1st & Ten (graphics system): Wikis

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The 1st and Ten line displays the yard line needed for a first down during an ESPN Sunday Night Football broadcast.

1st & Ten is the name for a computer system that generates and displays the yellow first down line that a TV viewer sees during a live broadcast of a college or professional American football or Canadian football game. The line, which is not physically present on the field and is seen only by the television audience, spans the width of the football field and indicates the location of the first down marker. The purpose of the line is to make it easier for television viewers to follow play on the field. Some television football broadcasts change the color of the line from yellow to red on 4th down, or show a second computer-generated line (usually blue in color) that marks the line of scrimmage.

The system is based on chroma key or "green screen" technology, which has been used in other applications for many years prior to the invention of 1st & Ten.

Contents

Conception

The idea of creating an on-field marker to help TV viewers identify 1st down distances was conceived by ESPN Programmer Gary Morgenstern, and executed by ESPN's NFL Coordinating Producer, Fred Gaudelli. The 1st & Ten line is made available by a private company called Sportvision and was developed in 1998. Similar graphics systems were developed by Princeton Video Image and SportsMEDIA which both compete with Sportvision.

Before the game

Each football field has a unique crown and contour (not perfectly flat) so a 3D model is made of the field prior to the game.[1] Due to the low amount of change throughout a football season, this 3D model is usually only generated once a season at most. It also has a unique color palette, typically various shades of green, depending on the type of surface (i.e. real or artificial grass) and the weather (e.g. bright, shady or even snowing).[1] In addition, after cameras are set up, the trigonometric position of the camera relative to the field is established to be used in in conjunction with the previously created 3D model of the field.

Cameras

There are usually a number of cameras shooting the field, but typically only three main cameras are used for a typical American football broadcast (one on the fifty-yard line, and one on each twenty-yard line). The cameras with video that will be used with the graphics system have electronic encoders within parts of the camera assembly (in the lens and the moving platform the camera sits on, sometimes called a "panhead") that monitor how the camera is used during the game (pan, tilt, zoom, focus and extender)[1]. The encoders transmit that info live 30 or more times per second to the broadcaster's production truck, where it is processed by Sportvision computers (typically one for each camera). A camera with this type of extra hardware is usually called an "instrumented" camera. This information helps keep the yellow 1st & ten line in the proper place without being distorted whenever the camera follows the players or the ball.

In the larger productions, several other cameras can be "instrumented" to work with the graphics system, but these are usually restricted to following additional types: a camera usually placed in a high position to see all the field, typically called the "all 22" camera, and a camera shooting from above one end-zone, called, not-surprisingly, an "end-zone camera", but in the industry often just "camera 4". The Skycam (or moving camera attached to cables above the field) can also be used to draw a yellow line over its video, but the mechanism has some major differences from the typical "instrumented" camera and will not be addressed in this article.

Crew

For the initial implementation, there were seven computers in total and a crew of four. Recent implementations require around four computers, one computer per camera plus a shared computer for chroma-keying and other tasks, that can be run by a single operator (although, two is more optimal). The primary operator usually uses a KVM to switch between camera computers and has an extra monitor, keyboard, and mouse setup for the chroma-keying computer.

Of the original four-member crew, two members, one inside the stadium and one in front of a computer, communicated the position of the real first down line to make sure everything was working. The third crew member was a troubleshooter. The last crew member monitored the various colors that make up the color palette onto which the line is drawn.

In recent setups only a single operator is required for all cameras. The operator clicks on the ball in the video to set the line of scrimmage and right-clicks where the first down line should be (or presses a button to automatically position it 10 yards in the direction of play). If lighting conditions don't change that much, the primary operator can also monitor chroma-key settings, but often a secondary operator is used when conditions get too variable.

Data

Each set of camera encoders on a camera transmits position data to an aggregator box that translates the digital information into modulated audio where it is sent down to the corresponding camera computer in the truck. This data is synchronized with the video from that camera. At the camera computer the camera position data is demodulated back to digital data for use by the program that draws the "yellow line" over the video.

Separately, the chroma-keying computer is told what colors of the field are okay to draw over (basically grass) and that information is sent to the camera computers.

The old way

The first computer in the truck gathers all the separate readings from the cameras and transmits a single, consolidated data stream to the central computer.

The central computer takes these readings, the 3D field model & color palette, the knowledge of which camera is on the air, and together using a geometrical calculation determines which pixels in the video frame would make up the first down line. All pixels that are obstructed by a player, a referee, the ball or any other object are identified and not included in the calculation. This will ensure that the 1st & Ten line will be projected only onto the field.

The PVI Virtual Media system relies on a signal on a single spotter to relay the down and distance, and a single operator at the studio as their vision system does not need camera data to perform the insertion. The primary operator of the Sportvision system does the spotting by merely clicking on the video to place the line.

Technology errors

The only pixels that should change are the ones that are the same color as the field, typically several shades of green. As a result, there are a few situations that are difficult. One is when the player's uniform color nearly matches that of the field (for example, the Green Bay Packers' jersey on a bright, sunny day). The other is when the field itself changes, like during a rain/snow storm or if the grass field becomes very muddy. In those cases, the field's color palette would need to include brown and/or white shades. The most difficult situations are when the shade of the field is constantly changing as in situations where moving clouds are shadowing the field on some spots, but not others, but continue to move across the field.

The data collection and computation also requires time. The audio feed goes to an audio delay to be synchronized with the delayed video. The total delay for the viewer from the live feed ends up being about 2/3 of a second.

Final result

After the camera computer has determined which pixels represent the 1st & Ten line and takes that pixel information and draws the yellow line in video format at around 60 times per second (depends on video refresh frequency).

In recent years the system has been upgraded to add more features. During Fox broadcasts, the Sportvision system also generates an arrow-like graphic on the field with down and distance text information inside of an arrow pointing in the direction of play. Competitors have also added this feature in recent years.

Additionally, the Sportvision system can also place virtual graphics that have another embedded video feed inside them like a video picture frame. This is sometimes called "video-in-perspective".

This technology is also the basis for showing ads where they may not appear (i.e. behind home plate in baseball during national broadcasts), and Race F/X in which images can be displayed on the race track, and info can follow a specific car, no matter what the camera does. This technology is used by CBS, ESPN, Fox, NBC, NFL Network, RDS, TSN, and TNT.

See also

References

  1. ^ a b c "Untitled Document". Archived from the original on 2009-09-26. http://www.webcitation.org/5k5GPrsZF. Retrieved 2009-09-24.  

External links

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