Sustainability of Digital Formats: Planning for Library of Congress Collections

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Digital Theater Systems Audio Formats

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Format Description Properties Explanation of format description terms

Identification and description Explanation of format description terms

Full name Digital Theater Systems (DTS)

A family of lossy formats designed for the efficient encoding of surround sound, originally developed to support motion picture presentations in theaters. This Web page provides general, introductory information about the whole family. Additional information will be added if the Library of Congress begins to acquire file-form examples (i.e., not DVDs) of content in one or more DTS formats.

DTS compression algorithms do not employ perceptual encoding and have relatively high data rates, e.g., 882 kb/s (4:1 compression) for the theatrical variant, sometimes referred to as apt-X100. In the theater, the sound is played from DVD-ROM disk media and synchronized with the picture by means of a special track printed on the film. A different algorithm called Coherent Acoustics is used to compress sound when DTS is delivered in home systems. In recent years this delivery has been accomplished via DVD disks that may contain either video-with-sound or audio only. See Notes for more information on encoding. Presentational variants include six channel sound as DTS NEO:X; encodings that embrace 96 kHz/24 bit LPCM as a source, called DTS 96 KHZ/24 BIT; DTS Extended Surround; DTS HD "high definition audio discs," and possibly others. DTS promotional literature mentions 8- and 10-track options.

Production phase Generally used for final-state, end-user delivery.
Relationship to other formats
    Used by MPEG-2 Multiplex for DVD may use DTS Elementary Stream, not documented at this time

Local use Explanation of format description terms

LC experience or existing holdings None
LC preference  

Sustainability factors Explanation of format description terms

Disclosure Technical papers available; there appear to be more for the Coherent Acoustics home-application codec than for the apt-X100 system for theaters. Specifications developed by DTS, Inc.
    Documentation has the following paper about DTS: White Paper: An Overview of the Coherent Acoustics Coding System (1999). Comments welcome.
Adoption Widespread adoption in theater and for DVD disks. Extent of adoption of files as self-standing and disseminated entities is unknown, although files with dts extensions may be downloaded from Web sites; these apparently require a player with DTS decoding capabilities, e.g., a DVD player (hardware or software).
    Licensing and patents In 2011, licensing appears to be managed by DTS Inc.
Self-documentation Not investigated at this time.
External dependencies Surround sound requires appropriate player, amplifier, and loudspeakers or headphone.
Technical protection considerations Not investigated at this time.

Quality and functionality factors Explanation of format description terms

Normal rendering Good support.
Fidelity (high audio resolution) Very good to excellent, given that this is a format for compression. Several commentators note the existence of a running debate over which is better for surround sound in theaters (including home theaters): DTS or AC-3_A (Dolby Digital).
Multiple channels DTS variants supports surround sound, including 7.1 (DTS HD).
Support for user-defined sounds, samples, and patches Not investigated at this time.
Functionality beyond normal rendering Synchronizes with moving images. The DTS-CSS Cinema Subtitling System provides captioned and/or spoken information for deaf, hard-of-hearing, blind and visually impaired audiences, and may also be used for alternate-language subtitles.

File type signifiers and format identifiers Explanation of format description terms

Tag Value Note
Filename extension dts
From the The File Extension Source.
Internet Media Type Not found.  Comments welcome.   
Pronom PUID See note.  See for description of DTS Coherent Acoustics (DCA) Audio, a subtype of the DTS family.
Wikidata Title ID See note.  No relevant match as of April 2017.

Notes Explanation of format description terms

General From DTS: Brief History and Technical Overview : "In the DTS theatrical system, apt-X100 achieves its 4:1 reduction by using subband coding with linear prediction and adaptive quantization, which identify and remove redundancy and pack the data efficiently." Regarding the home systems, "Coherent Acoustics uses more subbands (32) than apt-X100 (4). Again, linear prediction and adaptive quantization (ADPCM) are used. The effectiveness of prediction is signal-dependent, and in each subband, if the prediction process does not offer a coding gain, it is disabled. At low bit rates, masking thresholds are calculated and bits are allocated in accordance with the psychoacoustic model. Finally, variable-length coding is used: the code words generated by the ADPCM are mapped to another set of words such that the most frequently occurring are given the most compact codes, and so on." (p. 3)

Format specifications Explanation of format description terms

Useful references


Last Updated: 08/04/2021