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Feel the Noise: Dolby Versus dts for DVD

Michelle Manafy

EMedia Magazine, July 2000

July 2000 | The pursuit of art is in many ways a search for an experience outside our own. We seek complete transformation of our existence in great books, in music, and in paintings, though perhaps never been more palpably as in the case of film. The goal is immersion, which utterly transports the viewer into not just another place, but another reality. Each form has its own inherent advantages in achieving this goal, but film brings all of the pieces together--the images, the narrative, and the sound. In art, the choice of medium is often as important as message and this dictum holds true for film.

Losing oneself in the sound and fury of film has always been an essentially private pursuit, an individual journey not necessarily best taken in the crowded confines of a cinema. The advent of the VCR brought that experience home, but in personalizing the viewing experience, also diminished the visceral audio-visual punch that had made it so potentially engrossing in the theater. DVD, by contrast, brings it all home, ushering in a new era for film enthusiasts and with it a new expectation of both video and audio clarity. Surround sound promises not only an authentic theater experience at home, it offers more. It will deliver exactly what the filmmaker intended, right into our living rooms. No doubt, the lack of chattering, popcorn-eating, package-crinkling fellow theatergoers may for some enhance the audio experience of moviegoing, but as with all things DVD, there are other competing factions vying for your attention. Format wars continue, and two types of surround sound that are used in movie theaters are also currently jostling for position in the home theater market: Dolby Digital and dts. Unfortunately, the two systems do not play well with each other, and the movie industry, authoring houses, and the consumers are left to choose one or both, hoping not to miss out on the next big thing.

What's in a Name?

The name Dolby is almost synonymous with good sound. In 1966, the first generation of Dolby noise reduction (A-type NR) was used in Decca professional noise reduction units; two years later, the Dolby B-type NR logo first appeared on a consumer product. By 1970, no self-respecting audiophile would own a cassette deck not sporting the Dolby logo. During that decade, Dolby forged the way into theater sound and, in 1982, introduced Dolby Surround. Ten years later, Batman Returns was the first film released in Dolby Digital Surround.

Speed (1994) marked Dolby's 18th straight Academy Award for Best Achievement in Sound. It was also the first Dolby Digital film to win the award. One year earlier, however, a contender for the digital surround market entered the ring. In 1993, dts was introduced via Steven Spielberg's blockbuster, Jurassic Park. Five years later, all five Best Picture and Best Sound nominees were released in dts and Saving Private Ryan, a Spielberg dts release, won for Best Sound.

Considering the fact that the total number of movies released worldwide in Dolby Digital last year was 703 and dts releases totaled 242, this is no small feat.

Needless to say, the Jurassic Park co-venture proved to be a tremendous success. In fact, the dts experience was so successful that both Spielberg and MCA/Universal Studios immediately invested in Digital Theater Systems, and have since committed all of their major film productions to dts surround.

However, Universal and Spielberg (along with every other DVD-Video maker) are also releasing their films in Dolby Digital. Dolby placed itself at the forefront of the DVD landscape from the earliest stages of the format's evolution. As a result, in 1995, Dolby Digital (AC-3) was made a mandatory audio format for NTSC countries and an optional format elsewhere. Dolby Digital 5.1 and dts are optional formats worldwide.

The Compression that I Get

Both Dolby Digital 5.1 and dts are six-channel surround sound systems. Both encode six discrete channels of audio into blocks of information that are played back in left, right, and center front channels, two rear, and one optional subwoofer (the .1 in 5.1). The digital audio coding used on CDs (16-bit PCM) yields a total dynamic range of 96dB from the loudest sound to the noise floor. This is achieved by taking 16-bit samples 44,100 times per second for each channel, which is often too much data to store or transmit economically, especially when multiple audio channels are desired. This makes some form of compression essential in order to deliver multichannel audio. However, as Michael DiCosimo, vice president of Dolby's East Coast Division, describes it, "Compressed is a pejorative term. People think of compressed as MP3, but we think more in terms of data reduction."

