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Ready for Prime Time? - Mixonline

Ready for Prime Time?

Surround sound may seem relatively fresh and exotic in the world of music recording (unless you're old enough to remember mid-'70s efforts to launch quadraphonic),
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Surround sound may seem relatively fresh and exotic in the world of music recording (unless you're old enough to remember mid-'70s efforts to launch quadraphonic), but there's nothing new about the concept of surround in sound-for-picture applications. Multichannel playback in movie theaters has been with us off and on since the debut of Fantasia in 1941, and it became widespread with the introduction of 4-channel Dolby Stereo (left, center, right and "surround") in 1976. By 1982, Dolby Surround decoding (left, right, surround) was available to viewers of home video formats such as VHS and laserdisc, followed by full 4-channel Dolby

Surround Pro Logic in 1986.More recently, surround has gone digital, and the channel count has been upped to 5.1 with stereo rears (left and right surrounds) and a "Low Frequency Effects" (LFE) channel for subwoofers. 5.1-channel digital surround formats such as Dolby Digital and DTS are popular not only in theaters but also in homes for bringing the theater experience via DVD.

However, though surround formats are common in sound-for- picture, the most widespread moving-picture medium of all-television-remains largely unaffected. Broadcast TV didn't even go stereo until 1986, a quarter-century after stereo came to LPs (1958) and FM radio (1961). And despite the popularity of home theater systems, Dolby Surround broadcast on TV remains the exception rather than the rule. But, though surround is a relative rarity in TV's present, surround capabilities (if not actual usage) are certain to be part of the medium's future. That's because Dolby Digital is the mandated audio format for the ATSC system adopted by the FCC for digital television broadcasting.

With DTV being phased in during the first half of this decade, audio professionals who work in television will soon have a delivery platform supporting 5.1-channel mixes. But at this early stage of the game, a host of technical, aesthetic and practical issues remain unresolved. Do all types of shows lend themselves to surround mixes, or just a few? What's the best monitoring setup when mixing television for surround? What does 5.1-channel Dolby Digital offer that 4-channel Pro Logic does not? And how will 5.1-channel mixes get to viewers through a distribution system that currently supports only 2-channel delivery?

DOLBY OR DOLBY?The word "surround" is a useful general term for sound delivery settings in which at least one channel comes from behind the listener. But surround comes in many flavors, and the similarity of the names in common use make it easy for confusion to creep into the discussion. For television, the two relevant flavors are Dolby Surround Pro Logic and Dolby Digital.

Pro Logic decoders take a 2-channel analog signal and derive from it a 4-channel output. If the signal originated as a 4-channel signal and was "matrix encoded" into Left total/Right total (Lt/Rt) channels, a Pro Logic decoder will restore the original 4-channel mix. If no decoder is present, the mix will play back in stereo. Perhaps the biggest advantage of Lt/Rt is that surround may be delivered over storage and transmission media that support just two discrete audio channels.

Dolby Digital, meanwhile, is a digital codec (encode/decode) delivering 5.1 discrete channels (the ".1" is the limited- bandwidth LFE channel) with a combined bit rate as low as 384 kilobits per second. Dolby Digital playback requires a decoder that may be a stand-alone unit, or part of a receiver or video playback machine. To make matters a bit confusing, analog Lt/Rt mixes are often encoded into a 2-channel Dolby Digital signal (192 kbps) on DVD-Video; at playback, the Dolby Digital signal is decoded back to analog Lt/Rt, which may then be decoded by Pro Logic to 4-channel surround.

Dolby Digital is already established in the home, because support for the format is mandated on all DVD-Video players. But with DTV still in its infancy- fewer than 100 stations have begun simulcasting since the rollout began late in 1998-there is little demand so far for television programming with Dolby Digital soundtracks.

