Editing High Definition Compatible Digital

{{Short description|Proprietary backward-compatible CD audio format}}
{{Infobox media
| name = High Definition Compatible Digital
| logo = [[Image:HDCD logo.svg|class=skin-invert|150px]]
| image =
| caption =
| type = [[Optical disc]]
| encoding =
| capacity = Typically up to 700 [[megabyte|MB]]
| read = 780 nm wavelength semiconductor laser
| write =
| standard =
| owner = [[Pacific Microsonics]] Inc./[[Microsoft]]
| use = Audio storage
| extended from = [[Red Book (audio CD standard)|Red Book]]<br />[[Compact disc]]
| extended to =
| released    = {{Start date and age|1995}}
}}

'''High Definition Compatible Digital''' ('''HDCD''') is a proprietary audio encode-decode process that claims to provide increased [[dynamic range]] over that of standard [[Compact Disc Digital Audio]], while retaining [[backward compatibility]] with existing [[compact disc player]]s.

Originally developed by Pacific Microsonics, the first HDCD-enabled CD was released in 1995.<ref name="russo">{{cite web |url=http://www.hometoys.com/article/2008/11/classic-home-toys-installment-19-the-final-cd-format-hdcd/1106/ |title=Home Technology eMagazine - Classic Home Toys Installment #19 The Final CD Format: HDCD |publisher=HomeToys |date=30 November 2008 |access-date=5 August 2012 |archive-url=https://web.archive.org/web/20150621233156/http://www.hometoys.com/article/2008/11/classic-home-toys-installment-19-the-final-cd-format-hdcd/1106/ |archive-date=21 June 2015 |url-status=dead }}</ref> In 2000, the technology was purchased by Microsoft, and the following year, there were over 5,000 HDCD titles available.<ref>{{cite web|url=http://www.timefordvd.com/ref/HDCD.shtml |title=HDCD (High Definition Compatible Digital) from Pacific Microsonics |publisher=TimeForDVD.com |date=23 February 2002 |access-date=5 August 2012}}</ref> Microsoft's HDCD official website was discontinued in 2005; by 2008, the number of available titles had declined to around 4,000.<ref name="russo" />

A number of [[CD player|CD]] and [[DVD player]]s include HDCD decoding, and versions 9 and above of Microsoft's [[Windows Media Player]] on personal computers are capable of decoding HDCD.

HDCD is a favorite among artists who have a preference for high quality sound, such as [[Neil Young]], [[the Beach Boys]] and the [[Grateful Dead]]—all of whom have multiple CD titles (new and archival) in their catalogs mastered in this process.<ref>[http://wiki.hydrogenaud.io/index.php?title=List_of_HDCD-encoded_Compact_Discs List of HDCD-encoded compact discs] (with technical details) at HydrogenAudio wiki</ref><ref>[http://www.head-fi.org/t/65414/hdcd-list List of known HDCD compact discs] (names only) at Head-Fi.org</ref>

==Technical overview==
HDCD encodes the equivalent of 20 bits worth of data in a [[16-bit sample|16-bit]] digital audio signal by using custom [[dither]]ing, [[audio filter]]s, and some reversible amplitude and gain encoding:

* '''Peak Extend''', which is a reversible soft limiter; 
* '''Low Level Range Extend''', which is a reversible gain on low-level signals.

There is thus a benefit at the expense of a very minor increase in noise.<ref>{{cite web|last1=Johnson|first1=Keith O.|last2=Pflaumer|first2=Michael W.|url=https://www.aes.org/e-lib/browse.cfm?elib=7387|title=Compatible Resolution Enhancement in Digital Audio Systems|date=1996-11-01|publisher=Audio Engineering Society|access-date=2022-12-07|url-access=subscription}}</ref>

The claim that the encoding process is compatible with ordinary CD players (without audible distortion) is disputed: not being able to decode the peak soft limiting, a normal CD player will output distorted peaks.<ref>{{cite web|url=https://www.audiomisc.co.uk/HFN/HDCD/Enigma.html |title=The HDCD Enigma |publisher=Audiomisc.co.uk |access-date=2022-12-07}}</ref>

==History==
HDCD technology was developed between 1986 and 1991 by "Prof." [[Keith O. Johnson]] and Michael "Pflash" Pflaumer of [[Pacific Microsonics]] Inc. It was made publicly available as HDCD-enabled audio CDs (often identifiable by the HDCD logo printed on the back cover) in 1995.

