{{Short description|Audio file format}} thumb|200px|right|The Meridian Lossless Packing logo 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 Mbit/s, around 70 percent of the bit rate needed to store 6 ''uncompressed'' audio channels of 24-bit/96 kHz. Should MLP not be able to compress the stream below the maximum transfer rate – or in case there is a need to reduce the size to fit overall disc capacity – it can exploit (lossy) pre-quantization 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 – 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 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 kHz FLAC stream.
==MLP in packaged media formats== {| class="wikitable" |- ! Media format ! Status ! Channels ! Maximum bit rate |- ! HD DVD | Mandatory | 2 to 8 | rowspan=2|{{val|18|u=Mbit/s}} |- ! Blu-ray | Optional | 2 to 8 |- ! DVD-Audio | Mandatory | 1 to 6 | {{val|9.6|u=Mbit/s}} |- ! DVD-Video | colspan=3 align=center {{N/A}} |}
==See also== * Direct Stream Transfer * FLAC * Monkey's Audio * WavPack * Master Quality Authenticated
==References== {{Reflist}}
{{Compression formats}}
Category:Lossless audio codecs Category:DVD