Compression is where the differences between Dolby's version of surround and dts' surround begin. Dolby Digital and dts save space by transmitting only the data that is necessary to portray the original sound, in essence throwing away the rest. Dolby compresses these 5.1 channels of digital audio down to a data rate of 448kbps. With a data rate of approximately 1.5mbps and a much lower compression ratio, dts employs less data compression--about 4:1 compared to Dolby Digital's variable 10-12:1. The higher dts data rate means potentially higher quality audio, particularly in dynamic range and signal-to-noise measurements. Dolby Theater Systems (dts) also claims effective 20-bit resolution for each of the six channels (much better than CD standards allow). According to dts' director of marketing, David DelGrosso, "It is a matter of sonic perfection vs. space consumption."

Dolby counters that the data rate of a digital coding system does not in itself define its sound quality; the company asserts that the compression algorithm used to decide what is kept and what is thrown away is equally if not more important. Dolby Digital's algorithm (AC-3) is based on decades of Dolby Labs research into how sound is perceived--thus the term "perceptual sound".

Jeff Stabenau, president of prominent east coast post house, Crush Digital, agrees. He's done comparisons for clients and says, "While it is often anticipated that dts will sound better--primarily due to the assumption that the larger data stream will contain a more accurate sound image--the result is that people usually find the two formats comparable."

In the DVD market, Dolby clearly has the edge. Because Dolby is one of the most recognizable names in audio, an emergence as the standard for HDTV broadcast, and status as one of the two mandatory audio formats for DVD-Video discs, it has a daunting lead in the race for surround sound superiority.

Digital Theater Systems' DelGrosso says, "At this point, it is safe to say that dts digital surround is installed in every major brand around the world. Two years ago, we were at 10,000 in the field, a year ago 300,000 units in the field, now we are at 2 million." Dolby, on the other hand, can boast that every DVD player sold is equipped with Dolby Digital, though that doesn't mean every DVD owner is playing back in 5.1.

However, with the likes of Spielberg and Universal in its corner, and movies from Buena Vista, New Line, Paramount, Sony, MGM/UA, and Warner Bros. being released in dts, Digital Theater Sound continues to hold its own.

Artisan Entertainment's director of DVD production, Michelle Friedman, says she thinks "dts is just about the best sounding thing out there," but still comes up against the space versus sound issue on a regular basis. She says, "In the past, from what my authoring houses tell me, dts' bit rate was much larger. Thus, if you choose dts you have to sacrifice everything else on the disc. As I understand it, Universal and DreamWorks put out dts-only versions because of that." In Friedman's experience, DVD buyers are checking the boxes for the extras--commentary tracks, deleted scenes, bloopers--and she has had to allocate the space to these elements. However, she is planning to include a dts soundtrack on an upcoming release of Terminator, both because she believes movies warrant the best sound available and because she thinks that consumers want to hear what dts will sound like. "They see the dts logo and want to be able to hear both and compare the two."

For years, dts has been battling Dolby on a playing field of its own. Because of tight bit budgets, studios have had to put out two separate versions of movies to have a dts version on the market. Recently, dts has made a move that will provide studios with the option of variable bitrate--not quite the range that Dolby offers--but full (1.54mbps) and half bitrate (753mbps) versions. As with The Bone Collector, this allows studios to offer both dts and Dolby Digital 5.1 on one disc. This way, users can simply flip through the audio options on the disc and select their preferred sound. Perhaps this isn't exactly what dts had aspired to, but it will deliver dts into the ears of more consumers and, theoretically, allow them to make at-home comparisons that will convince them that dts is better. One could speculate that later in the life cycle of surround sound and DVD itself, dts could again reassert the full bitrate version as the superior alternative.

He Said, She Said

A popular urban legend surfaces in every discussion of the Dolby/dts rivalry. The story goes that when the dB levels of dts-encoded soundtracks are compared to those of the original studio masters, the dts versions (especially the subwoofer tracks) will be several dBs higher. For many, louder would be perceived as better. Though listeners might imagine that they are able to distinguish between clarity and volume, it isn't always that obvious. Peter Tribeman of Atlantic Technology provides an excellent analogy: "If you walked into a HiFi store back in the 70s, and a dealer could make a bit more by selling you one set of speakers over another, when the salesman put audio up on the switcher, they would punch the sound of the preferred speakers up a couple of dB. Those speakers invariably sounded better."

