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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 US Patent #5,956,674.
DTS transports up to 8 audio channels at up to a 192kHz sampling rate. DTS itself can be transported over SPDIF, 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.
DTS offers variable compression ratios targetting a wide variety of bit rates.
DTS has a base specification which allows for 5.1 channels of audio with a 48kHz sampling rate. An extended specification allows an additional 2 channels and/or additional high_frequency data to be transmitted. A full DTS system can receive 8 channels at 192kHz sampling rate.
The base specification encodes audio by splitting it into 32 subbands each with bandwidth 750Hz. Each subband is then encoded using ADPCM. There are 4 ADPCM coefficients and these are vector_quantized 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. DTS also allows these data bits to be entropy coded.
A global bit allocation scheme allocates bits to each subband of each discrete audio input channel.
DTS includes other low_bit_rate hacks such as joint frequency encoding which should not be encountered on high_quality DTS source material.
To place 5.1 or 7.1 audio onto a channel designed for 2_channel audio requires a compression ratio of about 1:4. This is the compression ratio most often used for DVD and cinema audio.
DTS encoding is particularly fast when compared to Dolby Digital, especially if a restricted HBR profile is used. Real_time DTS encoding is also inherently low_latency compared to the 130ms of Dolby Digital, making it much more suitable for games. There is a real_time DTS encoder for PlayStation 2.
An Open Source DTS decoder called libdts (http://www.videolan.org/dtsdec.html) is part of the VideoLAN project.
The DTS Coherent Acoustics standard (ETSI 102 114 v1.2.1), is published by the ETSI and available here (http://pda.etsi.org/pda/queryform.asp) (look for DTS Coherent Acoustics).
See also:
APTX100 is a trademark of Audio Processing Technology (APT).
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