Mar 1, 2008 12:00 PM, By Matt Hurwitz

ROCKING BAND TAKES CONCERT FOOTAGE TO NEW HEIGHTS

Complicating matters, says Modell, is that the band — Bono, guitarist The Edge, bassist Adam Clayton and drummer Larry Mullen Jr. — varied the phrasing in their performances from show to show, and that the 3-D film featured 10 to 20-second shots (as opposed to the customary quick cuts in concert films). “So you don't have a choice but to use the real audio from whatever picture you're seeing, because you'll run into lip-sync and instrument-sync issues that will be obvious to the audience,” Glanville explains.

The team then developed an “assembly line” of sorts at Effanel, with Adams constructing Pro Tools playlists of the recordings in one room and Glanville mixing in the other. It was decided to first assemble a playlist that matched the picture, shot for shot, of each song: a master wide shot, say, from Mexico City, with its associated audio recording, and then a close-up of The Edge playing a guitar riff from Buenos Aires with its recording, etc.

Adams' playlist contained the full group-ing of all tracks from each night's performance of each song, stacked one below the other on the list, allowing him to comp the track group of a night's show to match the image appearing onscreen.

“We just built an exact replica of what they had, and then started looking at what that meant to the performance, sonically,” Glanville explains. “Then, once we'd done that, we said, ‘Okay, now let's do another version of that edit, and pull out any unnecessary edits.’” Glanville found that, while it was literally accurate to switch to the recording from a different show, say, for a quick cut to a group of audience members singing along, doing so would unnecessarily interrupt a guitar or vocal performance.

“We spent a lot of time going through each song and removing those kinds of cuts,” says Adams. “For the most part, the main body of a song was from the single night's recording.” Sometimes, though, the picture might cut to, for example, The Edge playing his guitar lead or a drum bit from a different show. In many such cases, because the band was playing to a click track — providing a uniform rhythm for each song from show to show — Adams was able to simply reselect from within his comp the guitar track for the song appearing onscreen while bringing in the remainder of the backing track from the master performance.

Switching between performances wasn't always so simple, however, where ambience was concerned — particularly where Bono's lead vocals were involved. If a master shot of one night's performance, with its associated venue ambience, cut to a close-up of Bono singing a line taken from a different night's show, with its own associated ambience, Glanville was forced to use the recording from the close-up's shot during that close-up and then carefully switch back to the master when the close-up was over.

“What I ended up having to do was group his vocals, with all the audience mics, and then build a vocal performance, so that every time you saw him I could switch to a different playlist that included all of the audience mics. So when the vocal switches, his voice is always in the ambience,” Glanville says. He then staggered the edits of the ambient mics — anywhere from a millisecond to five seconds — to crossfade smoothly between the two takes, helping to mask any differences in echo/delays caused by differences in venues.

MIXING FOR 3-D

While mixing a concert film into 5.1 surround is not new, mixing one for 3-D is, requiring a different approach from that employed for a “flat” (2-D) film. “In 2-D,” explains Adams, “generally most of the action is happening in the middle of the screen. In 3-D, you've got so much detail: There's something happening in the top of that corner or that corner. If there's something happening in one corner, people will be looking there, so you put a little voice in. People watch it completely differently — it taps into their brains in a completely different way.” Adds Modell, “We had only one rule: What feels real?”

This is not to say that a 3-D 5.1 mix means things flying all about the auditorium. “It means if you cut to a close-up shot of The Edge, you pull the guitar forward slightly in the mix,” Modell notes. “Not in a gimmicky way. The idea is that both the visual part and the audio part should become transparent as media. If you're feeling a bunch of gimmicky stuff going on, it will pull you out of the experience.”

For Glanville, it was all a matter of finding the right moments, many of which were fairly organic. “When you see a presentation on a 50-foot-wide screen, and you suddenly hear Bono's voice come out of the left speaker, your eye is immediately drawn to the left side of the screen. You turn your head and out pops Bono from the edge of the screen, walking up the ramp, and then the audio tracks him to the middle of the stage. It's little moments like that that make it a very different experience from something that you would see in 2-D.”

Glanville also played with dynamics and ambience, and took advantage of the SM57 spot audience mics to create a different experience for the viewer. At the end of “Miss Sarajevo,” says Glanville, “Robbie had the idea of pulling out all the ambience, where you see Bono slowly walking up the ramp.” Adams adds, “He's just sung his heart out, and as he walks back, he just strikes a lonely figure. There's all these people scream-ing out his name and he can't even hear them. It just lets you get inside his head for that moment.”

Indeed, the audience mics played a crucial part in the 3-D experience, particularly with this band's following. “There's so much happening with a U2 crowd during the body of the song that as soon as you strip that out, the soul just disappears out of the whole performance,” says Glanville. “There's too much interaction between the two to just let it go. If there was a night where a crowd really sung their hearts out, we made sure to fish that out and use it, to really give you a sense of what it's like to be in that crowd.”

To counter the effects of unpredictable multiplex theater sound systems, the team spread bass material throughout the mix. “We were worried about relying too much on the subwoofer channel to give us the bottom end of this picture,” explains Modell. “This is different from a normal picture, where it's 90 percent dialog with the odd crash or gunshot or boom. This is driving eighth notes the entire time and a constant kick drum with a lot of bottom and energy. If we relied on the subwoofer to give us a lot of that, we'd be hosed in a lot of theaters.”

The case was different from IMAX 6 masters, where theaters have a bass-management system to take full advantage of low frequencies. “We actually brought a Pro Tools system into two IMAX theaters in Los Angeles and essentially remastered it for IMAX right in the theater,” Modell says.

In October, over a three-week period, the team reconvened at Warner Bros. Dub Stage 6 to do the film's re-recording. “Dub 6 has the largest ICON console in the world,” Modell says. “And having done all this work in New York on the ICON, it was great to just come and open stuff up and not have to wrestle with remapping anything.”

Glanville's stem layout comprised drums, bass, guitar, Bono guitar, Bono vocal, Edge vocal, keyboards, audience and supplemental audience. “Sometimes we'd split the audience across two sets of tracks, just to feather in some extra sounds to make transitions work between the songs,” he explains. Gaps between songs were also extended slightly. “It was felt that to have the songs just keep hitting you one after another like that in the movie theater could end up being a bit overwhelming. Adding an extra five seconds in between some of the songs gives you that little moment to come down from what you've just heard and then get ready for the next thing.”

There were actually two sets of stems — one dry and one containing the effects — allowing Glanville to rebalance at Warner Bros. as needed. “And that amounted to about 230-odd tracks of audio,” he adds.

U2 3D was a project of “firsts” on many fronts, Modell notes. “It's the first digitally captured 3-D live action film of its kind, the first time zoom lenses were ever used in 3-D, and it was Carl and Robbie's first re-record mix. And because it had never been done before, there were no rules to break. It was a wide-open canvas. And it was Carl and Robbie's creativity and meticulousness that made it happen.”