Between 1996 and 1999 Pacific Microsonics VP of OEM Sales, Steve Fields, made over 20 trips to Japan, visiting [[Sanyo]], [[Burr-Brown Corporation|Burr-Brown Japan]] and major audio companies, with the intent of licensing the HDCD technology. In 1998, Burr-Brown (now part of [[Texas Instruments]]) and Sanyo Electronics of Japan introduced low-cost [[digital-to-analog converter]]s with HDCD decoding included, allowing HDCD to be used in CD and DVD players in the $100 range. HDCD algorithms were included in DVD chips from many [[Integrated circuit|IC]] makers including [[Motorola]] and [[C-Cube]], allowing HDCD to be offered by mass-market DVD player makers such as [[Panasonic]] and [[Toshiba]].

In 2000, Pacific Microsonics folded and Microsoft acquired the company and all of its intellectual property.<ref>{{cite patent|country=US|number=5479168|pubdate=1995-12-26|title=Compatible signal encode/decode system|assign1=Pacific Microsonics Inc.|inventor1-last=Johnson|inventor1-first=Keith O.|inventor2-last=Pflaumer|inventor2-first=Michael W.}}</ref><ref>{{cite patent|country=US|number=5872531|pubdate=1999-02-16|title=Signal encode/decode system|assign1=Pacific Microsonics Inc.|inventor1-last=Johnson|inventor1-first=Keith O.|inventor2-last=Pflaumer|inventor2-first=Michael W.}}</ref> Microsoft discontinued the official HDCD website in 2005.

In January 2007, there were roughly the same number of titles available on [[Super Audio CD|SACD]] as on HDCD-encoded CDs.{{citation needed|date=September 2021}}

==Hardware players==
A number of manufacturers offer players with HDCD capability. Some Panasonic DVD players and the [[OPPO Digital|Oppo]] line of players all feature HDCD decoding.<ref>{{cite web|url=http://www.oppodigital.com |title=Universal Network 3D Blu-ray Players - Buy Direct from the Manufacturer |publisher=OPPO Digital |access-date=2012-08-05}}</ref><ref>{{cite web|url=http://watershade.net/wmcclain/UDP-203-faq.html|title=Unofficial OPPO UDP-203 Frequently Asked Questions|publisher=AVSForum|access-date=2017-03-03}}</ref> Several [[Yamaha Corporation|Yamaha]] Blu-ray players<ref>{{cite web|url=http://hometheaterhifi.com/reviews/video-player/universal/yamaha-bd-a1060-universal-blu-ray-player-review/|title=Yamaha BD-A1060 Universal Blu-Ray Player Review|publisher=Secrets of Home Theater and High Fidelity|date=2016-11-14|access-date=2017-03-04}}</ref><ref>{{cite web|url=http://forums.stevehoffman.tv/threads/2-new-yamaha-uni-players-including-one-with-balanced-analog-outputs.566747/|title=2 new Yamaha uni players - including one with balanced analog outputs|publisher=Steve Hoffman Music Forums|date=2016-07-16|access-date=2017-03-04}}</ref> as well as [[Emotiva]] CD players<ref>{{cite web|url=http://hometheaterhifi.com/reviews/audio-player/cd-players/emotiva-erc-3-differential-reference-cd-player-digital-transport-review/|publisher=Secrets of Home Theater and High Fidelity|title=Emotiva ERC-3 Differential Reference CD Player/Digital Transport Review|date=2014-09-02|access-date=2017-03-04}}</ref> decode HDCD.

