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DTS Coherent Acoustics is the full name for the audio format standard usually known as just DTS. It is covered in U.S. Patent 5,956,674 .

Contents 1 Overview 2 DTS in Cinemas (Film) 3 Open source decoder 4 See also

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, DVDs and stored on CDDAs. DTS codecs 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 hacks, such as 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 of 750 Hz, which are then encoded using ADPCM. There are 4 ADPCM coefficients, 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 encoded.

Due to less 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 real-time applications, such as games. There is a real-time DTS encoder for PlayStation 2.

The DTS Coherent Acoustics standard (ETSI 102 114 v1.2.1), is published by the ETSI and available at[1] (look for DTS Coherent Acoustics).

DTS is used in film prints, where it competes with the Dolby AC3 and SDDS standards. It is used less often than the competing formats because it is more complicated. Dolby Digital (AC-3) tracks are printed onto the physical film medium, as the low bit-rate allows it to be 'squeezed' in. 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 in addition to the various reels as a set of CD's. When the film is projected, the timecode is read from the film and the equivalent sound comes from a DTS CD rack.

It is argued that in a cinema environment DTS produces higher-fidelity sound than DD encoded film, but the extra complication of using multiple CD's shipped separately is less convenient for the projectionist and is more likely to be stolen/damaged.

An open source DTS decoder called libdca is part of the VideoLAN project, but it was temporarily withdrawn from official public distribution because of DTS patent infringement claims.

• Home cinema
• Codec
• AC3
• libdca