Difference between revisions of "WAV"

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'''WAV''' (WAVeform audio format), is a Microsoft and IBM audio file format standard for storing audio on personal computers. It is the main format used on Windows systems for raw, uncompressed audio.
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|{{external|[http://en.wikipedia.org/wiki/WAV WAV]}} (WAVeform audio format) is a Microsoft/IBM audio file container format. It is the main format used on Windows systems for storing uncompressed, lossless audio.
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|<span style="font-style:italic">WAV should not be confused with {{external|[http://www.wavpack.com/ WavPack]}} which is a compressed but lossless format with an optional "hybrid mode" that combines a compressed lossy file with a "correction file" to produce a compressed lossless file. WavPack is not currently supported by Audacity. </span>
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It is a variant of the [[RIFF]] bitstream format method for storing data in "chunks".
 
  
WAV is close to the [[IFF]] on Amiga and the [[AIFF]] format used on Apple Macintosh and Sun computers.
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=Description=
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WAV is a variant of the {{external|[http://en.wikipedia.org/wiki/Resource_Interchange_File_Format RIFF]}} bitstream format method for storing data in "chunks". It is thus similar to both the {{external|[http://en.wikipedia.org/wiki/Interchange_File_Format IFF]}} and [[AIFF]] formats used on Amiga and Apple Macintosh computers respectively.
  
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WAVs and AIFFs are in general equally compatible with either Windows and Macintosh operating systems. WAV files always have {{external|[http://en.wikipedia.org/wiki/Endianness little-endian]}} byte order whereas the original AIFF format was {{external|[http://en.wikipedia.org/wiki/Endianness big-endian]}} until Apple modified it for use on their  OS X operating system.
  
== Description ==
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While the RIFF format can act as a container for various audio compression [[Codecs|codecs]], more typically it contains uncompressed pulse-code modulation ({{external|[http://en.wikipedia.org/wiki/Pulse-code_modulation PCM]}}) audio that retains all the samples of the original signal, and is thus known as "lossless". PCM is the format standard of [[Audio CD|audio CDs]], conveying two channels with a [[Sample Rates|sample rate]] of 44,100 Hz (samples per second), and a [[Bit Depth|bit depth]] of 16 bits per sample.  
Both WAVs and AIFFs are compatible with Windows and Macintosh operating systems. The format takes into account some byte order differences.
 
  
The RIFF format acts as a "wrapper" for various audio compression [[codec]]s.
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This "audio CD" standard consumes approximately 10 MB of disk space on a computer for each minute of audio. In comparison, some modern formats such as [[FLAC]] which are compressed but still lossless, take about 4 MB of space per minute for a comparable file. A  compressed, lossy format like [[MP3]] takes much less space. An MP3 exported from Audacity at its default 128 kbps [[bit rate]] uses about 1 MB of space per minute for either a mono or stereo file.  
 
 
Though a WAV file can hold compressed audio, the most common WAV format contains uncompressed audio in the [[PCM]] format. PCM audio is the standard audio file format for a CD at 44,100 samples per second, 16 bits per sample. (This equates to approximately 10 MB per minute of recording. For comparison an mp3 file at 192 kb/s will use approximately 1.4 MB per minute of recording.)
 
  
Since PCM uses an uncompressed, lossless 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. 
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The bit rate of MP3 can be compared with the much higher rates used in WAV and AIFF. Bit rate for WAV and AIFF is calculated thus:
  
WAV audio can also be edited and manipulated with relative ease using software because no compression or decompression needs to be done on the fly.
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{{code|<nowiki>(sample rate) * (bit depth) * (number of channels) =  kbits per second</nowiki>}}
  
==Popularity==
 
Uncompressed WAV files are quite large in size, so, as file sharing over the Internet has become popular, the WAV format has declined in popularity. However, it is still a commonly used, relatively "pure" file type, suitable for retaining "first generation" archived files of high quality, or use on a system where high fidelity sound is required and disk space is not restricted.
 
