Instant replay

Instant replay is a video reproduction of something that recently occurred which was both shot and broadcast live. The video, having already been shown live, is replayed in order for viewers to see again and analyze what had just taken place. Some sports allow officiating calls to be overturned after the review of a play. Instant replay is most commonly used in sports, but is also used in other fields of live TV. While the first near-instant replay system was developed and used in Canada, the first instant replay was developed and deployed in the United States.

During a 1955 Hockey Night in Canada broadcast on CBC Television, producer George Retzlaff used a "wet-film" (kinescope) replay, which aired several minutes later. Videotape was introduced in 1956 with the Ampex Quadruplex system. However, it was incapable of displaying slow motion, instant replay, or freeze-frames, and it was difficult to rewind and set index points.

CBS Sports Director Tony Verna invented a system to enable a standard videotape machine to instantly replay on December 7, 1963, for the network's coverage of the US military's Army–Navy Game. The instant replay machine weighed 1,300 pounds (590 kg). After technical hitches, the only replay broadcast was Rollie Stichweh's touchdown. It was replayed at the original speed, with commentator Lindsey Nelson advising viewers "Ladies and gentlemen, Army did not score again!" The problem with older technology was the difficulty of finding the desired starting point; Verna's system used audio tones activated as an interesting event unfolded, which technicians could hear during the rewinding process.

Replay from analog disk storage was tried out by CBS in 1965, and commercialized in 1967 by the Ampex HS-100, which had a 30-second capacity and freeze frame capability.

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