Random Access
Editing Systems
Nonlinear electronic video editing equipment that
allows the editor to build an edited work tape out
of sequence without having to rebuild or otherwise
modify material on either side of a shot, sequence,
or complete act. Random access editing systems are
picture and sound switching systems. Rather than
making electronic edits sequentially on piece of
tape, they store the edit information in a computer’s
memory and use it to switch from video playback
sources to generate virtual edits.
Since no scenes are physically
connected, they do not have to be reassembled
to be modified. Instead picture switching based
on computer data simulates edit frames accurately
on a monitor and these edits will be repeated
in the online session at a later date.
Resolution
A measure of the sharpness of an image. The ability
of a system to reproduce fine detail and sharp
edges. topˆ
Ringing
Seen on a monitor as a series of after-images
following a sharp, high contrast horizontal transition;
such as the trailing edge of a white object against
a dark background. Excessive image enhancement
used to increase the apparent resolution of a
video image may cause this effect to appear. Video
graphics devices (character generators, paint
boxes) are relatively immune from this effect
because of their controlled design. topˆ
Safe
Title and Safe Action Areas
Geometric boundaries within the television viewing
area used as a guide to insure the correct placement
of graphics, titles of other types of art work
so as not to lose the desired action or title
information as seen on a television receiver.
topˆ
Saturation
The intensity of the color in a video picture.
Intensity may range from pale vivid or intense.
The greater the color (chroma) saturation, the
more intense the color. Excessive saturation leads
to a form of transmission or recording distortion
called "over deviation" or "bearding",
or to color streaking sometimes know as bleeding
color. The amount of color saturation may be seen
on a vectorscope. topˆ
Scanner,
Video
A precision round metal drum in a VTR or VCR driven
by a servo motor on which two or more record/
play and erase heads are mounted along the circumference.
topˆ
SCH (SubCarrier
to Horizontal Phase)
Refers to the timing relationship that must exist
between the color burst and the leading edge of
sync to obtain clean color edits. The zero crossing
of SCH must be time coincident with leading edge
of horizontal sync. topˆ
Shedding
A condition of magnetic tape where the oxide that
is bonded to the base has begun to separate from
the base. When shedding is severe, the loose oxide
is deposited on video and audio heads sometimes
clogging them to a point of losing the image or
sound completely. Stopping the machine and carefully
cleaning the audio and/or video heads is the only
way to correct this problem. topˆ
SMPTE
Time Code
See Time
Code. topˆ
Standards
Converter
A device used to translate one television standard
to another. For example, videotape made using
the TNSC standard cannot be shown in a country
that uses either PAL or SECAM unless the tape
is first copied through a standards converter.
Tapes may be copied from any one standard to any
other standard through this device. topˆ
Standards,
World Wide
Current world television standards are identified
by country and format used. See World
Television Standards. topˆ
Submaster
A high quality videotape made by copying or dubbing
the edited master through VTRs equipped with time
base correcting equipment. Any number of submasters
may be made from a single master. A submaster
is generally used as a backup or for making additional
copies for broadcast, distribution, or viewing.
topˆ
Sync,
Electronic
The pulses in a video signal that provide a synchronizing
reference for each frame and scanning line of
the picture. Incorrect synchronizing pulses may
cause the picture to roll vertically, jump erratically
or tear out horizontally. topˆ
Sync,
Editorial
The frame-to-frame relationship between the picture
and sound during editing. Refers to no offset
of the sound track to its corresponding picture
frame. topˆ
Tape
To Film Transfer Systems
Kinescope Recording (Also
known as a "Kine")
The first of the video to film transfer systems.
A photographic image of a television picture made
by pointing a specially designed motion picture
camera at a high-resolution television monitor.
The image is photographed on 16mm or 35mm motion
picture film and the resulting film after developing
may be projected on a motion picture screen.
Several terms used interchangeably
to define kinescope recordings are:
TVR: television recording
Tape to film transfers
Kine recording (now obsolete)
Although videotape has generally replace kinescope
recordings for most applications, some film people
still find special needs and applications for
black and white kinescope recordings used as a
work picture to aid sound technicians in creating
sound effects or music cues. topˆ
Laser
Scanning System
A second method of transferring videotape to motion
picture film is illustrated in video to film laser
recording. The videotape reproducer feeds the
video into a "black box" that processes
the signal. This decodes or separates the video
into red, green, and blue components that modulate
the light emanating from the three lasers. These
light outputs are combined by mirrors into a single
beam of light that is then mechanically scanned
at the TV vertical and horizontal rate onto the
film by a multi-faceted spinning mirror assembly.
This light beam that has been adjusted for the
television horizontal and vertical frame rate
is focused onto the film plane of a special film
camera that pulls the film down at a very fast
rate during the vertical blanking period. Every
fifth field is discarded electronically, which
is how 30 television frames are converted to 24
film frames without severe motion artifacts. topˆ
EBR
(Electron Beam Recorder)
A third type of transfer system - video to electron
beam film recording - offers a high quality color
videotape-to-film transfer using an electron scanning
beam to sequentially expose a single film strip
of consecutive black and white film negative images
from red, green, and blue sources in a special
vacuum chamber that encloses the film transport
mechanism. Once developed, this black and white
negative is used to generate a full color negative
by sequentially printing on a frame-by-frame basis
each group of three black and white film images
through red, green, and blue filters directly
onto color film. Video-to-film transfers made
by this method are much higher quality than those
made by the kinescope recording method. topˆ
Telecine
A motion picture film projector and a television
camera or film scanner designed to transfer or
convert motion pictures or slides and their associated
sound elements to video and audio signals. topˆ
Telecine
Formats
The most popular type of television projector/camera
configuration is called a flying spot scanner.