"There aren't a lot of people doing television shows in 5.1 right now," says Ken Hahn, co-owner (with Bill Marino) of Sync Sound and Digital Cinema in New York City. Hahn's facility handles sound editing; Foley; ADR; sound design; and mixing for television, film and home video formats, with an emphasis on television. "We've been working with surround for many years," he says. "But most of it is Lt/Rt right now."

The same holds true at San Francisco's Green Street (a division of Music Annex), where senior mixers Patrick Fitzgerald and Jon Grier handle sound for television and film. "We specialize in mixing commercials," Fitzgerald says, "but we also do a lot of long-form mixing, including documentaries, network work and lots of independent films. Lt/Rt is the most prominent form of surround. Even those stations broadcasting in HDTV are not broadcasting much in 5.1, just a few experimental broadcasts."

At Crawford Audio Services, an Atlanta company that provides audio, video, film processing and transfer services to clients in television programming and advertising, sound designer Greg Crawford (no relation) sometimes sees both surround formats used side by side, but not for the same applications. "Most of our broadcast work is mixed in 5.1," he says, "but we generally use Lt/Rt for the on-air signal. The 5.1 is used for a DVD version or held for future delivery."

WHO, WHAT AND WHYBeyond the question of which type of surround to use is the larger issue of who is and is not using it-and why. "The thing that dictates the type of programs using surround is the viewers," says Hahn. "My guess is that the ones who have surround systems in their homes are young adults and baby boomers who used to have a pretty good stereo and now have a surround decoder and a big-screen TV. If you think about that audience, they are obviously interested in sports, concert performances and films, either made for TV or showing on TV. The movies made for TV get a fairly good sound budget, because the same people and the same mentality are involved in both dramatic television and dramatic film. Channels like HBO and Showtime want real high-quality production."

Green Street's Grier agrees that sports and music broadcasts are prime candidates for surround treatment. "Those kinds of shows can really be enhanced by surrounding the viewer in the environment," he says. "What we are getting at is creating a theatrical experience in the viewer's home-that feeling that you get in the theater of being enveloped by the sound." Grier estimates that 15% to 20% of the facility's projects are now mixed in surround.

"We currently average one surround project a month," Crawford says. "Sometimes it's two or three at once; other times it's none at all. For television, we mix in surround primarily for documentaries-documentarians tend to use surround as a way to evergreen their product-and for local PBS stations that are beginning to shoot and post in HD. Public broadcasting and universities have been driving surround use in our broadcast business. We also do a good amount of work in surround for trade shows like NAB, permanent exhibits and movie trailers."

Crawford says that projects involving outdoor environments are able to make particularly good use of surround. "You can put the audience in the scene by immersing them in the surround field," he says. "For example, you can really layer a thick swamp scene, and then you can pull the audience back out with a close-up of a hummingbird that relies only on the front speakers. And since documentaries rely a lot on narration and dialog, the ability to use the center channel for placement really opens up the mix and gives the narration more prominence."

Crawford says the use of channels in a surround mix varies from project to project, but that generally dialog and narration are assigned to the center, with primary music and effects going to the left and right. "The surrounds carry split-out musical content if any has been provided," he adds, "plus some reverbs and additional effects and backgrounds to fill scenes. The sub is used primarily for individual effects and some musical content when needed."

Hahn, meanwhile, finds his channel assignments fairly consistent from project to project. "We follow a film approach," he says, "and that means put the dialog down the center unless there is a very specific reason not to. Effects can be almost anywhere you want them to be. Music can be difficult because it doesn't always come from a scoring stage anymore, it often comes from someone's home studio, which may be barely set up for stereo. So we just have to work with what we get."

Hahn adds: "You have to know when you can and can't take risks with the surrounds, which gets back to knowing your audience. Are you doing an action adventure that takes place in outer space in the year 3000 or a dramatic comedy that takes place in a Manhattan apartment? The program content and the audience really dictate how far you're going to go. You don't want to make things too interesting in the surrounds unless it's really called for."

