Beginning in 2006, Turner Broadcasting System began using technology from Sigma Electronics to help deal with lip sync issues and has recently expanded its use to other networks under the TBS umbrella.
“We’ve got the devices to make corrections—we’ve always had them. They’re called delay lines,” said Ron Tarasoff, TBS vice president of Broadcast Technology and Engineering. “You can delay picture, you can delay sound—but how much do you delay them?”
(click thumbnail)TBS Senior Project Engineer Bob Peck works with the Arbalest unit.He said Arbalest gave TBS an opportunity to make accurate measurements to show how much the picture and the sound vary. It does this by comparing “snapshots” of the audio and video by Arbalest units at both ends of the transmission and computing a signature code to quantify how far apart the two snapshots are. This greatly facilitated correction.
Tarasoff said he first heard about Sigma’s technology at NAB2004, when the Turner delegation was actually looking for equipment that would better gauge lip sync. Calibration had gotten much more complicated since the advent of TNT in high definition in April 2004.
Dual carriage of multiple high-definition TV formats compound lip sync problems, said Tarasoff, noting that standard-definition video comes with stereo sound, while the HD signal comes with stereo and Dolby E surround sound. Thus, three different audio paths and two different video paths are transmitted.
“The standard-definition stereo signal arrives first—before the video,” said Tarasoff. “Dolby E sound arrives behind the picture.”
These discrepancies are multiplied by the fact that more and more feeds are coming back by fiber-optic cable, he said, noting that fiber optic isn’t just a straight line from the remote site to the TBS plant. It goes through switching systems that could end up routing the signal from Chicago down through Dallas before it comes to Atlanta.
As such, in the middle of a feed the path could switch and the timing between video and audio could change. And one wouldn’t necessarily notice that the lip sync wasn’t correct during coverage of a golf match, for example, because the announcers are off-camera for such long periods of time. Then, all of a sudden, the problem would be obvious.
SON OF OCTRASTREAM
Sigma Electronics President and CEO Bill Swilley said TBS had actually seen Arbalest’s predecessor at NAB2004. That device, “OctaStream” encompassed AES audio delay modules that plugged into a frame, providing for adjustable delay and mixing of AES audio.
“We re-engineered a totally different platform that’s software [versus hardware] based,” he said. “NAB2005 was the first time Arbalest became a product.”
Swilley noted that the historic arbalest was “a giant crossbow that launched missiles.” For him the image serves as an icon to “see how we could knock down walls.”
According to Swilley, Arbalest is an agonistic machine, easily exchanging roles as an encoding or decoding platform. And all Arbalests are alike.
“We go and upgrade every machine that we have out there so they’re the same platform—everybody’s got the same feature sets,” he said.
TBS bought eight units in 2006. Arbalest was first tested for standard-definition TV on Court TV after TBS expanded its ownership to 100 percent and became responsible for all distribution. It then moved on to monitor TNT in HD.
Two more units were subsequently added for the new control rooms that the company began building in April 2007 for TBS in HD and Cartoon Network in HD, which launched Sept. 1.
So far, the Arbalests in the TBS plant measure picture and sound synchronization as it comes down from a satellite, said Tarasoff, with the units comparing A/V snapshots from the satellite to A/V snapshots coming out of the master control switcher. That way, staff can make sure that the signal—which is in good synchronization coming out of the MC switcher—goes through the entire chain (including encoding and encryption) to cable headends, in synchronization.
Although the units enable automatic picture adjustment, Tarasoff said TBS has chosen to do the adjustment manually. And TBS runs a separate cable in-house from one Arbalest to another to accommodate the signature code rather than trusting its embedding in an audio channel.
TBS will also occasionally use it within the plant to check on sports feeds coming back from the field, said Tarasoff. Using it off-site is discouraged by the impetus to minimize the amount of gear transported and difficulty in transmitting the signal, he said.
Some have suggested that Sigma Electronics have its next-generation Arbalest embed its signature code in many parts of the signal (video, various audio paths) in the hopes that one of those will survive all the encryption and encoding that take place along the way.
Swilley noted that the product already embeds its signature code in both Dolby E and AC-3 streams. But, he said, the company is also looking at multiple paths for sending data back to the decoder.
“I’d hoped to have something along those lines by next year,” he said.