Instant replay Instant replay is the replaying of video footage of an event or incident very soon ( or even instantly ) after it has occurred . In television broadcasting of sports events , instant replay is often used during live broadcast , to show a passage of play which was important or remarkable , or which was unclear on first sight . Some sports organizations allow referee s or other officials to consult replay footage before making or revising a decision about an unclear or dubious play . This is variously called video referee , video umpire , instant replay official , television match official or third umpire . Other associations allow video evidence only after the end of the contest , for example to penalize a player for misconduct not noticed by the officials during play . History . 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 . Slow motion replay was initiated a few years later by ABC . CBS Sports Director Tony Verna invented a system to enable a standard videotape machine to " instantly " replay on 7 December 1963 , for the network ' s coverage of the Army – Navy Game . The instant replay machine weighed 1300 pounds . After technical hitches , the only replay broadcast was Rollie Stichweh ' s winning touchdown . It was replayed at the original speed , with commentator Lindsey Nelson advising viewers " Ladies and gentlemen , Army did not score again ! " 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 . Instant replay has been credited as a primary factor in the rise of televised football , although football was popular on television even before then . While one camera was set up to show the overall “ live ” action , other cameras , which were linked to a separate videotape machine , framed close - ups of key players . Within a few seconds of a crucial play , the videotape machine would replay the action from various , close - up angles , in slow motion . Prior to instant replay , it was almost impossible to portray the essence of a football game on television . Viewers struggled to disseminate the action from a wide shot of the field , on a small black and white television screen . However , with replay technology , “ brutal collisions became ballets , and end runs and forward passes became miracles of human coordination . ” Thanks in large part to instant replay , televised football became evening entertainment , perfected by ABC - TV ’ s Monday Night Football , and enjoyed by a wide audience Marshall McLuhan , the noted communication theorist , famously said that any new medium contains all prior media within it . McLuhan gave Tony Verna ' s invention of instant replay as a good example . " Until the advent of the instant replay , televised football had served simply as a substitute for physically attending the game ; the advent of instant replay – which is possible only with the television – marks a post - convergent moment in the medium of television . " In television . In television broadcasting of sports events , instant replay is often used during live broadcast , to show a passage of play which was important or remarkable , or which was unclear on first sight . Replays are typically shown during a break or lull in the action ; in modern telecasts , it will be the next break , though older systems were sometimes less instant . The replay may be in slow motion , or from multiple camera angles . Video server s , with their advanced technology , have allowed for more complex replays , such as freeze frame , frame - by - frame review , replay at variable speeds , overlaying of virtual graphics , instant analysis tools such as ball speed or immediate distance calculation . Sports commentator s analyze the replay footage when it is being played , rather than describing the concurrent live action . Instant replays are used today in broadcasting extreme sports , where speed is too high to allow comfortable view for eyes ( diving , darts , cricket … ) , using combination of different advanced technologies ( high - speed camera s up to several thousands of frames per second , video server s controlled by special controllers , such Multicam ( LSM ) , which allow to keep recording multiple angles still playing out the action , preventing to miss any new action during replay ) . Use by officials . Leagues using instant replay in official decision making include the National Hockey League , National Football League , Canadian Football League , National Basketball Association , and Major League Baseball . The role of the video referee differs varies , often they can only be called upon to adjudicate on specific events . Due to the cost of television cameras and other equipment needed for a video referee to function , most sports only employ them at a professional or top - class level . Basketball . In NBA basketball , the officials must watch an instant replay of a buzzer beater to determine if the shot was released before time expired . Since 2002 , the NBA also has mandated installation of light strips on both the backboard and the scorer ' s table that illuminate when time expires , in order to assist with any potential review . Instant replay first came to the NBA in the 2002 – 03 season . In Game 4 of the 2002 Western Conference Finals , Los Angeles Lakers forward