OK, so you've had your current home theatre system for a few years, and after visiting your friendly audio dealer you've decided it's time to upgrade. The only problem is, there are a couple of new audio systems that appear to do exactly the same thing. What's worse, no two salespeople you've spoken to seem capable of agreeing on anything when asked a few simple questions about how these competing systems actually sound. It's all getting a little frustrating. After all, all you need are a few straightforward answers to a few straightforward questions, such as: "just what do those strange abbreviations stand for?" "How do they sound?" "How do they work?" "How do they compare?" Well, hopefully the following article will provide you with a plethora (a cornucopia, even) of useful (and not so useful) information to answer nearly every question you can think of concerning the fascinating (I jest not) topic of digital cinema sound. If you're just a beginner, there's a crash course in the basics of movie sound, a history of the major digital formats, and a bare-bones technical guide to how the new audio formats work. You'll also find out just how the newest wunderkind of home theatre, DVD, fits into the picture. So, without any further ado, let the journey begin!

There are currently three competing multi-channel digital audio formats in theatrical use: Dolby Digital, DTS Digital Sound and SDDS. Of these three, two are available in domestic variants: Dolby Digital and DTS Digital Sound (as 'DTS Digital Surround'). Dolby Laboratories' Dolby Digital is the most common of these audio systems in cinemas (42,790 Dolby Digital equipped screens as of March 18, 2004), and by far the most common in homes. Digital Theater Systems' DTS Digital Sound is the second most common digital format in cinemas (passing 20,000 DTS equipped screens in March, 2001) and has a growing base of domestic-users. Sony's SDDS (Sony Dynamic Digital Sound) system, while not available as a domestic format, remains in regular use in cinemas throughout the world.

Although there are occasionally format-specific variations in channel configuration, in general, all three systems use the same layout: three channels across the screen soundstage (LCR: Left, Centre and Right), two channels at the rear (LS and RS: Left-Surround and Right-Surround) and an optional LFE or Low Frequency Effects channel. The LFE channel is designed to enhance the impact of low frequency sound effects (and occasionally to support bass in musical content) with greater headroom than the five (or more) main channels are capable of. This configuration is generically called '5.1', the .1 being the LFE channel

Dolby Laboratories, the creators of the oldest of the three digital formats, began work on their multi-channel digital system in 1987: the year standardisation of HDTV (High Definition Television) began in the US. Although initially intended to be a 2-channel audio system, as the surrounding technology evolved, Dolby Labs found that they could create a more flexible 'adaptive' coding system that would allow up to 5.1 channels of audio to be recorded at extremely low bitrates. The new coding system was called simply 'AC-3' (or 'Audio Coder 3').

At the time, High Definition Television was still years away from commercial reality, leading Dolby to choose an already-established format as AC-3's first carrier: celluloid film. Dolby decided, not least due to the introduction of the rival CDS system in 1990, that AC-3's first practical application would be as a 5.1-channel cinema sound-system; a high performance, lower cost alternative to the then nearly 40 year-old 6-channel magnetic sound systems in use. Dolby SRD (Dolby Digital's professional nomenclature) was officially launched at the American premiere of 'Batman Returns' in June 1992.

Because the new AC-3 encoded 35mm film system carried both the 5.1-channel AC-3 data and a conventional optical soundtrack, dual-inventories of films became unnecessary. Up until this time 6-channel sound was generally reserved for the expensive 70mm format, while 35mm prints usually carried only an optical 2-channel soundtrack. 70mm film prints with 6-channel magnetic soundtracks can cost up to 14 times their optical 35mm 2-channel equivalent to produce, so were used only in a limited number of premier cinemas. Before the introduction of Dolby Digital, studios were forced to maintain inventories of 35mm and 70mm prints (for films in which a 4/6-channel soundtrack was produced) in order to supply both 35mm and 70mm equipped theatres. The new single-inventory AC-3 system eliminated the prohibitively high cost of producing, distributing and storing two versions of the same film.

At the time of AC-3's theatrical introduction the only other 5.1-channel digital sound system in use was Kodak's CDS (Cinema Digital Sound) delta modulation-based format. Between 1990 and 1992 the CDS system was used on 9 films, including 'Terminator 2' and 'Edward Scissorhands'. CDS's developers, Eastman Kodak and the Optical Radiation Corporation, officially withdrew support for their system in 1993 following the near universal studio acceptance of Dolby Digital and numerous technical difficulties with their system. This left Dolby Digital the sole digital audio format available... but not for long.

