Jun 15, 2010ARS Technica - February 2008
First and 10: the technology behind the Super Bowl broadcast
By Nate Anderson | Last updated February 3, 2008 10:55 AM
The low-tech NFL?
[Note: ... The article first appeared online 1 year and 1 day ago, just before Super Bowl XLI. While some things have changed .. the article still gives some insight into how the production of the TV experience is accomplished.]
Steaming bodies in the snow. Bone-snapping tackles. The stiff-arm.
These are the iconic images of pro football, and they're low-tech in the extreme. While the game itself remains a contest of brute strength, raw speed, and little red challenge beanbags, the entire transmission infrastructure that brings the games into our homes and plasters them on our televisions in HD is exactly the opposite: millions of dollars of the most complicated broadcast technology on the planet.
With the Midwest basking in the unseasonal glow of the Super Bowl spotlight, it's a fitting time to take a closer look at the tech that will power this Sunday's contest. In 2007, CBS covered Super Bowl LXI, deployed a crew of hundreds to Miami to man the HD cameras, run the first-down line, and show you the slowest of slow-motion replays. FOX is doing the same for Super Bowl XLII in Glendale, Arizona.
Here's a rundown of the equipment that will bring the game home.
First and ten
Consider the humble yellow line, now a staple of football broadcasts in the US. Companies like Princeton Video Image and Sportvision have developed and marketed the technology so well that it has a 98 percent approval rating from fans, and it's hard to imagine football without it anymore.
The line is overlaid on the field to show how far each team has to go for a first down. It's the kind of effect that is immediately intuitive to viewers, and it looks like the sort of thing that should be simple to generate. Just slap a graphic on the field and be done with it, right? After all, networks have doing fancy computer-generated graphics for years, so a line would seem to be well within their capabilities.
But the tech is is actually quite advanced. For the line to function properly, computers in the production truck must know exactly where the various cameras are pointing, how far they are zoomed in, and whether they are tilted at all. To make things worse, football fields are not entirely level, and players are constantly running back and forth across the line. In addition, the computer model of the stadium needs to be so accurate that the line can be projected within a foot or two of the official sideline chains.
Making the system work requires several hours of pregame setup. Sportvision, for instance, takes a laser surveying system out to the center of the field, then uses it to precisely map elevations and contours. This information is used to create a detailed stadium model that is then passed to computers in the production truck. The cameras on the field are equipped with specialized sensors that measure pan, tilt, and zoom data so that the line can be properly projected and kept in the correct perspective as the camera moves. (This last requirement is also the reason why many replay angles do not include the line; it only functions with sensor-equipped cameras.)
Out in the truck, techs use color keying to paint the line only on the field, not on the players. One palette tells the system what colors it can paint on, while another palette includes skin tones and uniform colors that cannot be painted on. Another operator is responsible for manually entering the first down yard line number whenever it changes, and the digital model of the stadium is then used to draw the line in the right place.
While cameras have been omnipresent at NFL games for decades, the "flying" overhead camera is a recent twist that enables broadcasters to provide views directly from behind the quarterback or from the middle of the defense—a view long-familar to fans of EA's Madden and NCAA Football franchises. Suspending a camera on guy wires doesn't sound particularly difficult, but it's hard enough to require specialized winches, gimbals, software—and Linux?
Cablecam is one of the best-known of these suspended camera systems, and the company has provided equipment for both CBS and Fox broadcasts. The system they offer for sports events is a 100-pound assembly with an HD camera, a gyroscopic assembly to keep the camera level, and a fiber optic connection back to the control booth. Two wires, arranged to form an X, are strung the length of the field and then doubled back to their origin, where they are connected to winches. The camera is controlled by an operator who "flies" the camera around the field with a joystick while another person controls the pan, zoom, and tilt of the camera.
A recent TV Technology article identified the Super Bowl camera on the Cablecam as the Sony HDC-F950, a $115,000, 3-CCD monster used only by movie and TV pros (though a recent Panasonic statement announced that Cablecam had just purchased a new Panasonic AK-HC1500G for use with A-list sporting events).
Cablecam also announced a recent move to RTLinux from FSMLabs, an OS designed for real-time, mission-critical applications. "RTLinux was chosen for its reliability," said Cablecam head Jim Rudnusky. "It keeps personnel safe and ensures that the camera keeps flying when the game is on the air. The deterministic timing available from RTLinux is crucial to achieving smooth motor motion at high torque. The Cablecam application could not be achieved by anything less than a hard real-time OS."
Image courtesy of FSMLabs
The camera's position is updated 200 times each second by the Overdrive motion control software, which runs on RTLinux, and control information is fed to a set of winches outside the stadium. The winches are driven by 20hp motors that can spin up to 3,000rpm and can position the camera anywhere in the field of play by reeling in cable and playing it out. The system is now sophisticated enough that an operator can fly the camera behind the ball carrier on a kickoff and follow his return up the field, all the way to endzone if necessary.
In 2007, CBS went all-out with its Super Bowl coverage; 500 techs setup and ran the network's gear and 50-odd high definition cameras will capture the spectacle. In 2008, FOX will have 30+ HD cameras on hand and will use some 80 microphones throughout the stadium.
It's a great way to capture the action, but it's not so hot for slow-motion replays, which jerk along one frame at a time during controversial plays. To smooth out slo-mo, broadcasters turn to special slow-motion replay technology. CBS called theirs "SuperVision."
To make it work, CBS used special cameras from Vision Research and NAC Image Technology. Vision's Phantom V10, the camera that will be used in the big game, shoots at 2400x1800 at up to a staggering 480 frames per second (at lower resolutions, the camera can shoot much faster). While CBS won't crank the camera quite this high, they'll still shoot fast enough to make even a center's gut jiggle a thing of slo-mo beauty.