SURROUND CHALLENGESWhile film sound provides a good starting point for working with surround, television is a different context with its own set of challenges, starting with finding the right tools for the job. "As far as mixing consoles, there are a lot available," Hahn says. "We've had 5.1-capable consoles in our two main mixing rooms for five or six years now, because they were designed for mixing feature films. But when it comes to out-board gear, that's a real problem. There aren't a lot of 5-channel compressors or reverbs. There's a void there that needs to be filled."

More important, perhaps, to the overall sound is the question of creating a monitoring environment that translates across the vast range of systems on which a given mix might be heard, from a tiny mono TV speaker to a full-blown home theater. "The major concern is 'what's it going to sound like at home?' " Hahn says. "Unfortunately, in television we don't have the luxury of doing several passes for different mixes. We need to make one mix and get it right, and it better sound good on everything. That makes it crucial to have good monitoring and metering. In every room you should be able to just hit a button to hear what your surround mix will sound like in stereo."

Beyond easy monitor switching in its mix rooms, Sync Sound is also borrowing the "mastering room" idea from the world of records. "We are setting up a room right now," Hahn says, "as a pre-mastering room for all the different sound-for-picture formats. It will have a theatrical surround system, a full-frequency 5.1 system, bookshelf speakers and a mono TV speaker. You'll also be able to switch the bass management in and out. So you'll be able to listen to a mix in any speaker configuration to tell what it will sound like. And if you give us a discrete mix or even the stems of a mix, we'll be able to rebalance or suggest what needs to be rebalanced to make everything matrix, decode and downmix properly."

Whether for "premastering" or mixing, good monitoring in sound-for-picture settings generally means starting with a room alignment based on ITU recommendations. "We set up in the standard film style for mixing," Crawford says. "And we assume the listener's system will use bass management. We also assume that if people have a sub, they will crank it up. So we go a bit lighter on adding the low-frequency content. These mixes hold up well in many environments."

As far as maintaining compatibility for mono or stereo playback, Crawford says, "the main technique is to try not to overdo the surrounds and sub. Clients initially want things flying all over the place and the walls shaking the entire time. Generally that doesn't translate well. Checking between stereo and surround during the mix is important. I usually plan on a light remix from the stems to get a good stereo mix."

Grier agrees that it's important to remember that many viewers will hear the mix on a small mono set. "When mixing television," he says, "I try to keep the lowest common denominator in mind. That generally means taking a relatively conservative approach. My goal is to maintain as much clarity and dynamics as possible regardless of the playback system. In some ways, it often works better approaching the 2-channel mix as the primary mix and the surround mix as the secondary. The bottom line is that the stereo mix is the mix that most people will hear, so it is important to give it its due."

Crawford adds that creating sound tracks and mixing for surround is "a very satisfying experience, but the tough part is what happens next. The 5.1 mix-along with an Lt/Rt and, in many cases, a mono mix-has to be encoded to fit on a digital video tape. Instead of just 'play' and 'record,' we now have to figure out things like Dolby E, AC3 and metadata. Setting proper metadata, for instance, is a very important new step in post that requires a bit of education. And quite honestly, it's not like many of us can go home and flip on the TV and check out our mixes via broadcast TV."

Hahn illustrates the problem of 5.1 distribution by recalling his recent work on a six-hour PBS special called Abraham and Mary Lincoln, which is set to air in 2001. "We have the 5.1 mix sitting on DA-88," he says. "We decided not to do anything else with it right now, because we figure that by the time it's close to airing someone will have decided on the best way to deliver to the network. As of today, that specification hasn't been written yet." He adds, however, that if he had to deliver the mix right away he would use Dolby E (see Technology Spotlight on page SFP 44), because "that way the audio and video are on a single carrier."

THE 5.1 FUTUREBecause it requires just two storage/ transmission channels, Lt/Rt surround doesn't face the same obstacles in the television distribution system that come up for 5.1. It can be and is being used for a number of shows today, but it hasn't yet become the norm, and with DVD in the home and DTV on the horizon, 5.1 is the format widely seen as the future.

