Grass Valley Dictionary

Dictionary of Technical Terms - P

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packing fraction

The area in a fiber optic fiber bundle occupied by the core material, expressed as a fraction of the total bundle area.

Phase Alternate Line. The name of the color television system in which the E'V component of burst is inverted in phase from one line to the next in order to minimize hue errors that may occur in color transmission. PAL-B (also called PAL-I) is a European color TV system featuring 625 lines per frame, 50 fields per second, and a 4.43361875 MHz subcarrier. Used mainly in Europe, China, Malaysia, Australia, New Zealand, the Middle East, and parts of Africa. PAL-M is a Brazilian color TV system with phase alternation by line, but using 525 lines per frame, 60 fields per second, and a 3.57561149 MHz subcarrier.

Programmable array logic. An IC containing a large number of logic gates whose interconnections are programmable for specific applications.

PAL ID (PAL identification)

The control signal that indicates where the phase inversion of the E'V component takes place in PAL video signals.

A transmission standard for 16:9 625 line signals.

A digital effect that enhances a vanishing point effect by applying curvature to the parallel lines of video extending away from the viewer.

A multi-conductor cable carrying simultaneous transmission of digital data bits. Analogous to the rows of a marching band passing a review point.

Transmission of data bits in groups along a collection of wires (called a bus). Analogous to the rows of a marching band passing a review point. A typical parallel bus may accommodate transmission of one 8-, 16-, or 32-bit byte at a time.

parallel digital

A digital video interface which uses twisted pair wiring and 25-pin D connectors to convey the bits of a digital video signal in parallel. There are various component and composite parallel digital video formats.

parallel video mixer

Video mixing architecture where two identical sets of multipliers are used to create a multilevel effect.

parallel video processing

A mixing architecture where the outputs of several video multipliers are summed to create a composite effect.

1. A method of verifying the accuracy of transmitted or recorded data. An extra bit appended to an array of data as an accuracy check during transmission. Parity may be even or odd. For odd parity, if the number of 1's in the array is even, a 1 is added in the parity bit to make the total odd. For even parity, if the number of 1's in the array is odd, a 1 is added in the parity bit to make the total even. The receiving computer checks the parity bit and indicates a data error if the number of ones does not add up to the proper even or odd total.

A manual method of routing signals using a panel of receptacles for sources and destinations and wire jumpers to interconnect them.

path length (propagation delay)

The time it takes for a signal to travel through a piece of equipment or a length of cable.

In digital picture manipulators, the values of the field rate information produced by in-betweening two key frames. Visually, the path corresponds to the motion route that the image on the screen takes to move from one key frame to the next. May also include size changes, picture rotation, etc.

In a production switcher, a variety of geometric shapes called patterns are available that can be used for wipe transitions, key masks, etc.

A variable-width border that occurs at the edges of a wipe pattern. Typically, the border can be filled with matte video from a border matte generator.

pattern control

In production switchers, the group of controls used for selecting and modifying wipe patterns.

See preset pattern.

In video switchers, a special wipe edge modulation effect produced by summing a matrix pattern and an analog pattern together.

pattern modulation

An oscillation or modulation of the vertical and/or horizontal dimensions of a wipe pattern edge.

pattern positioning

In video switchers, moving a wipe pattern using a joystick.

pattern selector pushbuttons

In a production switcher, the pushbuttons used to select wipe patterns.

Private branch exchange.

PCB (printed circuit board)

An insulating board onto which a circuit has been printed or etched.

Personal communications network.

Personal communications service.

The point of highest amplitude of a waveform or voltage.

peak-to-peak (p-p)

The amplitude (voltage) difference between the most positive and the most negative excursions (peaks) of an electrical signal.

1. In the video waveform, the signal level corresponding to black. Also called setup. 2. A pulse (usually with a flat peak) that elevates the base level of another waveform.

In GVG editing systems, a tool that provides for timed execution of programmed motion, E-MEM recall, GPI events, or character generator strings.

A GVG wideband 10 x 1 routing switcher.

A serial communications bus between a master controlling device and peripheral or slave devices. The master sends out commands to remotely control the peripherals.

personality programming

Feature of some Grass Valley Group equipment that lets the user customize the default settings.

A digital picture manipulator effect that modifies an object's shape in order to create the illusion of disappearing points.

A type of telecommunications cable.

Program. The on-air crosspoint bus of a video or audio switcher. The final on-air output signal of video or audio equipment.

phase (chroma phase, hue, tint)

The relative timing of a signal in relation to another signal. If the time for one cycle of a signal is represented as 360 degrees along a time axis, the phase position for the second signal is called phase angle expressed in degrees. The subcarrier phase of TV colors can be adjusted and this changes the hue of the colors themselves.

phase distortion

A picture defect caused by unequal delay (phase shifting) of different frequency components within the signal as they pass through different impedance elements—filters, amplifiers, ionospheric variations, etc. The defect in the picture is ``fringing'' (like diffraction rings) at the edges where the contrast changes abruptly.

