:''For other uses of the term "Instant replay", see Instant replay (disambiguation).''

'''Instant replay''' refers to a system where plays in a sporting match can be reviewed (or replayed) using recorded video feeds of the sporting match. This was introduced in broadcast television to allow the viewer to get other views of sports plays during the game. It was combined with '''Slow Motion''' to give viewers a better idea of the development of the game.

'''Instant Replay Challenge''' takes advantage of the video technology and introduces it into the rules of the game itself in order to ensure that the correct call is made on the play.  

Instant replay is used in many professional sports leagues including the National Hockey League, the National Football League & Canadian Football League, and the National Basketball Association.

The first use of Instant Replay occurred December 7, 1963 during the Army-Navy Game played in Philadelphia and telecast by CBS-TV.  The program was directed by one of CBS Sports' top directors, Tony Verna.  (For details of the football game, see a December 7, 2003,Tribune-Review article by Joe Starkey "Instant Replay born 40 years ago today" at wwws.pittsburghlive.com;/x/tribune-review/sports 168827.html)  A personal account of the telecast can be found in the autobiography of the game announcer Lindsey Nelson "Hello Everybody, I'm Lindsey Nelson.")

Confusion caused by other claims of the  first use of Instant Replay is probably best explained by the difference between "In-Game" Replays--replays shown while the game was still being telecast but not immediately after the play on the replay.  None of the replays could occur until the middle of the 1950s when Ampex developed a commercially usable videotape.  For a recap of the technical data, see www.cedmagic.com/history/instant-replay-hs-deck.html.)  Director Verna's account of how he was able to combine the limited abilities of the videotape machines can be found in two of his early books, "Live TV " and "Global Television" (both Focal Press) and a 2008 book "Instant Replay, The day that changed Sports Forever" from Creative Publishers International.)

Slow-Motion Replays, often referred to as slo-mo, were introduced by ABC-TV's "Wide World of Sports" in 1960.  ABC-TV Engineer Bob Trachinger developed the process, but it could not be "Instant" because the original images had to be reprocessed to slow the motion.  ABC-TV Sports Director (also later ABC-TV News Director) Roone Arledge gives his account of the development of slo-mo in his autobiography "Roone".  Unfortunately, he also claims to have created the idea of Instant Replay.  In Tony Verna's book "Instant Replay," there is an explanation of a German film camera from 1935, a camera mounted on a truck that also contained a film processor and was able to produce images within a minute and a half.  The idea came early, but the "Instant" part of "Instant Replay" had to wait until Director Verna was able to combine an audio signal with the unreliable counters on the videotape machines in order to be able to reproduce the image immediately after the play occurred. 

Replay made its Canadian debut in 1955, by George Retzlaff at the Canadian Broadcasting Corporation during a broadcast of Hockey Night in Canada.<ref>[http://www.cbc.ca/inventions/inventions.html?inventionID=24 CBC.ca Greatest Canadian inventions]</ref> Jim Wheeler erroneously claims to have invented Instant Replay in 1964.

Starting with the 2005 season, the Division I-A football conferences, just a year after the three-pointer) or to determine which player should shoot foul. 

==American football==
===National Football League===
thumb|350px|[[Bill Cowher, former head coach of the Pittsburgh Steelers, throws the red challenge flag (visible in the upper left corner of the picture), indicating his desire to challenge the referees' ruling.]]

The 1999, bringing in the opportunity to "challenge" on-field calls of plays. The current system mirrors a system used by the now defunct USFL in 1985. Each coach is allowed 2 opportunities per game to make a ''coach's challenge''. Prior to the 2004 NFL season, the instant replay rule was slightly changed to allow a third challenge if ''both'' of the original two challenges were successful.

A challenge can only be made on certain reviewable calls before the time-out remaining in the half. When a coach decides to challenge a call, he throws a red flag onto the field, indicating the challenge to the referees. Up until the 2005 season, coaches could also signal a challenge via an electronic pager, now used only by the replay assistant.<ref>[http://www.nfl.com/news/story/8319452 NFL News: Owners to vote on several major changes]</ref> 

The referee has 60 seconds to watch the instant replay of the play and decide if the original call was correct. The referee must see "indisputable visual evidence" for a call to be overturned. If the challenge fails, the original ruling stands and the challenging team is charged with a timeout. If the challenge overrules the previous call, the call is reversed with no loss of a timeout. 

