A and B Rolls
The process used to create optical effects, such as dissolves or wipes
in film or videotape. The A roll contains the outgoing scene and the B
roll contains the incoming scene. The point where the A and B scenes begin
to overlap is the start of the effect. The length of the overlap is known
as the duration of the effect.
American Standard Code for Information Interchange. A standard for data
coding, particularly in computers. It is a list of encoded letters, numbers,
characters, and other symbols similar to those on a standard typewriter
keyboard. It is pronounced as "AS-KEY."
The computer assisted compilation of a series of edits. Information on
each edit’s source, duration, and nature may be fed into the computer
from punched paper tape or a floppy disk. Auto-assembly is the fastest
method of editing videotape since all creative decisions have been made
and previously entered into the computer for the auto assembly.
The video signal level corresponding to black areas in a scene. For a
composite signal, black is standardized at +7.5 units as viewed on a waveform
monitor IRE scale. This elevated black level is often referred as "setup"
and serves as a guard band between video and sync. For component video,
black is at 0 units. .
The process of turning off the electron scanning beam of a camera or picture
tube so it will not be seen while it repositions itself for the next scan
of a field or line. There are two forms of blanking pulses in a television
signal. The horizontal (H) blanking pulse cuts off the beam during the
retrace period from the right to left side of the picture. The vertical
(V) pulse cuts off the beam as it moves from the bottom of the screen
back to the top to start the scan of the next picture field. Blanking
widths are chosen to provide adequate time for beam retrace in a practical
TV set. Since the width and position of the blanking pulses (relative
to sync) establish the height, width, and position of the picture as viewed
on a monitor, their values must be carefully monitored. This is particularly
important when switching between camera and/or VT sources to obviate shifts
of the picture area.
A color reference signal included as part of the overall composite video
signal. Eight to ten cycles of color sub-carrier (3.579545 MHz, often
abbreviated as 3.58) are inserted before the start of every horizontal
line. It can be seen just following the H sync pulse in the H blanking
interval. It provides color-synchronizing information for the color decoding
circuits in monitors, receivers and other TV equipment. These have "color
killer" circuits that disable the color decoded if the burst is not
present so that the signal is processed as monochrome. The burst must
be precisely timed in relation to H sync.
The color information in a television picture. Seen on a waveform monitor
as the color subcarrier riding on top of the luminance signal. Low chroma
means that the color picture is pale looking or washed out. Excessive
or high chroma means that the color is too intense and has a tendency
to bleed into surrounding areas, contaminating nearby colors or in sever
cases, causing video breakup. See Hue, Saturation.
A form of video distortion. It is seen as a loss of detail in the black
or white areas of the picture. It may be caused by excessive video levels
that cannot be handled by the television system. To avoid these problems
in transmission or recording situations where such overloads could cause
serious problems in transmission or recording situations where such overloads
could cause serious problems, controls are provided on cameras, proc amps,
and recorders that allow an operator to constructively clip extraneous
peaks. Example: A camera is viewing a scene that contains bright lights
and/or specular reflections. The video operator would adjust the camera
for appropriate skin tone levels and allow the extraneous super-white
peaks to be clipped. See Compression.
An electronically generated standard set of colors used as a reference
for proper equipment setup. Color bars include the three additive primary
colors (red, green, and blue) and their complements (cyan, magenta, and
yellow) displayed in vertical rows, plus gray and black. The bars appear
left to right in order of decreasing luminance – yellow, cyan, green,
magenta, red, and blue. Videotape machines, cameras, telecine chains,
and monitors all use color bars as a reference for proper setup. The waveform
can be examined on a waveform monitor or vectorscope to verify that the
encoding process was proper and/or that it was not changed by any subsequent
transmission or recording process. Color bars are readily available and
easily interpreted and so have become a de-facto set standard. There are
several variations of color bars. Full field bars show the color bars
running the full height of the screen. EIA (Electronic Industries Association)
bars assigns the bottom third of the pattern to the –I, Q, and black
level set signals, which are useful for setup of camera encoders. SMPTE
bars are the same as EIA, but insert another set of short color bars above
the I and Q bars. These bars run in the reverse color order of the regular
bars and are a convenient aid for the setup of color monitors. All versions
allow the overall amplitude of the subcarrier (chrominance) to be set
at 100% or 75% of the standard value. The 75% value is usually used for
recording to avoid possible overload problems from highly saturated yellows
and cyans. The amplitude of the gray bar can be set at 100% or 75% IRE
The color subcarrier (SC) frequency is chosen to minimize its appearance
in monochrome receivers. A side effect of this choice is that the SC phase
is not contiguous between frames since the color frame sequence takes
2 frames to complete. If color disturbances are to be avoided, seen as
horizontal picture shifts, edits should be made only between even numbered
time code frames or between odd numbered frames. Editing systems automatically
made these choices.
