Audio file formats

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Peter 29Apr16: capturing an email comment from Gale: "I'm not sure of the purpose of that Audio file formats page. ATM it just serves as an index to Wiki file format pages, and I don't think we should maintain a duplicate of the comparison table there. That (this) Wiki page could become mainly a page for tips and tricks about managing audio files. Then the link to the context menus page makes sense."

Contents

Supported audio file formats

Audacity supports many audio formats including:

  • WAV (Windows Wave format)
  • AIFF (Audio Interchange File Format, a PCM format used on Macintosh and similar computers)
  • MP3 (MPEG-1, layer 3) (export requires separate encoder. see Lame Installation FAQ in the Audacity Manual )
  • MP2 (MPEG-1 Layer 2) is a size-compressed, lossy audio format from which the popular MP3, MPEG-1 Layer 3, format was developed.
  • Ogg Vorbis
  • FLAC
  • Sun Au / NeXT
  • IRCAM (Institut de Recherce et Coordination Acoustique / Musique) SF format
Audacity supports import and export of additional formats such as AC3, AMR(NB), M4A AAC and WMA if you install the optional FFmpeg library. See this Frequently Asked Question for details.

Audacity project format

The structure of a saved Audacity project is:

  • An AUP project file - the name of the project followed by ".aup", for example "my_song.aup"
  • A _data folder with the same project name and in the same folder as the .aup file, for example "my_song_data"
  • Within that _data folder, a sub-folder structure with lots of little AU files which are individual segments of the audio data.
Note that default behavior on Windows and Mac is to hide certain file extensions; if this applies, the .aup file will only appear as "my_song" in the computer. On Windows, the .aup extension will be hidden if Audacity was installed from the .exe installer and "Hide file extensions for known file types" remains checked in Windows Explorer. You can unhide extensions on Windows by following these instructions.

The project file describes how Audacity links these AU files together to make up the clips and tracks in the project; it also contains gain, pan and envelope information, data to manage the waveform display and carries links to any dependent audio files being read directly from their source location.

The AUP file is in XML format and can be opened in a text editor if required. The AU files are stored in a lossless uncompressed format. Their default size is 1 MB or less. This Audacity Project Format is designed to make editing audio faster in Audacity. By updating individual AU files during editing, Audacity can change audio or move it around in the project without copying large quantities of data from one place to another.

See Managing Audacity Projects in the Audacity Manual for more details.

Warning icon Audacity's project format is not compatible with and cannot be opened in any other audio application.

How to open audio files using operating system context menus

Please see this page for details on how to do this.

File size and channel comparisons by export format

See this table in the Audacity Manual which gives typical achieved mono and stereo file sizes with different formats at default Audacity settings (that is, 44100 Hz sample rate and default bit rate or quality settings in the case of compressed formats). Where VBR compression is employed, the achieved size will vary depending on the content.

Some formats can be exported as multi-channel files containing more than two channels, if you enable this at "Use custom mix" in the Import / Export Preferences. The final column in the table shows the maximum number of channels per exported file.

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