Dolby's DiCossimo argues that the dts crowd is pumping up the volume in just the same manner to curry listeners' favor. "dts' mastering is not true to original film masters," he says. "What they do is encode their own dts masters; we've found that there are level errors in terms of fidelity to the master." He goes on to say, "How could one not stick to the fidelity of the originals? These are made in the sound stations of Woody Allen, and Brian DiPalma--why would anyone want to take that work and change anything?"

In dts' defense, DelGrosso suggests that the impression of a manipulated master is simply a product of dts' superior compression algorithm when its results are compared with Dolby's. "Because of Dolby's continuous lobbying that their compression doesn't affect the sound, there are those who think that we must play with the master. Several years ago, Roger Dressler from Dolby found a laserdisc where the dts surrounds were three dBs hotter than Dolby's. We found that one of our post-houses was marking the surround levels incorrectly--surround levels are created differently for cinema and home at a 3dB difference--and we would have compensated if we'd known. We don't do the encoding anymore, so this should never be a problem again."

Whatever the origins or veracity of the rumor, the point may soon be moot. Recently, Spruce Technologies and dts partnered to provide a fully enabled solution for encoding and authoring DVD titles using the dts digital surround audio standard. DVD producers can now, for the first time, encode dts audio directly into their authoring projects at their own workstations rather than sending material to dts for encoding, which should prevent this sort of error (and rumor) from surfacing again.

This capability could make a big difference to authoring houses in terms of offering the dts choice to their clients at similar cost and turnaround times to Dolby Digital. Wolfgang Martens, head of technique premastering at Sonopress in Germany, calls dts audio "an important technology for advanced DVD production." He says, "The reliance on other facilities interrupts our production processes and adds expense to a project. We have been looking forward to having the ability to handle dts encoding, since this is a standard within the DVD specifications. In conjunction with our Spruce DVD Maestro systems, the new dts encoder makes this high-quality audio technology much more feasible for Sonopress and our customers."

Crush's Stabenau agrees that the ability to encode dts in-house could change things considerably. "The process for creating a Dolby Digital 5.1 has been easier than creating dts for an authoring house because there was not a dts encoder available to the marketplace, so all material had to be sent to dts for them to encode. This can cause difficulties if there are changes in the DVD title at the last minute."

Same Difference?

"Because of Dolby's continuous lobbying that their compression doesn't affect the sound, there are those who think that dts must play with the master."
Both Dolby and dts are perceptual coders, but they employ different sound algorithms to eliminate redundant data, thereby reducing data rates with a minimum of perceived loss of sound quality.

Again, the approach to compression is key. DelGrosso says, "Engineers make a lot of decisions in deciding how much data to eliminate, but the bottom line is that Dolby throws out more than they should."

Dolby's approach, according to DiCossimo, is to "achieve the highest quality digital audio at the lowest possible bandwidth."

Another in which difference can be perceived is dynamic range--how high the highs are and how low the lows. DelGrosso thinks people associate this with the loud sounds, but argues that it is most evident in the subtle nuances. His favorite dts example is in Dances with Wolves. He instructs, "Listen to Costner's legs move through the branches. In our version, you feel like you are in the experience rather than watching a movie."

Lastly, full six-channel discrete separation is a tricky business, and it requires a lot of data to keep all six channels where they belong. The front channels always carry a lot of information, and if the rear suddenly also has a lot of information, the sound will get shifted to the front, which results in less surround.

Artisan's Friedman says, "I really truly believe that dts is a cleaner, crisper sound. DVD is about having the cleanest, clearest picture you've ever seen and the sound should be the same way. I'm not knocking Dolby, but I think dts does it better. Just compare the first 20 minutes of Saving Private Ryan and you can't miss the difference."

Perhaps no one is more passionate about what DVD brings to sound than Larry Walsh, a mixer in the Universal Studios' sound department. Interspersed with comments like: "We have lifted the veil so you can hear it better;" "Be kind to your neighbors...invite them over and introduce them to DVD." Walsh holds the phone out into his studio to demonstrate his point. He's in the process of mixing a digital remaster of Jaws, which he thinks takes DVD to new depths of sound. "They have added another dimension to the movie. You are in the water, you gulp the seawater as she does [in the opening scene], you hear sounds she makes as she is being bitten in half. The technology has advanced to the point where you hear things you never could have in the past. You may have seen Jaws, but you've never heard it before."

