Dolby TrueHD

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Dolby TrueHD logo as introduced in 2012. Dolby TrueHD.svg
Dolby TrueHD logo as introduced in 2012.
Dolby TrueHd
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.thd

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 the intended successors to the Dolby Digital (AC-3) lossy surround format. Dolby TrueHD competes with DTS's DTS-HD Master Audio (DTS-HD MA), another lossless surround sound codec.

Contents

The Dolby TrueHD specification provides for up to 16 discrete audio channels, each with a sampling rate of up to 192 kHz and sample depth of up to 24 bits. Dolby's compression mechanism for TrueHD is Meridian Lossless Packing (MLP); prior to Dolby TrueHD, MLP was used for the DVD-Audio format, although the two formats' respective implementations of MLP are not mutually compatible. A Dolby TrueHD audio stream varies in bitrate, as does any other losslessly compressed audio format.

Like its predecessor, Dolby TrueHD's bitstream carries program metadata, or non-audio information that a decoder uses to modify its interpretation of the audio data. Dolby TrueHD metadata may include, for example, audio normalization or dynamic range compression. In addition, Dolby Atmos, a multi-dimensional surround format encoded using Dolby TrueHD, can embed more advanced metadata to spatially place sound objects in an Atmos-compatible speaker system.

Blu-ray Disc

In the Blu-ray Disc specification, Dolby TrueHD tracks may carry up to 8 discrete audio channels (7.1 surround) of 24-bit audio at 96 kHz, or up to 6 channels (5.1 surround) at 192 kHz. [1] The maximum bitrate of an audio stream including metadata is 18 Mbit/s (instantaneous, since it is variable bitrate), [2] and a TrueHD frame is either 1/1200 seconds long (for 48000 Hz, 96000 Hz or 192000 Hz) or 1/1102.5 seconds long (for 44100 Hz, 88200 Hz or 176400 Hz). Uncompressed (LPCM) it can be >35 Mbit/s. Any Blu-ray player or AV receiver that can decode TrueHD can also mix a multi-channel TrueHD track into any smaller amount of channels for final playback (for example, a 7.1 track to a 5.1 output, or a 5.1 track to a stereo output) by merging discrete channels' signals (except the low-frequency effects channel, the ".1," in a stereo mixdown, which is discarded due to its sound not playing back well without a dedicated subwoofer).

Dolby TrueHD is an optional codec, which means that Blu-ray hardware may decode it, but also may not (for example, inexpensive or early players, Blu-ray computer software, or pre–Blu-ray AV receivers). Consequently, all Blu-rays that include Dolby TrueHD audio also include a fail-safe track of Dolby Digital (AC-3), a mandatory codec. Unlike the competing DTS-HD Master Audio, which encodes its primary (optional) track in terms of differences from the companion mandatory track, a Dolby TrueHD-equipped Blu-ray's primary and companion tracks are redundant; the Dolby TrueHD bitstream has no data in common with the AC-3 bitstream, but AC-3 is used to construct E-AC3 stream. Similarly to DTS-HD MA, however, Dolby TrueHD's dual tracks are opaque to the user; a Blu-ray player loaded with a Dolby TrueHD disc will automatically fall back to AC-3 if it cannot decode or pass through the lossless bitstream, with no explicit selection required (or offered).

Dolby TrueHD's prominence relative to DTS-HD MA began to decline around 2010. [3] It has experienced a mild resurgence as the encoding used for Dolby Atmos audio (especially in Ultra HD Blu-ray titles), [4] but DTS-HD MA is still more common on titles with non-Atmos lossless audio. Regardless, publishers such as Paramount Home Entertainment, [5] [6] [7] and Crunchyroll [8] [9] [10] [11] still use Dolby TrueHD for their releases. Universal Pictures Home Entertainment has recently used Dolby TrueHD on occasion. [12] [13] [14]

Transport

Audio encoded using Dolby TrueHD may be transported to A/V receivers in one of three ways depending on player and/or receiver support: [15] [16]

Because S/PDIF does not have sufficient bandwidth to carry a TrueHD bitstream, or more than two channels of PCM audio, using S/PDIF requires either falling back to a disc's Dolby Digital track or mixing the TrueHD track down to stereo.

Related Research Articles

A codec is a device or computer program that encodes or decodes a data stream or signal. Codec is a portmanteau of coder/decoder.

Windows Media Audio (WMA) is a series of audio codecs and their corresponding audio coding formats developed by Microsoft. It is a proprietary technology that forms part of the Windows Media framework. WMA consists of four distinct codecs. The original WMA codec, known simply as WMA, was conceived as a competitor to the popular MP3 and RealAudio codecs. WMA Pro, a newer and more advanced codec, supports multichannel and high-resolution audio. A lossless codec, WMA Lossless, compresses audio data without loss of audio fidelity. WMA Voice, targeted at voice content, applies compression using a range of low bit rates. Microsoft has also developed a digital container format called Advanced Systems Format to store audio encoded by WMA.

