DTS-HD

DTS-HD is a family of audio codecs, primarily used in Blu-ray and HD-DVD – optionally, competing with the Dolby codecs family. It is an extension of the older DTS Coherent Acoustics cocec found in DVDs, and maintain compatibility with devices that only support those.

• DTS-HD Master Audio, previously known as DTS++, provides for lossless audio. It is a hybrid lossless/lossy codec with a "core" DTS CA stream, for devices only supporting that format, and a correction stream called XLL. DTS-HD devices will decode both to reconstruct the signal losslessly. In Blu-ray it supports streams up to 192/24 at 5.1 surround, and up to 96/24 at 7.1 surround.

• DTS-HD High Resolution works a similar way with an extension stream, but is a lossy codec working at 6 kbit/s or 3 kbit/s constant bit rates (for use when disc space is a constraint). For example, the core stream can be 5.1 at 48 kHz sampling rate, and the extension stream can contain the additional two channels – and even doubling the sampling rate for the extra (inaudible!) ultrasonic octave.

The above description is incomplete. In particular, the DTS-HD codec suite offers configurations not found in Blu-ray, like sacrificing backwards compatibility to operate without core stream (XLL then becomes an ordinary lossless audio codec) – that includes a Low Bitrate codec / coding profile that can encode 5.1 surround down to 192 kHz sampling rate, intended for streaming purposes when bandwidth is constrained.

Open source DTS-HD decoders are available through FFmpeg and libdca (used by VideoLAN/VLC). The Matroska container format supports DTS-HD.

For additional information: Wikipedia or the Multimedia Wiki entry.

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