DTS (formerly known as Digital Theater Systems) is a multi-channel surround sound format used for both commercial/theatrical and consumer grade applications (with significant technical differences between home and commercial/theatrical variants: the latter being a traditional ADPCM compression system and the former a sophisticated hybrid perceptual and signal-redundancy compressor).
It is used for in-movie sound both on film and on DVD, and during the last few years of the format's existence, several Laserdisc releases had DTS soundtracks. The company which created it, Digital Theater Systems, is now referred to simply as DTS. One of the company's initial investors was film director Steven Spielberg, who felt that theatrical sound formats up until the company's founding were no longer state of the art, and as a result were no longer optimal for use on projects where quality sound reproduction was of the utmost importance.
Work on the format started in 1991, four years after Dolby Labs started work on their new codec, Dolby Digital. The basic and most common version of the format is a 5.1 channel system, supporting five primary speakers and a subwoofer, referred to as an LFE (Low Frequency Effects) channel. Note however that encoders and decoders support numerous channel combinations and stereo, four-channel and four-channel+LFE soundtracks have been released commercially on DVD, CD and LaserDisc.
Other newer DTS variants are also currently available, including versions that support up to 7 primary audio channels (DTS-ES). DTS's main competitors in multichannel theatrical audio are Dolby Digital and SDDS, although only Dolby Digital and DTS are used on DVDs and implemented in home theater hardware. Spielberg debuted the format with his 1993 production of Jurassic Park, which came slightly less than a full year after the 'official' theatrical debut of Dolby Digital ('Batman Returns'). In addition, Jurassic Park also became the first home video release to contain DTS sound when it was released on Laserdisc in January 1997, two years after the first Dolby Digital home video release ('Clear and Present Danger' on LaserDisc) which debuted in January 1995.
In theatrical use, information in the form of a modified time code is optically imaged onto the film, a DTS processor in the projection booth uses this timecode to synchronize the projected image with the soundtrack audio, which is recorded in compressed form on standard CD-ROM media at 1.5 Mbit/s. The processor also acts as a transport mechanism, it holds and reads the audio discs. The units can generally hold 3 discs, allowing a single processor/transport to handle 2-disc film soundtracks along with a 3rd disc containing sound for theatrical trailers. In addition, specific elements of the imprinted timecode allow identifying data to be embedded within the code, ensuring that a certain film's soundtrack will only run with that film.
One of the main advantages of DTS is that it has a much higher bitrate than an equivalent Dolby sound track. DTS uses 768-1536 kbps, while Dolby only uses 192-448 kbps. This extra bandwidth translates into higher fidelity and dynamic range, making DTS sound richer and more life-like. With good speakers or professional headphones, the quality gain from DTS tends to be readily apparent on every DVD that offers it.