Export Formats supported by Audacity

Gale 17Dec14: P1: IMHO this page is not useful on its own merit, and the table changes have created a P1. This looks like word for word duplication of File Export Dialog with some expansion of uncompressed formats. I thought you did not like duplication? By "draft" I meant in your user space, not for publication yet. Surely we can fix Export Multiple without duplicating so much? Just link it to File Export Dialog.

The only other alternative could be to trim File Export Dialog to an interface description pointing here for information about the different formats. Perhaps the first image on that page would expand the dropdown menu to show the format types. If you want to try that please do it in your own user space.

• Peter 18Dec14: I beg to differ Gale - the reason that this page has true merit is that the contents required by two different pages Export Audio and Export Multiple as you recognize - plus I may yet want to link to it from a third page Tutorial - Exporting to iTunes. And yes, right now it duplicates (and improves imho) what is already on File Export Dialog - it was created from that. The plan is to hone this page and then remove the material from File Export Dialog replacing it with a link to this page giving us just one place to maintain this information in the Manual.

  I already had to change Export Multiple as previously it just had a note saying that format choice and options were "same as those available in the Export Audio Dialog" - when they are not the same only similar (as you know well from my recent Bugzilla post #798) and thus may well puzzle or even confuse the reader. I really don't want to link the reader of Export Multiple over to Export Audio as to me it makes far more sense to link to a more detailed page (for readers of both pages) as many readers will come to that page already well aware of precisely which format they wish to export to. The other option would be to duplicate the information in-line in Export Multiple - and I really don't want to do that as it involves duplication (which is something we always try to avoid for ease of maintenance).

  I have reverted the Channels numbers in the table which caused the P1 - Steve and I were confused by the fact that the former text did not make it clear that the table showed and Audacity limit rather than the format's limit. I have tried to clarify the text.

• Peter 18Dec14:I'll work on a mock-up of what the re-worked File Export Dialog would look like in my user space
  • Peter 18Dec14 later: Ok I spent some time mocking up that page and improving and extending the documentation it contains (including an image of the formats dropdown as you suggested - an excellent idea) - see: User:PeterSampson/Strawman for Export Audio. I Really think that that page in that extended form is now long enough for the reader and that it makes good sense to link it to this sub-page rather than incorporating the material from this page there.

Peter 11Dec14: The information contained in the bottom half of the Export Audio page on the various file formats and the table for comparison of file sizes would be equally useful in the Export Multiple page. There all we say is "Export format: Choose one of the available export formats from this menu".

1. Rather than duplicate this material there (and we do always try to avoid duplication) I propose to spin that section off to a separate page.
2. This would also be useful in the Forum situation I encountered yet again yesterday where the user was enquiring about formats and I found myself directing him/her to an inadequate page in the Wiki.
3. It would also have the benefit of shortening this page for the reader who already knows what format they wish to export to.

• Gale 11Dec14: http://wiki.audacityteam.org/wiki/FileFormats is really only a landing page but at least the WAV, MP3 and OGG Wiki pages it links to have some useful content not necessarily neatly pulled together elsewhere. http://wiki.audacityteam.org/wiki/OGG looks too detailed to be in the Manual. As it is now we link from Manual to the Glossary for descriptions of formats.

  I don't object to a page in the Manual about Audacity-supported formats, but it creates a need for another click through versus leaving the information here. Perhaps you would like to make a draft page so we can see what it would contain? Note that the table below excludes formats mentioned in How can I export to formats not listed in the Export Audio Dialog? and excludes many of the "Other uncompressed" formats. How much detail do you want about all FFmpeg and other uncompressed formats? And what will you do about the WAV/AIFF/OGG and MP3 pages on Wiki?

• Peter 12Dec14: My main concern is occasioned by the fact that Export Multiple has absolutely no information on choice of format, apart from the fact that you can choose. Sure I could link from there to an anchor section on this page - but that then occasions a click from that page anyway so it may as well go to the new proposed page.

  My feeling is that I would probably leave the WAV/AIFF/OGG and MP3 pages on the Wiki as there we can provide more detail if required, plus there may well be links to them - which probably means I'd also retain the Wiki parent page that links to them and probably upgrade it.

