Import - Export Preferences

• Peter 11Nov09: Checked for spelling/typos/consistency.
• Peter 24Nov09: Checked and repaired Links
• Bill 06Apr11: Need new image with Extended Import in the list and Allegro export section
• Need description of the Allegro export section.
  

Roger Dannenburg wrote on -devel:
The "Allegro" (.gro) file format is an ASCII text representation for the information in Note Tracks. By design, the Allegro representation is a superset of MIDI. The text format for Allegro can represent time in terms of beats or in terms of seconds. For example, time appears in seconds in the line:

   T1.3330 V0 K66 P66 U0.6660 L127

meaning play key number 66 at time (T) 1.333s for duration (U) 0.666s. Alternatively, time appears in beats in the line:

   TW0.5000 V0 K66 P66 Q1.0000 L127

meaning play key number 66 at time (T) 0.5 whole notes (W) for duration 1 quarter notes (Q). The two representations are equivalent to within rounding error, and the translation between beats and seconds is determined by the tempo data, which is also part of the file, so the choice between seconds or beats is mainly for convenience to human readers.

When importing audio files

Audacity always makes a copy of compressed files like MP3, OGG and FLAC when it imports them. The data is copied either into the temporary folder, or into the _data folder of an open project. Uncompressed files (WAV or AIFF) are very much larger, so may lead to a shortage of disk space if copied in. Audacity therefore allows you to choose from the following two options when importing WAV or AIFF files:

• Make a copy of uncompressed audio files before editing (safer): Audacity makes a copy of all imported file(s), so you can then move, rename or delete them if you wish. Also choose this option if you need to open your Audacity .aup project file on another computer, or send it to someone else. Note: you don't need to choose this option if you are sending an exported audio file like an MP3 to someone else.
• Read uncompressed audio files directly from the original (faster): Audacity reads imported files from the computer folder you first imported them from, without copying them in. Therefore with this option set, you must not move, rename or delete imported uncompressed files, or the folder they are in. The advantage of this option is that long files can be imported in only a few seconds, using On-Demand Loading.

If the waveform has no audio or contains visible gaps after importing files, this usually means that Audacity didn't make a copy of these files and can no longer find the location to read them from. To fix this, open the Dependencies Dialog to view the name and location of the files Audacity is looking for, and restore the files to the path stated in that dialog.

• Normalize all tracks in project: The imported file (in any format) and all audio tracks already on screen will be normalized to your current setting for the normalize effect.

When exporting tracks to an audio file

• Always mix all tracks down to stereo or mono channel(s): This is Audacity's default behavior and means that if your project contains only mono tracks panned to center, they will be mixed upon export to a file containing a single mono channel. The audio will still play equally out of both speakers on most systems. If you have any stereo tracks in your project (or any mono tracks panned away from center) the exported file will be stereo, containing two channels (left and right).
• Use custom mix: When this option is enabled, an Advanced Mixing Options window appears immediately after the completing the File Export Dialog. Advanced Mixing gives you much greater flexibility in mapping your audio tracks to specific output channels in the exported file. In particular it allows export of multichannel files (that is, having more than two channels of audio) in WAV, AIFF, OGG and FLAC formats.
• Show Metadata Editor prior to export step: By default, the Metadata Editor pops up every time you export a file with the File > Export... or File > Export Multiple... commands. Uncheck this option if you don't want to add embedded information tags to your files.

Users of the previous stable 1.2.x Audacity will recall that bit rate and bit depth for exported files were set on this Preferences tab (which was then called "File Formats"). Now however, you choose export settings for the various formats at the time of export by clicking Options in the File Export Dialog. This saves the separate step of going into Preferences each time you want to change export settings.

When exporting track to an Allegro (.gro) file

The Allegro (.gro) file format is an ASCII text representation for the information in Note Tracks. By design, the Allegro representation is a superset of MIDI. The text format for Allegro can represent time in terms of beats or in terms of seconds.

The translation between beats and seconds is determined by the tempo data, which is also part of the file, so the choice between seconds or beats is mainly for convenience to human readers.

Bill 12Apr11: We probably don't want this here, as it is now documented in Warnings Preferences. Leaving it here for now until we decide just what to do with this dialog, and if we prefer Peter's text over mine.

Warning dialog on first use of the Import Audio command

On the first use of the File > Import > Audio command to import uncompressed files, the preference is set to "copy in" (safer) and the following dialog is presented explaining the difference between copy-in and read-directly and asking which method should be used. This setting will be stored in your Audacity Preferences. If the check-box at the bottom is left un-checked then this warning dialog will re-appear the next time the File > Import > Audio command is used to import uncompressed audio.