==Software players==
===Windows Media Player===
Since version 9 of Microsoft's [[Windows Media Player]] (WMP), HDCD enabled CDs can be played on personal computers fitted with a 24-bit [[sound card]].<ref>{{cite web|url=http://www.microsoft.com/windows/windowsmedia/player/9series/features.aspx |title=Features of Windows Media Player 9 Series |publisher=Microsoft.com |access-date=2012-08-05}}</ref><ref>{{cite web|url=http://www.microsoft.com/windows/windowsmedia/mp10/jukebox.aspx |title=Smart Jukebox Features |publisher=Microsoft.com |access-date=2012-08-05}}</ref>

With some HDCD discs and some DVD players using WMP, the first track may not be recognized as HDCD, but all subsequent tracks are. This is because HDCD has a control signal, and if the signal is not detected by WMP at the beginning of the song, the HDCD decoder is not activated.

===Other software===
In 2007, a member of the [[Doom9|Doom9 forum]] authored a Windows [[Command-line interface|CLI]] utility, ''hdcd.exe'',<ref>[http://forum.doom9.org/showthread.php?t=129136 utility]</ref>{{Unreliable source?|date=January 2015}} to extract and decode the HDCD data in 16-bit [[WAV]] files [[CD ripper|ripped]] from HDCD discs. This utility writes [[24-bit audio|24-bit]] [[WAV]] output files with four bits of padding per sample. The author of the utility decided not to make the source code publicly available as the HDCD technology is patented.<ref>{{cite web|url=http://forum.doom9.org/showthread.php?p=1044539#post1044539 |title=HDCD Software Decoder - Doom9's Forum |publisher=Forum.doom9.org |access-date=2012-08-05}}</ref>

Illustrate's ''dBpoweramp Music Converter'', a Windows [[Graphical user interface|GUI]] program, has an HDCD [[Digital signal processing|DSP]] effect that acts as a front-end to the utility listed above.<ref>dBPoweramp's DSP Effects page [http://www.dbpoweramp.com/dbpoweramp-dsp.htm]; dBpoweramp's local help file</ref>

A plugin is available for ''[[foobar2000]]'' that will decode HDCD data in any 16-bit [[Pulse-code modulation|PCM]] passed through it, resulting in a 20-bit PCM stream.<ref>{{cite web|url=http://www.foobar2000.org/components/view/foo_hdcd |title=foobar2000 HDCD decoder component |publisher=Foobar2000.org |date=2012-07-18 |access-date=2012-08-05}}</ref>

[[FFmpeg]]'s ''[[libavfilter]]'' includes an HDCD filter as of ''FFmpeg 3.1'' (June 2016) that will convert 16-bit PCM with HDCD data to 20-bit PCM.<ref>{{cite web|title=June 27th, 2016, FFmpeg 3.1 "Laplace"|url=https://ffmpeg.org/index.html#pr3.1|website=FFmpeg.org|access-date=2 July 2016}}</ref>

An open-source HDCD decoder library exists as ''libhdcd''.<ref>{{cite web|title=libhdcd - An HDCD decoder library|website=[[GitHub]]|url=https://github.com/bp0/libhdcd|access-date=21 August 2016}}</ref>

==See also==
*[[DualDisc]]
*[[DVD-Audio]]
*[[Extended Resolution Compact Disc]] (XRCD)
*[[Super Audio CD]] (SACD)
*[[Super Bit Mapping]] (SBM)

==References==
{{Reflist}}

==External links==
*{{webarchive |url=https://web.archive.org/web/20050622080528/http://www.hdcd.com/ |title=Microsoft's now discontinued HDCD official website}}
*{{webarchive |url=https://web.archive.org/web/20041204171913/http://www.hdcd.com/about/whatisHDCD.html |title=Microsoft's now discontinued HDCD official FAQ}}
*{{cite web|title=HDCD - An Overview|url=http://www.goodwinshighend.com/hdcd.htm|website=Goodwin's High End|archive-url=https://web.archive.org/web/20150402044617/http://www.goodwinshighend.com/hdcd.htm|archive-date=2015-04-02|language=en}}
*[http://wiki.hydrogenaud.io/index.php?title=High_Definition_Compatible_Digital High Definition Compatible Digital] at HydrogenAudio wiki

{{Audio formats}}

[[Category:Compact disc]]
[[Category:120 mm discs]]
[[Category:Windows media players]]
[[Category:Microsoft Windows multimedia technology]]
[[Category:Computer-related introductions in 1995]]
[[Category:Audiovisual introductions in 1995]]
[[Category:Digital audio storage]]