According to Walsh, Universal is not just committed to dts, it is committed to delivering the best possible sound to enhance the cinematic experience and consequently doesn't take sides. He says, "Dolby Digital and dts are both a good compromise to get quality audio and quality picture into the home."

Metal Health: Is Surround Always Sound?

dts has been at the forefront of surround mixes for music discs, and holds a worldwide patent on delivering surround on CD. Dolby has taken a more cautious approach to surround for CD: "Nobody is more enthusiastic about multichannel sound than Dolby. However, we also recognize the importance of standardization and compatibility. As a result, we will not release CDs with Dolby Digital soundtracks or encourage others to do so." DelGrosso believes that dts' experience delivering sound on CDs will give it the edge in providing multichannel mixes for DVD-Audio.

According to DelGrosso, there are two basic approaches to 5.1 mixing for music. The first is the snapshot approach: "The band is onstage in front of us, and let's take a picture of what that would sound like. A lot of engineers want to capture the live appearance."

The second approach to mixing is what DelGrosso calls better than live. He says, "Live is performed that way for a reason because of the limitations"--in other words, because artists aren't constrained by the limitations of live performance (i.e., standing on a stage and playing to a crowd). He continues, "A lot of artists would prefer to paint the whole room." He says he heard a quote once that best describes the difference between stereo and 5.1: "Stereo is like looking at a picture of someone you love; 5.1 is like having them in the room with their arms around you."

Atlantic Technology's Tribeman disagrees, recalling the not-so-good old days of Quadraphonic sound, "With the surround music remixes, they've gone back to the old four-channel tricks; they place the listener in seemingly impossible situations as opposed to creating true-to-life concert hall sound."

Dolby's caution about applying surround to CD approach rings true for conflicting formats as a whole. Dolby "recognizes the reluctance of producers to release, and retailers to stock, more than one version of a given program." Dolby's business savvy seems tough to beat. The battle for surround sound dominance appears to have less to do with audio quality than industry momentum and consumer reluctance to contend with a multitude of formats.

Akira Kurosawa said, "Cinematic sound is that which does not simply add to, but multiplies two or three times, the effect of the image." It seems likely that Kurosawa was not talking about simply turning up the volume and neither are Dolby or dts.

DelGrosso and dts are positioned as surround sound mavericks. And DelGrosso argues that surround is simply advancing the musical vanguard in the spirit of their forebear. "If Jimi Hendrix were here, he wouldn't be looking at surround as a strange thing."


Sounds Like Business

Erik Corrigan, president of 12 Centimeter Multimedia, has noticed that requests for surround sound are suddenly cropping up in corporate presentations. He says producers are now able to pitch surround sound mixes because they have the option of DVD. Corrigan says, "When they want to play something, the most that digital beta has to offer is four channels of audio and then the client has to rent a $40,000 deck to play those four channels back. So for a single day's setup for a presentation, $1,000 for the digital beta rental is really high. If they use DVD instead, they are able to keep their presentation budgets lower so they can spend more on a projector and include 5.1-channel surround sound. I don't know how many presentations are using surround sound, but I do know that it has become viable."

Corrigan, who works with WaveGroup Sound for audio, has not had any requests for dts, "even out of curiosity." Wave's senior engineer Mark Lee says, "I think our clients are just discovering surround sound and the distinction between Dolby and dts just doesn't come into it. They are not A/B testing the two formats. They are impressed enough with multichannels."

Lee goes on to say, "In the music arena, dts is doing better, but for our clients or at least corporate applications, Dolby Digital seems much more prevalent. There is just more Dolby Digital out there." So companies taking on their first DVD projects naturally conclude that it's the way to go.

