WAV

Waveform Audio File Format (WAVE, or more commonly known as WAV due to its filename extension),^[3][6][7][8] (also, but rarely, named, Audio for Windows^[9]) is a Microsoft and IBM audio file format standard for storing an audio bitstream on PCs. It is an application of the RIFF bitstream format method for storing data in "chunks", and thus is also close to the 8SVX and the AIFF format used on Amiga and Macintosh computers, respectively. It is the main format used on Windows systems for raw and typically uncompressed audio. The usual bitstream encoding is the linear pulse-code modulation (LPCM) format.

Description

Both WAVs and AIFFs are compatible with Windows, Macintosh, and Linux operating systems. The format takes into account some differences of the Intel CPU such as little-endian byte order. The RIFF format acts as a "wrapper" for various audio compression codecs.

Though a WAV file can hold compressed audio, the most common WAV format contains uncompressed audio in the linear pulse code modulation (LPCM) format. The standard audio file format for CDs, for example, is LPCM-encoded, containing two channels of 44,100 samples per second, 16 bits per sample. Since LPCM uses an uncompressed storage method which keeps all the samples of an audio track, professional users or audio experts may use the WAV format for maximum audio quality. WAV audio can also be edited and manipulated with relative ease using software. The WAV format supports compressed audio, using, on Windows, the Audio Compression Manager. Any ACM codec can be used to compress a WAV file. The user interface (UI) for Audio Compression Manager may be accessed through various programs that use it, including Sound Recorder in some versions of Windows.

Beginning with Windows 2000, a WAVE_FORMAT_EXTENSIBLE header was defined which specifies multiple audio channel data along with speaker positions, eliminates ambiguity regarding sample types and container sizes in the standard WAV format and supports defining custom extensions to the format chunk.^[4][5][10]

There are some inconsistencies in the WAV format: for example, 8-bit data is unsigned while 16-bit data is signed, and many chunks duplicate information found in other chunks.

WAV files can contain embedded IFF "lists", which can contain several "sub-chunks".^[11][12][13]

Metadata

As a derivative of the Resource Interchange File Format (RIFF), WAV files can be tagged with metadata in the INFO chunk. In addition, WAV files can embed Extensible Metadata Platform (XMP) data. Applications may not handle this extra information or may expect to see it in a particular place. Although the RIFF specification requires applications ignore chunks they do not recognize, some applications are confused by additional chunks.

Popularity

Uncompressed WAV files are large, so file sharing of WAV files over the Internet has declined in popularity. However, it is still a commonly used file type, suitable for retaining "first generation" archived files of high quality, for use on a system where disk space is not a constraint, or in applications such as audio editing, where the time involved in compressing and uncompressing data is a concern.

More frequently, the smaller file sizes of compressed but lossy formats such as Ogg Vorbis, MP3, ATRAC, AAC, Musepack and WMA are used to store and transfer audio. Their small file sizes allow faster Internet transmission, as well as lower consumption of space on memory media. However, lossy formats trade off smaller file size against loss of audio quality, as all such compression algorithms compromise available signal detail. There are also lossless codecs, such as FLAC, Shorten, Monkey's Audio, ATRAC Advanced Lossless, Apple Lossless, WMA Lossless, TTA, and WavPack, but none of these is yet a ubiquitous standard for either professional or home audio.

The usage of the WAV format has more to do with its familiarity, its simplicity and simple structure, which is heavily based on the RIFF file format. Because of this, it continues to enjoy widespread use with a variety of software applications, often functioning as a 'lowest common denominator' when it comes to exchanging sound files among different programs.

Use by broadcasters

In spite of their large size, uncompressed WAV (though that format can be different from the Microsoft WAV) files are sometimes used by some radio broadcasters, especially those that have adopted the tapeless system. BBC Radio in the UK uses 44.1 kHz 16-bit two-channel .wav audio as standard in their VCS system. A phased migration to 48 kHz sample rate has been announced[1]. BBC English Regions already uses 48 kHz.

• The ABC "D-Cart" system, which was developed by the Australian broadcaster, uses 48 kHz 16-bit two-channel .wav files, which is identical to that of Digital Audio Tape.
• The Digital Radio Mondiale consortium uses WAV files as an informal standard for transmitter simulation and receiver testing.

Limitations

The WAV format is limited to files that are less than 4 GB, because of its use of a 32-bit unsigned integer to record the file size header (some programs limit the file size to 2–4 GB).^[14] Although this is equivalent to about 6.8 hours of CD-quality audio (44.1 kHz, 16-bit stereo), it is sometimes necessary to exceed this limit, especially when greater sampling rates or bit resolutions are required. The W64 format was therefore created for use in Sound Forge. Its 64-bit header allows for much longer recording times. The RF64 format specified by the European Broadcasting Union has also been created to solve this problem.

