Surround Sound Past, Present, and Future

A history of multichannel audio from mag stripe to Dolby Digital Surround Sound Past, Present, and Future

ilm sound, television audio, reserved for the occasional dramatic and music playback formats effect—ethereal voices in religious used to be distinctly different epics, for example. Some formats F products of industries often switched this channel off by means workingF in isolation. In recent years, of trigger tones when it wasn’t however, this has changed. The needed because the track on the popularity of surround sound in the film was particularly narrow, and thus home has brought these industries very hissy. A history of and their sound formats closer Although film stereo lost favor in together. And now digital multichan- the 1960s and early 1970s due to high multichannel audio nel technology is fostering an even costs of the magnetic formats and a from mag stripe more consistent approach to sound slump in the film business, sound reproduction, easing the burden on mixers continued to experiment with to Dolby Digital both consumer and producer while the effects channel. Formats such as providing unparalleled fidelity not just six-track 70 mm magnetic (see to the tonality of live sound, but also sidebar) provided consistent signal-to- to its spatiality. noise ratios on all channels, so mixers could use the effects channel to Origins of surround sound envelop the audience in continuous low-level ambient sounds. The effects The first commercially successful channel came to convey greater sonic multichannel sound formats were realism overall, not just the occasional developed in the early 1950s for the dramatic effect. cinema. At the time, stereophonic This expanded, more naturalistic sound, a concept new to the public, application came to be known as was heavily promoted along with new surround sound, and the effects wide-screen formats by a film industry channel as the surround channel. The feeling threatened by the rapid extra speakers at the rear—and now growth of television. Unlike the two- along the sides of the cinema as well channel format later adopted for to create a more diffuse soundfield— home stereo, film stereo sound started came to be known within the industry out with, and continues to use, a as “the surrounds.” minimum of four channels. With such film formats as four- Home stereo and track CinemaScope (35 mm) and quadraphonic sound six-track Todd-AO (70 mm), multi- ple sound channels were recorded Bell Laboratories’ famous experi- on stripes of magnetic material ments with stereo sound in the 1930s applied to each release print. To play used three channels. Cinema stereo in these prints, projectors were fitted the 1950s was using no less than four with playback heads like those on a channels, and as many as seven. Yet tape recorder, and cinemas were when stereo finally made it into the equipped with additional amplifiers home in 1958, only two channels were and speaker systems. used. This was not because of listener From the outset, film stereo preference, or some predisposition on featured several channels across the part of audio professionals. Rather, the front, plus at least one channel two channels (left and right) were all played over speakers towards the rear that the then-prevalent LP phono- of the cinema. At first the latter was graph record could accommodate. known as the effects channel, and was

1 By Joseph Hull Marketing Communications Manager Dolby Laboratories Inc.

Two-channel stereo music in cinemas, and the term “surround 1,2 3 4 5,6 reproduction was a dramatic advance sound” still wasn’t heard outside over mono and comparatively easy to the film industry. After all, the only implement, so it soon became the popular home visual medium at norm, even as filmmakers continued the time was broadcast TV, which to regard four channels as the mini- provided distinctly low-quality A mum necessary to create a lifelike mono sound. For the next decade soundfield. A few years later two- home stereo, cinema stereo, and channel stereo FM broadcasting was TV sound would remain separate introduced, further entrenching two- entities supported by essentially channel sound in the consumer’s isolated industries. mind as “stereo.” Indeed, as time 1 2 3 4 5 went on, only dedicated film buffs Dolby and film sound B were aware that film stereo, rare as it had become, continued to use more In the mid-1970s, Dolby Labora- than two channels. tories introduced a new sound As home stereo grew in popular- technology for 35 mm prints origi- Optional stereo surround ity, equipment manufacturers began nally called Dolby Stereo. Instead of to look for ways to expand their being based on magnetic striping, it 6 market. This was one motivation used the photographic, or optical, behind the ill-fated four-channel, or soundtrack technology used to put 70 mm magnetic: quadraphonic (“quad”), home stereo mono sound on film since the 1930s. format promoted in the early 1970s. To enable compatible playback in forerunner of today’s It required two additional speakers in mono cinemas, it was necessary to fit digital sound the rear corners of the listening room, the new stereo soundtrack into the to reproduce two extra channels from same space on the print occupied by n the 1950s, movie prints with specially encoded program sources. the traditional mono track. Experi- magnetic stripe soundtracks pro- Ivided the first multichannel sound Because the existing home stereo ments showed that two tracks, treated ever heard by the public. 70 mm prints media had only two channels and with Dolby A-type noise reduction, (A), for example, featured six tracks, could not easily accommodate more, could give excellent fidelity. But originally configured as five identical several schemes were developed to trying to squeeze in more than two channels across the front plus a sur- encode the basic two channels with tracks raised noise to an unacceptable round channel to the sides and rear of additional sound information. Most level, even with noise reduction. the auditorium (B). As screens became smaller, reduc- were based on matrixing techniques Two channels, however, were not ing the need for five screen channels to that enabled folding extra channels enough for movie stereo. Movie carry dialogue, Dolby Laboratories into the two regular channels by screens are so wide that as well as proposed the configuration shown recording them with different the usual left and right channels, above, which has been standard since relative phase. a separate center channel and speaker the late 1970s: left, center, and right main screen channels (1,3,5), one Quad failed to capture much of a are required to localize dialogue for surround channel (6), and two low- market. For one thing, there were viewers seated off-center. In addition, frequency-only “bass extension” chan- several incompatible encoding/ “stereo” and “surround” had become nels (2,4). decoding systems, which created synonymous to most of the film Dolby also developed a technique consumer confusion. For another, industry, so a surround channel was enabling 70 mm prints to carry two surround channels, instead of the usual producers and recording engineers also a must. Thus a way had to be one, at the option of a film’s producers. couldn’t agree on how to best use the found to encode just two physical This “stereo surround” 70 mm format extra channels. And most significant tracks on movie prints with four thus became the forerunner of today’s of all, few consumers perceived any channels of information: left, center, “5.1”-channel Dolby Digital surround real advantage from the format. right, and surround. format with its three front channels, two surround channels, and low-frequency Quad was never associated with The solution was found in the effects channel (see page 5). the multichannel stereo formats used matrixing techniques first tried for

