Dolby TrueHD Lossless Audio

The ultimate high-definition audio experience

Developed for high-definition (HD) audio entertainment, Dolby® TrueHD is a 100 percent lossless technology that brings studio-master audio quality to the home entertainment experience. Dolby TrueHD unlocks the full potential of Blu-ray Disc™ and future HD (streamed and downloadable) media.

Hear exactly what the recording engineers hear

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Dolby TrueHD offers playback that’s as close as it gets to the sound captured at a live concert. Its powerful sound is bit-for-bit identical to what is created in the recording studio or mixing stage.

Dolby TrueHD brings a spacious soundstage, highly accurate effects, and unsurpassed dynamic range to home theaters, delivering a compelling “you are there” surround sound experience.

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    Studio-Master Quality

    100 percent lossless, bit-for-bit identical to the original studio recording.

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    Better Stereo Sound

    Capability to support an independent two-channel “artist’s mix” in a single bitstream.

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    Conserves Disc Space

    4:1 compression efficiency to maximize disc space, minimize bandwidth.

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    Faithful to Artistic Intent

    Viewers hear soundtracks exactly as the program producers intended.

Dolby TrueHD Offers Product Differentiation and Ultimate Audio Quality

With Dolby TrueHD’s 100 percent lossless audio coding technology, equipment manufacturers and content producers can now stand out from the competition by delivering studio-quality surround sound that is identical to the original recording.

For playback through a home theater system, Dolby TrueHD is transported via HDMI® (High Definition Multimedia Interface) version 1.3 or later, a single-cable digital connection for audio and video. Dolby TrueHD content may also be introduced to a playback system via Ethernet or USB connections.

The power of metadata

The powerful Dolby metadata parameters give content creators comprehensive control over how their artistry will be heard in the home.

Dialogue normalization (dialnorm) maintains consistent volume levels when switching between Dolby TrueHD and Dolby Digital or Dolby Digital Plus programming.

Dynamic range control enables reduced peak volume levels without impacting overall sound quality. It’s ideal for late-night viewing.

Downmixing allows the content creator to enable stereo playback from the original multichannel source or to provide an independent stereo “artist’s mix” that is incorporated into the Dolby TrueHD bitstream.

Three presentations, one bitstream

A single Dolby TrueHD stream can contain up to three separate mixes (presentations): a 7.1-channel surround mix, a 5.1-channel surround mix, and a two-channel “artist’s” stereo mix. This gives content creators the ability to tailor each mix for optimum listening on any playback system.

Advanced 96k upsampling

Movie soundtracks and TV shows are often recorded using a 48 kHz (48k)  sampling frequency. The brickwall filters required for 48k analog-to-digital (A-to-D) conversion in the recording process introduce artifacts called preringing, heard as an unnatural hardness or edginess.

To deliver clearer, more natural playback sound from this content, Dolby TrueHD encoding now includes a proven 96 kHz (96k) upsampling process developed by Meridian Audio. It significantly improves the sound from a Blu-ray Disc in any channel configuration.

The process applies higher sample rates and increased playback quality through an advanced apodizing filter that masks undesirable digital artifacts in 48k material. The upsampling takes place before Dolby TrueHD encoding.

By applying the upsampling in software, Dolby TrueHD creates content that’s compatible with all Blu-ray™ players and all A/V receivers with 96k digital-to-analog converters (DACs). It does not add any computing burden in playback. Although the upsampling increases file size and data rates, the optional Dolby Mapping (noise-shaping) feature, specifically designed for Dolby TrueHD, minimizes or eliminates these increases.

Content producers can employ the upsampling feature at their discretion. The process is designed to improve 48k audio files and is not needed for native 96k material.

Ready for the future

Dolby TrueHD can deliver up to 16 channels of pristine audio, so it is ready for any future HD streamed formats. On Blu-ray Disc today, it delivers up to eight full-range channels of 24-bit/96 kHz audio and supports up to 24-bit/192 kHz for stereo and 5.1 content.

Technology Details

Leverages interchannel correlations to reduce data rates for lossless matrixing and more efficient downmixing

Employs decorrelation to take advantage of the predictive nature of audio

Allows fewer bits to be assigned for commonly occurring values within the data stream for a more efficient coding process using Huffman (entropy) coding

Smooths the encoded data rate with managed FIFO buffering throughout transmission

Technology Specifications

Sampling frequency: 44.1 kHz to 192 kHz

Sampling rate: Variable bit rate; CBR rendering for transport over HDMI

Word length: Up to 24 bits

Blu-ray Disc channel support: Up to eight channels of 24-bit/96 kHz audio; designed to be expandable should the Blu-ray Disc standard adopt additional channels

Two- to six-channel support: Up to 24-bit/192 kHz

Maximum bit rate: Up to 18 Mbps on Blu-ray Disc

White Papers

Dolby TrueHD Encoder with Advanced 96k Upsampling
Dolby TrueHD upsamples 48 kHz (48k) PCM content to 96 kHz (96k) using Meridian’s world-class upsampling algorithm. Content created with this feature is fully playback compatible on all Blu-ray devices.

Elevating the Performance of Lossless Audio in the Home Theater
Discover why Dolby TrueHD with advanced 96k upsampling is an uncompromised, studio-grade algorithm likely to perform even better than DSP upsamplers in consumer products.

Technical Paper

Dolby Audio Coding for Future Entertainment Formats
The high compression efficiencies of Dolby TrueHD and Dolby Digital Plus permit the incorporation of separate lossy and lossless soundtracks, with no resulting penalty in disc space.