Panels at AES Show Have Decidedly Broadcast Bent
This year’s AES Show (Nov. 4-7, San Francisco) had a stronger than usual broadcast-audio component to its conference side, and it covered a lot of ground.
The session titled Broadcast Facility Design looked at, among other things, the new ESPN broadcast facility at the LA Live complex in downtown Los Angeles. After an opening by panel moderator and architect/acoustician John Storyk, ESPN Principal Engineer/VP of Technology Planning Jim Servies discussed the creation of the sports network’s facility to take some of the burden off of its Bristol, CT, headquarters and spread reporting capabilities across U.S. time zones.
The big hurdle, he pointed out, was noise management. “It’s part of the LA Live center, and there’s a lot of noise outside and inside,” he explained, noting that audio-operator stations had to placed just on the other side of a wall separating the broadcast-control rooms and an ESPN Zone recreation center in the same building. “You have people at workstations sitting 6 ft. away from someone bowling next door.”
The solution to interior noise lay in keeping HVAC-handling components, such as heat exchangers and air handlers, as far away from audio as possible. (It helped that this was a design/build project, allowing the ducting to be routed without being constrained by existing interior architecture.) Interior spaces have offset-stud walls to reduce noise transmission.
The biggest challenge, though, was the three massive 250-ton chillers on the roof, just above one of the facility’s studios. Servies said a considerable amount of padding and isolation was used to muffle and decouple the chillers with the roof, the configurations of which had to be carefully planned.
“You can’t correct that later” was Storyk’s understated summation.
During the Innovations in Digital TV panel, Linear Acoustic President Tim Carroll pointed out that sports and other broadcasts that typically use 5.1 surround sound are increasingly adding distribution and playback platforms, creating challenges for mixers, particularly in downmixing 5.1 to mobile devices that are at best capable only of stereo or mono.
“The downmix issue concerns preparing audio for Mobile DTV transmission,” Carroll explained. “Since [mobile-device streaming is] currently capable of only mono or stereo, any larger number of channels must be downmixed to fit. Traditional practice is to create a phase-encoded Lt-Rt signal so that any downstream legacy matrix decoders can produce a surround experience. However, for mobile DTV, Lt-Rt is not strictly mono-compatible and can sound really odd through earbuds. It can also sometimes affect dialogue intelligibility.
“So the option,” he continued, “is to do an Lo-Ro [left-only/right-only] downmix, which uses only simple level combining and no phase encoding, or a hybrid of the two methods, called Lo-Ro90, which adds only some of the phase encoding back without affecting mono or stereo compatibility. Our suggestion is to use one of these two methods, preferably the latter.”
Further information can be found on the Website of the Open Mobile Video Coalition.