2 Left Subwoofer Center Right

(Subwoofer optional)

Power amplifiers 35 mm stereo optical print Dolby cinema processor

Dolby stereo optical playback in the cinema.

Surround quad home stereo, but with the did quite the opposite. Movie atten- Stereo comes to video playback channels configured in the dance actually increased with the cinema stereo norm—left, center, growth of the prerecorded video As the video revolution got right, and surround—and with the cassette. Films that proved popular in underway, consumers were not only addition of sophisticated new elec- theatrical exhibition proved just as accustomed to high-quality stereo tronic steering techniques. popular for home viewing, and in sound from their music systems at The Dolby stereo optical format some instances, films that did not do home, but were also becoming used proved so practical that today there well at the box-office fared better in to high-quality stereo sound in the are tens of thousands of cinemas video release. cinema as the Dolby multichannel worldwide equipped with Dolby The video cassette was not optical soundtrack format spread processors, and for many years the only element of the video revolu- throughout the film industry. virtually every major title has been tion. More homes than ever were While at first the video cassette released in the format (even today, connected to cable systems, providing offered only relatively low-fidelity movie prints with digital soundtracks viewers with still more program mono sound, machines and prere- have Dolby analog soundtracks as sources (and the film industry with corded tapes with stereo sound were well, to ensure compatible playback still more program producing oppor- soon offered, first by means of linear in all cinemas). What’s more, the film tunities). The laser disc, the highest- soundtracks and then by the “HiFi” industry experienced a kind of quality home video program source technology. The laser disc was renaissance in the 1980s, helped by ever, was introduced. Television set conceived from the outset to provide a new commitment to high-quality manufacturers began to offer high-quality stereo sound. presentations exemplified by the products with what might be called In addition, a stereo TV broad- adoption of Dolby Stereo. That high-fidelity picture quality, and casting system was soon adopted for rebirth was also assisted by the consumers bought them. Thus over-the-air and cable use. Thus the “video revolution.” “television” became “video,” and familiar two-channel stereo format the home TV set became a “video long established for home music The video revolution monitor” to display a wide variety of reproduction was adopted for all visual program sources, much as video media. The first video cassette recorders stereo systems play music from a were introduced in the early 1970s. variety of sources. They were promoted initially as time shifting devices to record TV broadcasts for viewing at more convenient times. A Surround Before long, the video cassette og took on another, hugely popular Sound function: the playback at home of Timeline theatrical films. This created a D ol voracious appetite for program Compact Disc (2-ch.) A Consumer formats 1958 stereo1961 LP (2-ch.) stereo1970 FM Dolby (2-ch.)1972 B cassette video cassette (2-ch.)1978 stereo(mono)1980 video laser cassette1982 disc Dolby (2-ch.) (2-ch.) Surround1986 stereo (3-ch.—1987 TV L, (2-ch.) DolbyR,S); Surround1993 Pro first L material, which the film industry was (4-ch.—L, C, R, S) D Cinema sound more than happy to satisfy. A whole 1941 new business grew up around the

