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DTS-HD Master Audio (DTS-HD MA; known asDTS++ before 2004[1]) is amulti-channel,lossless audiocodec developed byDTS as an extension of thelossyDTS 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 forBlu-ray media; it competes in this respect withDolby TrueHD, another lossless surround format.
DTS-HD MA can store up to 8 discrete channels of audio (7.1 surround) at up to a 24 bitsample depth and 192 kHzsampling frequency (96 kHz for 6.1 or 7.1 surround).[2] Although DTS-HD MA, and the related DTS-HD, allow virtually any number of channels in the abstract,[3] these limits are imposed for practical reasons of limited storage andbitrate 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).[4]
TheBlu-ray 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.[4] Alternatively, even if a player is MA-capable, the base stream may be needed forbackward compatibility with an olderAV receiver (for example, one manufactured during theDVD era).[5]
DTS-HD MA is the encoding format forDTS:X, anobject-based surround-sound format that competes withDolby Atmos. 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").[6]
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.[7]
DTS-HD MA audio, including DTS:X audio, can be created and edited using DTS'sDTS: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.[8]
DTS-HD Master Audio may be transported toAV receivers in5.1, 6.1, or7.1 channels, in full quality, in one of three ways depending on player and/or receiver support:[7]
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 downmixedstereo PCM.
DTS-HD can natively support over 2,000 individual channels, so according to DTS adding any number of discrete height channels would be easy.
DTS-HD Master Audio delivers sound that is bit-for-bit identical to the studio master. It can deliver audio at variable bit rates which are significantly higher than standard DVDs. DTS-HD Master Audio can provide up to 7.1 audio channels at a 96k sampling frequency / 24-bit depth or 5.1 audio channels at 192 kHz that are identical to the original master. The DTS-HD Master Audio bit stream also contains the DTS 1.5 Mbps core for backwards compatibility with existing DTS-enabled home theater systems, and delivery of 5.1 channels of sound at twice the resolution found on most standard DVDs.