Samaki Walker made a three - point field goal from the half court at the end of the second quarter . However , the replay showed that Walker ' s shot was late and that the ball was still in his hand when the clock expired . The shot cost the Kings the game and the use of instant replay was instituted afterward . Beginning with the 2007 – 08 season , replay also can be used in determining players being ejected from contests involving brawls or flagrant fouls . In the 2008 – 09 season , replay may also be used to correctly determine whether a scored field goal is worth two or three points . It may also be used to determine the correct number of free throws awarded for a missed field goal . It may also be used in cases where the game clock malfunctions and play continues to decide how much time to take off the clock . In college basketball , the same procedure may also be used to determine if a shot was released before time expired in either half or an overtime period . In addition , NCAA rules allow the officials to use instant replay to determine if a field goal is worth two or three points , who is to take a free throw , whether a fight occurred and who participated in a fight . The officials may also check if the shot was made before the expiration of the shot clock , but only when such a situation occurs at the end of a half or an overtime period . Such rules have also required the NCAA to write new rules stating that , when looking at instant replay video , the zeros on the clock , not the horn or red light , now determine the end of the game . In Italy , host broadcaster Sky agreed with Lega A for the adoption of instant replay for special tournaments and playoff games , and in 2005 , for the entire season . Instant replay would be used automatically on situations similar to the NCAA , but coaches may , like the NFL , have one coach ' s challenge to challenge a two or three point shot , officials may determine who last touched the ball in an out - of - bounds situation , or back - court violations . The adoption of instant replay would be crucial in the 2005 Lega A championship between Armani Jeans Milano and Climamio Bologna . Bologna led the best - of - five series , 2 - 1 , with Game 4 in Milan , and the home team leading 65 - 64 , as Climamio ' s Ruben Douglas connected on a three - point basket at the end of the game to apparently win the Lega A championship . Officials , knowing the 12 , 000 fans on both sides would learn the fate of the series on their call , watched replays of the shot before determining it was valid . The ULEB adopted instant replay for the 2006 Euroleague Final Four and made a rule change determining the lights on the backboard , not the horn , will end a period , thus assisting with instant replay . On April 6 , 2006 , FIBA announced instant replay for last - second shots would be legal for their competitions . " The referee may use technical equipment to determine on a last shot made at the end of each period or extra period , whether the ball has or has not left the player ' s hand ( s ) within the playing time . " Field hockey . In field hockey , the International Hockey Federation allows the match umpire to request the opinion of a video umpire as to whether or not a goal has been validly scored , and whether there was a violation in the build - up to a goal . The video umpire can advise on whether the ball crossed the line there was a violation . Ordinarily , teams are not allowed to make such a request or to press the match umpire to do so . On a trial basis , the 2009 Men ’ s Champions Trophy allows for " team referral " by each team captain , to query a goal , penalty stroke , or penalty corner decision . The team retains the right to a referral if its previous referrals were upheld . Baseball . In Major League Baseball , Instant Replay has been introduced to address " boundary calls , " which include questions on whether or not a hit should be considered a home run ( HR ) . Among reviewable plays are Fair Ball - HR / Foul Ball , Ball Clearing Wall - HR / Ball Staying in Play - Live Ball , Ball Leaving Field of Play - HR / Ball or Player interfered with by spectators ( called Spectator Interference ) . The latest MLB collective bargaining agreement , pending agreement by the umpires ' union , expands instant replay to include Fair Ball / Foul Ball along foul lines , or Ball Caught for Out / Ball Trapped Against Ground or Wall , as well as expanding Interference calls to all walls regardless of whether it is a " boundary call " or not . In Little League Baseball , Instant Replay was adopted for the Little League World Series only , and includes all " boundary call " plays reviewable at the Major League Level , in addition to adding review to plays involving force outs , tag plays on the basepaths , hit batters , and for defensive appeals regarding whether a runner missed touching a base . Tennis . In tennis , systems such as Hawk - Eye and MacCAM calculate the trajectory of the ball by processing the input of several video cameras . They can play a computer rendering of the path and determine whether the ball landed in or out . Players can appeal to have the system ' s calculation used to override a disputed call by the umpire . In March 2008 , the