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As one of the most recognizable brand names in the world, many agree that Dolby is synonymous with great audio. From its roots in cinema audio, consumers can now experience excellent theater-quality sound in their own family room via home entertainment systems powered by Dolby technologies. Experiencing enhanced multichannel sound at home is no longer limited to DVD viewing - Dolby Digital is the standard for Advanced Television Systems Committee (ATSC), high-definition television (HDTV), digital cable, and digital broadcast satellite (DBS) transmissions. As a result, many of today's television programs are broadcast in multichannel audio for playback on home theatre surround sound systems.
Dolby surround audio is currently broadcast by all major television networks as part of a variety of content, including sports programs like "NFL on Fox," music and variety programs like "Saturday Night Live" and "Austin City Limits," and many other popular programs like "CSI: Crime Scene Investigators," "NYPD Blue" and "Sex and the City." Recently, CBS broadcast the 46th Annual Grammy Awards live in HDTV and Dolby Digital 5.1. Viewers enjoyed live musical performances by artists including Sting, Dave Matthews, OutKast, and Beyoncé in their homes with exceptional sound quality that rivaled being there in person. Dolby Digital 5.1 was also used to broadcast the opening night of Prince's Musicology tour via satellite from Los Angeles to other major markets in the United States.
All that's needed to experience digital television programming in Dolby multichannel audio is a capable set-top box and home theater audio system. There are currently 40 million Dolby Digital-capable systems in households today from well-known manufacturers like Denon, Kenwood, Sony, Yamaha, and more.
The remainder of this document will provide explanations of the various Dolby technologies that are instrumental in enhancing broadcast audio as well as guidelines on how individuals can set up their own set-top box and home theater audio system to guarantee the best television audio possible. Viewers will be able to feel the crush of a defensive tackle, be in the middle of the cheering crowd during a rousing guitar solo, and enjoy the clamor and rustling of background noises in a bustling city street scene with Dolby-powered audio. Dolby truly brings viewers into the program.
Dolby Technologies
In order to fully understand multichannel television audio, it's important to have a grasp on the enabling technologies powered by Dolby.
Dolby Surround is the most basic four-channel surround sound format used to encode multichannel audio for consumer applications. When a Dolby Surround soundtrack is produced, four channels of audio information (right, left, center, and surround) are matrix-encoded onto two audio tracks (right and left) by a Dolby Pro Logic system. These two tracks are then delivered into the home on stereo program sources such as videotapes and TV broadcasts where a Dolby Pro Logic decoder can process them to recreate the original four channels and the surround sound experience.
Dolby Pro Logic decoding relies on amplitude and phase differences between the right and left signals to extract the four channels. Dolby Surround-encoded content is compatible with multichannel playback systems as well as with conventional two-channel stereo and mono playback. Dolby Surround (see logo and diagram in Figure 1) has been used to encode new and older television programming for multichannel audio environments. Thousands of feature films on home video as well as many television shows are encoded in Dolby Surround.
Dolby Pro Logic II technology is much like Dolby Surround, but it has several major enhancements. Most significantly, Dolby Pro Logic II decoding allows five independent channels of full-range audio to be assigned to right, left, center, right surround, and left surround speakers (see logo and diagram in Figure 2).
A Dolby Pro Logic II decoder features improved matrix decoding technology that provides better spatiality and directionality of Dolby surround-encoded content.
Dolby Pro Logic II also creates a convincing three-dimensional sound field during playback of conventional two-channel stereo content, such as two-channel television programming and stereo music recordings. While conventional surround programming is fully compatible with Dolby Pro Logic II decoders, some programs are specially encoded to take full advantage of Dolby Pro Logic II playback with more-precise channel assignment, especially in the right and left surround channels.
Dolby Digital 5.1 is a high-quality discrete multichannel audio coding system that consists of five full-bandwidth channels (right, left, center, right surround, and left surround) and one bass-only channel called LFE (low frequency effects), which sends sounds to the subwoofer (see logo and diagram in Figure 3). Dolby Digital 5.1 can encode up to 5.1 channels of audio into a single, compact digital bitstream, which can be decoded by any receiver equipped with Dolby Digital decoding capabilities. Set-top boxes and televisions with a digital signal output (usually labeled SPIDF, Optical, or Digital Out), can deliver the Dolby Digital signal through an enabled set-top box to a Dolby Digital home receiver via a single digital connection. Dolby Digital audio is used extensively today on digital satellite, cable, and DTV and HDTV terrestrial services.
Home Theater Audio System Hardware
There are several different home theater hardware options for consumers who want to get the full Dolby surround sound experience when watching television programming. The secret to choosing the right system is simply to determine your needs and budget and to make sure the products feature the Dolby logos listed above.
Ideal for entry-level consumers, low-cost and low-power personal 5.1 systems are the least expensive option when creating a home theater audio system. These systems include five main speakers and a small plastic subwoofer. They pack 15-35 watts for the five main channels and retail for around $150. These systems are often purchased to enhance the playback experience of videogames encoded with Dolby surround sound technologies.