In 1993 both DTS Digital Sound and Sony's SDDS systems were introduced in 'Jurassic Park' and 'Last Action Hero', respectively. Steven Spielberg (Jurassic Park's director) and MCA/Universal had become major shareholders in Digital Theater Systems earlier in 1993 following a private demonstration and evaluation of the DTS Digital Sound system. Both had agreed to use DTS's system in all of their films from that point (beginning with Jurassic Park). It was in both Spielberg and Universal's interests that the format succeeded. Universal's support, combined with Spielberg's massive influence in Hollywood, ensuring that DTS's widespread theatrical acceptance was almost a foregone conclusion. At the same time, Sony's ownership of the Columbia Pictures Studios and part-ownership of the Loews Theatres chain guaranteed SDDS's widespread industry acceptance. Both systems had strong support from major Hollywood studios and together constituted a serious threat to Dolby's nearly 20 years of theatrical sound-system dominance. In the years following their introduction, all three theatrical sound-systems have managed to survive, with no single format able to claim dominance over the others.

The digital data needed for the theatrical version of AC-3 to function is recorded on small optical patches located between the film's sprocket holes. A CCD-based optical reader, located just in front of the film-gate, reads the data (stored as optical pixels) which is converted into a form readable by the AC-3 analogue-to-digital converter (ADC). This digital data then passes through the AC-3 decoder, and then through DACs (digital-to-analogue converter), producing the 5.1 channels of analogue audio needed (this audio is then delayed slightly, synchronising the sound with the projected image). AC-3 encoded films also carry a standard optical stereo soundtrack: if the AC-3 encoded optical patches are damaged or otherwise unreadable the optical stereo track can be used instead, preventing disruption of the movie. CDS's lack of a backup 2-channel soundtrack, for use if the digital soundtrack failed, was the system's Achilles' heel and a major contributor to its downfall. DTS, unlike AC-3, is not recorded on the film itself. Instead, DTS is stored on CD-ROM and synchronised with the film using standard SMPTE time codes, located between the film's optical soundtrack and picture area. Like AC-3, DTS eliminates the need for dual-inventories by also carrying an optical stereo soundtrack, but because of its independent optical (laser-read) data storage, is far less susceptible to dropouts resulting from damage to film stock than either SDDS or AC-3. SDDS's data, like AC-3's, is physically recorded on the film. Unlike AC-3, though, it is recorded on continuous optical strips along both edges of the film. SDDS's optical strips are located between the edge of the film and the sprocket holes, making it, of the three systems, the most susceptible to damage. All three formats can be supported on the same film print, making format-specific prints unnecessary.

Dolby Digital, SDDS and DTS (the consumer version) all use 'lossy compression' data reduction systems, utilising 'perceptual coding' to reduce the data needed to accurately reproduce 5 full-bandwidth audio channels (up to 7 in SDDS and DTS's case) plus a limited-bandwidth bass-only channel. Unlike conventional data compression schemes, which allow the retrieval of 100% of stored data upon decoding, 'lossy compression' schemes 'throw away' some data, which cannot subsequently be retrieved. Perceptual coding lies at the heart of all three systems, ensuring that only the 'right' information is discarded. Using a theoretical model of the auditory system, all three perceptual coding systems use a technique called 'acoustic masking'. Acoustic masking exploits our inability to detect quiet sounds while louder sounds are produced at a similar frequency. The louder sounds generate a 'noise mask' capable of completely obscuring quieter sounds around the same frequency: frequencies above these louder sounds are masked more effectively than frequencies below. Because we can't hear these quieter sounds, they can be removed from the original signal without making an audible difference to the listener.