International Tennis Federation , Association of Tennis Professionals , Women ' s Tennis Association and Grand Slam Committee agreed unified challenge rules : a player can make up to three unsuccessful challenges per set , and a fourth in a tie - break . Television broadcasts may use the footage to replay points even when not challenged by a player . Rugby league . Since being introduced by Europe ' s Super League in 1996 , video referees have been adopted in Australasia ' s National Rugby League and international competition as well . In rugby league the video referee can be called upon by the match official to determine the outcome of a possible try . The " video ref " can make judgements on knock - on s , offside , obstructions , hold - ups and whether or not a player has gone dead , but cannot rule on a forward pass . If a forward pass has gone un - noticed by the on - field officials it must be disregarded by the video ref , as such judgements cannot reliably be made due to camera angle effects . Rugby union . Use of video referee was introduced to rugby union in 2001 . The laws of the game allow for " an official who uses technological devices " to be consulted by the referee in decisions relating to scoring a try or a kick at goal . The decision to call on the video referee ( now called " Television Match Official ( TMO ) " ) is made by the referee , then the call is made by the replay referee , who takes his place in the stand of the host team or more usually in the Television Outside Broadcast van . He either tells the pitch referee by radio link - up or by the use of a big screen during televised matches . Unlike in the NFL , a coach cannot challenge a call made by the pitch referee . Cricket . Cricket also uses an instant replay . It is used in the areas of run outs , stumpings , doubtful catches and whether the ball has crossed the boundary for a six or short of a four . The International Cricket Council decided to trial a referral system during the Indian tour of Sri Lanka through late July and August 2008 . This new referral system allows players to seek reviews , by the third umpire , of decisions by the on - field umpires on whether or not a batsman has been dismissed . Each team can make three unsuccessful requests per innings , which must be made within a few seconds of the ball becoming dead ; once made , the requests cannot be withdrawn . Only the batsman involved in a dismissal can ask for a review of an " out " decision ; in a " not out " , only the captain or acting captain of the fielding team . In both cases players can consult on - field teammates but signals from off the field are not permitted . A review request can be made by the player with a ' T ' sign ; the umpire will consult the TV umpire , who will review TV coverage of the incident before relaying back fact - based information . The field umpire can then either reverse his decision or stand by it ; he indicates " out " with a raised finger and " not out " by crossing his hands in a horizontal position side to side in front and above his waist three times . The TV umpire can use regular slow - motion , or high - speed camera angles usually called ultra - motion or super - slow replays , the mat , sound from the stump mics and approved ball tracking technology , which refers to Hawk - Eye technology that would only show the TV umpire where the ball pitched and where it hit the batsman ' s leg and it is not to be used for predicting the height or the direction of the ball . Snicko and Hot Spot can also be used . Ultra Motion or Slo - mo is the predecessor of Hi Motion , its superior and easier - to - use successor which was started in 2006 , Ultra Motion shot at 1000 frames a second to produced some remarkable images . For the first time viewers could see the amazing way that bats bent and twisted as they made contact with the ball , and even the way the bones in the hand reverberate when a catch is made . Perhaps it is at its most useful when used to show just where on the batsman ' s bat or body a ball glanced , rarely does a replay fail to clear that issue up . Often used by TV productions during closing sequences or musical interludes . The latest addition that is not yet widespread used is the super slow motion cameras , showing the frames that are missed out by the regular cameras . Rodeo . The Professional Bull Riders organization , beginning with the 2006 - 07 season , has instituted an instant replay system in cooperation with the Versus network . A bull rider , a fellow competitor , or a judge may request a replay review by filing a protest to the replay official within 30 seconds of any decision . Any competitor ( it does not have to be the rider who is riding the bull in question , as fellow riders can observe the action and spot fouls by bull or rider ) may file the complaint to the replay official by sounding a signal at the arena and pay a fee of $ 500 to PBR before explaining to the replay official why he is filing the request . The replay official ( usually a former bull rider ) may request different angles and / or slow motion , as well as freeze particular frames . The replay judge will use all available technology to assess the call in question and supply his ruling . This includes using his