Hawk-Eye Officiating has been a well-known name among tennis fans since 2006. The electronic line-calling system, with between eight and 10 high-speed cameras, computers and a big screen, can capture the movement of the ball from different angles and then produce a three-dimensional image of the ball's route and falling point on the screen. The umpire makes a decision based on the digital image. Players have two chances per set to challenge the line calls.

After the successful implementation of Hawk-Eye at many major tennis tournaments, International Tennis Federation (ITF) President Francesco Ricci Bitti said, "The system has worked extremely well and was a very popular addition with players, officials, the media and the general public. It added a new, exciting element to the game and enhanced the important role played by our officiating professionals."

The system has worked so well in tennis that some badminton players think their sport, which is also troubled by the bad line calls, should follow suit.

At the 2006 Badminton World Championships in Madrid, Indonesian star Taufik Hidayat was the first player to have the idea, saying the 2008 Beijing Games organizers should consider using Hawk-Eye in their sport.

The willful world champion has had frequent disputes with linemen and has even withdrawn from major events because of referee issues. He said referees always favor host players and at the Beijing Olympics he hopes he will be treated as fairly as his Chinese rivals.

Soccer officials are hesitant to use video technology despite huge pressure from players and fans about incorrect line calls.

"At the Beijing Games, we are not using video refereeing system to monitor the matches," BOCOG competition director of soccer Lin Weiguo told China Daily without elaborating.

Though video referees are still controversial, those sports that do choose to employ them have learned the controversy human error can cause is often much worse.