Audacity Project Format

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This is in an appendix that describes various audio file formats. It should be in the same style as pages describing MP3 WAV etc Aup isn't an audio file format, its just a text file referencing audio data in .au format. We could have audio files as an "appendix", but they already have a brief note in glossary, so reference material could be a bit more expansive. I really would not put aup files in audio files at all. I think it just perpetuates the confusion. Gale


Bill: I realize this may be a low priority, but I and a few others (based on posts on the forum) would love to see a specification of the Audacity XML. Also, I'm not sure that the 'summary files' exist any more - every .au file seems to contain data for drawing the waveform. Perhaps my projects aren't big enough to require summary files?

-- Ed 16 November 2009 Added the green "intro" box, could the heading more appropriately look like (note the period before the file extension):

.aup

or even better:

AUP

Peter 29Apr09: looked at Ed's suggestions - but decided a fuller H2 title would improve things - and I did incorporate the dot that Ed suggested..

Audacity project files store information about the entirety of the project - the number of tracks and their time positions, details of clips within the tracks, amplitude envelope points, labels and gain and pan data. In addition, "summary information" is stored which enables the display to be redrawn rapidly without Audacity examining the entire contents.

The .aup and .au files

Audacity projects have a master file that ends with the extension ".aup". In the same directory as the master file is a folder called "_data". This contains one or more subfolders with many small audio files in .au format of size 1 MB or less. The master file describes how to link these smaller files together to make up the clips and tracks in the project. The .aup file is in an XML format and can be opened in a text editor. The individual .au files are uncompressed, using 4 byte floating point numbers. The summary files have the same format as the audio files, but there are fewer of them.

The structure of the project files is designed to make editing audio faster in Audacity. By updating the .aup file, which is much smaller than the _data folder, Audacity can move audio around in the project without copying large quantities of data from one place to another.


Opening an Audacity project

When you re-open a project with Audacity you should always open the <project_name>.aup top level file.

You should not attempt to open or manipulate any individual .au files.

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