  
==References==
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For example, 44 100 Hz, 16 bit stereo equates to (44 100 * 16 * 2) = 1411 kbps.
* http://en.wikipedia.org/wiki/WAV
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* http://www.webopedia.com/TERM/W/WAV.html
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=Popularity=
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Uncompressed WAV files are quite large in size, so as file sharing over the internet has become popular, the WAV format has declined in popularity. However, it is still a commonly used, relatively "pure" file type, suitable for retaining "first generation" archived files of high quality, or use on a system where high fidelity sound is required and disk space is not restricted.
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=Compressed WAVs from portable recorders=
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WAV and AIFF files containing PCM audio can be edited and manipulated with relative ease using computer software, because no decompression or compression needs to be done as part of the processing.
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On the other hand the type of WAV files typically used in portable recorders with limited memory and/or disk space are often some kind of compressed [[ADPCM]] file inside a WAV container. Many software programs including Audacity can have problems with these sort of WAV files. If you import a WAV file from such a recorder into Audacity and it says it cannot recognise the file format, the easiest general solution is to convert the file to a standard PCM WAV in other software. You can convert to standard WAV in {{external|[http://www.erightsoft.com/SUPER.html#Dnload SuperPlayer]}} for Windows, {{external|[http://www.ffmpegx.com/ FFMPEGX]}} on a Mac, or {{external|[http://www.mplayerhq.hu/design7/news.html mplayer]}} on Linux.
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Alternatively, iTunes users can convert the file to  WAV by right-clicking or control-clicking over the file in iTunes and using the "Convert to" option on the context menu. If this does not show WAV, set the conversion format to WAV in iTunes Preferences at {{menu|Advanced > Importing: Import using WAV encoder}}.  
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=Working with WAV or AIFF in Audacity=
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When importing WAV or AIFF files into Audacity, the default behaviour is for Audacity to read the audio data direct from the disk rather than making a copy of it. This is done for speed and disk space considerations. However it does mean that unless you change Preferences so as to copy in the data, you need to keep the original WAV or AIFF file accessible in the same location it was in when you imported it. For more explanation, see [[File_Management_Tips#Loss_of_audio_in_Project_due_to_missing_dependent_file|this section]] of our [[File Management Tips]].
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Additionally, if you choose to read the WAV or AIFF data direct from disk, you can't (except in Audacity Beta 1.3.2 and later) overwrite that WAV or AIFF file by exporting to the same file name and location. For more explanation, see [[File_Management_Tips#Directory_write-protected_or_disk_full_error_when_writing_WAV.2FAIFF|this section]] of [[File Management Tips]].
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[[Category:Audio Formats]]

Revision as of 00:38, 6 November 2007

WAV  (WAVeform audio format) is a Microsoft/IBM audio file container format. It is the main format used on Windows systems for storing uncompressed, lossless audio.
WAV should not be confused with WavPack  which is a compressed but lossless format with an optional "hybrid mode" that combines a compressed lossy file with a "correction file" to produce a compressed lossless file. WavPack is not currently supported by Audacity.


Description

WAV is a variant of the RIFF  bitstream format method for storing data in "chunks". It is thus similar to both the IFF  and AIFF formats used on Amiga and Apple Macintosh computers respectively.

WAVs and AIFFs are in general equally compatible with either Windows and Macintosh operating systems. WAV files always have little-endian  byte order whereas the original AIFF format was big-endian  until Apple modified it for use on their OS X operating system.

While the RIFF format can act as a container for various audio compression codecs, more typically it contains uncompressed pulse-code modulation (PCM ) audio that retains all the samples of the original signal, and is thus known as "lossless". PCM is the format standard of audio CDs, conveying two channels with a sample rate of 44,100 Hz (samples per second), and a bit depth of 16 bits per sample.

This "audio CD" standard consumes approximately 10 MB of disk space on a computer for each minute of audio. In comparison, some modern formats such as FLAC which are compressed but still lossless, take about 4 MB of space per minute for a comparable file. A compressed, lossy format like MP3 takes much less space. An MP3 exported from Audacity at its default 128 kbps bit rate uses about 1 MB of space per minute for either a mono or stereo file.

The bit rate of MP3 can be compared with the much higher rates used in WAV and AIFF. Bit rate for WAV and AIFF is calculated thus:

(sample rate) * (bit depth) * (number of channels) = kbits per second


For example, 44 100 Hz, 16 bit stereo equates to (44 100 * 16 * 2) = 1411 kbps.

Popularity

Uncompressed WAV files are quite large in size, so as file sharing over the internet has become popular, the WAV format has declined in popularity. However, it is still a commonly used, relatively "pure" file type, suitable for retaining "first generation" archived files of high quality, or use on a system where high fidelity sound is required and disk space is not restricted.

Compressed WAVs from portable recorders

WAV and AIFF files containing PCM audio can be edited and manipulated with relative ease using computer software, because no decompression or compression needs to be done as part of the processing.

On the other hand the type of WAV files typically used in portable recorders with limited memory and/or disk space are often some kind of compressed ADPCM file inside a WAV container. Many software programs including Audacity can have problems with these sort of WAV files. If you import a WAV file from such a recorder into Audacity and it says it cannot recognise the file format, the easiest general solution is to convert the file to a standard PCM WAV in other software. You can convert to standard WAV in SuperPlayer  for Windows, FFMPEGX  on a Mac, or mplayer  on Linux.

Alternatively, iTunes users can convert the file to WAV by right-clicking or control-clicking over the file in iTunes and using the "Convert to" option on the context menu. If this does not show WAV, set the conversion format to WAV in iTunes Preferences at Advanced > Importing: Import using WAV encoder.

Working with WAV or AIFF in Audacity

When importing WAV or AIFF files into Audacity, the default behaviour is for Audacity to read the audio data direct from the disk rather than making a copy of it. This is done for speed and disk space considerations. However it does mean that unless you change Preferences so as to copy in the data, you need to keep the original WAV or AIFF file accessible in the same location it was in when you imported it. For more explanation, see this section of our File Management Tips.

Additionally, if you choose to read the WAV or AIFF data direct from disk, you can't (except in Audacity Beta 1.3.2 and later) overwrite that WAV or AIFF file by exporting to the same file name and location. For more explanation, see this section of File Management Tips.