Though Crush Digital has used dts, thus far they have had a similar experience to that of 12 Centimeter. They've used 5.1 in numerous projects of many types, but only used dts in a few music projects. Crush has created many music DVD titles for artists that have included Whitney Houston, Bob Dylan, Talking Heads, and the Dave Matthews Band, among others. In Stabenau's experience, musicians are very likely to want to include a 5.1 track along with a stereo source.


Feel the Noise

Space Jam

At 14.5 feet wide and 31 feet long, our living room is hardly the perfect listening room. In an effort to get as close to THX (Lucasfilm's own strict criteria) and the manufacturer specs as possible, to allow for a fair comparison of dts and Dolby Digital, I scoured every scrap of paper that accompanied the equipment. By the time I turned the last page, my obsession had taken on a life of its own; I was ready to do whatever it took to achieve optimal sound, even if it meant moving every piece of furniture in the house.

Compromising Positions

I prefer to position my monitor higher than most, so the 373C center channel position was the only speaker I was not able to place in the first choice position on top of the monitor so I placed it centered below, which was listed as the next best. It sits on rocking chair legs and a base so its sound can be directed at the listener. Peter Tribeman of Atlantic Technology offers a trick to optimize bass: place the 372PBM subwoofer in your favorite listening position (in my case, the Le Corbusier chair carefully positioned in the sweet spot). Then, put in a DVD and set the bass to a reasonable level, go forward to the wall and put your back to it. Move along the wall until the bass sounds good to you, then swap yourself and the subwoofer, letting physics do the rest. The 371LR left and right front channels are placed the same distance away from the listener as the center channel at the two other corners of an equilateral triangle from the listening position. The 374SR left- and right-specific dipole surround speakers belong to the sides to put the listener in the null zone.

The Parasound power amp and A/V controller should not be cloaked in a rack, though of course they can be. They are pieces of art. The power amp is outfitted with cooling fins on three sides, giving it an ominous look. Anyone who has to lift the 87-lb beast will appreciate the well-placed handles in each corner. The controller is of comparable beauty--its simple face is home to 11 buttons and one rotary knob, which serves a number of tasks.The Parasound power amp and controller generate some of the cleanest, crispest sound I've ever heard.

I Got the Hook-Up

I've always invested in good cables purchased at my local high-end audio/video shop, thinking that was enough to satisfy my sound standards. However, when I unpacked Sound Connections International's Vampire Wire ST-1 speaker cables and the CCC (continuous cast copper) series 2 audio interconnect cables, I questioned that premise. The sheer girth of these connections is impressive, but the quality and precision of the terminations demonstrate an exceptional level of workmanship. Stuart Marcus, president of Sound Connections, says, "A good rule of thumb for cable purchases is 15 to 20 percent of the entire system." That number may seem high, but now that I have had the chance to compare and hear the amount of bass that can reach the surround channels, I'm a convert.

The cables are directionally marked and employing them was pretty straightforward. Though the 90 possible connections on the back of the Parasound AVC-2500 stunned me, they are grouped together in an intuitive layout that left me feeling a bit foolish for reading every word of the manual.

Unlike some, the Onkyo DV-C600 six-disc DVD changer has a complete compliment of connection options on the back to support any system configuration (Sound Connections suggested and supplied a Vampire Wire toslink connection, which I chose over possible analog or digital coaxial). Though you can plug the DV-C600 in and use it right out of the box, it also provides extensive setup options for both audio and video interfaces.

Two days after the boxes arrived (overhaul of home complete), I plugged the last cord into the outlet. Ever looming in the background was the daunting prospect of a two-hour minimum setup time for the AVC-2500 once I finally turned it on (or so I guessed given the manual's description of the process).

Absolute Power

Both the Parasound A/V controller and Atlantic Technology-powered subwoofer and center channel have easy-to-understand default settings that conform to THX certification. Each input has a level control on the HCA-2205A with THX noted at the proper knob position. Much to my surprise, the entire process of setting up the A/V controller only took 15 minutes. Parasound provides a microphone so the "smart system" can hear test tones it plays and adjust for speaker location, room shape, and listening position to calibrate channel levels and delay times--resulting in one hell of a sweet spot.

Then I loaded 13 hours of entertainment into the Onkyo DV-C600 and, with remote in hand, dug in for some listening pleasure. The Onkyo remote makes navigating easy--audio track selection and menu access are available right off the remote, rather than wading through on-screen menus.