"I expect the transition to 5.1 to happen faster than the changeover from mono to stereo," Crawford says, "mostly because of the DVD market. Consumers seem to have embraced the idea of surround playback for the home. Lt/Rt will be the interim step because there are so many homes already set up for Dolby Surround. But with DVD, consumers are becoming aware of the vast improvement that 5.1 provides, and that will be what drives a fast changeover." Ramping up for the expected demand, Crawford Audio Services is in the process of building a brand-new ten-studio audio facility with five surround mix rooms, including three SSL Avant-based 5.1 mix rooms designed by Tom Hidley.

Green Street has responded to surround demand as well, Grier says. "We've converted existing 2-channel rooms to 5.1 and purpose-built a new 5.1 mix room." But the expectation at the facility is that television will experi- ence a fairly gradual move toward 5.1. "Lt/Rt will be around for a long time," Fitzgerald says, "as will stereo and mono. 5.1 will come along over time, but I don't see other formats going away." Grier adds that it will "take a few years before the dust settles on this ongoing change of formats. As more and more consumers upgrade to 5.1, the broadcasters will have to answer the demand for 5.1."

Hahn, meanwhile, suspects that the producers of television programming will have their hands full for a while trying to get up to speed with the implications of DTV for the visual side of production, and that they won't focus on audio unless prodded. "For a lot of people in the television industry," he says, "picture comes first. The hurdle they have to get over with DTV is how to shoot for high definition, and that is much more complicated-and much more of an issue to my television clients-than the sound."

Eventually, Hahn says, for the industry to take full advantage of DTV's 5.1-channel capabilities it may take one influential network to put its full weight behind it. "MTV really led the charge for stereo," he recalls, "even when everyone said that nobody would be able to listen in stereo in the home. So it's going to take somebody who is in a position to say, 'If you want to have your program on my network, it's got to be 5.1.'"

Ron Estes is chief engineer at KTLA Los Angeles, which was the first station to produce a simultaneous standard definition and HDTV signal from a single remote truck. He has now mixed two Tournament of Roses Parades and two Dodgers baseball games in true 5.1 High Def, from the oxford-equipped NMT HD-2 truck. He had these thoughts to share:

At this point most TV stations are dealing with 5.1 surround sound mixes as a "pass-thru" situation. It is both difficult and costly to provide a master control environment that can cope with 5.1 audio in a realistic nature-just dealing with the meta-data parameters that vary from program to commercial and back to program is overwhelming! KTLA, like most DTV stations, is up-converting most of its NTSC programs, including live news programs and Warner Brothers Network programs.

The four HDTV programs I have been associated with have been consistent in their channel assignments. Dialog only is assigned to the center. The baseball effects were panned so that the TV audience would feel like they were seated in the middle of the stadium. The Rose Parade had the stereo street mics assigned hard left and right. The crowd mics and reverb return from the street mics was panned to the left and right interior. The reverb returns were crossed so that the left mic send appeared as a right return, giving an extra ambience. In retrospect, I feel that it might have been better to assign some of the crowd to the center channel also to keep the dialog from feeling too "naked."

For our DTV broadcasts from HD-2, the "main" speakers for the 5.1 mix were calibrated with a meter to 85 dB SPL. The .1 speaker was given a cursory check to see if it was within specs. As very little audio information from a parade or baseball game was fed into the .1 mix, not too much attention was paid to this channel.

In an ideal world with unlimited time and money, the best mix would be a separate mix for each situation. So much for fantasy! The best way of ensuring compatibility of your mix is to set up your monitoring environment so that you switch between the various mixes. At this point in time the stereo surround mix (Lt-Rt) is probably your biggest concern as this is where most of your listeners (and money) are. Don't forget mono! Things that sound great in stereo can be totally lost in mono due to the sum/difference method of transmission. If you are fortunate enough to be able to record a 5.1- and 2-channel mix on a multitrack recorder such as a DA-88 or DA-98, do so.