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Dolby Digital, originally synonymous with Dolby AC-3, is the name for a family of audio compression technologies developed by Dolby Laboratories. Called Dolby Stereo Digital until 1995, it is lossy compression. The first use of Dolby Digital was to provide digital sound in cinemas from 35 mm film prints. It has since also been used for TV broadcast, radio broadcast via satellite, digital video streaming, DVDs, Blu-ray discs and game consoles.

<span class="mw-page-title-main">S/PDIF</span> Standardized digital audio interface

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<span class="mw-page-title-main">DVD-Audio</span> DVD format for storing high-fidelity audio

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Dolby Pro Logic is a surround sound processing technology developed by Dolby Laboratories, designed to decode soundtracks encoded with Dolby Surround. The terms Dolby Stereo and LtRt are also used to describe soundtracks that are encoded using this technique.

<span class="mw-page-title-main">Meridian Lossless Packing</span> Audio file format

Meridian Lossless Packing, also known as Packed PCM (PPCM), is a lossless compression technique for PCM audio data developed by Meridian Audio, Ltd. MLP is the standard lossless compression method for DVD-Audio content and typically provides about 1.5:1 compression on most music material. All DVD-Audio players are equipped with MLP decoding, while its use on the discs themselves is at their producers' discretion.

<span class="mw-page-title-main">Dolby</span> Audio technology company

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<span class="mw-page-title-main">HDMI</span> Proprietary interface for transmitting digital audio and video data

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 controller, to a compatible computer monitor, video projector, digital television, or digital audio device. HDMI is a digital replacement for analog video standards.

High definition or HD may refer to:

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DTS, Inc. is an American company. DTS company makes multichannel audio technologies for film and video. Based in Calabasas, California, the company introduced its DTS technology in 1993 as a competitor to Dolby Laboratories, incorporating DTS in the film Jurassic Park (1993). The DTS product is used in surround sound formats for both commercial/theatrical and consumer-grade applications. It was known as The Digital Experience until 1995. DTS licenses its technologies to consumer electronics manufacturers.

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<span class="mw-page-title-main">Sony BDP-S1</span>

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<span class="mw-page-title-main">AV receiver</span> Consumer electronics component

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<span class="mw-page-title-main">DTS-HD Master Audio</span> Lossless audio codec for home theater

DTS-HD Master Audio is a multi-channel, lossless audio codec developed by DTS as an extension of the lossy DTS Coherent Acoustics codec. 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, another lossless surround format.

<span class="mw-page-title-main">Comparison of high-definition optical disc formats</span>

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Dolby Atmos is a surround sound technology developed by Dolby Laboratories. It expands on existing surround sound systems by adding height channels, interpreted as three-dimensional objects with neither horizontal nor vertical limitations. Following the release of Atmos for the cinema market, a variety of consumer technologies have been released under the Atmos brand. The initial cinema Atmos systems used in-ceiling speakers, then upward-firing speakers were introduced as an alternative for consumer products. Atmos is also used on some devices that do not have a height channel, such as headphones, televisions, mobile phones, and tablets.

References

  1. ↑ "Dolby TrueHD". Dolby Laboratories . Retrieved August 22, 2014.
  2. ↑ "Technology Dolby Audio Dolby TrueHD | Dolby Developer". developer.dolby.com. Retrieved 2021-08-30.
  3. ↑ "DTS-HD Master Audio Becoming the Blu-ray Standard". Blu-raystats.com. January 15, 2010. Archived from the original on November 13, 2016. Retrieved November 15, 2010.
  4. 1 2 3 "Dolby Atmos for the Home Theater" (PDF). Dolby Laboratories . Archived from the original (PDF) on May 21, 2020. Retrieved 2018-06-29.
  5. ↑ Wonder Park Blu-ray Release Date June 18, 2019 , retrieved 2021-05-18
  6. ↑ Like a Boss Blu-ray Release Date April 21, 2020 , retrieved 2021-05-18
  7. ↑ Popeye Blu-ray Release Date December 1, 2020 , retrieved 2021-05-18
  8. ↑ Violet Evergarden: The Movie Blu-ray , retrieved 2024-01-12
  9. ↑ One Piece Film: Red Blu-ray , retrieved 2024-01-12
  10. ↑ Dragon Ball Super: Super Hero Blu-ray (Blu-ray + DVD) , retrieved 2024-01-12
  11. ↑ Dragon Ball Super: Complete Series Blu-ray (SteelBook) , retrieved 2024-01-12
  12. ↑ Easter Sunday Blu-ray (Blu-ray + DVD + Digital HD) , retrieved 2023-12-12
  13. ↑ The Fabelmans Blu-ray (Blu-ray + DVD + Digital HD) , retrieved 2023-12-12
  14. ↑ Ruby Gillman, Teenage Kraken Blu-ray (Collector's Edition) , retrieved 2023-12-12
  15. ↑ Maestra, Rodolfo La (August 8, 2006). "HDMI Part 5 - Audio in HDMI Versions". HDTV Magazine. Archived from the original on May 12, 2008. Retrieved November 15, 2010.
  16. ↑ "HDMI versions". 17 January 2017. Thursday, 19 January 2017
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