One popular option is a home theater-in-a-box system. These products include a Dolby Digital receiver, five main speakers, a subwoofer, and all the wiring necessary to connect the system. Most home theater-in-a-box systems deliver between 50 and 100 watts of power to each of the main speakers. Prices begin at $199 and extend beyond $2,500 depending on the quality and performance of the system.
The subwoofers in home theater-in-a-box systems are matched to the other speaker components and can usually handle quite a bit of power. Home theater-in-a-box systems offer a good price/performance value. Setup simplicity is another advantage. They're often a good choice for those with space or budget considerations. Most home theater-in-a-box systems feature Dolby Digital and Dolby Pro Logic technology, and many stepped-up models offer the newer Dolby Digital and Dolby Pro Logic II combination.
Many home theater-in-a-box systems also feature an integrated device such as a built-in DVD-Video player or DVD-Video recorder. These systems generally cost more than a traditional home theater-in-a-box system, but offer the additional convenience of integration of components into one single system. Stepped-up and high-powered systems may also offer Dolby Pro Logic II in addition to Dolby Digital decoding.
Component-based systems provide another home theater hardware option. They work much like the systems described above, but instead of purchasing all of the speakers together as a matched set, a consumer would purchase the receiver, speakers, subwoofer, and other components separately. This option allows the greatest degree of flexibility and quality for those in the mid to high price range.
Setting Up Home Theater Audio Speakers
When you're ready to set your system up, you'll need to follow a few basic rules about speaker placement.
Rule 1: Position the right and left speakers at either side of your television. About 25 degrees from center is an ideal position. Position them too far apart and the sound field will collapse.
Rule 2: Place the center speaker on top of or directly below your television set. This speaker locks sound to the screen and is often used for speech and first-person character sound effects.
For people with older systems, make sure your right, left and center speakers are magnetically shielded. If they are not magnetically shielded, be careful where you place these speakers in the proximity of a color television set. Magnetic interference from a non-shielded speaker cabinet may interfere with your color television's picture performance.
Rule 3: Experiment with the placement of the subwoofer. Position it in various locations until you get the most satisfying performance. For maximum "boom" effect, you can locate the subwoofer in a corner of your room - though this may not always offer the best overall performance.
Rule 4: Make sure that the right surround speaker is behind the television seating area on the right side, and the left surround speaker is behind the television seating area on the left side. Optimum position for each surround speaker is 90-110 degrees from its respective side of the seating area.
Working with Various Television Receiver Styles
There are several styles of television transmission available currently, and each varies slightly in its reception of multichannel audio. Many stereo programs are Dolby Surround-encoded and increasingly, many analog cable signals are Dolby Pro Logic II-encoded. These signals can be decoded by your A/V receiver.
Often, people think that if they subscribe to basic analog cable they are out of luck as far as listening to their programming in multichannel audio. This is not the case. If an individual subscribes to basic analog cable that comes directly into the television (no set-top box) audio can be decoded by Dolby Pro Logic and Dolby Pro Logic II receivers by connecting the home theater system's receiver directly to the television using the right and left RCA cables (the red and white cables that are typically used to connect the other components to the receiver).
DBS cable systems like DirecTV, Dish Network, VOOM, and others often broadcast programming in Dolby Digital audio. These programs are usually notated by a "DD" logo on the menu guide. Consumers can hear these programs in digital surround sound by connecting their home A/V receiver to their DBS set-top box (See diagram in Figure 4).
Digital cable systems often require set-top boxes with Dolby Digital audio or optical outputs. Set-top boxes with these outputs can be connected to receivers to produce Dolby Digital surround sound. If a consumer enjoys digital cable via an HDTV or an HDTV receiver, they can often receive Dolby Digital 5.1 surround sound. HDTV adoption is growing rapidly and Dolby Digital is the audio standard for HDTV.
Increasingly, more and more HDTVs will incorporate built-in over-the-air and digital cable tuners. These sets will be equipped with a coaxial or optical digital output which can be connected to an A/V receiver for decoding of broadcast- or digital cable-based Dolby Digital audio (See diagrams in Figures 5 and 6).
The Future of Broadcast Audio
Clearly, multichannel surround sound signifies the future for television broadcast audio. With hit television programs encoding their shows for multichannel listening environments, and cable broadcasters offering hardware that easily integrates with the latest digital surround sound systems, it won't be long before all viewers experience their favorite programs with sound quality comparable to that which they hear in the cinema. Dolby continues to work with its partners in the broadcast and hardware industries to guarantee that high-quality multichannel broadcast audio will be available and affordable for all consumers.
For more information about TV Audio for the professional, visit www.dolby.com/tvaudio/.
For more information about home theater for the consumer, visit www.dolby.com/ht/.
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Craig Eggers is the consumer electronics marketing director for Dolby Laboratories.
Related Sites: Digital Producer , Hollywood Industry , Digital Post Production , Digital Pro Sound , Film Imaging , Oceania , CEN - Consumer Electronics Net , CEN - HomeTheatre
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