production, sales, and rental of Fantasia* Sur Mag. stripe 1950s chann 35/70 mm 4/6-ch. prerecorded video cassettes. Stereo surround 1978 (on 70 mm magnetic) L: Left (all surro While the increased penetration Dolby Digital opticalC: Center 1992 (all) Dolby SR optical (4-ch.) 1987 R: Right (all) of broadcast television had contrib- Dolby stereo optical 4-ch. 1976 5.1-ch.—L, C, R,S :LS, Surround RS, LFE (4- (wider dynamic/frequency range) LS: Left Surrou uted to the film industry’s woes in the *Walt Disney’s animated feature Fantasia was the first film shown publicly with multichannel BS: Back Surro 1950s and 1960s, the video cassette sound, using three optical tracks on separate 35 mm film played in sync with the picture. RS: Right Surro LFE: Low-Freq

3 Dolby Surround encoded Broadcast radio stereo program sources Left Center Right

Broadcast TV (Subwoofer optional)

Satellite CD, DVD TV

LD Multichannel audio electronics with Dolby Pro Logic decoding Surround Surround

Cable Video cassette Audio cassette Dolby Surround playback in the home.

Surround sound comes home surround channel at home. Soon film, prerecorded software, consumer more sophisticated Dolby Surround electronics, and PC industries. By the early 1980s, high- Pro Logic decoders made it possible performance stereo music systems to decode the center channel as well, Dolby Digital– were the norm. Audio as well as video and utilize the advanced steering the next generation had expanded to include new program circuitry developed originally for sources (audio cassettes, CDs). Car theatrical playback. In the late 1980s, Dolby Labora- stereo was coming of age, and Unlike quad, Dolby Surround tories undertook the application of personal headphone portables were gained, and continues to gain, digital audio technology to 35 mm providing a new way to listen to considerable marketplace acceptance. film sound in response to growing music. A generation had grown up For one thing, the channel configura- interest from the film industry. In listening to rock music that was as tion and best use of it were firmly order to retain an analog track so that dependent upon audio technology as established within one industry release prints could continue to play musicianship—the same generation (cinema) in advance of its introduc- in any cinema, it was decided that a that was now being regularly exposed tion to another (consumer electron- separate new Dolby Digital optical to multichannel surround sound in ics). For another, it was developed track be placed between the sprocket the cinema. Against this background, with a specific objective: to enhance holes. It was also decided that six Dolby Surround was introduced late the viewing experience. And third, discrete sound channels be provided in 1982 for playing videos of theatri- software and hardware standards for in the “5.1” configuration that by cal films originally produced with both the film and consumer electron- now had been documented by various Dolby encoded soundtracks. ics industries are defined by one film industry groups as best satisfying The original four-channel Dolby organization—Dolby Laboratories— the requirements for theatrical film encoding of their soundtracks remains which is independent of, and has presentation. intact when such films are transferred credibility with, both. As a result, The 5.1 configuration features to stereo video cassettes and laser millions of consumers have perceived five discrete full-range channels—left, discs, or broadcast on stereo TV. At Dolby Surround sound as well worth center, right, left surround, and right first, simple Dolby Surround decoders the investment. surround—plus a sixth channel for made it possible to decode the Today Dolby Surround has gone those powerful low-frequency effects on to include TV broadcasting—not (LFE) that are felt more than heard in only films with Dolby encoded cinemas. As it needs only about one- soundtracks, but also regular series, tenth the bandwidth of the others, specials and sports events. And the LFE channel is referred to as a although Dolby Surround was “.1” channel. Dolby Digital debuted ic og developed as a sound-with-picture in cinemas in 1992, and today is the format, record companies such as leading digital film sound format in Delos, RCA Victor/ BMG Classics both releases and cinemas equipped olby Digital IC (Zoran); D by Digital chosen for and Concord Jazz release music-only to play them. ol TSC digital TV (5.1-ch.) A CDs and audio cassettes encoded with 1995 Dolby Digital1996 FCCon laser (U.S.) disc adopts (5.1 ch.); ATSC DTV Dolby Digital chosen1997 for DVD DVD-Video, (5.1 ch.)1998 DVD-ROM DTV broadcasting with Dolby begins in U.S. with Dolby Digital Digital (5.1-ch.) reaches market with Dolby (5.1-ch.) Digital audio (5.1-ch.) Dolby Surround. It is also providing Picture more excitement and viewer area involvement for an increasing rround sound number of video games and other Digital nel designations soundtrack data ound formats) multimedia applications.

