How Dolby Surround Works Essay, Research Paper

Where surround sound came from

Back in the early 1950s, the film industry introduced a technology so revolutionary and complex that it was to be nearly 30 years before it made it into the home. They called it stereophonic sound. Today we call it surround sound (or less poetically, multichannel audio) to distinguish it from conventional two-channel home stereo.

From its outset, movie stereo was multichannel, featuring at least three channels across the front of the auditorium, plus one or more surround channels towards the sides and rear. But the complicated and costly technology that made it possible multiple soundtracks recorded on narrow stripes of magnetic oxide applied to each movie print confined it exclusively to theaters.

It was not possible to fit multichannel audio onto a phonograph record, the dominant home music format of the day. Therefore, when stereo made its popular debut for the home in 1958, it was by means of the two-channel (left and right) stereo LP record. While two-channel stereo fell far short of movie theater multichannel stereo, it was so much better than mono that it soon became the norm for home music playback. The stereo record, of course, was followed by two-channel stereo FM, then by the two-channel audio cassette, and ultimately by two-channel video formats (cassettes, TV broadcasts, laser discs).

How surround sound came home

For years it seemed we were destined to enjoy true multichannel sound in the theater, and only two-channel sound at home. But then in the mid-1970s, Dolby Laboratories introduced a new way to bring multichannel sound into the movie theater. Based on the optical soundtrack technology that had put sound on film in the first place, the new Dolby format used just two tracks encoded with four channels of information (left, center, right, and surround). These four channels could then be reconstructed in the theater by means of special decoders.

This so-called 4:2:4 process, which is based on phase matrixing, enabled multichannel sound to reach many more film audiences than the older magnetic formats. Indeed, it soon became the norm for motion picture sound. And it proved to be the key, at long last, to multichannel surround sound for the home listener.

There were now dozens of feature films being released every year with stereo soundtracks encoded with four channels of information. What s more, these films were being released on two-track stereo video cassettes and laser discs, and being broadcast over stereo TV, with their original four-channel surround-sound encoding intact. So in 1982 Dolby Laboratories introduced an economical way to decode the four channels for listening in surround at home: Dolby Surround. On a living-room scale, Dolby Surround provides the same thrilling surround experience previously confined to the movie theater. It has been the driving force behind the most rapidly growing consumer electronics product category of the past five years, home theater.

The standard in surround sound

Today Dolby Surround is everywhere, with more than 38,000 movie theaters equipped with Dolby multichannel sound processors and more than 24 million Dolby Surround playback systems in consumers homes worldwide. Sales of Dolby Surround systems are growing rapidly, at a current rate of over 5 million units a year.

Owners of these systems have nearly 7,000 Dolby Surround programs to choose from on video tapes, laser discs, television, radio, compact discs, audio cassettes, video games and CD ROMs. This widespread use has established the system as the standard for high-quality surround audio. Clearly, consumers have discovered Dolby Surround, are buying it in record numbers, and are eager for more: more software, and more formats.

True surround sound, not just an effect

Dolby Surround is a true surround sound system, not just a playback effect. It involves encoding sounds during production to create a Dolby Surround soundtrack, and then decoding the soundtrack on playback using a Dolby Surround Pro Logic decoder. This means that producers can control the placement and movement of sounds in a way that creates a remarkably realistic experience, drawing the listener right into the action.

In addition, Dolby Surround soundtracks benefit those listeners who do not have Dolby Surround playback systems, because a Dolby Surround soundtrack creates a wider, more enveloping soundfield even when played in normal stereo. Using Dolby Surround, therefore, gives producers the best of both worlds: true surround sound for listeners with Dolby Surround playback, and improved stereo sound for listeners without Dolby Surround. This is clearly a win-win situation for producers and listeners alike.