One thing I'd heard about, but hadn't heard before, was the difference a unified speaker system makes (my personal setup is patched together from three vendors). As Peter Tribeman, president of Atlantic Technology, explained it, "When purchasing a stereo you wouldn't buy a left speaker from one company and a right from a second, so why would you do it with surround?" With the Atlantic speakers, the sound track fills the room, but I did not find myself looking for any particular sound's point of origin; the 275-watt-powered subwoofer's bass resonated through my bones. For me, it did its job too well. I was so completely enveloped by the sound, that I almost forgot to listen to the products.


Theory and Practice

Many have discussed side-by-side, A/B testing of the two surround sound systems. Few would admit to having a preference--on the record. Business is political, after all. So, I took the liberty of setting up a surround-sound test lab of my own (see sidebar), and while not exactly scientific, the results were startlingly clear.

I did not explain any technical differences between the two systems beforehand. I simply said I would be playing clips of DVDs at identical sound levels using two surround sound alternatives. Using Antz and Saving Private Ryan (Universal/DreamWorks), I chose one scene from each to illustrate a variety of sound types that would be demonstrative of surround capabilities. Between each pair of scenes, I asked for comments from the six participants.

With Antz, perhaps the most telling comment came from Claire, a 60-something woman who does not own a CD player, not to mention an in-home theater. "With the first one, the sound seemed like it all came from the front. It was toned down." Not a fan of loud movies, she preferred toned down. With Saving Private Ryan, the responses were unanimous; the first version sounded "muffled." It sounded "pretty good, but not nearly as good as the second one." Regarding the second choice, comments included: "I could feel the impact;" "The sounds of the shells falling and tanks grinding over the rocks were so clear, so real." In both comparisons, the first selection was Dolby Digital 5.1 and the second was dts.

Perhaps more remarkable, however, were the responses to who thought which was Dolby and which was dts and why. Almost all of the participants thought that the second selection must be Dolby because it sounded better--proving once again that perception is the name of the game.


Companies Mentioned in This Article

12 Centimeter Multimedia
3350 Scott Boulevard, Bldg. 61, Santa Clara, CA; 95054; 408/350-9000; Fax 408/350-9012; http://www.12cm.com

Artisan Entertainment
2700 Colorado Avenue, Santa Monica, CA 90404; 310/449-9200; http://www.artisanentertainment.com

Atlantic Technology International Corp.
343 Vanderbilt Avenue, Norwood, MA; 02062; 781/762-6300; 781/762-6868; http://www.atlantictechnology.com

Crush Digital Video 147 West 25th Street, 4th Floor, New York, NY, 10001; 888/278-7438, 212/ 989-6500; Fax 212/645-9093; info@ crushdv.com; http://www.crushdv.com

Onkyo U.S.A. Corporation
200 Williams Drive, Ramsey, NJ 07446; 201/825-7950; Fax 201/825-8150; http://www.onkyo.com

Parasound Products, Inc.
950 Battery Street, San Francisco, CA, 94111; 800/822-8802, 415/397-7100; Fax 415/397-0144; http://www.parasound.com

Sound Connections International, Inc. (Vampire Wire)
203 Flagship Drive, Lutz, FL; 813/948-2707; Fax 813/848-2907; http://www.vampirewire.com

Sonopress
Carl-Bertelsmann Strasse 161, 4830 Gutersloh, Germany; +49-5241-80 5200; Fax +49-5241-7 35 43; http://www.sonopress.de

Spruce Technologies
1054 South De Anza Boulevard, Suite 200, San Jose, CA 95129; 408/863-9700; Fax 408/863-9701; http://www.spruce-tech.com

Universal Studios
10 Universal City Plaza, Universal City, CA 91608; 818/777-3114; http://www.universalstudios.com

WaveGroup Sound
3350 Scott Boulevard, Bldg. 6101, Santa Clara, CA; 95054; 408/727-8444; Fax 408/727-0180; http://www.wavegroup.com


Michelle Manafy is Associate Editor of EMedia Magazine.

Comments? Email us at letters@onlineinc.com.


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