A form of video, in which the luminance and chrominance signals are generated,
transmitted and/or recorded on videotape as two independent signals, usually
on individual video tracks. Unlike composite video, where the chrominance
and luminance signals are combined as one signal; component video signals
retain maximum bandwidth and avoid mutual interference through many generations
of editing or duplication.
A video signal that combines luminance and chrominance by using one of
several world wide electronic encoding methods, such as NTSC, PAL, or
SECAM. Encoding a video signal reduces the bandwidth, and therefore the
resolution, since a single channel is used to carry all the information.
Current practice is to use composite video signals for most applications,
although component video editing is gradually replacing composite editing.
The lack of gray scale separation in signal levels. A lack of detail in
the white areas of the picture is called white compression and a lack
of detail in the very dark areas is called black compression. However,
controlled white compression is often introduced in camera signal processing
to show detail in white areas that might otherwise have to be clipped.
A guide pulse acting as an electronic sprocket hole recorded on the videotape.
Control track pulses are used by servo systems to maintain a tape speed
that allows precise playback head tracking. Control track pulses are recorded
one per television frame and are used in lieu of time code by very basic
editing systems to locate edit points and make edits. Missing control
track signals may cause the video signal to break up or mistrack. This
type of problem is analogous to that resulting from torn sprocket holes
A secondary audio channel used to record time code or other non-program
To erase or remove recorded data from a magnetic medium by subjecting
the recording to an alternating magnetic field of gradually diminishing
To remove residual magnetism from audio or video heads that could materially
degrade the signal or affect the recorded signal on the magnetic medium.
A digital recording standard in component form used for both studio and
post production applications. Its advantages include excellent color keying
capabilities and the ability to copy many generations with almost no degradation
of the video signal. Its primary disadvantage is that each digital VCR
costs over $100,000. Recording time is limited to two sizes of cassette,
either 34 minutes or 76 minutes on standard tape. The D-1 format has high
performance standards than the D-2 format.
A composite digital recording standard used in studio and post production
applications. Its basic advantage is that the VCRs are less expensive
than those used in the D-1 format. The D-2 format offers up to 208 minutes
of recording on a special 19mm (¾ inch) videotape. It also is capable
of producing more generations than standard analog composite recording
without noticeable degradation and gives very good slow motion performance.
The D-2 format is generally used in cases where the higher performance
of the D-1 VCR is not needed. It has made inroads in broadcasting in automated
playback applications. It seems a likely replacement for the type "C"
Drop Frame Time Code
An SMPTE Time Code (TC) option that allows indicated TC to agree with
clock time. The color frame rate for color TV is actually 29.97 frames
per second, not 30, so that over a 60 minute period a TC reader would
count 108 frames (3.6 seconds) short. To correct this situation, at the
beginning of each minute frames 0 and 1 are "dropped" so that
the frame count starts at 2. This would result in 120 frames added in
an hour, 12 more than needed. By negating this correction at the beginning
of every 10th minute, time code is forced to agree with clock time.
When the drop frame mode is selected on a Time Code Generator (TCG), a
bit is set in the code that tells the reader and editing systems that
they are dealing with drop frame TC. Many editors prefer to work with
non-drop frame TC to eliminate the confusion caused by the missing frames.
Note that color is always 29.97 frames/second, but that is not necessarily
synonymous with drop frame. See Time Code, Non-Drop Frame Time Code.