A picture defect caused by the incorrect relative timing of a signal in relation to another signal.

phase inversion

The condition whereby the output of a circuit produces a wave of the same shape and frequency but 180 degrees out of phase with the input.

The phase of a signal follows exactly the phase of a reference signal.

phase locked loop (PLL)

A circuit containing an oscillator whose output phase or frequency locks onto and tracks the phase or frequency of a reference input signal. To produce the locked condition, the circuit detects any phase difference between the two signals and generates a correction voltage that is applied to the oscillator to adjust its phase or frequency.

Adjusting the delay of a video signal to match a reference video signal. This includes horizontal and subcarrier timing.

The movement in relative timing of a signal in relation to another signal.

Primary interexchange carrier.

Sample point of a signal.

0.000000000001 farad.

Positive-intrinsic-negative. A type of semiconductor material used to build diodes with fast switching characteristics. See also positive-intrinsic-negative photodiode coupler.

pink signal (pink panther)

In telecommunications, a video test signal that produces pink when viewed on a monitor.

The smallest distinguishable and resolvable area in a video image. A single point on the screen. In digital video, a single sample of the picture. Derived from the words picture element.

In desktop editing, a single frame of video that serves as an icon to represent a particular video clip.

In video effects, levels of imagery contained in a composite effect.

Programmable logic device. An IC containing a large number of logic gates whose interconnections are programmable for specific applications.

PLUGE (black set)

Picture line-up generation equipment. Used for aligning monitors and other video devices. In some versions of color bars, PLUGE is the black set at the bottom of the red bar that contains bars that are blacker than black, black, and whiter than black. Used to adjust monitor brightness by watching the PLUGE so that the whiter than black bar is just visible and both the black and blacker than black bars are no longer distinct.

Point of presence.

A connection point between a computer and other hardware devices.

A joystick control that allows a wipe pattern or manipulated image to be moved and/or sized within the active picture area.

positioning a picture

photodiode coupler

A coupling device that enables the coupling of light energy from an optical fiber or cable onto the photosensitive surface of a positive-intrinsic-negative (PIN) diode of a photon detector at the receiving end of an optical-fiber data link.

posterize, posterization

A digital video effect where all possible colors are converted to a smaller number of colors, removing gradations and creating color steps to produce a poster effect.

post production

The editing process after the video footage has been shot. See production house.

To continue to roll videotape for some number of frames after the out-point during an edit preview. Useful in viewing how well the edit was performed.

In some GVG digital picture manipulators, the two-dimensional space in which the X-axis translates the image left and right, the Y-axis moves the image up and down, and Z-axis controls the 2-dimensional image size.

potentiometer (pot)

A resistor that has a variable contact so that a portion of the potential applied between its ends may be selected.

Plain old telephone service.

Unit of measure of weight. One pound equals 0.453592370 kilogram.

Pseudo-random bit stream. A telecommunications test signal.

An amplifier that raises the gain of a low-level signal so that it may be further processed without appreciable degradation in the signal-to-noise ratio.

pre-equalization (pre-emphasis)

To emphasize certain frequencies in a signal, usually before transmission, in order to improve the signal-to-noise ratio or to reduce distortion of the signal.

pre-lasing condition

The condition of an injection laser corresponding to the emission of predominantly incoherent or spontaneous radiation.

In telecommunications, a pre-stored list of connect commands that can be implemented by a single MML statement.

A regulator used to deliver reduced voltage to all amplifier modules to ensure cooler operation.

A specific amount of time allowed for tape machines to run prior to an edit in order to get them up to speed and synchronized for the edit. In preparation for the edit, tapes are cued to a point ahead of the edit point to provide a proper preroll. The amount of preroll required varies with each type of VTR.

In video switchers, to make a crosspoint selection prior to performing a transition that will take the selection to air.

presentation switcher

Another term for "master control switcher" used in Europe and some other countries outside the U.S. There are minor differences applicable to the specific area of use.

1. To select a video source in preparation for taking it to air. 2. A source selected on the preset bus or the action of selecting a source on the preset bus.

In video and audio switchers, a row of crosspoint pushbuttons used to select the video or audio input that will be placed on-air during the next background transition. Also called preset background bus.

A transition mode in which one video signal is faded to color black before the other video signal is faded up.

An effect in which a wipe pattern that has been preset to a size limit by the user becomes the key source (cuts the key hole). The characteristics of the pattern are set using the pattern controls.