  Note too that Tutorial - Exporting to iTunes also has some material on choosing formats. Here it is limited, by design, to the smaller set of formats one is sensibly likely to use for iTunes/iPod usage. But is does have some material on why you'd choose compressed or uncompressed that may be valuable to include on the proposed now formats page.

Uncompressed formats

The following are all uncompressed, lossless formats that do not lose any information from the audio:

• Other uncompressed files: includes all the uncompressed audio formats that Audacity can export, including 8-bit, 24-bit and 32-bit options. 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: 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: 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.

Lossless formats produce large files and are best suited for use on computers and for creating CDs.

Compressed formats

Compressed formats produce files that are usually significantly smaller than uncompressed formats, see the table below. Thus they are well suited for use on portable devices where storage space is smaller and at a premium. The following compressed audio formats are supported by Audacity:

• GSM 6.10 WAV (mobile): produces a mono WAV file encoded with the compressed, lossy GSM 6.10 codec as used in mobile telephones.
• 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.
  You must download the optional LAME encoder to export to MP3.
• 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 larger file sizes than MP3 and OGG.
• MP2 Files: MP2 is a compressed, lossy format similar to MP3, producing slightly larger files than MP3 for the same quality.
• (external program): sends audio via the command-line to an external application either for processing or for encoding as a file. This is a method to export to an alternative MP3 encoder, or to a format not supported by Audacity.

FFmpeg formats

The following export types marked "(FFmpeg)" 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.

• M4A (AAC) Files: 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: the common name used for the compressed, lossy format used in Dolby Digital.
• AMR (narrow band) Files: 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: Windows Media Audio v2 is a compressed, lossy format developed by Microsoft. Optional permitted extensions: .asf or .wmv.
• Custom FFmpeg Export: Allows choice of the specific codec to use in the formats listed above, or to export to some additional formats not otherwise available. 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.

AMR (wide band) export using 3GP extension (mono, 16000 Hz sample rate) may be made by choosing Custom FFmpeg Export (see below) if you obtain or compile a "shared" build of FFmpeg 1.2 or later that supports such encoding. The recommended FFmpeg library for Windows or Mac is suitable. Alternatively you can export AMR Wide Band using Audacity's command-line encoder pointing to a suitably built "ffmpeg" executable.

Peter 17Dec14 ToDo-2 Do we need a section here on all the "Other uncompressed files" that we support. Maybe it would be better to put that on a subpage. I'm thinking a subpage linked to from the "Compressed formats" section above.

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, 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 supported by Audacity (rather than the theoretical maximum for that format).

Peter 17Dec14: I reordered the table by size descending order. I updated the Channels information after discussions with Steve and looking at the Wikipedia page: http://en.wikipedia.org/wiki/Comparison_of_audio_coding_formats .

• Gale: 17Dec14: The table contained information on the number of export channels supported *by Audacity* so is now incorrect. I don't think we'll be be expanding "Use custom mix" for 2.1.0 to support 255 OGG channels rather than 32. If you want to add theoretical maxima for the formats (-1 from me) then you will need another column. We could link to http://en.wikipedia.org/wiki/Comparison_of_audio_coding_formats in the text though.
• Peter 18Dec14: I think Steve and I were both fooled by the fact that the text didn't make it clear that the upper channels limit is one imposed by Audacity and not the theoretical limit of the formats. I have reverted to the former values in the table and tried to clarify the text. I don't think I want to include a link to that Wikipedia page as I don't want to excite readers getting them thinking about numbers of channels that Audacity doesn't support.

ToDo-2 I plan to do some export experiments later to check the size comparisons as it is fairly clear that this table has not ben updated or verified for a fair while.

• Gale: 17Dec14: I very much doubt it was wrong before you changed it. The table was updated by me for 2.0.6.

N.B. the blank lines, seen only when editing, are deliberately left in to facilitate readability and any re-ordering that may be necessary, they do not affect the display of the table.</p>

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
WMA v2	Yes	CBR	1.3	1.3		2
M4A (AAC)	Yes	VBR	-	1.1		32
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.