Chains - for batch processing and effects automation - Audacity Development Manual

# Chains - for batch processing and effects automation

From Audacity Development Manual

A Chain is a sequence of preconfigured commands in a set order (mainly effects) that can be applied automatically to projects or audio files. Any built-in, LADSPA, LV2, Nyquist, VST or Audio Unit (Mac) effect shown in the Effect Menu can be added to a Chain. You can also add plug-ins in any format that are shown in the Generate or Analyze Menus (including VAMP analysis effects), the built-in Find Clipping analyzer and a number of export commands.

  Click, or hover, on any menu item in the image to read about that command. Skip the image

There are two related Chain commands accessible from the File Menu called Edit Chains and Apply Chain:

## How to use Chains

The two uses of Chains are for:

- Batch processing (where many audio files are processed unattended with one or more effects then exported to a new file)
- Effects automation (where the selected audio in the track or tracks in the current project is subjected to the same prescribed sequence of effects, and optionally, a file exported from the entire audio.)

Look first at Edit Chains to determine if an existing Chain will suit your needs (Audacity only ships with one) or to create a new chain. Next, use Apply Chain to perform the action on your selected audio.

See the examples below.

## Edit Chains

Use File > Chains > Edit Chains... if you need to create a new Chain or to edit an existing Chain.

- The Chain can include a number of common Audacity functions and effects to be executed in any order you specify.
- To create an audio file as part of the Chain process you must include an "Export" command (such as ExportWAV).
- In many cases the parameters for each command in the Chain can be specified within the Edit Chains dialog.

The left hand box in the dialog (labeled Chains) contains a list of already defined Chains. Until you add a new Chain, it only has a single built-in "MP3 Conversion" Chain. You can:

- Use the Add button to create a new Chain
- Use left-click (or use the Up or Down arrow on the keyboard) to select the Chain you want to work on
- Delete any user-added Chain with the Remove button
- Rename any user-added Chain with the Rename button

The Remove and Rename buttons are grayed out when the MP3 Conversion Chain is selected.

The right-hand box (labeled Chain) lists the ordered sequence of commands for the Chain selected in the "Chains" box on the left. You can:

- Add or remove commands for the selected Chain
- Change the order in which the commands execute in the Chain
- Edit the parameters for some effects in the Chain

For further details on creating, editing and sharing Chains, see the Edit Chains page.

## Apply Chain

Use File > Chains > Apply Chain... to show the existing chains. Select the chain you require by using left-click (or using the Up or Down arrow on the keyboard) to select the Chain you want to work on, then either:

- choose Apply to Current Project to run the Chain on the entire project in the current window or
- choose Apply to Files... to run the Chain on selected external audio files in a single directory

| If you already have audio in the current project window, you must save and close that project using File > Close before applying a Chain to files.

For more details see the Apply Chain page.

## Chain Examples

In this section we look at a couple of examples of how a Chain might be used. In the image below we have added two additional Chains. It is important to note that the only Chain that Audacity ships with is MP3 Conversion (shown as selected in blue). All other Chains must be added by the user.

### Example 1: Loud MP3

A batch processing Chain to compress and normalize WAV files then convert them to MP3:

1. Insert Compressor to reduce the dynamic range of each WAV, also normalizing them to maximum amplitude of 0 dB
2. Insert ExportMP3 to convert them to MP3 format
3. Click OK to close the "Edit Chains" window
4. Finally, choose File > Chains > Apply Chain..., select the "Loud MP3" Chain then click Apply to Files... where you can select the files on which to run the Chain.

### Example 2: NR&EQ

An effects automation Chain for the current project that applies noise reduction and equalization:

1. Insert Normalize with settings of:
   1. Remove any DC offset
   2. -10 dB (to allow for boosting frequencies later in the Chain without clipping)
2. Insert Noise Reduction
3. Insert Equalization (to perform the frequency adjustment)
4. Insert another Normalize at different settings (without offset removal, setting a final amplitude of -1 dB)
5. Click OK to close the "Edit Chains" window
6. Finally, choose File > Chains > Apply Chain..., select the "NR&EQ" Chain then click Apply to Current Project to apply the Chain to the selected track(s) in the current project window.

| If a Noise Profile exists, that Noise Profile will be used. It is often best to capture a suitable Noise Profile before running a Chain. If a Noise Profile does not exist: If the Chain is applied to the current project (as above), the current selection is used to create the Noise Profile. Therefore, other effect commands in the Chain will also only apply to that selection. If an export command is added, the entire file will be exported. If the Chain is applied to files, the first file (all of it) is used to create the Noise Profile. It may be useful to prepare a file containing a suitable Noise Profile and name it so that it is alphabetically the first file of those to be run in the Chain.

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