DTS Coherent Acoustics 3036976 223906636 2008-07-06T13:09:05Z SmackBot 433328 Date the maintenance tags or general fixes {{Merge|Digital Theater System|date=July 2008}} '''DTS Coherent Acoustics''' is the full name for the audio format standard usually known as just [[Digital Theater System|DTS]]. It is covered in {{US patent|5956674}}. ==Overview== DTS can transport audio up to 8 audio channels at up to a 192kHz [[sampling rate]]. It can be transported over [[S/PDIF]], or can be encapsulated in wave files, [[DVD]]s and stored on [[Compact Disc Digital Audio|CDDA]]s. DTS [[codec]]s exist for desktop computers as well as being embedded into many [[home cinema]] AV receivers. The format offers variable compression ratios, targeting a wide variety of bit rates, although the most often used compression ratio for DVD and cinema audio is about 1:4, resulting in a fairly high [[bitrate]]. DTS also includes several low-bitrate [[hack]]s, such as [[joint (audio engineering)|joint frequency encoding]], that are generally frowned upon in this context, and should not be encountered on high quality DTS source material. The base specification allows for 5.1 channels of audio with a 48kHz [[sampling rate]]. Further specification extensions allow for an additional 2 channels and/or additional high frequency data to be transmitted. It encodes audio by splitting it into 32 subbands, each with a [[Bandwidth (signal processing)|bandwidth]] of 750 [[Hertz|Hz]], which are then encoded using [[ADPCM]]. There are 4 ADPCM [[coefficient]]s, which are processed with [[vector quantization]] for transmission (there is a 4,096-entry codebook). The residual (prediction error) is quantized either linearly (using a variable number of bits), or using VQ, depending on the bit allocation to the subband - a global bit allocation scheme allocates bits to each subband. Data bits may also be [[entropy encoding|entropy encoded]]. Due to fewer calculations involved in higher bitrates, DTS encoding is particularly fast and CPU-easy compared to [[Dolby Digital]]. Real-time DTS encoding is also inherently low-latency compared to the 130ms of Dolby Digital, making it much more suitable for interactive (real-time) applications, such as video games. Several Playstation 2 games have offered DTS 5.1 surround output, in addition to stereo Pro-logic encoded PCM. DTS 5.1 output is also offered on several models of [[HD DVD]] players, where the player converts an original soundtrack (of Dolby Digital +, Dolby True-HD, or multi-channel LPCM) into a DTS 5.1 bitstream. Theatrical DTS uses a different codec, called APT-X 100.<ref name=tozer>{{cite book|first=Edwin Paul J.|last=Tozer|year=2004|isbn=0240519086|title=Broadcast Engineer's Reference Book|publisher=Focal Press| url=http://www.google.com/url?sa=t&ct=res&cd=1&url=http%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DDL73f4vFeEwC%26pg%3DPA152%26lpg%3DPA152%26dq%3DDTS%2BAPT-X%2B100%26source%3Dweb%26ots%3D9-bmApJqRm%26sig%3DwICsUo4QulHNYu-aJJD3VGqcI4Q%26hl%3Den&ei=ZlnjR_KcK4LSgQSH6vi_Bw&usg=AFQjCNE5U39Cg0IFsx0E_h-C3h7F4S5LvQ&sig2=8-C0IgZ4kRZqtukxmKD74A}}</ref> Home-theater receivers cannot be used with theatrical DTS programming, and vice versa. The DTS Coherent Acoustics standard (ETSI 102 114 v1.2.1) is published by the [[ETSI]].<ref>[http://pda.etsi.org/pda/queryform.asp ETSI Publications Download Area, search for DTS Coherent Acoustics]</ref> This standard specifies an algorithm for the decoder. Also, a white paper is available from DTS Inc.<ref>[http://www.dts.com/media/2007/support/pro-audio/products/TechnicalDocumentation/DTS_Coherent_Acoustics_White_Paper.pdf DTS Coherent Acoustics White Paper]</ref> This white paper puts more accent on encoding the stream. ==DTS in cinemas== DTS is used on film prints, where it competes with the Dolby Digital (AC-3) and SDDS standards.<ref name=dtsguide>[http://www.film-tech.com/warehouse/manuals/DTSPOSTPROD.pdf DTS Postproduction Guide]</ref> It is used less often than Dolby Digital. Dolby Digital and SDDS tracks are printed onto the physical film medium, as their bit-rates allows them to fit in limited space. A DTS track, however, has a higher bitrate and therefore cannot be printed onto the film. Instead, a timecode is printed onto the film and the DTS soundtrack shipped to the cinema as a pair of CDs in addition to the film reels.<ref name=dtsguide/> When the film is projected, the timecode is read from the film and the equivalent sound comes from the DTS CD-decoding equipment.<ref name=dtsguide/> It is argued that in a cinema environment DTS produces higher-fidelity sound than DD encoded film, and greater robustness in the event of damaged film, but the extra complication of using CDs is less convenient for the projectionist and they are more likely to be missing or damaged. ==References== {{reflist}} ==See also== * [[Digital Theater System]] * [[libdca]] {{Compression Software Implementations}} [[Category:Audio codecs]] [[ru:DTS]]