View source for WavPack

{{Short description|Open-source lossless audio codec}}

{{distinguish|WAV}}{{Infobox file format
| name          = WavPack file format
| icon          = [[File:WavPack logo.svg|frameless|class=skin-invert]]
| logo          = 
| screenshot    = 
| caption       = 
| extension     = .wv (for both lossless and hybrid files), .wvc (correction file for hybrid files only)
| mime          = audio/x-wavpack (.wv), audio/x-wavpack-correction (.wvc)
| type code     = 
| uniform type  = 
| magic         = wvpk
| container for = 
| contained by  = Matroska (not required)
| extended from = 
| extended to   = 
| standard      = 
| open          = Yes
| free          = Yes
| type          = [[Lossless compression|Lossless]] [[Audio file format|audio]]
}}

{{Infobox software
| name = WavPack software
| logo = 
| screenshot = WVUNPACK screenshot.webp
| caption = Screenshot of <code>wvunpack</code> showing information of a .wv file
| developer = David Bryant
| latest release version = {{wikidata|property|preferred|references|edit|P348|P548=Q2804309}}
| latest release date = {{Start date and age|{{wikidata|qualifier|preferred|single|P348|P548=Q2804309|P577}}|df=yes}}
| operating_system = [[Cross-platform]]
| genre = [[Audio codec]] Container
| license = [[BSD licenses|BSD license]]
| website = [https://wavpack.com/ wavpack.com]
}}

'''WavPack''' is a [[free and open-source]] [[Audio compression (data)#Lossless|lossless audio compression]] [[file format|format]] and application implementing the format. It is unique in the way that it supports hybrid audio compression alongside normal compression which is similar to how [[FLAC]] works. It also supports compressing a wide variety of lossless formats, including various variants of [[Pulse-code modulation|PCM]] and also [[Direct Stream Digital|DSD]] as used in [[Super Audio CD|SACDs]], together with its support for surround audio.

==Features==
WavPack compression can compress (and losslessly restore) 8, 16, 24, and 32-bit [[fixed-point arithmetic|fixed-point]], and 32-bit [[floating-point]] [[PCM]] audio files in the .[[WAV]] file format. It can also handle DSD input in DSDIFF or DSF format.<ref name="wavpack_doc">{{cite web |title=WavPack User Documentation |url=https://www.wavpack.com/wavpack_doc.html |website=www.wavpack.com}}</ref> It also supports [[surround sound]] streams and high [[sampling rate]]s. Like other lossless compression schemes, the data reduction rate varies with the source, but it is generally between 30% and 70% for typical popular music and somewhat better than that for classical music and other sources with greater dynamic range.<ref>{{cite web
| last = Heijden
| first = Hans
| title = Compression and speed of lossless audio formats
| date = 11 July 2006
| url = http://web.inter.nl.net/users/hvdh/lossless/lossless.htm
| access-date = 17 July 2009
| archive-date = 3 July 2009
| archive-url = https://web.archive.org/web/20090703042443/http://web.inter.nl.net/users/hvdh/lossless/lossless.htm
| url-status = dead
}}</ref>

===Hybrid mode===
WavPack also incorporates a "hybrid" mode, which still provides the features of lossless compression, but creates two files: a relatively small, high-quality, lossy file (.wv) that can be used by itself; and a "correction" file (.wvc) that, when combined with the lossy file, provides full lossless restoration. This allows the use of lossy and lossless codecs together. The lossy algorithm is similar to [[ADPCM]].<ref>{{cite book |chapter=7.11 WavPack |last1=Bryant |first1=David |editor1-last=Solomon |editor1-first=David |title=Data Compression: The Complete Reference |page=773 |url=https://www.wavpack.com/WavPack.pdf}}</ref>

Hybrid mode can handle floating-point data, but only when "exception" values like infinities or NaNs are not present. It cannot handle DSD because there is no lossy algorithm for DSD.<ref name="wavpack_doc"/>

A similar "hybrid" feature is also offered by [[OptimFROG DualStream]], [[MPEG-4 SLS]] and [[DTS-HD Master Audio]].

