About ACVL
ACVL Member Directory
Officers & Directors
ACVL Principal's Dinner
Guide to Film Laboratory Procedures
Working with your ACVL Laboratory
Film Laboratory Services
ACVL Recommended Film Practices
Release Prints
Sound
Slide Duplicates & Filmstrips
Storage
Glossary of Video Terms & Definitions
World Television Standards
Business Practices
Film Industry Calendar
Film Resources
Information About Digital Intermediates
Film Laboratory Home
   
 
 

 
Home>U-Z
 
User Bits
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. topˆ

Vectorscope
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. topˆ

Video
Communication medium that electronically transmits images and sounds. May use magnetic tape as a recording method.
The visual, or picture, component of an electronically based communication medium. This includes the black and white part of the electronic signal, color information, and synchronizing signals.

Video Cassette
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. topˆ

Videotape
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. topˆ

VITC (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. topˆ

VTR
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. topˆ

Waveform Monitor
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. topˆ

Window Dub
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. topˆ

 

 

 

 


© 2013 Association of Cinema & Video Laboratories. All Rights Reserved.