Dolby TrueHD logo as introduced in 2012. Dolby TrueHD is a lossless, multi-channel audio codec developed by Dolby Laboratories for home plate video, used chiefly in Blu-ray Disc and compatible hardware. Dolby TrueHD, along with Dolby Digital Plus 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 overcome Audio ( DTS-HD MA ), another lossless environment sound codec. The Dolby TrueHD specification provides for up to 16 discrete audio channels, each with a sampling rate of up to 192kHz and sample astuteness 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.
Reading: Dolby TrueHD – Wikipedia
Like its harbinger, 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 case, audio standardization or dynamic range compression. In summation, Dolby Atmos, a multi-dimensional besiege format encoded using Dolby TrueHD, can embed more advanced metadata to spatially place sound objects in an Atmos-compatible loudspeaker system .
Blu-ray Disc [edit ]
In the Blu-ray Disc specification, Dolby TrueHD tracks may carry up to 8 discrete audio channels ( 7.1 wall ) of 24-bit audio at 96 kilohertz, or up to 6 channels ( 5.1 environment ) at 192 kilohertz. [ 1 ] The maximum bitrate of an audio flow 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 hanker ( 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 besides mix a multi-channel TrueHD track into any smaller amount of channels for final playback ( for exemplar, a 7.1 track to a 5.1 output, or a 5.1 traverse 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 second well without a consecrated subwoofer ). Dolby TrueHD is an optional codec, which means that Blu-ray hardware may decode it, but besides may not ( for model, cheap or early players, Blu-ray computer software, or pre–Blu-ray AV receivers ). consequently, all Blu-rays that include Dolby TrueHD audio besides include a fail-safe track of Dolby Digital ( AC-3 ), a compulsory codec. Unlike the competing DTS-HD Master Audio, which encodes its primary ( optional ) track in terms of differences from the companion compulsory track, a Dolby TrueHD-equipped Blu-ray ‘s chief and companion tracks are excess ; the Dolby TrueHD bitstream has no datum 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 double tracks are opaque to the drug user ; a Blu-ray player loaded with a Dolby TrueHD disk will automatically fall back to AC-3 if it can not decode or pass through the lossless bitstream, with no denotative selection required ( or offered ). Dolby TrueHD ‘s bulge relative to DTS-HD MA began to decline around 2010. [ 3 ] It has experienced a mild revival as the encoding used for Dolby Atmos audio ( particularly in Ultra HD Blu-ray titles ), [ 4 ] but DTS-HD MA is hush more common on titles with non-Atmos lossless audio. Regardless, publishers such as Paramount Home Entertainment, [ 5 ] [ 6 ] [ 7 ] and Funimation [ 8 ] [ 9 ] [ 10 ] still use Dolby TrueHD for their releases.
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transport [edit ]
Audio encoded using Dolby TrueHD may be transported to A/V receivers in one of three ways depending on player and/or receiver support : [ 11 ] [ 12 ]
- Over 6 or 8 RCA connectors as analog audio, using the player’s internal decoder and digital-to-analog converter (DAC).
- Over HDMI 1.1 (or higher) connections as 6 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 Dolby TrueHD bitstream encapsulated in MAT[4] (Metadata-Enhanced Audio Transport) frames, with decoding and DAC both done by the AV receiver. This is the transport mode mandated by Dolby Atmos.[4]
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 magnetic disk ‘s Dolby Digital track or mixing the TrueHD track down to stereo .