Unlike formats like FLAC, WAV files don't usually have information fields, for instance, in the case of a song, title, artist, album, year, etc.^[15]

Non-audio data

Since the sampling rate of a WAV file can vary from 1 Hz to 4.3 GHz, and the number of channels can be as high as 65536, .wav files have also been used for non-audio data. LTspice, for instance, can store multiple circuit trace waveforms in separate channels, at any appropriate sampling rate, with the full-scale range representing ±1 V or A rather than a sound pressure.^[16]

Audio CDs

Audio CDs do not use WAV as their sound format, using instead Red Book audio. The commonality is that both audio CDs and WAV files have the audio data encoded in PCM. WAV is a data file format for a computer to use that cannot be understood by CD players directly. To record WAV files to an Audio CD the file headers must be stripped and the remaining PCM data written directly to the disc as individual tracks with zero-padding added to match the CD's sector size. In order for a WAV file to be able to be burned to a CD with most burners it should be in the 44100 Hz, 16-bit stereo format.

WAV file compression codecs compared

As mentioned wav files can be encoded with a variety of codecs to reduce the file size (for example the GSM or MP3 codecs).

This is a reference to compare the monophonic (not stereophonic) audio quality and compression bitrates of the different codecs available for .wav files including PCM, ADPCM, Microsoft GSM 06.10, CELP, SBC, Truespeech and MPEG Layer-3.

The above are WAV files; even those that use the MP3 codec have the ".wav" extension.

See also

• Audio Compression Manager
• Broadcast Wave Format (BWF)
• RF64, an extended file format for audio (multichannel file format enabling file sizes to exceed 4 gigabytes)

References

1. ^ Microsoft Corporation (June 1998). "WAVE and AVI Codec Registries - RFC 2361". IETF. http://tools.ietf.org/html/rfc2361. Retrieved 2009-12-06. 
2. ^ http://filext.com/file-extension/WAV
3. ^ ^{a b} IBM Corporation and Microsoft Corporation (August 1991) (TXT), Multimedia Programming Interface and Data Specifications 1.0, http://www.kk.iij4u.or.jp/~kondo/wave/mpidata.txt, retrieved 2009-12-06 
4. ^ ^{a b} P. Kabal (2006-06-19). "Audio File Format Specifications - WAVE or RIFF WAVE sound file". McGill University. http://www-mmsp.ece.mcgill.ca/Documents/AudioFormats/WAVE/WAVE.html. Retrieved 2010-03-16. 
5. ^ ^{a b} "Multiple Channel Audio Data and WAVE Files". Microsoft Corporation. 2007-03-07. http://www.microsoft.com/whdc/device/audio/multichaud.mspx. Retrieved 2010-03-16. 
6. ^ IBM Corporation and Microsoft Corporation (August 1991). "Multimedia Programming Interface and Data Specifications 1.0". http://www.tactilemedia.com/info/MCI_Control_Info.html. Retrieved 2009-12-06. 
7. ^ Library of Congress (2008-09-12). "WAVE Audio File Format". http://www.digitalpreservation.gov/formats/fdd/fdd000001.shtml. Retrieved 2009-12-06. 
8. ^ Microsoft Corporation (June 20, 1999). "Waveform Audio File Format, MIME Sub-type Registration - INTERNET-DRAFT". IETF. http://tools.ietf.org/html/draft-ema-vpim-wav-00. Retrieved 2009-12-06. 
9. ^ "Information about the Multimedia file types that Windows Media Player supports". Microsoft Help and Support. Microsoft Corporation. 12 May 2008. http://support.microsoft.com/kb/316992. Retrieved 29 May 2009. "Windows uses the Wave Form Audio (WAV) file format to store sounds as waveforms. One minute of Pulse Code Modulation (PCM)-encoded sound can occupy as little as 644 kilobytes (KB) or as much as 27 megabytes (MB) of storage." 
10. ^ EBU (2009-07) (PDF), EBU Tech 3306 - MBWF / RF64: An Extended File Format for Audio, http://tech.ebu.ch/docs/tech/tech3306-2009.pdf, retrieved 2010-01-19 
11. ^ "WAVE File Format". archive.org. 1999-11-15. Archived from the original on 1999-11-15. http://web.archive.org/web/19991115123323/http://www.borg.com/~jglatt/tech/wave.htm. Retrieved 2010-03-16. 
12. ^ "WAVE PCM soundfile format". archive.org. 2003-01-20. https://ccrma.stanford.edu/courses/422/projects/WaveFormat/. Retrieved 2010-03-16. 
13. ^ "The WAVE File Format". http://www.lightlink.com/tjweber/StripWav/WAVE.html. Retrieved 2010-03-16. 
14. ^ 1 GB = 1024 MB; 1 MB = 1024 KB; 1 KB = 1024 B
15. ^ ID3#Implementation_in_non-mp3s_and_alternatives
16. ^ http://ltspice.linear.com/software/scad3.pdf#page=98
17. ^ 1 kbit = 1000 bit
18. ^ 1 KB = 1024 B

External links

• WAVE file format specifications - from McGill University, (Last update: 2006-06-19)
• A summary of the WAVE file format
• WAVE_FORMAT_EXTENSIBLE Specification from Microsoft (Updated on March 7, 2007)
• More information on WAVE_FORMAT_EXTENSIBLE - University of Bath
• WAVE File Format - technical details (1999)