Compact Disc uses roughly 706kbps (kilobits per second) to reproduce one uncompressed 16-bit linear PCM audio channel. DTS's Coherent Acoustics coding scheme reduces the number of bits needed by up to a factor of eight, requiring 754kbps, 1235kbps, or 1509kbps, to reproduce six (and up to seven using DTS's ES Discrete 6.1 system) audio channels. Note that these figures are consumed datarates; utilised datarates are 768, 1411 and 1536kbps respectively. By using a variation of the ATRAC compression system (as used in Sony's MiniDisc format) the SDDS system manages to reduce the bitrate required even further. SDDS functions at a maximum bitrate of 1411kbps (SDDS-8) and a nominal bitrate of 1060kbps. The more aggressive compression system utilised by Dolby's system allows a 5.1-channel soundtrack to function with a recommended minimum bitrate of only 320kbps. That's a compression factor of 15:1 (at 20-bit/48kHz), an extremely impressive technical feat.

In the home, Dolby Digital 5.1 normally operates at either 384kbps or 448kbps (Dolby Digital's maximum bitrate on DVD-Video), but can operate at bitrates as low as 224kbps as used on some IMAX DVDs, or as high as 640kbps. More recently Lion's Gate used 256kbps Dolby Digital 5.1 for its Cube Signature Edition. DTS runs at 882kbps in its theatrical application and 1235kbps on LaserDisc/CD (please note: DTS's domestic and theatrical variants do not use the same audio codec), and 1509kbps or 754kbps on DVD. Dolby Digital has been available on LaserDisc since January 1995 ('Clear and Present Danger') and on DVD since March 1997. DTS (Coherent Acoustics) became available on LaserDisc in January 1997 ('Jurassic Park') and first appeared on DVD in November 1998 ('The Legend of Mulan').

Dolby Digital and DTS are capable of using sampling frequencies of 32, 44.1, or 48kHz (DTS can also function at up to 192kHz). Until 1999, DTS functioned only at 44.1kHz. DTS had, up until then, used only the standard CD format (16-bit 44.1kHz) as a carrier. Consumer Dolby Digital operates exclusively with a 48kHz sampling frequency. DTS on DVD also uses a sampling rate of 48kHz. Both Dolby Digital and DTS are capable of 24-bit resolution, but currently nominally operate at 18-bit resolution, allowing a dynamic range of approximately 108dB. Theoretically, 24-bit resolution allows dynamic range of 144dB which, though higher, would be indistinguishable from the lower 108dB figure given the current limitations of playback hardware. For all practical purposes, both Dolby Digital and DTS Digital Surround operate at near, or above, 18-bit resolution and dynamic range (108dB). Dolby Digital at 384kbps has an audio frequency response of 20Hz-18kHz with joint frequency coding above 10kHz, while 448kbps has a frequency response of approximately 20Hz to 20kHz with joint frequency coding above 15kHz. DTS at 754kbps has a maximum frequency response of 20Hz-19kHz although DTS's standard hardware encoder, the CAE-4, begins to roll off frequencies at 15kHz. 1509kbps DTS has a maximum frequency response of 20Hz-24kHz. Neither 754kbps nor 1509kbps DTS use joint-frequency coding. 

Dolby Digital and DTS Digital Surround were created with completely different design objectives in mind. DTS was designed to offer multiple channels of higher-than-CD resolution audio within the bandwidth constraints of the Compact Disc system, using a combination of signal-redundancy coding (ADPCM) to reduce bandwidth and perceptual coding to increase the perceived resolution of the coded signal. Dolby Digital's primary objective was to dramatically reduce the bandwidth needed to reproduce multi-channel audio (preferably to 320kbps or below) without significantly altering the quality of the original linear PCM signal. DTS's compression is accomplished primarily through the use of sub-band ADPCM compression, while Dolby Digital's compression is primarily the result of aggressive psychoacoustic coding and hybrid forward/backward-adaptive bit-allocation. Given that DTS was designed without many of the limitations imposed on Dolby's system, the fact that Dolby Digital and DTS Digital Surround are so often compared with one another is a tribute to the perceptual coding expertise of Dolby Laboratories.

The human auditory system is capable of detecting sounds between roughly 20Hz and 20kHz, but at high and low frequencies (below 200Hz and above 3kHz) the human ear becomes progressively less sensitive. Dolby Digital and DTS exploit this insensitivity to high and low frequencies to reduce their respective bandwidth requirements. Both systems divide the full range of audible frequencies into sub-bands. Sub-bands containing frequencies the human ear is most sensitive to are replayed with greater accuracy and with less distortion (quantization noise) than sub-bands the human ear is less sensitive to, which are allowed to reproduce audio with more distortion (or aren't reproduced at all). Standard linear PCM audio reproduces all coded frequencies with equal detail. Unfortunately, much of the high-resolution detail offered by these systems is wasted on our insensitive ears. Because DTS and Dolby Digital code only the information that our ears are sensitive to, high quality audio can be reproduced with a fraction of the bandwidth needed by linear PCM audio systems.