Dolby Surround for multimedia

As Dolby Surround moves into the multimedia market, it is bringing the excitement and realism of true theater-like surround sound to computer and video game users. For interactive multimedia titles, Dolby Surround can reproduce multi-dimensional sound effects that actually move in real time to follow the action on the screen. Several companies are already producing CD ROMs and games in Dolby Surround, including Argonaut/Jaleco, Electronic Arts, Europress Software, Graphix Zone, Interplay Productions, Nova Logic, Ocean Software, Prolific Publishing, Sony Psygnosis, Takara and Voyager.

Dolby Surround Pro Logic playback systems specifically for computers have also been introduced by companies such as Altec Lansing, SSI, and m� Computer Products. Other companies in the computer industry have also expressed their support of Dolby Surround, including Microsoft and Intel, who see surround as the future of computer audio. This strong support will ensure the widespread use of Dolby Surround technology throughout the computer marketplace.

Multimedia doesn t require multiple speakers

A new Dolby Surround playback system called Virtual Dolby Surround has been developed especially for computer applications. Unlike home theater systems, which use separate surround speakers to reproduce the surround channel, Virtual Dolby Surround combines Dolby Pro Logic decoding with advanced 3D signal processing techniques to create a virtual surround sound field with just two speakers. Companies that have 3D audio processes suitable for Virtual Dolby Surround include JVC, Matsushita, Aureal, Harman, QSound, Spatializer, SRS, and EMI/CRL.

Producing in Dolby Surround

Producing Dolby Surround program material is surprisingly easy and economical. The soundtrack starts with a four-channel mix (left, center, right, surround), which is then mixed down to a Dolby Surround encoded stereo soundtrack using a Dolby Surround encoder. Dolby Surround encoding and monitoring can be accomplished either with hardware manufactured by Dolby Laboratories (SEU-4 encoder and SDU-4 decoder) or Dolby Surround encoder and decoder TDM Plug-Ins for Pro Tools workstations. Details and advice on equipping and aligning studios for surround mixing, as well as training in mixing techniques, are available at reasonable engineering rates from Dolby Laboratories offices worldwide.

A famous name in sound on your product

Once a Dolby Surround soundtrack has been mixed, producers can inform their audiences by marking the finished product with the Dolby Surround logo. A simple, royalty-free Trademark and Standardization Agreement with Dolby Laboratories will let producers take full marketing advantage of one of the best known and widely respected names in audio around the world.

Dolby Digital the next generation

Dolby s state-of-the-art 5.1-channel surround system, known as Dolby Digital, will soon be making its debut in the computer arena. Using Dolby AC-3 audio coding technology to store and transmit high quality audio using far fewer bits than conventional systems, Dolby Digital has already established itself as the premier digital audio system in movie and home theaters. It has also been chosen as the audio standard for next-generation systems such as DVD and digital television.

More than 60 companies worldwide have signed on to develop Dolby Digital decoding ICs and implementations, with ICs currently available from C-Cube Microystems, Fujitsu, Matsushita, Motorola, Thomson, Yamaha, and Zoran. Dolby Digital will enter the computer market via the upcoming DVD-ROM, and several companies are already looking at ways to use Dolby Digital to store high quality audio on computers and distribute it via the Internet. As with Dolby Surround, 3D processing techniques may be combined with Dolby Digital decoding for Virtual Dolby Digital surround playback over two speakers.

On the Internet

The concept of quality Internet audio has also caught the attention of several companies in the industry, and efforts are currently underway to provide this capability to computer users. For real-time streaming audio, a low bit-rate version of Dolby Digital called Dolby Net recently made its debut with Progressive Network s RealAudio System 3.0, which delivers stereo sound over 28.8 kbps modems and near-CD-quality sound over ISDN and LAN. More than 40 companies are currently planning to offer program material utilizing RealAudio 3.0, including major record labels and national broadcasting networks. Liquid Audio has announced a Music on Demand system which will utilize this new technology to allow users to preview music in real time from an Internet server. They will then be able to purchase and download CD-quality versions of their selections, using a customized version of Dolby Digital.