DTS-HD Master Audio is a lossless

Lossless data compression

Lossless data compression is a class of data compression algorithms that allows the exact original data to be reconstructed from the compressed data. The term lossless is in contrast to lossy data compression, which only allows an approximation of the original data to be reconstructed, in exchange...

 audio codec

Codec

A codec is a device or computer program capable of encoding or decoding a digital data stream or signal. The word codec is a portmanteau of "compressor-decompressor" or, more commonly, "coder-decoder"...

 created by Digital Theater System

Digital Theater System

DTS is a series of multichannel audio technologies owned by DTS, Inc. , an American company specializing in digital surround sound formats used for both commercial/theatrical and consumer grade applications...

. It was previously known as DTS++. It is an extension of DTS which, when played back on devices which do not support the Master Audio or High Resolution extension, degrades to a "core" track which is lossy. DTS-HD Master Audio is an optional audio format for Blu-ray Disc

Blu-ray Disc

Blu-ray Disc is an optical disc storage medium designed to supersede the DVD format. The plastic disc is 120 mm in diameter and 1.2 mm thick, the same size as DVDs and CDs. Blu-ray Discs contain 25 GB per layer, with dual layer discs being the norm for feature-length video discs...

 format exclusively. DTS-HD Master Audio has been steadily becoming the standard for Blu-ray lossless audio format.

One goal of the DTS-HD Master Audio format was to allow a bit-to-bit representation of the original movie's studio master soundtrack. To accomplish this, DTS-HD MA supports variable bit rates up to 24.5 Mbit/s on a Blu-ray Disc and up to 18.0 Mbit/s for HD DVD. The format supports a maximum of 192 kHz sampling frequency and 24-bit depth samples in 2 channels stereo mode, and 96 kHz/24bit resolution in multichannel mode with up to 8 channels.

DTS-HD is capable of virtually any number of discrete channels (over 2000) but is limited by storage media.

According to DTS-HD White Paper, the DTS-HD Master Audio contains 2 data streams: the original DTS core stream and the additional "residual" stream which contains the "difference" between the original signal and the lossy compression DTS core stream. The audio signal is split into two paths at the input to the encoder. One path goes to the core encoder for backwards compatibility and is then decoded. The other path compares the original audio to the decoded core signal and generates residuals, which are data over and above what the core contains that is needed to restore the original audio as bit-for-bit identical to the original. The residual data is then encoded by a lossless encoder and packed together with the core. The decoding process is simply the reverse. Note that DTS-HD lossless audio coding is always variable bit rate.

DTS-HD Master Audio may be transported to AV receivers in 5.1

5.1 surround sound

5.1 is the common name for six channel surround sound multichannel audio systems. 5.1 is now the most commonly used layout in both commercial cinemas and home theaters. It uses five full bandwidth channels and one low frequency enhancement channel . Dolby Digital, Dolby Pro Logic II, DTS, and...

, 6.1 or 7.1 channels, at lossless quality, in one of three ways depending on player and/or receiver support:

• Over 6, 7 or 8 RCA connector
  RCA connector
  An RCA connector, sometimes called a phono connector or cinch connector, is a type of electrical connector commonly used to carry audio and video signals...
  
  s as analog audio, using the player's internal decoder and digital-to-analog converter
  Digital-to-analog converter
  In electronics, a digital-to-analog converter is a device that converts a digital code to an analog signal . An analog-to-digital converter performs the reverse operation...
  
   (DAC).
• Over HDMI
  HDMI
  HDMI is a compact audio/video interface for transmitting uncompressed digital data. It is a digital alternative to consumer analog standards, such as radio frequency coaxial cable, composite video, S-Video, SCART, component video, D-Terminal, or VGA...
  
   1.1 (or higher) connections as 6-, 7- or 8-channel linear PCM, using the player's decoder and the AV receiver's DAC.
• Over HDMI 1.3 (or higher) connections as the original DTS-HD Master Audio bitstream, with decoding and DAC both done by the AV receiver.