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Production Switcher Terms

by John Carter, Switcher Product Manager, Snell

Production switchers are central to the professional television production environment. Installed in television studios, cable broadcast facilities, commercial production facilities, and mobile production trucks and OB vans, the production switcher not only enables cuts between different video sources, but also gives the operator the flexibility to perform these transitions with efficiency, accuracy, and creativity in the live production setting. Today’s production switchers offer a wide range of capabilities for processing and outputting video according to the demands of the program or delivery network.

Alpha Channel

Extra information carried in a graphic, along with actual color data, to determine the color characteristics, such as transparency and edge characteristics, of the image.

Aspect Ratio Conversion

Conversion of the TV picture geometry to preserve the scanning standard, typically for conversions between the 4:3 anamorphic format and 16:9 letterbox format.

Color Corrector

A device that processes video signals to correct for color errors (such as that introduced by incorrect lighting or by equipment during the production process) and to adjust colors for artistic purposes.

Deinterlacing

Upconversion process through which the number of lines per frame and frame rate are preserved, but the interlace ratio is modified, usually from 2:1 to 1:1 to achieve a progressive frame of video in which all the horizontal scan lines are painted on the screen from top to bottom in a single pass. This process also serves as an intermediate stage of standards conversion, used to enable frame rate conversion.

Digital Video Effects (DVE)

Effects (2-D or 3-D) applied digitally, either through a switcher’s built-in processing capabilities or through an external system, to enhance the artistic features of video.

Dissolves/Pattern Wipes

Visual effects by which one scene or picture gradually fades out as another fades in. A dissolve is a simple fade in/fade out, while a more complex pattern wipe makes the transition from one picture to another using shapes or patterns, which often move across the screen.

Key and Fill

The process of superimposing video from one source (the foreground) on top of another source (the background) using a cut-out or “key” signal to control which of the two signals is visible at any one point. The key electronically cuts a hole in a video picture, and the “fill” is the video signal that fills that hole.

Keyer

An electronic circuit that creates a control signal (“key”) based on information contained in the video signal.

Keyframe

Used in production switchers and DVEs to create a sequence of independent events, each keyframe specifies an important point in an effect trajectory or the rate of change of effect parameters.

Master Control Room

Area of the broadcast facility dedicated to routing and switching functions, typically including program and commercial playout. For live broadcasts, the signal goes from the production control room to master control, and then out to the transmitter.

Mix/Effects Banks

The parts of the production switcher control surface that enable the operator to combine video signals from several sources to create mixes, fades, keys, and other effects.

Multiformat

Capable of handling multiple video formats, which may include both analog and digital (SD and varieties of HD), with support for different formats depending on the system. Multiformat systems often feature integrated processing that enables conversion between formats.

Production Control Room

The area within a television studio in which the composition of the outgoing program takes place.

Production Switcher

A device that enables the selection of and transition between different video sources, often with the generation and application of special effects. Known also as a vision mixer, vision switcher, or video mixer.

RU

Rack unit. A unit of measure describing the height of equipment intended for mounting in a 19-inch rack, the broadcast industry standard.

Still Stores and Clip Stores

Devices used to store one or several static TV pictures (stills) or video clips.

Source

Any system that provides a video and/or audio signal that may be fed into a broadcast system, such as a production switcher.

Transitions

A production switcher’s changeover from one source picture to another picture, or from one keyframe to another keyframe.

Up/Down/Crossconverters

Systems that convert video from one picture resolution to another, typically between SD (480i) and HD (720p, 1080i, or 1080p), but also across HD formats.

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