WavPack

WavPack

Hybrid Lossless Audio Compression
Developer(s)	David Bryant
Release information
Initial release	{{{released}}}
Stable release	5.5.0 (2022-07-07)
Preview release	None
Compatibility
Operating system	Windows, MacOSX, Linux/BSD/Unix, ...
Additional information
Use	Encoder/Decoder
License	BSD license
Website	http://www.wavpack.com/

WavPack (pronounced "wave-pack") is a lossless audio codec, also offering optionally a hybrid lossless/lossy mode. It is distributed as a free open-source encoder/decoder with a library and a large number of tools, including a Windows GUI and a range of plugins for both audio players and other software. Third party implementations are available, including ffmpeg. WavPack supports and/or can be played back on a large number of platforms/OSes including mobile (Android, iOS), portable (Rockbox) and even web apps.

WavPack is arguably the most feature-rich lossless compressor, supporting a unique range of audio signals including Direct-Stream Digital. While many special features might require the user to apply the WavPack executable directly (which may be achieved with drag+drop, see the Using WavPack section below), everyday use is supported by a wide range of players and taggers.

Performance-wise, WavPack defaults to a fast codec – compressing around FLAC's default size, albeit not decoding as ultra-light. The user might fine-tune performance through a wide range of options, but all will decode faster than the high-compression Monkey's Audio/OptimFROG codecs. There is only one codec (TAK) which is able to outperform WavPack on both compression and encoding speed and decoding speed simultaneously.

WavPack has inspired other codecs and their features. For more on WavPack, including on its history and technology, see the Wikipedia entry.

Features

For an end-user considering WavPack as a an audio format, its feature-richness might be the big selling point. WavPack supports pretty much all the more common features noted at HA Wiki's Lossless Codec Comparison as in the following first list, but several users might consider the more unique features listed under the subsequent headline.

• Seekable and streaming playback.
• Error handling: upon playback, it will detect and report corrupted frames, mute to protect against static/noise output, and continue playback. Since version 5, WavPack can also check for corruption without decoding, hence quicker than any decoding format. Optional MD5 audio checksum can also be added upon encoding for file fingerprinting.
• High-resolution audio support up to 32-bit (both 32-bit integer and 32-bit float) and gigaherz sampling rates.
• Multichannel support: currently capped at 256 channels, supports WAVEFORMATEXTENSIBLE channel masks.
• Piping support for encoding, and support for RAW PCM input/output.
• RIFF chunks supported for recreating also non-audio chunks of the original files; by default, WavPack will restore to a file bit-identical to the original.
• Tagging: APEv2. (ID3v1 is possible, but not advisable.)
• Cuesheet support. In practice, some applications handle embedded cuesheets better in WavPack than in some other formats.
• Unicode support.
• Can be used in the Matroska container.
• Windows GUI available.

WavPack also handles bit depths not divisible by 8, and is known to employ a "wasted bits" strategy: For, say, a 20 bit signal in a 24 bit container, WavPack will detect that bits 21 to 24 are "wasted" and compressed as 20-bits without size penalty.

Special/unique features

Most of these features are shared with only a few if any notable codecs, or extend to signal types or file types others do not support (comparisons given).

• DSD support: can losslessly compress Philips DSDIFF and Sony DSF files (see "Using WavPack" below); can import ID3v2.3 tags from DSF. (No other end-user codec compresses DSD.)
• High-resolution support for bit depth 1-bit to 32-bit integer and sampling rates up to 2 GiHz in integer steps. (Officially, 1 GHz is supported – it is gigaherz, not MHz, the upper limit being in the UHF radio frequency band. Monkey's Audio, OptimFROG and MPEG-4 ALS support the entire WAVE range up to 4 GiHz.)
• 32-bit floating-point supported – also including CoolEdit/Adobe Audition's 32-bit float format (use the -a option only if the .wav was generated by CoolEdit/Audition). (This line like OptimFROG.)
• Multi-channel support, currently (5.5.0) capped at 256 channels (can be extended to the thousands – for even more, MPEG-4 ALS supports 66536.)
• Hybrid lossy/lossless mode (can also be used as lossy). (Like OptimFROG.)
• Can in addition to PCM in WAVE files also read and output to RF64, Sony's Wave64, and CAF (including > 4 GB files and both endianness CAF – the latter apparently unique among lossless formats). Also, WavPack will upon decoding recreate any (standards-compliant) file bit by bit including non-audio parts, to whatever input format it supports. (Monkey's/OptimFROG/TAK do the same to the input formats they support.)
• Recompression: Can recompress .wv files in place, with tag transfer. (Like FLAC on .flac files.)
• Drag and drop support: Dropping a file on to wavpack.exe/wvunpack.exe will encode/decode it to source directory. (Like FLAC.) From 5.5.0, one can also apply options to drag and drop by renaming the executable, and drop several files.