Because of the limited number of challenges, and the possible penalty of a lost timeout, coaches must reserve their challenges for key plays. A questionable call may not be challenged once the next play is underway, so coaches may be forced to make a quick decision without the benefit of seeing a replay on television or on the stadium screen.  Often players on the field will signal to the coach if they believe the play should be challenged.

After the 2-minute warning of each half, and in overtime, reviews can only take place if the replay assistant, who sits in the press box and monitors the network broadcast of the game, determines that a play needs review; coaches may not challenge during these times. In those cases, the replay assistant will contact the referee by a specialized electronic pager with a vibrating alert.

One concern about replay that was addressed some years ago was the situation where a coach would seek a review of a non-challengeable call (such as being forced out of bounds, or in some cases to challenge a runner down by contact).  Prior to the rule being clarified, a team would lose the challenge and a time-out.  The current rule does not penalize a team in such a case, provided the rule is not abused or taken advantage of.

The NFL replay system currently only covers the following situations:
*Scoring plays
*Pass complete/incomplete/intercepted
*Runner/receiver out of bounds
*Recovery of a loose ball in or out of bounds
*Touching of a forward pass, either by an ineligible receiver or a defensive player
*Quarterback pass or fumble
*Illegal forward pass
*Forward or backward pass
*Runner ruled not down by contact
*Forward progress in regard to a first down
*Touching of a kick
*Other plays involving placement of the football
*Whether a legal number of players is on the field at the time of the snap

Note that the spot of the ball may be challenged in certain cases. In such cases, a decision to respot football is not enough to win the challenge; Only when ball is respotted ''AND'' ruling on the field is reversed by remeasurement, the challenging team would not be charged their timeout.

The current replay system replaced a previous system used during from 1986 through 1992; procedure similar to that of college football was used. From prior to 1986, and from 1993-1998, there was no replay system utilized. While there is occasional controversy over the appropriateness of overturned calls, the system is generally accepted as an effective, and necessary way to ensure a fair game.

===College football===
thumb|right|Head referee talking with the replay official
In 2006, the NCAA Football Rules Committee enacted instant replay guidelines and added them to the football playing rules. For games involving two schools from the same conference, league policy determines whether replay will be used. For non-conference games, the home team makes the determination.

Plays involving the sideline, goal line, end zone and end line, as well as other detectable situations, are reviewable (e.g., fumble/no fumble, pass complete/incomplete, touchdown/no touchdown, runner down/not down, player or ball inbounds/out of bounds, clock adjustments). Most fouls (e.g., holding, offside, pass interference) are not reviewable, except that in 2006, illegal forward passes, handoffs and punts from beyond the line of scrimmage, and too many players on the field are reviewable and the foul may be called after replay review. Also, while the foul of pass interference is not reviewable, it can be overturned on review based on touching of the pass. By rule, pass interference cannot apply if a pass has been touched by any player before the foul occurs, and the touching of a pass is a reviewable call.

When replay is used, a Replay Official (usually a former college, NFL or XFL game official) reviews every play at its conclusion from a secure booth in the press box. Most plays are routine and the game continues without interruption. If, however, the following criteria are met, the Replay Official may interrupt the contest by paging the game officials to stop the game before the next play starts. The criteria are:

*There is reasonable evidence to believe an error was made in the initial on-field ruling.
*The play is reviewable.
*Any reversal of the on-field ruling, which can only result from indisputable video evidence, would have a direct, competitive impact on the game.

Once per game, each head coach may also call a timeout and challenge the ruling on the previous play before the next play starts. A coach must have at least one timeout remaining in order to challenge (teams receive three timeouts per half). If the challenge is successful and the on-field ruling is overturned, the team keeps its timeout. If not, the team loses its timeout. In either event, the head coach may not challenge again during the game.