Unlike linear PCM systems, neither Dolby Digital nor DTS allocate a fixed numbers of bits to any channel. Instead, Dolby Digital and DTS feed their sub-bands/channels from 'global bit-pools'; the total number of bits allocated to any single channel constantly varies as a result. Sub-bands containing frequencies the human ear is more sensitive to are allocated more bits from the available bit-pool than sub-bands the human ear is less able to detect. Individual frequencies within these sub-bands are allocated data depending on their relative perceptibility when compared to neighbouring frequencies (as determined by the perceptual codes' masking algorithms). In DTS's case, a technique called 'forward-adaptive bit-allocation' is used. Using this technique, the allocation of data to each sub-band is pre-determined exclusively by the encoder. This information is explicitly conveyed to the decoder along with the actual bits to be used. Forward-adaptive bit-allocation's primary advantage is that the psychoacoustic model used resides exclusively within the encoder. Because the model is encoder-based, extremely complex psychoacoustic coding algorithms can be used (as decoder processing ability isn't a limiting factor). Forward-adaptive bit-allocation also allows psychoacoustic model modifications and improvements to be passed directly on to installed decoders, essentially 'future-proofing' DTS decoders from premature obsolescence.

Forward-adaptive bit-allocation's primary drawback is that explicit 'side-information', or 'metadata', is needed to direct and control the decoder's allocation of data to sub-bands; this extra information takes up space that might otherwise have been used for audio reproduction. Dolby Digital uses a hybrid technique incorporating elements of both forward- and backward- adaptive bit-allocation. Like DTS encoders, Dolby Digital encoders must also instruct their decoders to allocate bits to particular sub-bands, but don't need to transmit these instructions with such explicit detail. Dolby Digital decoders already include a very basic 'core' copy of Dolby Digital's perceptual coding algorithm. Because the decoder already 'knows' roughly how the bits should be allocated the encoder only needs to transmit information about specific variations from the decoder's own internal algorithm. Dolby Digital's metadata uses relatively little of the available bandwidth, leaving more data available for audio reproduction (which is a good thing, considering Dolby Digital's bit-pool is considerably smaller than DTS Digital Surround's).

Because DTS's sophistication resides almost entirely within the encoder, DTS decoders are 'passive' and relatively simple. Improvements in the Coherent Acoustics coding system can be passed directly to the decoder, allowing improvements in overall audio performance to be utilised by all decoders, regardless of age. Despite the fact that Dolby Digital decoders contain a fixed core AC-3 algorithm, Dolby Digital is also encoder biased. As such, Dolby Digital decoders can also benefit from advances in the AC-3 coding system. Dolby Digital manages to utilise most of the advantages of both backward-adaptive bit-allocation techniques (decoder-based processing, minimal metadata requirements) and forward-adaptive bit-allocation (encoder-based 'intelligence', fully upgradeable coding), while eliminating many of their respective drawbacks.

Dolby Digital primarily codes information above the threshold of detection. While DTS also codes this information, its larger bit-pool sometimes allows the selective reduction of sub-bands' noise-floors further below the limits of detection than possible for Dolby Digital. As a result, some of DTS's sub-bands may contain most of the original PCM signal, and may even be lossless under some conditions. DTS constantly attempts to reconstruct as much of the original signal as possible. The extra information coded by DTS is theoretically below the threshold of detection, so shouldn't be consciously perceptible (which isn't to say it may not be perceptible on some level).