Limitations

The following limitations are certainly not unique to WavPack. None seem to be able to force WAVE version (though some can force RF64), only FLAC can force decoding to AIFF (big-endian only) and only Monkey's support AIFF with full file structure restore (big-endian only) or the legacy AU/SND format.

• Despite being available for several platforms, PCM in AIFF is currently not supported. (See below for workarounds.)
• Although output can be forced to various filetypes, there seems not to be an easy way to force output to a given version of the WAVE format, nor to force RF64 if less than 4 GiB output.
• DSD: Will reject DST-compressed DSD (which are already compressed heavier than WavPack does); can currently not import ID3v2.4, only ID3v2.3 (use Mp3tag to copy tags).

As of version 5.4.0, some features are discontinued. XP support is officially dropped (though an "unofficial" build is available – otherwise, 5.3.0 released April 2020 supports XP), version 5 does no longer offer compression to Windows .sfx self-extracting file (cf. OptimFROG) nor the -p feature. Furthermore, WavPack version 3.x files are no longer supported. To recompress these files (if any are still around, WavPack 4 was released in 2004) to WavPack 5 files (for the fast decoding-free error checking feature), one must first recompress by WavPack 4.80 (still available) or lower, and then by WavPack 5.

As of July 2022, WavPack for MacOS through HomeBrew is still at version 5.4.0.

WavPack has traditionally had less hardware support than FLAC (Rockbox having been the most notable platform, others listed at https://www.wavpack.com/index.html#Hardware ), but with WavPack playback through Android and iOS players, the distinction between "hardware" and "software" is arguably blurred.

Using WavPack

WavPack files can be played back in supported players (see below), and several of these can encode to WavPack. However, there are situations where certain WavPack features are accessible only through the WavPack executables directly. For example, you cannot count on RIFF support by encoding through players which often deliver only the audio to the encoder – and you cannot count on such players to restore non-audio data faithfully. Also, the input format might exceed the player's internal decoding; e.g. trying to convert 32-bit integer or DSD with foobar2000 will yield a warning that it will not be lossless (also, converting DSD to PCM leads to files many times the size).

Drag and drop (Windows)

The simplest encoding/decoding might be dragging and dropping a (supported) file to wavpack.exe (/wvunpack.exe). Then the file will be encoded/decoded with the default options. Dropping a .wv file onto wavpack.exe will recompress it, prompting before overwrite (again, using default settings – possibly a bad deal if it was encoded with high -x switches). Also it works on a shortcut to the executable. It is not possible to drop a folder, but from version 5.5.0, there is a way to drag and drop several files.

From version 5.5.0, drag and drop supports options by renaming the executable. The user can make a copy of the executable, rename it according to preferred settings, and those settings will be applied to the process upon drag and drop. The example given by the author in this forum post also gives encoding options that many WavPack users will recommend, and novice users can choose to copy that filename for the executable. For fine-tuning performance or performing more specialized tasks, one will however have to learn the options, see next subsection.

Options and the command line (Windows command-line hints here)

For tuning performance, one might want to apply command-line options. Some options are called by external encoders without the user having to type – e.g. encoding with foobar2000, there are two compression sliders, one for the fast-to-extra-high and one for the -x settings (see below) – but in the Windows GUI one will want to type them in. Options can be concatenated for short, like for example writing -hh -x2 -m -v -y as -hhx2mvy.

The user should beware that the wavpack encoder and the wvunpack decoder (and wvtag/wvgain) have to "re-use letters" for different purposes, and e.g. -b, -c do not have related functions upon decoding as upon encoding. However some do the same in the wvunpack and wavpack (like -d for delete input file, -y for "yes to all" and -l for "run with low priority" (Windows only)) – and others cover the same purpose in both executables (like -m and -v).

Encoding

The basic encoding usage is wavpack filename.extension (which creates filename.wv) – this is what drag and drop accomplishes. Wildcards are supported, e.g wavpack *.wav. For a single input file, one can specify output like e.g. wavpack infilename.wav -o outfilename.wv. Input file extension ".wav" can be dropped, and output ".wv" extension as well – but wavpack foo will only find foo.wav, not e.g. foo.w64. For Windows, the -o can be dropped, i.e. wavpack infilename.wav outfilename.wv. The manual (online, or included as wavpack_doc.html in the distribution) gives an exhaustive reference, and the following is merely a selection. Encoding using -hxm seems a sensible trade-off between compression and CPU load.

• Compression. WavPack has four compression modes that affect compression as well as encoding and decoding time: fast (-f), default (no switch), high (-h) and very high (-hh). The CPU load of -hh is measured to around twice that of -f. The WavPack manual does (still as of 2022) warn against -hh for portable use due to its decoding CPU usage, although it does decode faster than any Monkey's. On top these modes, the optional extra processing -x1 to -x6 settings will apply extra compression effort that does not increase decoding CPU load. -x without number is synonymous to -x1, which is often recommended (in all modes, fast/normal/high/extra high). The official manual calls -x4 to -x6 "extremely slow", but the size gains might be significant for high resolution audio in particular (van Beurden's revision 5, testing -x4).