Phantom has released a tweaked version of the camera for use in the playoffs and the Super Bowl that should better handle the (relatively) dim Dolphin Stadium lighting—cameras that operate this fast need a lot of light. The new V10 is also supposed to better match colors with the main broadcast cameras, which will reduce the feeling that you are watching video from a separate event when the slow-motion replays begin.
The camera can shoot in 1080p at 60fps, though it can drop as low as 720p at 24 fps if needed. 1.5GB of flash memory comes standard, but the camera can handle anything up to 24GB—only enough for a few seconds of storage at maximum speed and resolution.
And this is only for SuperVision shots; for normal, slow-motion replays, CBS used a totally different set of traditional Sony slo-mo cameras. In 2008, FOX will have their own setup, but according to Broadcasting and Cable, they won't be doing anything out of the ordinary.
Are broadcast engineers and network executives immune from geek lust? If the CBS-developed EyeVision replay system is any indication, the answer is resounding "no." There's no functional reason for deploying 33 cameras around the top of a stadium at the cost of $400,000 just to show replays that look they came out of the Matrix—but it sure looks cool!
This was the apparent rationale behind EyeVision, a system that used a hardware and software package to capture video of the game from multiple angles and then synchronized the video streams and interpolated between them. The result was replays that could pause the action, rotate 180 degrees around it, and resume viewing from the other side.
The system was developed in collaboration with Carnegie Mellon professor Takeo Kanade, who had already been hard at work on something that he called "Virtualized Reality." Kanade's goal was to use many cameras to create three-dimensional models of real events that could be then be viewed even from angles that were not originally recorded.
This approach requires cameras—lots of them. Even the 33 CBS settled on generated images that were more "Keystone Kops" than The Matrix, though the effect was intriguing. To make it work, one camera was designated as the "master" and contained special pan, zoom, and tilt sensors. A computer then used this information to calculate the angles and zoom levels that the remaining 32 cameras (each spaced exactly six degrees apart) would need in order to focus on the same part of the field. All 33 streams of video passed through a Sierra Video Yosemite 64x64 digital video routing switcher that funneled the streams to individual video servers, which stored the data for replays.
The program cost CBS more than $2.5 million to develop and a few hundred thousand more to implement each time the system (and there was only one) was rolled out. Crews could take more than a week to fully install it at a new stadium, and it only shot in standard definition. After using it in a pair of Super Bowls, CBS decided not to revive EyeVision for 2007, in large part over cost concerns with the move to HD cameras.
EyeVision, you were gimmicky, but we missed you. For 2008, FOX has nothing similar planned, either.
All the HD cameras in the world won't make a football broadcast look complete without the addition of a broadcast graphics system to display the score, pop up stats and Aflac trivia questions, and produce Fox's ridiculous "stomping football robot" (if you've seen it, you'll know).
For Super Bowl XLI, CBS stuck with Vizrt, a Norwegian firm that has become one of the world's leaders in broadcast graphics. The company produces a suite of programs, all built around the core Viz|Engine renderer, and all of them run on off-the-shelf PC hardware.
The complete application suite includes 3D modeling software and an interface called Viz|Trio that CBS uses to the control the complicated array of graphics its artists have prepped for the big game. Viz|Trio features a non-linear editing (NLE) plugin for Avid and Pinnacle editing systems that allows those editors to use content directly from the Vizrt software, making it faster to deploy time-sensitive sequences like halftime highlights.
CBS and the NFL Network both migrated to Vizrt in August 2006, in a deal that cost $750,000.
Most of the production work actually takes place outside the stadium in gigantic tractor-trailers operated by production companies like New Century Productions, who will be providing some of the trucks for this year's Super Bowl.
These trucks are complete mobile production vehicles that house audio mixing rooms, production areas, and editing suites. Specs vary by truck, but a representative vehicle from NCP is stuffed with a 72-input Yamaha audio mixer with programmable faders, CD recorders, compressors and limiters. The video production part of the truck houses a Grass Valley 64-input video switcher, Digi-Beta VTRs, and graphics production units. The truck also features more monitors than Elvis could shoot out with an entire box of shotgun shells.
Image courtesy of NCP
Posher trucks have ditched CRT displays for LCDs and used the weight savings to install even more gadgetry. The biggest trucks also allow their sides to pop out for expanded interior space, making some of these vehicles nearly as large as a mobile home.
Events of this scale require multiple trucks from multiple production companies, making the entire event a logistical nightmare that always turns out to have fewer glitches than its complexity would suggest. When you're putting on an event for 100 million viewers, though, things have to go right the first time, and crews will spend as much time prepping for the game and rehearsing their roles as the players do (though the tech crew will suffer fewer dislocations and internal bruising).
As if the CBS production effort wasn't lavish enough, NFL Films will be on hand with its own crew, as it is for every game of the season. During regular season games, the league sends out at least two camera operators; if a coach or player is wearing a microphone, another cameraperson films them for the entire game.
NFL Films shoots, as its name suggests, on film. They value the look of 16mm film and shoot more than 25,000 ft of it, making them Kodak's number one 16mm film stock customer.
They are no small outfit; their production offices and studios are housed in a 200,000 sq. ft. facility. They employ more than 275 people and have won over 80 Emmys in the last 25 years. At last year's Super Bowl, NFL Films deployed 22 film and audio crews to cover the game, and all of this was separate from network coverage of the event.
The footage is used to produce specials that end up on daytime ESPN or the new NFL Network channel, for which NFL Films produces hundreds of hours of new content each year.
And that's not all...
We've only scratched the glossy surface of the tech that goes into a Super Bowl production—HD transmission facilities, SD mixdown units, and surround sound processing (with stereo mixdown for SD broadcast) all have their own racks of gear, their own support crews, and their own expenses.