own hand - held stopwatch to time bull rides , as the official eight - second clock used in PBR competition starts when the bull usually exits the bucking chute . The replay will be used to evaluate timing issues , fouls against the rider for touching the bull or ground with his free hand or using the fence to stay on the bull , or fouls by the bull , such as dragging the rider across the fence . If an appeal is successful , the $ 500 is returned to the competitor filing the request . If the appeal is unsuccessful , the $ 500 is forfeited and sent to PBR charities such as the Resistol Relief Fund to assist injured bull riders . Motor sports . NASCAR utilizes instant replay to supplement their electronic scoring system . Video replays are used to review rules infractions and scoring disputes . IndyCar also utilizes instant replay for similar reasons . The most notable use of replay in recent years occurred during the 2008 Peak 300 at Chicagoland Speedway . On the final lap , Scott Dixon and Helio Castroneves crossed the finish line side - by - side , with computer scoring showing Dixon the winner by a margin of 0 . 0010 seconds . However , video replay evidence clearly showed that the nose of Castroneves ' car touched line first . Castroneves was declared the winner officially by 0 . 0033 seconds or 12⅛ inches , in the second closest finish in the twelve - year history of the series . It was later determined that the improper installation of Dixon ' s scoring transponder was the source of the scoring error . Video replay was also used extensively in the aftermath of the controversial 2002 Indianapolis 500 . However , fully conclusive evidence was lacking . Broadcast stations utilize replays to show viewers a crash in greater detail . Association football . In association football , FIFA does not permit video evidence during matches , although it is permitted for subsequent disciplinary sanctions . The 1970 meeting of the International Football Association Board " agreed to request the television authorities to refrain from any slow - motion play - back which reflected , or might reflect , adversely on any decision of the referee " . In 2005 , Urs Linsi , general secretary of FIFA , said : There have been allegations that referees had made or changed decisions on the advice of a fourth official who had seen the in - stadium replay of an incident . This was denied by FIFA in relation to the Zidane headbutt of Materazzi in the 2006 World Cup final , and in relation to the 2009 FIFA Confederations Cup match between Brazil and Egypt , in which Howard Webb signalled initially for a corner kick but then a penalty kick . It has been said that instant replay is needed given the difficulty of tracking the activities of 22 players on such a large field , FIFA officials approached researchers at the University of Glasgow in Scotland for help , but came up with nothing that could satisfy the league ' s stringent requirements . Opponents of instant replay like FIFA President Sepp Blatter argue that refereeing mistakes add to the " fascination and popularity of football . " It has been proposed that instant replay be limited to use in penalty incidents , fouls which lead to bookings or red cards and whether the ball has crossed the goal line , since those events are more likely than others to be game - changing . In 2007 , FIFA authorized tests of two systems , one involving an implanted chip in the ball and the other using a modified version of Tennis ' s Hawk - Eye system , to assist referees in deciding whether a ball had crossed over the goal line . The following year , however , the IFAB and FIFA halted testing of all goal line technology , fearing that its success would lead to its possibly expansion to other parts of the game . Sepp Blatter claimed the technologies were flawed and too expensive to be implemented on a widespread basis , adding , " Let it be as it is and let ' s leave ( soccer ) with errors . The television companies will have the right to say ( the referee ) was right or wrong , but still the referee makes the decision — a man , not a machine . " This sudden change of course surprised and angered Paul Hawkins , as the inventor of the Hawk - Eye system had invested a great deal of money into adapting the Hawk - Eye technology to football . In 2009 , Hawkins sent an open letter to Blatter refuting the FIFA president ' s assertion that the Hawk - Eye goal line technology was flawed and arguing that Hawk - Eye met all of the criteria established by the IFAB for a suitable goal line technology system . The controversy over goal line technology was re - ignited in 2009 after Brazil had a potential equalizing goal disallowed during the 2009 Confederations Cup Final and during the 2010 FIFA World Cup after England ' s Frank Lampard ' s shot off the underside of the crossbar was not ruled a goal despite replays clearly showing it was 60 cm over the line . Racewalking . Instant replay is not authorized for officiating in racewalking , because practically all competitors leave the ground during each stride . This " loss of contact " can be caught in a slow motion replay , but happens too fast to be seen by the naked eye . Only visible loss of contact is judged to violate the rules of the sport .