With DSD files, there are only two compression settings, normal (selected by -f or no switch) and high (selected by -h or -hh), and the -x switches are silently ignored.

• Guarding against errors upon encoding: The "-m" switch will compute an audio MD5 sum (like FLAC does by default) and store it for later verification. The "-v" switch will verify by decoding the file after encoding and writing the file to disk. -mv will do both. (Using the corresponding switches in wvunpack will check without producing output file, however wvunpack also has a faster corruption check switch -vv for WavPack 5-encoded files.)
• --import-id3 will import ID3v2.3 tags (currently not v2.4) present in the source file – typically in Sony DSF files – and convert them to WavPack's preferred APE tags. (It will still keep the chunk for restoring the original file.) By default, this is limited to 1 MB; for more, use --allow-huge-tags. Same option works in wvtag.
• -r: remove extra (non-audio) chunks. By default, WavPack will store these in the .wv file for later bit-by-bit restoration of everything, not only the audio. Use -r to throw them away – like encoding through most players appear to do.
• --pause: (Windows only!) waits for keypress at the end. Useful for reading output before exit when calling wavpack/wvunpack in a separate window (which the Windows front-end does).
• -y: "yes" to everything. Use with caution, will overwrite. From 5.5.0 there is also a --no-overwrite that will skip instead of asking to overwrite.
• -d: delete source file upon successful completion. Again, use with caution.
• -l will force WavPack to run at low priority (Windows only)
• -c with -b to select lossy quality: Create correction file for hybrid lossless/lossy use.

WavPack can recompress .wv files in place (using a temporary file until done). For example, wavpack -hx4mvy wavpackfile.wv will recompress wavpackfile.wv the file in high mode using -x4 extra processing, write audio MD5 to it, open the temp file and re-read for verification – and once verified, replace the old wavpackfile.wv. Tags will be transferred. wavpack -hx4rlmvy wavpackfile.wv will also run with low priority (assuming the Windows platform), and will discard non-audio chunks – that is, the ones used to restore the original file's metadata; the .wv file's APE tags will still be copied. As an example, one can compress an ID3v2.4-tagged DSF file by drag and drop; WavPack will then store the tag chunk, but WavPack cannot import v2.4. Then open both in Mp3tag, copy the ID3v2.4 tags to the WavPack file, decide that there is no need to restore the original file's ID3v2.4 upon ucompressin, and apply the wavpack -hx4rlmvy wavpackfile.wv command; it will then discard that chunk (but keep the tags that Mp3tag wrote!), recompress using high (silently ignoring the -x4 that has no effect on DSD) with low priority, write an MD5 sum, verify the process and replace the .wv file by the new recompressed file.

(To fill in:) hybrid encoding

(... by someone who knows the details. DSD can currently not be hybrid-encoded.)

Decoding

{stub-subsection, incomplete}

Basic decoding usage – as will be accomplished by drag and drop – is wvunpack filename.wv. If encoded from file, the default operation is to restore the exactly same file, with suffix as appropriate: filename.wav / filename.w64 / filename.caf. (Though WavPack then knows the original input format, it does not store the original file name.) If only audio was encoded (from a player, pipe or -r), output defaults to filename.wav.

Again, file extensions can be dropped; e.g., using wvunpack foo bar will decode foo.wv to bar.wav/bar.w64/bar.caf, extension chosen from original format. Assigning an output extension – like bar.w64 – will override input format.

Other file handling

{stub-subsections, incomplete}

Error checking and other file info

To get information about WavPack files without decoding to file, use wvunpack. For use with the Windows front-end, the --pause switch is essential to read the output.

• --pause: (Windows only!) waits for keypress at the end.
• -vv: Quick verify without decoding (WavPack 5 files only). This functionality seems to be unavailable outside the official wvunpack (other applications which verify will fall back to the next item, -v):
• -v: Verify (will decode to check that everything is OK – but not write any file).
• -s/-ss: -s displays summary of the file, -ss a long summary including tags
• -x FIELD: Shows tag, e.g. -x comment shows the <comment> field. Also wvtag -x does the same thing.
• -c: Like -x cuesheet. Also wvtag -c does the same thing.

(To fill in:) Tagging (wvtag) and replaygain management (wvgain)

(... most of these options are available in HA's fave taggers/player?)

Using 3rd party tools; FFmpeg's WavPack encoder/decoder, and others

FFmpeg can encode/decode to/from WavPack, with some limitations. FFmpeg can decode WavPack 5 files, but will only write WavPack 4 (thus, no fast verification). Also, compression presets are different, defaulting to fast but not particularly good compression. On the other end, FFmpeg offers even slower modes than -hhx6.

