Export Formats supported by Audacity - Audacity Manual

# Export Formats supported by Audacity

From Audacity Development Manual
This page describes audio file formats which can be exported to using the Export Audio / Export Selected Audio and Export Multiple dialogs.

To export to formats listed as "FFmpeg" you must install the optional FFmpeg library.

| Many format types have size, quality or encoding options. Select the format type then click the Options... button in the Export Audio / Selected Audio or Export Multiple dialog to view the options for that selected format. You can click the first link in each format listed below to view the Options page for that format.

## Contents

1. Uncompressed format types
2. Compressed format types
3. External encoder program
4. FFmpeg format types (mostly compressed)
5. Custom FFmpeg Export
6. File size and channel comparisons by export format
7. Exporting to formats not listed in the Export Audio Dialog

## Uncompressed format types

The following are all uncompressed audio formats in which every sample of sound is represented by a binary number. The most common uncompressed formats are WAV and AIFF.

There is no loss of quality compared to the original audio when playing uncompressed formats, except for some possible loss of low frequencies in the 4-bit (A)DPCM formats. Those 4-bit formats and the lossless 8-bit U-Law/A-Law formats save file size by reducing their bit depth, in a similar way that any of the uncompressed formats can be made proportionately smaller by reducing their sample rate (and thus reducing the high frequencies they can contain). GSM 6.10 WAV (mobile) will also exhibit considerable loss of quality as it was a format designed for mobile telephony.

- Other uncompressed files: includes all the uncompressed audio formats that Audacity can export, including 4-bit (A)DPCM, 8-bit U-Law/A-Law, 24-bit, 32-bit and 64-bit options. Also GSM 6.10 WAV (mobile) which produces a mono WAV file encoded with the compressed, lossy GSM 6.10 codec as used in mobile telephones. This menu item defaults to WAV (Microsoft) signed 16-bit PCM on Windows and Linux and to AIFF (Apple/SGI) signed 16-bit PCM on Mac.
- AIFF (Apple/SGI) signed 16-bit PCM No options for this format: AIFF is a lossless format that can both be played on Mac and Windows computers, though it is far more likely to be selected by Mac users. AIFF 16-bit PCM is suitable whenever you want to burn your exported file to an audio CD.
- WAV (Microsoft) signed 16-bit PCM No options for this format: WAV is a lossless format that can both be played on Windows or Mac computers. WAV 16-bit PCM is eminently suitable whenever you want to burn your exported file to an audio CD.
- WAV (Microsoft) signed 24-bit PCM No options for this format: 24-bit PCM gives higher quality than 16-bit PCM, but takes up more space.
- WAV (Microsoft) 32-bit float No options for this format: 32-bit float WAV is a lossless format, a maximum quality "raw capture" file. 32-bit float resolution gives the highest quality of the three uncompressed choices, but takes twice the storage space on disk compared to 16-bit resolution. It will not play on many players or player apps. It is mostly useful as a backup archive of raw captured recordings or finished projects.

16-bit WAV and AIFF formats produce large files and are best-suited for use on computers rather than portable players or devices.

### Size limits for WAV and AIFF PCM-encoded files

WAV and AIFF files are limited to a maximum size of 4GB (this is a general restriction and not an Audacity one).

See the following table for how this translates to approximate time durations:

  Maximum sizes for files in time duration (hours:minutes)
  Sample Format | Stereo | Mono
  16-bit (default) | 6h:45m | 13h:31m
  24-bit | 4h:30m | 9h:01m
  32-bit | 3h:22m | 6h:45m

| These timings are the theoretical maximum times. You would be well-advised to restrict yourself to slightly lower limits to afford some head-room.

## Compressed format types

Size-compressed formats produce files that are usually significantly smaller than uncompressed formats, as seen in the table below. The file formats that are significantly smaller are always of lower quality than the original audio, but are well suited for use on portable devices where storage space is limited.

- MP3 Files: MP3 is a popular compressed, lossy format producing much smaller files than WAV or AIFF, at the expense of some loss of quality.
- OGG Vorbis Files: Ogg Vorbis is the compressed, lossy Vorbis codec in an OGG container. Vorbis offers higher quality than MP3 for the same file size, and is useful for good quality small-sized mono files, but fewer applications can play the OGG format.
- FLAC Files: FLAC is a compressed but lossless format, giving much larger file sizes than MP3 and OGG but only about half the size of WAV.
- MP2 Files: MP2 is a compressed, lossy format similar to MP3, producing slightly larger files than MP3 for the same quality.

## External encoder program

- (external program): sends audio via the command-line to any executable binary application either for processing or for encoding as a file. This is a method to export using an alternative compressed or uncompressed encoder or to a format not otherwise supported by Audacity.