Dolby Digital's low bitrate 'global bit-pool' system is both its strongest and weakest point. If the total bit-pool is large enough it can reproduce 5.1-channel audio almost indistinguishable from the studio-master. However, when the drain on the bit-pool reaches the pool's limit, compression artefacts (quantization noise, bandwidth restriction, or even audible joint-frequency coding in extreme circumstances) may become detectable. Dolby foresaw this problem, explaining why the domestic version of their system has a larger bitrate (384kbps for LaserDisc), and therefore bit-pool, than the theatrical version (320kbps). This larger bit-pool significantly reduces the possibility of detectable artefacts in the more revealing domestic environment. DVD-Video has the capacity to store 448kbps Dolby Digital, as used in most Universal, Fox, Paramount, DreamWorks, New Line and more recent Columbia TriStar DVDs, further reducing the possibility of audible distortion.

When comparing DTS with 448kbps Dolby Digital (and even, to a lesser degree, 384kbps Dolby Digital) any difference noticeable can more likely be attributed to differences in mastering or production than coding schemes. Under identical mastering conditions the two systems should be nearly indistinguishable from one another.

Any attempt to compare the domestic versions of Dolby Digital and DTS with one another is extremely difficult due to one major technical difference. The domestic version of Dolby Digital incorporates a feature, called 'dialog normalization', designed to maintain a consistent centre-channel volume from all Dolby Digital sources. The dialog normalization system is designed to ensure that the average centre-channel volume is always between -25 and -31dBFS (decibels below digital full-scale), regardless of source. As a result, if dialogue is recorded at a higher volume, the Dolby Digital decoder automatically attenuates the volume of all channels to the level at which the centre-channel outputs dialogue at the set 'dialnorm' level (usually -31dBFS for Dolby Digital on DVD). Most movies' centre-channels are recorded at -27dBFS, which results in an overall lowering of 4dB in all channels. Movies can be recorded at anything from -23dBFS (e.g. 'Wild Things') to -31dBFS (e.g. 'Air Force One', non-SuperBit and 'Twister: SE'), resulting in nominal overall volume attenuation of up to 8dB ('Wild Things') or more. All channels maintain their correct relative balance, so no detrimental sonic effects can be attributed to the dialnorm process. But, because the result can be up to an 8dB reduction in volume, there is no easy way to compare DTS and Dolby Digital versions of a film's soundtrack. The overall volume of the DTS version may be 8dB or more higher than the Dolby Digital soundtrack, making direct comparisons nearly impossible. As dialnorm is constantly variable in 1dB increments, the exact difference in overall volume between Dolby Digital and DTS soundtracks often varies from film to film.

Any argument for or against a particular system must be based on competing coding schemas. DTS's supporters claim that it is superior to Dolby's system because it uses a higher bitrate and less aggressive compression scheme. These two facts are essentially irrelevant in determining whether DTS is 'better' than Dolby Digital: neither automatically equates to higher sound quality. The quality of both systems stands or falls on the effectiveness of their respective compression and perceptual coding systems. Both systems use extremely effective coding systems. As both systems are based on completely different technologies, and rely on human perception, there is no technical or scientific means to determine which is 'better'. An apt analogy is that of the Porsche and the Corvette: the Corvette has a powerful V8, while the Porsche has a smaller engine but is turbo-charged. Both cars use very different power sources, yet both are extremely effective at performing their desired functions. Undoubtedly there will be those who argue for one system over another, but any such argument must be based on individual preference rather than scientific theory. There are no technically valid grounds for believing either audio system is inherently better sounding than the other.

Image, Universal and DreamWorks were the sole Region One (US, US territories and Canada) distributors of theatrical DTS DVD software prior to Dimension's release of 'Teaching Mrs. Tingle' in December 1999. These three distributors elected to include only Dolby Surround encoded Dolby Digital 2.0 soundtracks (192kbps), in addition to DTS, on their initial DTS DVD releases: not full 5.1-channel Dolby Digital. DVD has a maximum all-up bandwidth (mux rate) of 10.08 Mbps (Megabits per second), including both audio and video. The MPEG-2 video compression system requires at least 3-4 Mbps to produce acceptable picture quality: DVD's 'average' video bitrate is approximately 4Mbps, while rates of 8Mbps and higher allow picture-quality that is nearly indistinguishable from the video master. This leaves, theoretically, 2Mbps of bandwidth free; enough for 5 384kbps Dolby Digital soundtracks, 4 448kbps Dolby Digital soundtracks, or a combination of 1 1509kbps DTS soundtrack and 1 448kbps Dolby Digital soundtrack. There are no technical restrictions preventing both 1509kbps DTS and 448kbps Dolby Digital 5.1-channel soundtracks from being presented on the same disc (as on Warner Brothers' Twister SE and Interview With The Vampire SE titles). However, if only one 1509kbps 5.1-channel DTS soundtrack were to be recorded on a DVD, the size of the single track would reduce the maximum bandwidth available for video by nearly 13%. A single 448kbps Dolby Digital soundtrack would reduce the bandwidth available for video by less than 2%.

