Dolby True HD
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||
| Type of format | Lossless audio format | |
|---|---|---|
| First released | 2005 | |
| Developer | Dolby Laboratories | |
| Compression Type | VBR | Bitrate | 18.64 Mbps |
| Channels | 8 (48kHz, 96kHz), 6 (192 kHz) | |
| Bits | 16-24 | |
| Sample | 48 KHz, 96 kHz, 192 kHz | |
| Filename extension | ? | |
| Open Format? | ? | |
| Free Format? | ? | |
| Magic Number | ? | |
Dolby TrueHD (also known as Dolby Lossless) is an extension of Dolby Digital and successor of Dolby Digital Plus developed by Dolby Laboratories. It adds more channel support (up to 8 channels), more bitrate (18.64 Mbps), sampling frequency up to 192 Khz, and up to 24-bit resolution.
Dolby TrueHD is an optional audio codec included in the BD specifications for developers. While Blu-ray hardware may decode it, some inexpensive or early players may not support it. Therefore, all Blu-rays containing Dolby TrueHD audio also include a fail-safe Dolby Digital (AC-3) track, a mandatory codec.
Unlike, Dolby Digital and Dolby Digital Plus, Dolby TrueHD is not based on the MDCT compression algorithm, but a completely new one. It is based on Meridian Lossless Packing (MLP), a lossless compression technique for PCM audio data developed in 1997 by Meridian Audio, Ltd. Dolby acquired the company to create Dolby TrueHD. Before Dolby, MLP was one of the main audio codecs for DVD-Audio content, although the two formats' respective implementations of MLP are not mutually compatible.
Like its predecessors, 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.
Dolby TrueHD's prominence relative to DTS-HD MA began to decline around 2010. It experienced a mild resurgence as the encoding used for Dolby Atmos audio, especially in Ultra HD BD titles. However, DTS-HD MA is still more common on titles with non-Atmos lossless audio. Nevertheless, publishers such as Paramount Home Entertainment and Crunchyroll (Funimation) continue to use Dolby TrueHD for their releases. Universal Pictures Home Entertainment has also recently used Dolby TrueHD on occasion. For DVD-Audio releases, they are very uncommon and niche today and still use the "MLP" logo instead of Dolby TrueHD.
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Author(s) : Æ Firestone
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