After reviewing the play from available video angles, the Replay Official decides if the call should be upheld or overturned.  If the call is overturned, the Replay Official provides the proper information to restart the game, such as the team in possession, the yardline where the ball should be placed, the correct down and distance, and the correct time on the stadium clock.

College football instant replay started in the 2004 season, when reviews were used experimentally in the Big East, Big Ten, Big 12, MAC, Pac-10, and SEC used replay in 2005. The Sun Belt and Western Athletic did not.

In 2005, the Big 12  initially sought to provide field monitors which would allow the on-field referee to assist the replay official; however, by the first game of the season, they decided to only provide equipment to the instant replay booth.  Conference USA used a similar system, but the on-field referee made the decision after viewing a TV monitor on the sideline. The Mountain West Conference was the only league to allow a head coach's challenge.  Each head coach got one challenge per half. If the call was overturned, the challenging coach kept his timeout and got a second challenge for that half. If not, the challenging coach lost one of his three timeouts for the half. No more than two challenges per half per coach were allowed.

There is not currently an Instant Replay equipment standard, each conference must choose (and purchase) its own equipment. Therefore, systems are quite disparate: they can be as complex as high-tech custom systems similar to those used in the NFL to simply several large screens hooked up to TiVo boxes.

In 2005, the Big Ten, MAC, and SEC only allowed broadcast video (for games that are televised) to be used to determine the correct call. The other conferences allowed broadcast video and scoreboard video. Most conferences provided video equipment for games that were not televised.

Der '''Videobeweis''' bezeichnet im Sport die Zuhilfenahme der Kamerabilder zur Ergänzung oder Korrektur der Schiedsrichter-Entscheidungen.

==American Football==

Die umfassendste Nutzung des Videobeweises gibt es in der NFL, der amerikanischen Profi-Footballliga. Dort kann fast jede Entscheidung der Schiedsrichter vom Headcoach eines der Teams angegriffen (''challenged'') werden. Der Hauptschiedsrichter (''Referee'') benutzt dann eine spezielle Videokabine, wo er innerhalb von 90 Sekunden unter Zuhilfenahme aller verfügbaren Fernsehbilder die Entscheidung überprüft. Bleibt die Entscheidung bestehen (''the ruling on the field stands''), wird dem Team, das die ''Challenge'' ausgesprochen hat, dafür ein Time-Out abgezogen.

==Eishockey==

Im Tor. Außerdem wird der Videobeweis angewandt um zu klären, ob der Puck regelkonform über die Torlinie befördert und nicht mit einer Trittbewegung, wie beim Fußball.

In der nordamerikanischen Eishockeyliga NHL nimmt den Videobeweis der Videorichter vor, der in der NHL-Zentrale in Toronto sitzt. Ist ein Videobeweis erforderlich, kann der Schiedsrichter den Videorichter anrufen, der alle ihm zur Verfügung stehenden Kameraperspektiven nutzen darf um eine Entscheidung zu fällen, die er innerhalb weniger Minuten dem Schiedsrichter telefonisch mitteilt.

==Basketball==

In der amerikanischen NBA wird der Videobeweis nur dazu benutzt, festzustellen, ob der Ball bei Ertönen der Sirene (z.&nbsp;B. wegen Ablauf der 24 Sekunden Angriffszeit oder der Spielzeit) die Hand bereits verlassen hatte.

==Fußball==
Die Notwendigkeit des Videobeweises sehen viele darin, dass er klare und offensichtliche Fehlentscheidungen des Schiedsrichters durch Zeitlupen, verschiedene Kamerawinkel etc. widerlegen kann. 

Dass es auch eine geteilte Meinung zum Videobeweis, durchaus auch in Chef-Etagen, gibt, zeigt dieses Zitat vom Vorsitzenden des Schiedsrichter-Ausschusses beim Deutschen Fußball-Bund (DFB), Volker Roth:
:''Nichts halte ich hingegen vom Videobeweis, denn Fußball ist ein fließendes Spiel, das nicht zerhackt und ständig unterbrochen werden sollte.''