD) converts
the light that has been reflected from anobject through the cameras lens.
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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.