===Summary===
* [[Open-source software|Open-source]], released under a [[BSD license|BSD]]-like license
* Multiplatform
* Error robustness
* Fast encoding
* Higher compression ratios than other widely used (FLAC/ALAC) open-source lossless audio codecs
* [[Streaming media|Streaming]] support
* Supports multichannel audio and high resolutions
* Native support in WavPack 5.x for compressing [[Direct Stream Digital]] without converting the source file to PCM.
* Hybrid/lossy mode
* Hardware support (provided by [[Rockbox]] firmware)
* Metadata support ([[ID3]], [[APEv2 tag|APE]] tags; APE tag is the preferred format)
* Supports [[RIFF (File format)|RIFF]] chunks
* Compatible with [[ReplayGain]]
* Ability to create self-extracting files for the Win32 platform
* Supports 32-bit floating-point streams
* Supports embedded [[Cue sheet (music software)|CUE sheets]]
* Includes [[MD5]] hashes for quick integrity checking
* Can encode in both symmetrical and asymmetrical (slower encoding to speed up decoding) modes

==History==
David Bryant started development on WavPack in mid-1998 with the release of version 1.0 (1998-08-15). This first version compressed and decompressed audio losslessly, and it already featured one of the best efficiency vs. speed ratios among lossless encoders.<ref>{{cite web
| last = Speek
| title = Performance comparison of lossless audio compressors
| date = 7 February 2005
| url = http://members.home.nl/w.speek/comparison.htm
| access-date = 17 July 2009
| archive-date = 25 November 2010
| archive-url = https://web.archive.org/web/20101125045330/http://members.home.nl/w.speek/comparison.htm
| url-status = dead
}}</ref>

Very soon after the release of version 1.0, v. 2.0 (2&nbsp;September 1998) was released, featuring lossy encoding (using only quantization of prediction residue for data reduction{{snd}} no [[Psychoacoustics#Masking effects|psychoacoustic masking model]] was applied to the stream).

In 1999, version 3.0 (12 September 1999) was released, with a new "fast mode" (albeit with reduced compression ratio), compression of raw (headerless) [[Pulse-code modulation|PCM]] audio files, and error detection using a 32-bit [[cyclic redundancy check]].

A feature added in late 3.x versions is the "hybrid" mode where the encoder generates a lossy file and a correction file such that both can be decompressed back to a PCM stream that has same quality as the original.<ref>{{cite web |url=https://www.wavpack.com/#About |title = WavPack Audio Compression}}</ref>

In WavPack 4, a new file format structure is introduced. A "roadmap" is also published by the author with 4.40, containing possible hints on future development.<ref>{{cite web |url=http://www.hydrogenaud.io/forums/index.php?s=&showtopic=50911&view=findpost&p=456571 |title = WavPack 4.40 released}}</ref> WavPack 5 introduced support for compressing DSD.

==Support==
===Software===
Some software supports the format natively (like [[DeaDBeeF]], [[foobar2000]],<ref>{{Cite web|url=http://foobar2000.org/|title=foobar2000|website=foobar2000.org|access-date=2019-11-19|archive-date=2019-11-20|archive-url=https://web.archive.org/web/20191120014639/http://www.foobar2000.org/|url-status=live}}</ref> and [[Jack! The Knife]]), while others require plugins. The official WavPack website offers plugins for [[Winamp]], [[Nero Burning ROM]], MediaChest 2.1, and several other applications, as well as a [[DirectShow]] filter.<ref name="wpdl">{{Cite web|url=https://www.wavpack.com/downloads.html|title=WavPack downloads|website=www.wavpack.com|access-date=2021-01-28|archive-date=2021-02-01|archive-url=https://web.archive.org/web/20210201115600/https://www.wavpack.com/downloads.html|url-status=live}}</ref> [https://www.dbpoweramp.com/cd-ripper.htm dBpoweramp CD-Ripper],<ref>{{Cite web|url=https://www.dbpoweramp.com/codec-central.htm|title=dBpoweramp Codec Central|website=www.dbpoweramp.com|access-date=2019-11-19}}</ref> by the author of foobar2000, as well as foobar2000<ref>{{Cite web|url=http://www.foobar2000.org/encoderpack|title=foobar2000: Free Encoder Pack|website=www.foobar2000.org|access-date=2019-11-19|archive-date=2019-11-18|archive-url=https://web.archive.org/web/20191118133723/http://www.foobar2000.org/encoderpack|url-status=live}}</ref> itself, and [[Asunder (software)|Asunder]] allow ripping Audio CDs directly into Wavpack files.