DTS on DVD would be extremely difficult without Dolby Digital. The (NTSC) DVD-Video standard requires either a PCM or Dolby Digital soundtrack on all DVDs. Without Dolby Digital, the combination of a PCM and DTS soundtrack on the same DVD would reduce the maximum video bandwidth available by nearly 30%. The combination would also dramatically reduce the maximum running time possible on each disc. The extremely small bandwidth required by Dolby Digital allows the (relatively) bit-hungry DTS system to be a practical proposition on DVD.

DTS encoded DVDs retailed for approximately $35 US (MSRP) upon release, while Dolby Digital encoded DVDs generally retailed for between US $10 and $30, although both could be purchased on-line for considerably less. Most DTS DVDs released prior to January 2000 were, unlike their Dolby Digital counterparts, film-only versions. That is, without extensive production material, documentaries, directors' commentaries etc. (with the notable exception of Image's 'Dances With Wolves', which includes a running commentary). As a result, 'Collector's Edition' DVDs have generally been available only in Dolby Digital. However, this began to change in early 2000, when DTS encoded 'Collector's Edition' titles such as 'The Bone Collector' started to appear on the market, thanks largely to the introduction of 754kbps DTS.

Apart from its early inclusion of supplemental material, Image's 'Dances With Wolves' is unique in another respect: it is the only theatrical DTS DVD split over two discs, one RSDL (DVD-9) and one single-layered (DVD-5). In November 1999, DreamWorks released a DTS DVD edition of Steven Spielberg's 'Saving Private Ryan'. At 169 minutes, 'Saving Private Ryan' was one of the longest films presented on DTS DVD up to that time: only 12 minutes shorter than 'Dances With Wolves'. DreamWorks realised that using full 1509kbps DTS would force them to spread 'Saving Private Ryan' over two discs, as had been the case with 'Dances With Wolves'. Consumers accustomed to films presented on single discs generally pick the single disc version of a film when competing one- and two-disc versions of the same film are available (as Image learned with their two versions of 'Dances With Wolves'). DreamWorks were determined that both the Dolby Digital and DTS Digital Surround versions of 'Saving Private Ryan' would be presented on single discs. To accomplish this feat, DreamWorks released the DTS version of 'Saving Private Ryan' with a bitrate of only 754kbps, making it the first DTS DVD product to use a bitrate other than 1509kbps. Using 754kbps DTS, DreamWorks managed to shoehorn 'Saving Private Ryan' into a single RSDL disc, albeit without the 25 minute documentary included with the Dolby Digital version. It would be preferable from an audiophile perspective for 754kbps DTS's use to be restricted to longer duration films (i.e. over 160 minutes) that require 754kbps in order to be presented on a single disc. However, studios have found themselves unable to resist the practical advantages offered by 754kbps DTS, and this datarate is now the defacto standard for all DTS releases. Digital Theater Systems themselves have been unwilling to state that 754kbps DTS is "effectively transparent", a claim they make for 1509 and 1235kbps DTS, and an assertion based largely on their format's higher bitrates.

Regardless of which system (if any) becomes the domestic 5.1-channel format of choice, the future of Dolby Digital is secure. It has already been chosen as the audio standard for DSS, DTV, DVD and HDTV. DTS's future as a domestic format is less clear, however. Image Entertainment is currently pushing DTS on CD more aggressively than on DVD, and has essentially abandoned DTS on LaserDisc. Image, the producer of nearly all DTS LaserDiscs, has halted production of new DTS LaserDiscs, and shown little interest in re-pressing previously issued discs. This can be attributed to the general decline of the LaserDisc format, not to any specific failing of DTS Digital Surround.