## FFmpeg format types (mostly compressed)

The following export types are listed in released builds of Audacity on Windows and Mac, and in other builds where FFmpeg is enabled. They will only function if you install the optional FFmpeg library.

The following four formats are small-sized compressed formats giving file sizes comparable to or smaller than MP3.

- M4A (AAC) Files (FFmpeg): Advanced Audio Coding is a compressed, lossy format used in Apple applications, generally achieving slightly better quality than MP3 for the same file size. By default, the exported file will be given an "m4a" extension. Optional permitted extensions: .mp4, .m4r (ringtone) and .3gp (mobile).
- AC3 Files (FFmpeg): the common name used for the compressed, lossy format used in Dolby Digital.
- AMR (narrow band) Files (FFmpeg): the Adaptive Multi-Rate codec is a patented compression scheme optimized for speech, but also used for mobile telephone ringtones. The wide band variant uses higher bandwidth for higher quality.
- WMA (version 2) Files (FFmpeg): Windows Media Audio v2 is a compressed, lossy format developed by Microsoft. Optional permitted extensions: .asf or .wmv.

### Custom FFmpeg Export

- Custom FFmpeg Export: Allows interface-based export of some additional compressed or uncompressed formats not listed above, and options for exporting formats containing alternative codecs (for example, WAV format containing MP3 or OGG format containing FLAC). Note: not all formats and codecs are compatible, and some exports might result in zero-byte or invalid files if FFmpeg does not support the combination chosen.

  The most flexible method to export to more formats using FFmpeg (or using any alternative encoder of your choice) is therefore to select (external program) as above and use the command-line encoder. See How can I export to formats not listed in the Export Audio Dialog? for more information.

## File size and channel comparisons by export format

The following table gives typical achieved mono and stereo file sizes with different formats at default Audacity settings (that is, 44,100 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 Audacity can export for each format. Some formats may theoretically support more channels than Audacity can export.

  Format | Lossy | Compression | File size (MB per minute): | File size limit: | Channels
  mono | stereo
  WAV 16-bit PCM | No | None | 5.0 | 10.0 | 4 GB(1) | 32
  AIFF 16-bit PCM | No | None | 5.0 | 10.0 | 4 GB(1) | 32
  FLAC 16-bit | No | VBR | 2.5 | 5.0 |  | 8
  M4A (AAC) | Yes | VBR | - | 1.1 |  | 32(2)
  WMA v2 | Yes | CBR | 1.3 | 1.3 |  | 8(3)
  AC3 | Yes | CBR | 1.1 | 1.1 |  | 7
  MP2 | Yes | CBR | 1.1 | 1.1 |  | 2
  MP3 | Yes | CBR (optional VBR) | 1.0 (CBR) | 1.0 (CBR) |  | 2
  Ogg Vorbis | Yes | VBR | 0.5 | 1.0 |  | 32
  GSM 6.10 WAV | Yes | CBR | 0.5 | - |  | 1
  AMR (NB) | Yes | CBR | 0.1 | - |  | 1

  (1) | The practical file size limit is 2 GB in many player applications due to their interpretation of the file size header. This also applies to 24-bit and 32-bit files where those bit depths are valid. |
  (2) | More than 2 channels output is not supported with the recommended FFmpeg 2.2.2 library, unless you export using (external program) with a command that tells Audacity to explicitly use the native FFmpeg encoder. This produces maximum 6 channels. For up to 8 channels, point the same command to the latest FFmpeg-git. |
  (3) | A maximum of 2 channels can be written using the "WMA (version 2) Files (FFmpeg)" export choice or FFmpeg at the command-line using (external program). To encode other WMA formats, export using (external program) and point to a command-line WMA encoder. lvqcl's command-line WMA encoder can export as WMA V9, WMA Lossless and WMA 10 Professional (but limited to maximum 6 channels, despite WMA 10 Professional supports 8 channels).

## Exporting to formats not listed in the Export Audio Dialog

If you install the optional FFmpeg library you can use the (FFmpeg) choices in the Export Audio Dialog to export M4A (AAC), AC3, AMR (narrow band) and WMA. If you do not see a choice for one of those specific FFmpeg formats, then the build of FFmpeg you are linking to was not compiled to support encoding in that format.

The most flexible method to export to more formats is to choose (external program) in the Export Audio Dialog which opens the dialog for Audacity's command-line encoder. Point your command to an encoder that supports the format you want to write to, which could be FFmpeg or some other encoder (for example, an alternative AAC or MP3 encoder). On Windows, the recommended EXE installer of FFmpeg includes an ffmpeg.exe which you can use for this purpose. On Mac, you can download a standalone "ffmpeg" binary if you search online.