DTS

DTS is the brand name for a set of digital audio technologies developed by DTS, Inc. In consumer-grade discs and media materials, “DTS” when used on its own typically refers to DTS Digital Surround, a lossy multichannel encoding format based on DTS Coherent Acoustics. It belongs to the same family of technologies as the later-developed DTS-ES, DTS 96/24, DTS-HD Master Audio, and DTS:X; however, these extended formats have different bitstream structures and decoding capabilities and cannot be used interchangeably simply by referring to them as “DTS.”

DTS was originally used for movie theater screenings. *Jurassic Park*, released in 1993, was the first commercial film to use this system; the theatrical version stored the multichannel digital audio on a CD-ROM that played in sync with the film, while timecode was recorded on the edge of the 35mm film, allowing the projection equipment to maintain synchronization between the audio and video. The film itself could still retain an analog optical soundtrack as a backup in case the DTS decoding system was not installed or the digital playback failed.

DTS Coherent Acoustics, used for DVDs and other consumer media, employs a different method of program delivery than the early cinema systems. Audio data is written directly to the disc or media file, eliminating the need for an external CD-ROM. The base bitstream typically includes five full-range channels—left, right, center, left surround, and right surround—as well as a low-frequency effects channel, constituting a 5.1-channel program; The standard also allows for mono, stereo, and other channel configurations.

Coherent Acoustics uses lossy compression. The encoder decomposes the audio into multiple frequency bands, assigns quantization precision based on instantaneous signal characteristics and auditory models, and then performs entropy encoding on the result. The PCM data obtained from decoding is not bit-for-bit identical to the original. The sampling rate, source signal bit depth, and bit rate are independent parameters; a 24-bit designation in the audio stream does not mean that the lossy compression process preserves data that is exactly the same as 24-bit LPCM. DTS 5.1 audio tracks on standard DVDs typically use bitrates of approximately 754.5 kbit/s or 1,509.75 kbit/s, which are usually approximated in user interfaces as 768 kbit/s and 1.5 Mbit/s. The latter is also known as full-bitrate DTS. Both bitrates belong to the same basic encoding scheme, and the specific value cannot be determined solely by the DTS label; program length, disc capacity, and mastering choices all affect the actual bitrate used.

DTS’s core-plus-extension architecture provides a foundation for compatibility with subsequent specifications. Traditional decoders read the core stream, while advanced decoders can also utilize the extended data. DTS-ES can add rear surround information; DTS 96/24 can carry 96 kHz, 24-bit extended information in addition to the compatible core; and DTS-HD further adds more channels, higher bit rates, or lossless extensions. Devices that cannot recognize the extensions can usually still play the DTS core, but the output is limited to the channels and precision contained within the core.

On DVD-Video, DTS is typically an optional audio format. DVD-Video playback requirements vary by region, and commercial discs often include Dolby Digital, LPCM, or other basic audio tracks to ensure playback on devices without a DTS decoder. Blu-ray players, however, include basic DTS decoding as part of their mandated playback capabilities, and the DTS core is also used for backward compatibility with some DTS-HD audio streams.

DTS audio streams can be transmitted as compressed bitstreams via optical or coaxial S/PDIF, or they can be decoded by the playback device into PCM before being output via HDMI, analog interfaces, or other digital paths. The bandwidth of S/PDIF is typically sufficient to transmit basic DTS but cannot carry the full DTS-HD Master Audio; when playing high-specification extensions, whether the actual output is basic DTS, decoded multichannel PCM, or the full high-definition bitstream depends on the combined capabilities of the disc, player, interface, and receiving device.

DTS audio in media files can be encapsulated in containers such as MPEG program streams, MPEG-2 transport streams, and Matroska. The container file extension does not determine the internal encoding, and the fact that a file is identified as DTS is not sufficient to indicate that it is 5.1-channel, full-bitrate, or includes the DTS-ES extension. To accurately describe a DTS audio track, one must specify the channel layout, sampling rate, bit rate, and any detectable extensions.