See preset pattern.

Presto character generators

A series of affordable, high quality character generators made by Grass Valley.

1. To rehearse an edit without recording it. 2. To look at a video effect before taking it to air.

The crosspoint bus used for selecting the signal that will appear at the preview output of a switcher.

preview output (look ahead)

The output of the switcher that allows you to observe an effect before it is placed on-air.

Primary rate interface.

A small group of colors that, when combined, can produce a broad spectrum of other colors. In television, red, green, and blue are the primary colors from which all other colors in the picture are derived.

The main video inputs applied to the crosspoint buses of a switcher.

In video mixers and manipulators, the position of a layer of video relative to other layers. Layer A is said to have priority over Layer B when Layer A is placed on top of Layer B. See also layering.

processing amplifier (proc amp)

A device that stabilizes the composite video signal, regenerates the synchronizing pulses and color burst, and can make other adjustments to the video signal.

production element

In desktop editing, the building blocks of a video production, including clips, effects, transitions, and graphics.

production house

Also known as post production house. A facility that typically does everything to generate final video productions except shooting of original videotape. Services typically include editing raw master tapes, modifying, creating new effects, and correcting. Projects typically include advertising, training, promotion, music videos, and television shows and movies.

production switcher

A device that allows transitions between different video pictures. It may also contain a special effects generator.

professional video

A video production market segment that includes educational, corporate, military, and small commercial producers of video programs.

1. The on-air crosspoint bus of a video or audio switcher. 2. The on-air output signal of video or audio equipment. 3. A sequence of instructions used to tell a computer how to receive, process, store, and transfer information.

In video and audio switchers, a row of crosspoint pushbuttons used to select the on-air video or audio background output of the switcher or mix/effects. Also called program background bus.

program monitor

A video monitor dedicated to displaying the program output of a device or studio.

program (PGM) output

The on-air or final output of a switcher or other device, or a studio.

program/preset mixer

A video mixing system that combines two crosspoint buses with a video mixer. On live production switchers, a program/preset mixer is usually included following the mix/effects and includes pushbuttons for selecting the output of each mix/effect.

See background video.

programmable general purpose interface (GPI)

An interconnection scheme (usually serial) that allows remote control of certain selectable functions of a device by some other device that can be programmed to select the desired functions.

PROGRAMMED MOTION™

A trademarked GVG editor feature that allows control of VTR speed during editing.

Programmable Read Only Memory. A ROM that can be programmed by the equipment manufacturer (rather than the PROM manufacturer).

A cue to help the operator choose the next action.

Pronto Affiliate ID System

A Grass Valley system for playing network promos while keying effects, animations, and affiliate ID logos into the network signal under control of either the network or affiliate.

propagation delay (path length)

The time it takes for a signal to travel through a circuit, piece of equipment, or a length of cable.

A control panel function that locks a source-to-destination configuration so that other control panels may not change that configuration.

A set of conventions governing the format and timing of message exchanges to control data movements and correct errors.

Public Service Commission.

Preset pattern.

Public Utilities Commission

A change in voltage that has identifiable beginning and ending points. A momentary deviation from and return to a constant voltage level.

A method of editing in which the system counts control track pulses to find locations on the tape.

pulse delay distribution amplifier

A device used to replicate an input timing signal, typically providing 6 outputs, each of which is identical to the input signal but shifted in time by as little as a few nanoseconds to as much as a microsecond or more.

pulse distribution amplifier

A device used to replicate an input timing signal, typically providing 6 outputs, each of which is identical to the input signal. May also perform cable equalization or pulse regeneration.

A set of signals needed by some source equipment for timing purposes. The signal set may be composed of any of the following: sync, blanking, subcarrier, horizontal drive, vertical drive, burst flag, and burst gate/PAL pulse.

The leading or trailing edge of a pulse is defined as the 50% point of the pulse rise or fall.

pulse fall time

The interval of time required for the edge of a pulse to fall from 90% to 10% of its peak amplitude.

The voltage amplitude of a pulse.

pulse regenerator

Device which accepts reference color black or another composite color video input and processes it to produce sync, blanking, subcarrier, and burst flag (PAL only) reference pulses.

pulse rise time

The interval of time required for the leading edge of a pulse to rise from 10% to 90% of its peak amplitude.

pulse spreading

The widening of the input optical signals as they traverse the length of a fiber. Caused by the fact that different frequencies of light traverse the path at different velocities. This property limits the useful bandwidth of the fiber. Usually expressed in nanoseconds per kilometer.

A K-factor (distortion) measurement using a T pulse and bar video test signal. See also T-pulse to bar.

The interval measured between the 50% amplitude points of the leading and trailing edges.

Private virtual network.

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