ABSTRACT
The major use for live keying in the television world has of course been for weathercasting. What would the Weather Channel or readers local station do without live keying to allow the meteorologist to point to a map and explain the Doppler radar? Traditional analog switchers were set up with two main busses, usually A and B, with an additional keying bus. The type of source is selected in the keying controls, and can be derived from the original signal (as in chroma keying or luma keying) or supplied by a separate source. The GlobeCaster (from its Trinity beginnings) has always had an integrated virtual set function as part of the chroma keying section. Most local television studios use the built-in chroma keying capabilities of their production switcher for live keying. However, there are several standalone hardware units available that provide more sophisticated keying management that networks and better-equipped stations will use.