[[Linux]] support is available with a native port.

[[FFmpeg]] has a native WavPack encoder, which may be combined with software like [[GNU parallel]] to use multiple CPU cores to quickly transcode other lossless formats into WavPack, and from WavPack to any format that FFmpeg supports, without the need for additional software. However, FFMpeg's encoder is somewhat limited. 

As of 2023, FFmpeg's WavPack encoder has some considerable limitations. It can only produce version 4 bitstreams, which do not support fast verification for file integrity checks, or more than 16 channels. It will also discard RIFF chunks and may not behave predictably with 24-bit input. It also defaults to less than optimal compression to achieve faster encoding. Due to lack of support for Hybrid mode, FFmpeg-based playback software will fail to consider the .wvc correction file if there is one present, and will play or transcode only the lossy section. (However, this is not the usual mode of operation for WavPack.) As native Wavpack support for Direct Stream Digital was added in version 5 of the reference encoder, FFmpeg WavPack also is limited to encoding PCM input.<ref>{{cite web | url=https://wiki.hydrogenaud.io/index.php?title=WavPack#FFmpeg.27s_WavPack_implementation:_differences_and_quirks | title=WavPack - Hydrogenaudio Knowledgebase | access-date=2023-10-02 | archive-date=2023-10-09 | archive-url=https://web.archive.org/web/20231009131429/https://wiki.hydrogenaud.io/index.php?title=WavPack#FFmpeg.27s_WavPack_implementation:_differences_and_quirks | url-status=live }}</ref>

===Hardware===
Native support:
* [[Cowon A3]] PMP supports WavPack out of the box.{{Citation needed|date=May 2010}}

Non-native support:
* Apple [[iPod]] range of music players do not support WavPack out of the box, but can through open-source [[Rockbox]] firmware.
* [[iRiver H100 series]], through open-source Rockbox firmware.
* [[iRiver H300 series]], through open-source Rockbox firmware.<ref name="rockboxsoundcodecs">{{Cite web|url=https://www.rockbox.org/wiki/SoundCodecs|title=SoundCodecs < Main < Wiki|website=www.rockbox.org|access-date=2023-01-21|archive-date=2023-01-24|archive-url=https://web.archive.org/web/20230124233022/https://www.rockbox.org/wiki/SoundCodecs|url-status=live}}</ref>
* [[Android (operating system)|Android]] smartphones and tablets with the installation of third-party media-player software.
* [[ChromeOS]] devices using media-player software installed in the Linux subsystem or the Android Play Store.
The WavPack website also includes a plugin that allows support for the format on the [http://www.rokulabs.com/products/photobridge/features.php Roku PhotoBridge HD] {{Webarchive|url=https://web.archive.org/web/20050708003853/http://www.rokulabs.com/products/photobridge/features.php |date=2005-07-08 }}.<ref name="wpdl"/>

==Technology==
To ensure high-speed operation, WavPack uses a predictor that is implemented entirely in integer math.<ref>{{cite web
| last = Bryant
| first = David
| title = Forum comment by developer
| date = 21 March 2007
| url = http://www.hydrogenaud.io/forums/index.php?showtopic=52576&st=50&p=479913&hl=integer&#entry479913
| access-date = 17 July 2009}}</ref> In its "fast" mode the prediction is simply the arithmetic extrapolation of the previous two samples. For example, if the previous two samples were −10 and 20, then the prediction would be 50. For the default mode a simple adaptive factor is added to weigh the influence of the earlier sample on the prediction. In the example above the resulting prediction could then vary between 20 for no influence to 50 for full influence. This weight factor is constantly updated based on the audio data's changing spectral characteristics.