A loss of picture information that may appear as a short white flash and
include one or more picture scan lines. Dropouts are caused by minute
imperfections in the surface of the tape stock or by dust particles attracted
to the tape by static electricity. Stock imperfections are not easily
corrected, but if a dropout is caused by dust, then re-recording that
section of tape will generally eliminate the dropout.
Dropout Compensator (DOC)
An electronic device in a VCR or VTR that detects the presence of a dropout
and replace is with information from the preceding line, thereby covering
up the dropout.
In television, a copy of a videotape. dub is more commonly used than dupe
(short for duplicate), which generally applies to film copies.
In film, to mix and compose audio sound tracks from several elements by
balancing for levels, proportion, and equalization.
Edit Decision List (EDL)
A structured compilation of time code information defining each edit in
a sequence. The list may or may not be constructed for use in a computerized
editing system. If it is, another compatible computer editing system should
be able to use the EDL to edit or conform a videotape or audiotape. The
EDL consists of pertinent information such as time code edit points, notes,
and switcher data.
Editing System (Video)
A configuration of hardware and software designed to allow a user to build
continuity on videotape in a linear or nonlinear fashion. The following
items constitute a basic video editing system:
Computer hardware to interface with VCRs or VTRs and a keyboard or keypad
for entering data.
Software designed for videotape editing.
Controllers to communicate between the computer and the VCR or VTR.
A basic switcher to switch video sources from one or more play machines
to the record VTR or VCR.
A program monitor to view edits and optional source monitors for each
A floppy or hard disk for storing the operating program and edit decision
An optional printer for paper printouts of edit decision lists (EDLs)
A joystick to control the tape motion (optional).
Edit List Management
The organizing and processing of time code data that make up an edit ecision
list (EDL). When an editor creates an EDL, there may be some unwanted
edits, over recordings or edits out of place. Some computer editing systems
offer good list management features, allowing the editor to clean the
list before using it to build a finished master. Others have limited or
no list management capabilities and the editor must rely on commercial
software to perform this function.
A method by which pictures and sound recorded on videotape are transferred
from one videotape to another by electronic means. In essence, the original
material is played back through electronic circuits and is copied to another
tape. This new copy is regarded as a second-generation tape. The advantages
of this method are:
That the original source material is never altered in any way. That this
same material may be used as source as many times as desired with minimum
degradation since the audio and video signals are merely copied electronically
from one tape to another. Today, virtually all videotape editing is done
in this matter, as opposed to the physical cutting and joining of the
desired portions of tape as in film editing.
One-half of a NTSC television frame. A field contains 262.5 lines and
has duration of 1/60th of a second. The odd numbered scanning lines are
known as field 1, the even numbered as field 2. When these fields are
combined by interlacing, a 525 line frame results. See Frame, Interlace.
Flying Spot Scanner
A TV scanning device that scans the film frame in a continuous motion
using an electronic shutter rather than the conventional claw intermittent
pull-down. The most popular type uses a monochrome kinescope as the light
source and the pickup devices are red, green, and blue filtered photocells.
This type of telecine device is much easier on film than an intermittent
movement projector because it does not jerk the film down each time a
frame changes, but rather moves continuously past the scanner so there
is less chance of scratching or other film damage.
A standard unit of video information containing one complete image. The
NTSC system standard in the United States and many other countries transmits
nominal 30 frames per second. A frame is made up of two television fields,
one odd and one even. Each field is made up o 262.5 lines of information.
When interlaced the two fields generate a video frame of 525 lines. See
Color Frame. In other parts of the world, the PAL and SECAM systems use
25 frames per second, with each frame containing 625 interlaced lines.
These systems are not compatible with NTSC or each other. A standards
converter maybe used to translate one format to another with some loss
In video and film, the standard number of frames continuously displayed
per second of viewing time. TV frame rates were chosen to be one half
the power frequency in use by the country of origin. There are three main
international television standards;
NTSC system: 30 frames/60 fields per second (29.97 actual for color).
PAL: 25 frames/50 fields per second.
SECAM: 25 frames/50 fields per second.
Motion picture film for TV is projected at the standard sound speed of
24 frames per second in NTSC countries. In PAL and SECAM systems film
is run at 25 f/s, the TV frame rate. See the listing of International
A generic name for a solid state digital video storage device that is
capable of storing from 1 to 4 fields for an indefinite period of time.
