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Author
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Topic: Fancy Yellow First-Down Lines on NFL Football
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QuonoS
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posted 11-28-2000 05:36 PM
How do they do those really nifty Yellow Lines that go across the field signifing the first down line. Its really quite remarkable since the players can step on the line, and the line appears on the other side, they can turn on and off the line and the line goes through the field whether the grass is torn up and muddy or nice and green. They only way I can think is something like they do with the hockypuck on NHL games - have some type of buried transmitter every yard in the field, but that seems a little tough to do for every field every yard. Does anyone know how this is done? |
Movieman21
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posted 11-28-2000 05:59 PM
I have told someone this not too long ago, you could search for it, but I will tell you anyway. It is produced by a machine that costs somewhere around $25,000. The operator punches in the yards of the line of scrimmage, then the machine detects where there is no movement on the field, and displays a line on that yard line where there is no movement. It is run by the tv station who is announcing the game. The line is only visible to the home viewers, and only to that station. It works in kind of the same way that chromakeying works, except that it picks up movement, or heat, or something, instead of color. While it may seem so, this machine is not perfect. If you watch a game real closely, you can see that sometimes it "paints" the line OVER the players. It is quite funny when that happens. Anyway, considering the price, I doubt this is a machine that any of us will be getting any time soon (or ever, considering that is all that is designed to do)  . Not much good to us filmmakers, is it? ------------------
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And be sure to sign our guestbook. We love hearing from you. [This message has been edited by Movieman21 (edited 11-28-2000).] |
MikeDeuce
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posted 11-28-2000 06:07 PM
Here’s how it works. Each of the three main broadcast cameras is outfitted with encoders that record precise information about focus, zoom and angle of each camera. As the action unfolds, data from the encoders is processed by a computer at each of the cameras and forwarded to another computer that merges the three data streams. Meanwhile, yet another computer monitors the actual video feed that viewers see, providing information about graphics that appear on-screen.
Thirty times each second, all of that data is passed on to the central computer, which already possesses a 3-D model of the field, a palette of colors for players and referees and a palette of colors for the playing surface. In addition, a spotter on the field relays the exact position of the first-down marker to a producer in the Sportvision production truck, who keys in the information. The central computer crunches through the accumulated data to determine which pixels in each video frame to change to yellow so the line will look like it is actually drawn on the field and not over the players. There are 30 frames in one second of real-time video.According to a ZDNet article, it costs $20,000 _Per game_! Insane. You can read more at these two pages: ABCNews Article ZDnet Article -mike |
QuonoS
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posted 11-28-2000 09:38 PM
Thanks, although the details are really fuzzy about exactly how it works. |
SeeKae
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posted 11-28-2000 09:41 PM
well thats a mystery..maybe its magic... or maybe its just a lot of dollars |
EricM
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posted 11-29-2000 02:00 PM
Don't quote me on any of this, but I think it works something like this:The TV cameras probably have some sensors on them that tell the computer what direction they are pointing in. The computer knows what the playing field should look like if
no one was there. It lines up this empty field from memory with the image coming from the camera. Wherever something differs from the empty reference, the computer
considers this to be the players. It then draws the line only on the parts under the players.
There is bound to be a whole bunch of image tracking and shape recognition logarithms and other things beyond my comprehension, to make sure everything lines up. | |