The prediction generated is then subtracted from the actual sample to be encoded to generate the error value. In mono mode this value is sent directly to the coder. However, [[stereophonic sound|stereo]] signals tend to have some correlation between the two channels that can be further exploited. Therefore, two error values are calculated that represent the difference and average of the left and right error values. In the "fast" mode of operation these two new values are simply sent to the coder instead of the left and right values. In the default mode, the difference value is always sent to the coder along with one of the other three values (average, left, or right). An adaptive algorithm continuously determines the most efficient of the three to send based on the changing balance of the channels.

Instead of [[Rice coding]], a special data encoder for WavPack is used. Rice coding is the optimal bit coding for this type of data, and WavPack's encoder is less efficient, but only by about 0.15&nbsp;bits per sample (or less than 1% for 16-bit data). However, there are some advantages in exchange. The first one is that WavPack's encoder does not require the data to be buffered ahead of encoding; instead it converts each sample directly to bitcodes. This is more computationally efficient and is better in some applications where coding delay is critical. The second advantage is that it is easily adaptable to lossy encoding, since all significant bits (except the implied "one" [[Most significant bit|MSB]]) are transmitted directly. In this way it is possible to only transmit, for example, the 3 most significant bits (with sign) of each sample. In fact, it is possible to transmit only the sign and implied MSB for each sample with an average of only 3.65&nbsp;bits per sample.

This coding scheme is used to implement the "lossy" mode of WavPack. In the "fast" mode the output of the non-adaptive decorrelator is simply rounded to the nearest codable value for the specified number of bits. In the default mode the adaptive decorrelator is used (which reduces the average noise about 1&nbsp;[[decibel|dB]]), and both the current and the next sample are considered in choosing the better of the two available codes (which reduces noise another 1&nbsp;dB).

No [[floating-point]] arithmetic is used in WavPack's data path because, according to the author, [[integer]] operations are less susceptible to subtle chip-to-chip variations that could corrupt the lossless nature of the compression (the [[Pentium FDIV bug|Pentium floating-point bug]] being an example). It is possible that a lossless compressor that used floating-point math could generate different output when running on that faulty Pentium. Even disregarding actual bugs, floating-point math is complicated enough that there could be subtle differences between "correct" implementations that could cause trouble for this type of application.<ref name="Goldberg_1991">{{cite journal |last=Goldberg |first=David |date=March 1991 |title=What Every Computer Scientist Should Know About Floating-Point Arithmetic |url=http://perso.ens-lyon.fr/jean-michel.muller/goldberg.pdf |journal=[[ACM Computing Surveys]] |volume=23 |issue=1 |pages=5–48 |doi=10.1145/103162.103163 |s2cid=222008826 |access-date=2016-01-20 |archive-date=2006-07-20 |archive-url=https://web.archive.org/web/20060720140912/http://perso.ens-lyon.fr/jean-michel.muller/goldberg.pdf |url-status=live }} ([http://www.validlab.com/goldberg/paper.pdf] {{Webarchive|url=https://web.archive.org/web/20191212073228/http://www.validlab.com/goldberg/paper.pdf |date=2019-12-12 }}, [http://docs.oracle.com/cd/E19957-01/806-3568/ncg_goldberg.html] {{Webarchive|url=https://web.archive.org/web/20160406101256/http://docs.oracle.com/cd/E19957-01/806-3568/ncg_goldberg.html |date=2016-04-06 }}).</ref> A 32-bit error detection code to the generated streams is included to maintain user confidence in the integrity of WavPack's compression.