Framestores are used in Frame Synchronizers (FS), Digital video Effects
(DVE), and other devices where it is useful to manipulate picture elements
(pixels) in time and space.
The number of times an electronic signal is copied. First generation refers
to the original material, usually in its unedited form. The edited videotape
made from this material is considered to be second generation. All subsequent
copies or duplicates are one generation removed from the material from
which they were copied. Care must be taken to ensure that distortion and
other defects do not degrade the video and audio quality.
With analog duplication techniques, distortion and other noticeable problems
occur after only a few generations, typically 7 or 8. In the digital domain,
a minimum of 20 generations may be made before any defects are noticeable.
Also called a printout. A paper printout of computer data. In editing,
a printout of an EDL.
A television system that offers more than twice the picture resolution
of a conventional television. The SMPTE 240-M system contains 1125 horizontal
scan lines per frame while conventional television has 525 lines. The
screen aspect ratio is typically 16:9 (1.78:1) as opposed to 4:3 (1.33:1)
for standard television images.
HDTV videotape, when converted to film, compares favorably with the quality
of direct optical photography using motion picture film cameras.
Helical Scan (also known as slant track)
VTR or VCR recording format that wraps the tape around the video scanner
in a helix pattern. There are essentially two helical scan formats, the
alpha wrap and the omega wrap. The alpha wrap was the first format to
be used in early helical scan VTRs. The disadvantage of this format is
that it requires the videotape to be wrapped 360 degrees around the scanner.
This is cumbersome especially if the tape must be loaded or unloaded from
the VTR in the middle of the reel.
Current helical scan VTRs and VCRs use an omega wrap. This configuration
wraps the tape around the drum in a horseshoe or U pattern, allowing easy
threading or removal of the tape.
Heterodyne Color Recording (color under)
A method of recording that translates the encoded chroma signal to a lower
video frequency so that color recording may be effected in a limited bandwidth.
It also electronically compensates for the timing jitter inherent in helical
scat recorders. Used in consumer and industrial VCRs.
A specific color wavelength in the visible light spectrum, an attribute
of color perception. Flesh tones, for example, may be changed by adjusting
the hue control (sometimes marked color phase) on a television receiver
The combining of two sequential television field that make up a complete
frame in the NTSC system. Field 1 contains the odd numbered scan lines,
field 2 the even numbered line. When combined by interlacing, line 2 falls
between 1 and 3, line 4 falls between 3 and 5, and so on. Interlaced scanning
solves the problem of flicker at reasonable frame rates. An image repetition
rate of less than 48 per second appears to flicker under typical viewing
conditions. Interlacing provides a field repetition rate of 60 per second,
well above the flicker threshold. The PAL system, having a field rate
of 50 per second, often exhibits flicker to those not accustomed to it.
Motion picture projection gets around the problem by using a 2-blade shutter
assisted by viewing in a relatively dark room. Interlace bring with it
motion artifacts that are noticeable at times.
While exhibiting superior motion rendition compared to 24 frame may show
a double image particularly noticeable in sporting events or other fast
action because of the 1/60th of a second offset between fields. The equalizing
and vertical serrated pulses in the sync signal are essential to achieve
A control device allowing the user to manipulate videotape on a frame-by-frame
basis (jog) forward or backward at any speed from still frame to the maximum
search speed of the editing system or VCR being used. The maximum speed
and specific characteristics of the joystick depend on the editing system
or VCR. The joystick may be in the form of a stick, knob, lever, slider,
or push buttons.
A printing method of immersing motion picture film in a liquid of the
same refractive index as the base material used on the film, which tends
to hide scratches and other minor defects, but will not eliminate emulsion
scratches because the depth of the scratch may reveal one or more colors
within the dye image layer. Liquid gate printing is also used on some
film-to-video telecine systems to reduce the visibility of minor defects.
The intensity of light: specifically, the monochrome component or the
brightness potion of a video image. The symbol "Y" is used to
identify the luminance signal in composite and component color systems.
The original recorded material before it has been edited. Generally, master
videotapes and audiotapes are recorded in production to be used later
in editing (the post-production process) to generate an edited master.