Most film is transferred in the 35mm format in
the form of filmed television programs or feature
films. topˆ
Wide screen film formats such
as Cinemascope and Panavision may be transferred
to videotape for use on television by using a
sophisticated pan and scan method to select the
most desirable areas of a scene. This preprogrammed
information and selection of scene framing or
panning is stored in a computer and may then be
duplicated in real time as the film is recorded
on videotape. Color balance and scene density
information, as "painted" by the telecine
operator, is also stored in the computer for later
use. A relatively new form of telecine format
is the three-perforation frame as opposed to the
conventional four-perforation 35mm-picture frame.
Since only three perforations are used in each
film frame instead of four, an appreciable savings
results by using 25% less of the film raw stock
during production than would normally be used.
The three-perf format affords similar savings
for theatrical production and the entire frame
area is used. The ideal format for TV would be
three perf, 30 frame, which would result in slightly
less film being used as in the present format.
A 30-frame film format has greatly improved motion
rendition, less grain pattern and an apparent
increase in resolution. Most important for TV,
which is the ultimate market for theatrical films,
is the absence of 24 to 30 frame conversion artifacts,
which are quite noticeable. However, the cost
of theater conversion throughout the world, and
the fact that the rest of the world’s TV
systems demand 24/25 frame film make this an unlikely
improvement. Both the camera used in production
and the telecine used to transfer this special
format have to be modified to accommodate this
special format. topˆ
The second popular format is
16mm used in many industrial applications and
some television programming film. Although not
as widely used as in the past decade, 16mm, because
of its comparatively low cost, fine grain, and
good resolution, is still used to some degree
by the military, industrial and documentary producers.
A third format is Super 8mm. Although not as popular
as 16mm and 35mm, it has a following among industrial
and documentary producers who use this format
to shoot on location in difficult areas where
video may be too cumbersome to use. In many circumstances,
it may important to avoid the appearance of professional
equipment. topˆ
Another option is a device that
reduces or eliminates the side to side picture
weave of motion picture film. Conventional telecines
exhibit some small amount of side to side picture
weave because of the way the film is guided in
the gate. Now, mechanical and electronic methods
have been developed to almost completely eliminate
this problem, which is very noticeable when electronic
artwork or lettering is combined with moving motion
picture images.Variable speed telecines also provide
the film producer with limited special effects.
For example, film shot at 16 frames per second,
maintaining a real time look to the image. Other
frame rates may also be programmed for special
effects. topˆ
Television
World Standards
There are more than 165 countries in the world
that offer television to their citizens. Of these,
18% transmit black and white (monochrome), color
transmissions in NTSC = 23%, PAL = 35%, and SECAM
= 20%. The chart in Section 10 outlines in detail
the various formats and other specifications used
around the world. topˆ
Time
Base Error
The horizontal and/or vertical jitter inherent
in most videotape recording equipment. Broadcast
standards require a horizontal line-to-line timing
accuracy of better than one part in thousands,
which is impossible to attain in a mechanical
tape-scanning device. An electronic automatic
time delay device, known as a Time Base Corrector
(TBC) is necessary in all helical scan VTRs to
compensate for this inherent problem if the video
is to be broadcast or composited (dissolve, wipe,
matte) in any way. Consumer and industrial machines
cannot afford this feature and rely on fast horizontal
automatic frequency control (AFC) circuits in
monitor and receivers to cover this fault. topˆ
TBC (Time
Base Corrector)
An electronic processing device connected to the
output of a VCR or VTR that removes or masks the
jitter generated by unavoidable mechanical inaccuracies
in helical scan recorders. This is accomplished
by automatically delaying the video signal so
that each line starts at the proper time. The
TBC can be an integral part of the recorder (professional)
or may be an external stand-alone device (industrial/consumer).
It may also include a video-processing amplifier
that allows the adjustment of video and color
levels in the corrected signal. topˆ
Time
Code (TC)
A standardized numbering system referenced to
a 24 hour clock by which audio or video material
is specifically identified for editing or reference
purposes. The system assigns a unique, eight-digit
number to every frame on an audio or videotape.
This number assumes the following form:
Up to 23 hours
Up to 59 minutes
Up to 59 seconds
Up to 29 frames
The maximum time that could
be displayed would be 23:59:59:29. After that,
the display would start over again at zero. A
typical time code would be displayed as 14:23:06:17.
topˆ
Time
Code Generator (TCG)
An electronic clock that generates a digital serial
code that can be recorded on an audio track, which
assigns to each video or audio frame a unique
identification number composed of eight digits.
topˆ
Tracking
The process by which the video head precisely
follow the recorded video signal on playback.
Correct tracking assures a noise free reproduction
of the picture. Mistracking of the video head
with respect to the recorded signal on the tape
results in video distortion seen as noise; or
in the worst case, breakup of the image since
the video head is not riding directly over the
recorded signal on the tape. The control track
provides the reference for tracking. The tracking
control allows a "fine tuning" adjustment
for non-standard tapes. topˆ
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