WavPack source code is portable and has been compiled on several [[Unix]] and [[Unix-like]] operating systems ([[Linux]], [[Mac OS X]], [[Solaris (operating system)|Solaris]], [[FreeBSD]], [[OpenBSD]], [[NetBSD]], Compaq [[Tru64]], [[HP-UX]]...) as well as [[Microsoft Windows|Windows]], [[DOS]], [[Palm OS]], and [[OpenVMS]]. It works on many architectures, including [[x86]], [[ARM architecture|ARM]], [[PowerPC]], [[AMD64]], [[IA-64]], [[SPARC]], [[DEC Alpha|Alpha]], [[PA-RISC]], [[MIPS architecture|MIPS]] and [[68k|Motorola 68k]].

A cut-down version of WavPack was developed for the Texas Instruments TMS320 series Digital Signal Processor. This was aimed predominantly at encouraging manufacturers to incorporate WavPack compression (and de-compression) into portable memory audio recorders. This version supported features that were applicable only to embedded applications (stream compression in real-time, selectable compression rate) and dropped off features that only applied to full computer systems (self extraction, high compression modes, 32-bit floats). The TMS320 series DSPs are native integer devices, and support WavPack well. Some "special" features of the full WavPack software were included (ability to generate a correction "file" (stream), for example), and others were excluded. The port was based on version&nbsp;4.

WavPack support was added to [[WinZip]] starting with version 11.0 beta, released in October 2006.<ref name="winzip">{{cite web
 |url          = http://www.winzip.com/comp_info.htm
 |title        = WinZip – Additional Compression Methods Specification
 |access-date  = 6 January 2008
 |publisher    = WinZip International LLC
 |date         = 15 November 2006
 |archive-date = 14 April 2009
 |archive-url  = https://web.archive.org/web/20090414225734/http://www.winzip.com/comp_info.htm
 |url-status   = live
}}</ref> This extension to the [[ZIP (file format)|ZIP file format]] was included by [[PKZIP|PKWARE]], the maintainers of the format, in the official {{mono|APPNOTE.TXT}} description file starting with version 6.3.2, released on 28&nbsp;September 2007.<ref name="appnote">{{cite web
 |url          = http://www.pkware.com/documents/casestudies/APPNOTE.TXT
 |title        = APPNOTE.TXT – .ZIP File Format Specification
 |access-date  = 6 January 2008
 |publisher    = PKWARE Inc
 |date         = 28 September 2007
 |archive-date = 14 May 2007
 |archive-url  = https://archive.today/20070514200623/http://www.pkware.com/documents/casestudies/APPNOTE.TXT
 |url-status   = live
}}</ref>

==See also==
{{Portal|Free and open-source software}}
*[[Comparison of audio formats]]
*[[MPEG-4 SLS]]
*[[Free Lossless Audio Codec|FLAC]]
*TTA
*[[Monkey's Audio]]
*[[Apple Lossless Audio Codec|ALAC]]
*[[Meridian Lossless Packing]]

==References==
{{Reflist}}

==External links==
*[https://www.wavpack.com/ Official website]
*[https://hydrogenaud.io/index.php/board,68.0.html WavPack forum at Hydrogenaudio Forums]
*[https://www.rarewares.org/rrw/wavpack.php Historical versions at ReallyRareWares]
*[https://wiki.hydrogenaud.io/index.php?title=Lossless_comparison A comparison of several Lossless Audio encoders] at Hydrogenaudio Wiki.
*[https://wiki.multimedia.cx/index.php?title=WavPack  WavPack on MultimediaWiki]
*[https://members.home.nl/w.speek/wavpack.htm WavPack frontend]
*[https://www.wavpack.com/flash/wavpack.htm Flash WavPack player]
{{Compression formats}}
{{Compression software implementations}}

[[Category:Lossless audio codecs]]
[[Category:Computer file formats]]
[[Category:Free audio software]]
[[Category:Free audio codecs]]
[[Category:Open formats]]
[[Category:Software using the BSD license]]