The master is first generation in picture and sound quality. An original
generation film to tape transfer.
The final product resulting from an editing session, usually generated
from original source material. Also called a second generation master,
E-E or electronically edited master. Copies from edited masters are called
sub-masters, protection masters, or dubs.
Displays a color video picture, usually on a cathode ray tube. Red, green,
and blue phosphors can be individually excited to produce a wide gamut
of colors described by near infinite combinations of hue, saturation,
and luminance. Common sizes are 5", 9", 14", and 20"
measured diagonally. Today’s monitors are reasonably stable, but
still must be adjusted frequently in critical applications. SMPTE color
bars are used for this purpose. Precise matching of monitors is difficult
to achieve because of inherent variations between picture tubes. The human
eye is very critical in making side-by-side color comparisons, but poor
in making absolute judgments. Therefore, a color monitor is useful for
continuity viewing and spotting gross problems, but is not always dependable
for making critical evaluations
A random signal generated by most electronic equipment, which is present
throughout the video signal spectrum. Video noise is somewhat analogous
to film grain. In a home receiver, it is most obvious in the transmitted
signal in weak reception areas.
Non-Drop Frame Time Code
A time-based reference system for video and audio that was developed and
standardized by the SMPTE. The system assigns each frame a distinct eight-digit
number that is composed of hours, minutes, seconds, and frames. Because
of the nature of the NTSC color television system, non-drop frame time
code does not agree with clock time. Non-drop frame time code indicates
3.6 seconds less than one hour of clock time video information. Although
still in use for industrial and educational applications, non-drop frame
time code has been replaced by drop frame time code by the television
networks and most independent stations.
National Television Standards Committee. A committee formed in the late
1930’s that formulates, recommends, and approves standards for television
in the United States and other countries using the NTSC system.
One of three television standards used world wide, the others being PAL
and SECAM. The NTSC standard is used in North America, much of South America,
Japan, and South Korea, among other countries. NTSC is a black-and-white
and color compatible 525-line system that scans a nominal 30 interlaced
television picture frames per second.
The work print or decision making stage of videotape editing. The resulting
tape is not considered to be a broadcast quality master but is used to
create program continuity and generate accurate time code data that will
be stored and used after to conform a master quality tape from unedited
production material. An offline work print may have visible time code
numbers burned into the picture area for reference. This is called a window
The last stage of videotape editing, resulting in a final master tape.
The equipment used during online editing is generally designed to produce
broadcast quality tapes and costs much more than the equipment used in
offline editing. Online editing rates are about three to four times those
of offline editing. Nearly all online editing is performed on one-inch
videotape. These VTRs are capable of slow motion, still-framing with broadcast
quality and search and wind at 50 times play speed.
Also referred to as a laser disk. A semi-rigid plastic disk containing
aluminum or other substrate in which a laser beam embeds digital data,
allowing information to be stored. The substrate itself is sandwiched
between plastic to prevent damage to the data when the disk is handled.
The most commonly used is the WORM disk, meaning "Write Once, Read
A random failure of field interlace in which the scan lines of both the
odd and even fields fall directly on top of one another. This form of
video distortion reduces the picture resolution. The problem may be eliminated
by adjusting the vertical hold control until interlace becomes apparent.
In television, the colors red, green, and blue. These colors are additive
in nature and when missed in the correct proportions, produce white light.
Color film uses dye images to create color and thus requires the subtractive
primary colors yellow, magenta, and cyan.
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.
A measure of the sharpness of an image. The ability of a system to reproduce
fine detail and sharp edges. topˆ
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.
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.
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.
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.
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.
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.
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,
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
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.
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.
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.
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
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.
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.
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
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.
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.
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.
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.
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
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.
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.
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
Unassigned bits within the 80-bit SMPTE time code format that may be used
for the information such as the date, scene, or take number. A limited
group of letters (A-F) and the numbers (0-9) are available to code eight
characters of useful information. A user bit generator, which is often
built into modern TCGs, must be used to enter this special data, and special
time code readers are required to read this information.