In other words, surround sound Analog track -ch. formats) has crossed the traditional format und (5.1/6.1 formats) (6.1-ch.—L, C, R, LS, BS, RS, LFE) ound (6.1) Dolby Digital Surround EX optical 1999 boundaries, to the advantage of not ound (5.1/6.1) only the consumer, but also of the Dolby Digital prints feature both quency Effects (5.1/6.1) digital and analog soundtracks. 4 Low-frequency Left effects Center Right

Power 35 mm Dolby amplifiers Digital print Dolby Digital cinema processor

7.0

Dolby Digital AC-3 bitstream

Left Right Surround Surround Dolby Digital playback in the cinema.

Much like Dolby’s analog film effects can be achieved for an ex- passages from getting too loud or sound formats, Dolby Digital in the panded sense of depth, localization, when it’s necessary to keep the overall cinema has provided a springboard for and overall realism. playback volume low. What’s more, consumer formats with Dolby Digital Dolby Digital incorporates special the listener can program the Dolby audio, beginning with laser discs in features to satisfy listeners using Digital decoder to route non-direc- 1995, and soon followed by DVD, anything from small, monophonic tional low bass only to those channels

cable TV and DBS systems, digital TV L in the system that have wide-range Decoder C 5- or 5.1-channel R Dolby Digital broadcasting, and a variety of multi- “A” LS speakers or subwoofers. RS (subwoofer optional) media applications. That film sound Sub

L T has been the starting point for Dolby Decoder Pro Logic L Matrixed A bright future for Surround C 4-channel “B” decoder R R S Dolby Digital has enabled the accumulation T 5.1-channel Surround multichannel audio music of invaluable experience in mixing, Dolby Digital AC-3 data Decoder L recording, and distributing multichan- stream 2-channel So far, digital technology’s most “C” R stereo nel digital audio, and has fostered a direct benefit for the home listener

library of program material immedi- Decoder has been the compact disc. Yet for all Mono ately available for consumer release. “D” its ergonomic virtues and resistance to Dolby Digital’s downmixing feature wear the improvement afforded by the Dolby Digital in the home ensures li steni ng sati sfacti on for all. CD over the best analog formats is incremental. This will all change with The consumer equivalent of products through full home theaters. the arrival of the DVD-Audio disc. Dolby Digital film sound forms the While the same unrestricted multi- This new disc provides all the size, final link from multichannel program channel audio content is delivered to convenience, and longevity of the CD producer to home listener. Like the every system, the decoder can opti- plus multichannel surround sound film format, it provides left, right, mize the sound for the particular and improved sound quality. The center, left surround, right surround, listener. For example, decoders can inclusion of a Dolby Digital encoded and low-frequency effects channels. provide optimum downmixes from version of the mix will insure that Unlike analog Dolby Surround multichannel programming, such as a these discs can be played on all with its single band-limited surround matrix-encoded two-track mix for existing DVD-Video and DVD-ROM channel (usually played over two analog Dolby Surround decoding, a players. Glorious multichannel audio speakers), Dolby Digital features two conventional stereo mix, or even a via the DVD-Audio disc is well on its completely independent surround mono mix. way to bringing about a true revolu- channels, each offering the same In addition, the system can apply tion in the way music is quality as the three front channels. dynamic compression to preserve low- reproduced and enjoyed in As a result, true stereo surround level content and prevent dramatic the home.

Left Right

Multichannel audio Center electronics with DVD player, DTV tuner, Dolby Digital decoding satellite/cable box, etc. LFE (sub)

Left Right Surround Surround Dolby Digital playback in the home.

5 When is it surround sound?

Programming encoded for multi- channel D olby Pr o Logi c playback.

Home playback equipment equi pped wi th D olby Pro Logi c multichannel decoding.

Films and cinema presentations utilizing Dolby analog technologies.

Films, cinema presentations, consumer programming, and home playback equipment utilizing Dolby Digital technology.

6 Dolby Laboratories Inc. 100 Potrero Avenue • San Francisco, CA 94103 • Phone 415-558-0200 • Fax 415-863-1373 • e-mail: [email protected] Wootton Bassett, Wiltshire, SN4 8QJ, England • Phone (44) 1793-842100 • Fax (44) 1793-842101 • e-mail: [email protected] www.dolby.com “Dolby”, “Pro Logic”, and the double-D symbol are trademarks of Dolby Laboratories. ©1999 Dolby Laboratories Inc. S99/ 11496/ 12508