Editing Meridian Lossless Packing (section)

{{Short description|Audio file format}}
[[Image:Dolby MLP.svg|thumb|200px|right|The Meridian Lossless Packing logo]]
[[Image:AdvancedResolution logo.svg|thumb|200px|right|The Advanced Resolution logo]]

'''Meridian Lossless Packing''', also known as Packed PCM (PPCM),{{Citation needed|date=September 2007}} 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<ref>{{cite web |title=It's Official: DVD-Audio Version 1.0 Finally Set |url=https://www.stereophile.com/news/10379/index.html |website=Stereophile |access-date=15 May 2022 |archive-url=https://web.archive.org/web/20040825103643/https://www.stereophile.com/news/10379/index.html |archive-date=25 August 2004 |date=14 February 1999}}</ref> (often advertised with the Advanced Resolution logo) and typically provides about 1.5:1 compression on most music material. All DVD-Audio players are equipped with MLP decoding,<ref>{{cite press release |date=27 February 1999 |title=MLP mandatory for DVD-Audio players |url=https://www.meridian-audio.info/public/mlp_pr_11%5B2522%5D.pdf |location=Huntingdon |publisher=Meridian Audio |access-date=15 May 2022 |archive-url=https://web.archive.org/web/20210512105007/https://www.meridian-audio.info/public/mlp_pr_11[2522].pdf |archive-date=12 May 2021}}</ref> while its use on the discs themselves is at their producers' discretion.

[[Dolby TrueHD]], used in [[Archival Disc]] [[Blu-ray]] and [[HD DVD]], employs the MLP codec, but compared with DVD-Audio, adds higher bit rates, 32 full-range channels, extensive metadata, and custom speaker placements (as specified by [[SMPTE]]).<ref name="DolbyLabsDescription">
Dolby Laboratories.
[https://developer.dolby.com/globalassets/technology/dolby-truehd/dolbytruehdhighlevelbitstreamdescription.pdf "Dolby TrueHD (MLP) high-level bitstream description"].
2018 p. 6.
</ref>

Standard DVD has a maximum transfer rate of 9.6&nbsp;Mbit/s, around 70 percent of the bit rate needed to store 6 ''uncompressed'' audio channels of 24-bit/96&nbsp;kHz. Should MLP not be able to compress the stream below the maximum transfer rate &ndash; or in case there is a need to reduce the size to fit overall disc capacity &ndash; it can exploit (lossy) pre-quantification zeroing out least significant bits when necessary.<ref>
[http://www.hometheaterhifi.com/volume_8_4/dvd-benchmark-part-6-dvd-audio-11-2001.html#Meridian%20Lossless%20Packing%20(MLP)%20in%20a%20Nutshell Meridian Lossless Packing (MLP) in a Nutshell].
</ref><ref>
[https://web.archive.org/web/20010810061610/http://www.meridian-audio.com/w_paper/mlp_jap_new.PDF "MLP Lossless Compression"] by Bob Stuart of Meridian Audio, Ltd.
</ref><ref>[https://web.archive.org/web/20000820182419/http://www.meridian-audio.com/ara/ara13.pdf "A Proposal for the High-Quality Audio Application of High-Density CD Carriers"] proposal by Bob Stuart, 1996, Table 3.</ref> The MLP stream can also contain "substreams", like surround and stereo downmix, which need not be of the same bit depth or sampling frequency &ndash; this further enables (lossy) pre-processing to save space. TrueHD streams cannot do this<ref>[https://wiki.multimedia.cx/index.php?title=Meridian_Lossless_Packing MLP on MultimediaWiki]</ref> (likely because Blu-Ray discs have higher storage capacity).

MLP is ''streamable'': A decoder can pick up the stream and start decoding from that point on nearly instantly, where the encoder has inserted a "restart block" in the stream.<ref>Dolby Laboratories 2018, section 2.4</ref> Typically, restart information is inserted approximately every 5&nbsp;ms in the audio,<ref>
Robert C. Maher.
[https://www.montana.edu/rmaher/publications/maher_lossless_chapter_2003.pdf "Lossless Compression of Audio Data"].
p. 266.</ref> about the same as a typical 96&nbsp;kHz FLAC stream.