Legends Of The Wall, Part 3: Projection Is Served

For Roger Waters' The Wall tour, an Apple Xserve server with a genlocked AJA Video Systems Kona LHi HD-SDI I/O card and three-way Raid 0 per HD output running Virtual VTR (VVTR) software runs and locks each screens’ content to the incoming show timecode—five for the front projection and one for the circle screen.

“All content was rendered in the final 8,560x1,620 high output resolution as TIFF stacks, a discreet image file per frame,” says Richard Turner, screens technical director for the tour. “All content has been created to cover the whole canvas to allow for live masking to match both the arena bleacher profile and the wall build, and the expected mask state during each song has been used to composite the important elements within the safe zone. The TIFF stacks are then conformed in After Effects in preparation for splitting out into the required six HD channels as Apple ProRes HQ movies, mastered by Andy Jennison to keep his offline HD letterbox in Avid matched to the output projects.”

Each output Mac then runs its own screen’s Apple Final Cut Pro project, Turner says, “where we can institute pretty much instant changes, output as a reference movie which takes seconds, open in VVTR, and it’s there. It means a bit of Final Cut Pro plate spinning, but it’s all driven by the timecode numbers. Pretty much on every show so far, we’ve been doing tweaks based on Roger’s notes. He’s very involved, reviewing a DVD of a wide lock off shot every night.”

The front-projection projector footprint is kept within typical arena ice hockey dasher boards to facilitate custom three-way projector cradles made by SGPS, so the outer projector stacks point outward to the edges of the wall, according to Turner, “way more than the optimum.” This necessitates a final keystone correction to the outer screens to distort the image enough to get within the gamut of the FLM HD20s. “Quite a bit of AutoCAD 3D planning helped find the least bad projector positioning,” adds Turner.

For each of the five front-projection channels, the Barco Encore processor, also genlocked, keys the mask signal generated by an SAMSC Design Catalyst media server to black to avoid projecting on voids in the wall before it’s built, as well as to key another HD-SDI source to white for the puppet lighting. The Encore also acts as the seamless switcher between the main five Xserves and backup five Xserves. “The projection truss had to be as high as possible to clear as many sightlines as possible but also cater to the two cradles that have to hang 10' lower to get under the PA speaker clusters,” says Turner. “The four or five projectors, depending on venue specifics, rear-projecting the circular screen are fed directly from a VVTR channel.”

All this is tied into Medialon Show Control software, while a Barco High End Systems Full Boar console controls the Catalyst system as well as custom projector shutters built by Tait Towers that help create seamless projections. “They introduce a serrated blade to the edge of the projector beams,” says Turner. “A top and bottom DMX-controlled linear actuator per blade means we can alter the angle and incidence of the blade to match that day’s positions. It’s really the only way of achieving a good merge in the blacks where you have six projectors shining on the overlap areas.” Phil Haynes is the Full Boar/Catalyst board op.

While playback is locked in, a manual cue stack on the Full Boar provides live cues for masking out bleacher seating around the wall in each venue, as well as for specials, including a hotel room set that opens out of the wall and hangs from it. A television in the hotel room runs in sync with the source clip from the movie The Battle Of Britain, also used on the wall projections. The show’s timecode drives an Apple Mac Mini to achieve this special.