There is potential information loss in using ffmpeg; for example, RIFF metadata (or AIFF) will be lost, and WAVE/AIFF output will default to 16-bits (potentially lossy) – anything else must be specified.

From/to AIFF – preserving bit depth

Reference WavPack will encode a 20-bit (or 17, for that matter) .wav file and keep the information that it is 20 (/17) bits. FFmpeg on the other hand, will be upconverted to 24 bit .wv, deleting the information that it was ever 20 (/17) bits. As reference WavPack cannot handle .aiff (but handles .caf), the following procedure can be used on bit depths not divisible by 8:

• To decode .wv to AIFF and preserve bit depth: wvunpack "infile.wv" --caf-be - | ffmpeg -i - -codec copy "outfile.aiff"
• To encode AIFF, possibly with bit depths like 17 preserved: There are AIFF to WAVE conversion software that will preserve bit depth flags (here ffmpeg doesn't), but presuming a a lossless audio user has flac.exe around: flac --fast --lax "aiff infile.aiff" -o - | flac -d - -o - | wavpack - "wavpack outfile.wv" will do a flac encode/decode provided bit depth is 4 to 24.

(One limitation of ffmpeg is that RIFF chunks will be discarded – but for AIFF that is not an issue anyway, as WavPack cannot store AIFF metadata.)

Splitting WavPack files by cuesheet

wvunpack cannot split WavPack files by neither embedded nor external cuesheet, but some external applications can (and will have to decode/re-encode): CUETools can if it is CDDA (44.1 kHz 16-bit stereo), and can re-encode back to WavPack. refalac can decode split by cuesheets with the appropriate DLL files, outputting WAVE or ALAC-in-MP4.

Software support

With Android support and playback through ffmpeg, it might no longer be feasible to maintain a list of applications that can play WavPack files, and the following is most certainly incomplete – as is the list at https://www.wavpack.com/#Software .

Players

• foobar2000 advanced freeware audio player plays/decodes WavPack out of the box on both Windows, MacOS, Android and iOS (Windows: supports encoding if wavpack.exe is installed, and redistributes the official wavpack.exe through its "Free encoder pack" addon for encoding. With ReplayGain & cuesheets support.) Also Boom from the same author.
• VLC multiplatform media player
• VUPlayer (official plugin, supports encoding)
• NullSoft Winamp (plugin with ReplayGain & Media Library support) and Winamp-compatible players
• Windows Media Player and other directshow-based players (MPC, TCMP, RadLight) (with CoreWavPack directshow filter)
• Cog Audio player for MacOS X.
• JRiver Media Center
• XMMS (with Kuniklo's plugin)
• LAMIP (official plugin)
• MPXplay for DOS!
• Aqualung for GNU/Linux
• Cowon JetAudio Player and CD ripper
• XMPlay Plugin required (WavPack input plugin) and (bass library) to play 'wv' files

Converters, CD rippers etc.

Several of the players, like Cowon JetAudio, foobar2000 and VUplayer, also have converters that can create WavPack files. More:

• Custom Windows WavPack frontend (by Speekenbrink)
• dBpowerAMP Music Converter CD ripper/writer / Audio Player / (official addon)
• fre:ac multi-platform CD ripper/converter
• Exact Audio Copy CD Ripper (guide at this wiki)
• Nero
• CDex CD ripper
• Ease Audio Converter (Shareware / NOT Freeware)
• Media.io Online Audio Converter
• Konvertor
• CUETools converter and AccurateRip/CTDB checker
• refalac

Taggers

• Mp3tag Universal Tag Editor
• MusicBrainz Picard Tagger with audio identification
• The GodFather Tagger / Music manager
• Case's Tag command line tagger

Other tools

• Adobe Audition and Cool Edit (filter with 32-bit floats & extra info save support)
• Mr. QuestionMan
• mkvtoolnix – tool to multiplex WavPack streams inside the Matroska container

It's worth mentioning the Matroska guys decided to concentrate on WavPack as the lossless compressor of choice for their container. Quite an honor... :-)

• PKWare's .zip format compresses audio by WavPack since version 6.3.2 (2007). Beware that there is no expectation that other decompression software handles these zip files; even if PKWare co-designed the format and PKZip was the original .zip implementation, their subsequent compression methods are outside the ISO/IEC standardized zip format specification.

Links

• Official website
• Github repository
• Unofficial 4.32 multiplatform versions at RareWares
• WavPack at Wikipedia
• WavPack at Multimediawiki (not updated with version 5)
• HA Wiki's Lossless Codec Comparison originally by Rjamorim
• An older (2005) performance comparison of lossless audio compressors (archived on October 27, 2015) by Speek, using WavPack version 4.0