1st and 10

[Gregg Lengling]

HOW IT WORKS:
The central computer examines every frame of video in real time (i.e. 30 times per second) and determines which pixels to change to yellow. These are all the points in the image where an actual painted-on-the-field first down line would be visible, such as grass along the line that is not obscured by a player or referee. It determines which pixels to change based on very precise information about the camera's view, a 3D model of the field, which camera is on air, and a palette of colors for the field and another palette for players. Pixels along the line with colors from the field palette are changed to yellow unless that color is also in the palette for players. Player colors and other colors not on the field palette are left unchanged. This makes the virtual line visible where the field is visible and hidden where the field is obscured, just as a real line would be.
Each camera in the system, is instrumented with very precise encoders for pan, tilt, zoom, focus and extender (1x or 2x doubler). A computer at each camera reads the encoders and transmits these readings to the Sportvision production truck 30 times per second. Another computer in the truck gathers readings from all the cameras and transmits a consolidated data stream to the central computer. These readings and the 3D field model go into a geometrical calculation that determines which pixels in the video frame would be in an unobstructed view of a real first down line.

The final computer has only one simple but crucial task, draw the yellow line in video 60 times per second (every field, not just frame) and send that to a linear keyer to superimpose the yellow onto the program video


There are seven computers (three SGIs and one PC and three special purpose data acquisition computers), three sets of special encoders and abundant wiring dedicated to generating the virtual first down line in video format. The data collection and computation requires time, and the virtual first down line must be superimposed on the program video at exactly the correct field every 60th of a second, requiring substantial video and audio processing.

Program feed without the 1st & Ten line comes from the primary production truck into Sportvision's 1st & Ten equipment. Digital feeds from each of the three game cameras also come from main production to 1st & Ten. Program video then goes (undelayed) to the central computer and to a series of frame delays. The audio feed goes to an audio delay to be synchronized with the delayed video. To synchronize the computed virtual first down line with the program feed, the 1st & Ten system delays program video and audio a fixed number of frames. The delayed program video and the generated virtual first down line are both input to a linear keyer that combines the two and outputs the video that will go to air.

From:http://www.sportvision.com/

[davezen2]

Thanks Gregg!

I was just wondering how they do that while watching the Bears/Vikings game today.