DTS-HD Master Audio (DTS-HD MA; known as DTS++ before 2004) is a multi-channel, lossless audio

codec A codec is a device or computer program that encodes or decodes a data stream or signal. ''Codec'' is a portmanteau of coder/decoder. In electronic communications, an endec is a device that acts as both an encoder and a decoder on a signal or ...

developed by DTS as an extension of the lossy DTS Coherent Acoustics codec (DTS CA; usually itself referred to as just DTS). Rather than being an entirely new coding mechanism, DTS-HD MA encodes an audio master in lossy DTS first, then stores a concurrent stream of supplementary data representing whatever the DTS encoder discarded. This gives DTS-HD MA a lossy "core" able to be played back by devices that cannot decode the more complex lossless audio. DTS-HD MA's primary application is audio storage and playback for Blu-ray Disc media; it competes in this respect with

Dolby TrueHD Dolby TrueHD is a lossless, multi-channel audio codec developed by Dolby Laboratories for home video, used principally in Blu-ray Disc and compatible hardware. Dolby TrueHD, along with Dolby Digital Plus (E-AC-3) and Dolby AC-4, is one of th ...

, another lossless surround format. DTS-HD MA has enjoyed the greater share of this market since 2010, with the notable exception of the TrueHD-encoded

Dolby Atmos Dolby Atmos is a surround sound technology developed by Dolby Laboratories. It expands on existing surround sound systems by adding height channels, allowing sounds to be interpreted as three-dimensional objects with neither horizontal, nor vert ...

spatial surround format, which is more popular than DTS's competing DTS:X (encoded with DTS-HD MA).

Specifications

DTS-HD MA can store up to 8 discrete channels of audio ( 7.1 surround) at up to a 24 bit sample depth and 192 kHz sampling frequency (96 kHz for 6.1 or 7.1 surround). Although DTS-HD MA, and the related DTS-HD, allow virtually any number of channels in the abstract, these limits are imposed for practical reasons of limited storage and bitrate availability. A DTS-HD MA bitstream may have a bitrate no greater than 24.5 Mbit/s (instantaneous), of which no greater than 1.5 Mbit/s may be lossy DTS (as per the DTS CA specification). The

Blu-ray The Blu-ray Disc (BD), often known simply as Blu-ray, is a digital optical disc data storage format. It was invented and developed in 2005 and released on June 20, 2006 worldwide. It is designed to supersede the DVD format, and capable of s ...

specification stipulates DTS-HD MA as an optional codec, which means that some Blu-ray hardware may not decode it. This is the reason for the bifurcated nature of a DTS-HD MA audio stream; DTS CA, unlike its MA extension, is mandatory, so a player that is not MA-capable can automatically default to an MA-encoded disc's base DTS stream and simply ignore the supplementary data. Alternatively, even if a player is MA-capable, the base stream may be needed for

backward compatibility Backward compatibility (sometimes known as backwards compatibility) is a property of an operating system, product, or technology that allows for interoperability with an older legacy system, or with input designed for such a system, especially ...

with an older AV receiver (for example, one manufactured during the DVD era). DTS-HD MA is the encoding format for DTS:X, an object-based surround-sound format that competes with

. A DTS-HD MA bitstream carrying DTS:X can contain up to 9 simultaneous sound objects, which are dynamically mapped to a user's speaker system during playback, unlike the rigid number and placement of speakers required by channel-based surround (a DTS marketing executive referred to DTS:X in an interview as "whatever.1").

Encoding process

DTS-HD MA is encoded in three steps. First, the audio master is fed to a DTS CA encoder, which generates the core (lossy) audio stream. Next, this lossy audio is decoded and compared to the master, with "residual" data being recorded wherever the two differ. Finally, the residual data is compressed losslessly and merged with the core into one bitstream. A DTS-HD MA decoder simply performs this process in reverse. DTS-HD MA audio, including DTS:X audio, can be created and edited using DTS'
DTS:X Encoder Suite
The DTS-HD Master Audio Suite served the same function before the introduction of DTS:X, and can still be used for DTS-HD MA that does not carry DTS:X.

AV transport

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

5.1 5.1 surround sound ("five-point one") is the common name for surround sound audio systems. 5.1 is the most commonly used layout in home theatres. It uses five full bandwidth channels and one low-frequency effects channel (the "point one"). Dol ...

, 6.1, or 7.1 channels, in full quality, in one of three ways depending on player and/or receiver support: *Over 6, 7 or 8 RCA connectors as analog audio, using the player's internal decoder and

digital-to-analog converter In electronics, a digital-to-analog converter (DAC, D/A, D2A, or D-to-A) is a system that converts a digital signal into an analog signal. An analog-to-digital converter (ADC) performs the reverse function. There are several DAC archi ...

(DAC). *Over

HDMI High-Definition Multimedia Interface (HDMI) is a proprietary audio/video interface for transmitting uncompressed video data and compressed or uncompressed digital audio data from an HDMI-compliant source device, such as a display controll ...

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. (This is the transport mode required for DTS:X playback.) S/PDIF does not have the bandwidth to carry DTS-HD MA (or PCM in more than 2 channels). A setup using S/PDIF audio may output DTS-HD MA as either lossy DTS (which S/PDIF can carry) or downmixed stereo PCM.

References

{{Compression Software Implementations Blu-ray Disc HD DVD Lossless audio codecs Surround sound