VCR (Video Cassette Recorder)
An electro-mechanical device used to record and reproduce video and audio
signals in a helical scan fashion. The videotape is enclosed within a
plastic cartridge or cassette. A threading system in the tape transport
mechanism withdraws the tape from the cassette and wraps the tape around
numerous guides, the erase head, scanner drum, audio head, and drive capstan.
When the eject button is pressed, the threading mechanism unwraps the
tape from the transport and winds it back into the cassette.
An instrument used to setup color encoders and to confirm the proper transmission
and/or recording of color signal. A CRT displays the color subcarrier
in a circular pattern. The graticule contains a pattern of measuring boxes
in positions based on the hue and chroma characteristics of the color
bar signal. The individual bars appear as bright dots which should fall
within the small boxes if the color signal has been correctly encoded
and has not been altered in transmission or recording. The angular position
of the color vector indicates the hue (phase) of the color. The length
of the vector is a measure of the saturation. The color burst reference
marker, a horizontal bar situated at the 9 o’clock position on the
graticule, is the established reference with respect to the six colors
positioned in their respective boxes. Since luminance and chroma are often
processed separately in television equipment, it is necessary to check
at various stages to make sure that the color signal integrity is not
compromised. Color bars are usually recorded on the head of every reel,
preferably from the originating studio or camera. Unless otherwise instructed,
these bars should be used as a reference to make any necessary adjustments
(video levels, saturation, phase) on the videotape player. The phase (hue)
adjustment rotates the entire pattern. The saturation (chroma) adjustment
moves the dots inward or outward to fit into the calibration boxes. Any
subsequent changes, based on the appearance of program material viewed
on a color monitor, should be undertaken with caution. There should be
an understanding with the customer as to whether the operator is expected
to make gross color corrections on program material, or whether the head
end color bars are to be considered the absolute reference.
Note that one color cannot be changed without affecting the others. True
color correction is best done while video is in R-G-B-or component form.
During operation, the vectorscope can be used to observe excessive chroma
levels. A vectorscope and a waveform monitor are sometimes combined in
a single unit with a single screen and a switchable graticule.
A precision plastic container that holds prepackaged lengths of videotape
that may be inserted into a VCR. The most popular sizes of cassettes store
tape in 1/4 inch, 1/2 inch and 3/4 inch widths in lengths from 5 minutes
to 90 minutes.
A long narrow strip of Mylar film coated with a material capable
of being magnetized in uniform matter and holding these magnetic patterns
for an indefinite period of time. This tape is designed to record and
play back continuous visual images as well as aural components. Tape widths
vary from 8mm to 2 inches.
(Vertical Interval Time Code)
Also called VITC. Time code that is recorded on two lines of the vertical
blanking period in the video signal. Unlike time code recorded on a longitudinal
linear audio channel, VITC time code is scanned by the video head even
when in still frame. This time code then is converted to a readable time
code that maybe used to frame accurately, locate, and define edit points.
Videotape Recorder. An electro-mechanical device designed to record and
playback video and audio signals on magnetic tape wound on open reels.
The tape must be threaded carefully by hand through the transport and
attached to a take-up reel.
A display device that shows the electronic pattern of the video signal
on the face of a Cathode Ray Tube (CRT). Superimposed on the screen is
a scale vertically divided into 140 divisions, termed I.R.E. units. The
synchronizing pulses occupy the range between -40 and 0. The video waveform
starts at 0 with black at 7.5 and white at 100. A waveform monitor is
a very necessary and useful tool to allow the operator to accurately adjust
and monitor video signals. If video levels are recorded on a videotape
improperly; that is, either too high or too low, it may be impossible
to correct them once they have been copied to another tape. A WFM allows
the operator to view the video signal and make the appropriate adjustments
as necessary to keep the video signal within prescribed limits. It is
also used to measure sync signal parameters to be sure that they conform
to accepted standards. Common test signals such as color bars, multi-burst,
staircase and window can easily be evaluated to determine the performance
of an incoming source or the playback of a recorder.
A copy of original videotape with the eight-digit time code displayed
in a rectangular area generally at the bottom of the screen. This window
area may be surrounded by a black box so that the time code numbers stand
out against a light background. The window dub is used only as a viewing
copy or may be used as a work copy tape to edit with since the numbers
once recorded in the picture cannot be removed