Image and Universal experienced serious difficulties with DTS DVD, forcing them to delay the initial release of DTS encoded DVD titles four times in 1998. Both companies eventually released their first DTS DVDs in early 1999, nearly a year behind schedule. As of September 2001, fewer than 150 DTS encoded movie titles were available on Region One DVD compared with over 8000 Dolby Digital encoded DVDs (approximately 3,250 of which were recorded in Dolby Digital 5.0/5.1).

A significant barrier preventing DTS DVD's early widespread consumer acceptance, quite apart from the lack of software, was that no first-generation DVD players were capable of outputting DTS from DTS encoded DVDs. Second- and third-generation DTS-compatible DVD players have been widely available since early-'98.

DTS suffered a further setback when the first 'official' DTS DVD (i.e. the 48kHz version) was released by Digital Theater Systems in August 1998. The new 48kHz version of DTS turned out to be incompatible with some DTS decoders available at the time. Some decoders manufactured before mid-1998 had been designed to decode only the 1235kbps (44.1kHz) version of DTS, and were thus incapable of decoding 1509kbps (48 kHz) DTS. Decoders that didn't recognise the newer 48kHz version of DTS required internal re-chipping by the original manufacturer, often at the owner's expense.

Despite DTS's numerous setbacks, it cannot be counted-out as a viable format. It is unlikely it will ever become as commercially popular as Dolby Digital, but DTS may well survive as an 'audiophile' grade format for the immediate future, trading on the image of superior-quality audio. Up to this point DTS has relied on its reputation as the best sounding 5.1-channel system available in the home for its survival, while Dolby Laboratories, secure in their format's future have felt little need to dispute DTS's claims. However, following the DVD Forum's adoption of the Meridian Lossless Packing (MLP) system as the future DVD-Audio standard, DTS's claim to be the best sounding 5.1 system may be short-lived. The MLP system, as the name suggests, uses 'lossless compression' to allow, among other variations, true 24-bit PCM audio to be stored in the same space currently needed for conventional uncompressed 16-bit linear PCM: no perceptual coding of any kind is needed. The next-generation blue-laser (or higher wavelength) DVD system could well use the six-channel 24-bit 96kHz MLP configuration to provide ultra-high-fidelity uncompressed home theatre audio on blue-laser DVD-Video discs. MLP has been available in Meridian's range of processors since mid-'98, and DSP chips and DACs that support DVD-Audio started to appear on the market (e.g. Zoran's ZR38650, Cirrus Logic's Crystal CS49300, and Burr-Brown's PCM1737) in mid 1999. Consumer electronics products that support MLP/DVD-Audio began to trickle onto the market toward the end of 2000, and are now readily available. Six channel 24/96 MLP-compressed PCM audio requires around 9.2Mbps, easily within the capabilities of blue-laser DVD, but impossible for the current red-laser DVD-Video system. MLP will initially be used only for DVD-Audio.

The arrival of 6-channel DVD-Audio leaves DTS in a difficult position as neither the highest quality 5.1-channel audio system (MLP PCM) nor the most efficient (Dolby Digital). The long-term viability of the DTS system appears uncertain in the light of emerging technologies. DTS's low-compression and high-bandwidth may have sealed its fate, while Dolby Digital's extremely low bandwidth and high-compression has guaranteed its long-term viability.

Despite DTS Digital Surround's shaky introduction and uncertain future, I still believe it would be worth your while investing in a combination Dolby Digital/DTS Digital Surround amplifier/processor. Even though there are no compelling technical grounds for believing DTS is a better system, there are times when the DTS version of a soundtrack does sound considerably better than the Dolby Digital version. This can almost certainly be attributed to the way in which the DTS version has been mastered, although the DTS system itself cannot be discounted as a contributing factor. DTS titles often utilise higher quality masters and do not require alteration for optimised downmixing. These factors alone makes DTS worthy of serious consideration from an audiophile perspective.

In the end, any decision about which system(s) you choose to adopt must be based on your own individual preferences; your own two ears will always be the best judge when it comes to deciding which system sounds best to you. Likewise, your individual priorities (and wallet) will be a factor in determining which system offers you the most bang-for-the-buck (and what type of 'bang' you prefer).

Interested in learning the bitrate of your Region One DTS DVDs? Click here for the DVD bitrate list.
Click here for the Dolby Digital Surround EX and DTS-ES DVD list.