manual/include/io-plugins.html

<p>
  I/O plugins are a way to process audio outside the normal Ardour session or
  connect to sources typically unavailable in a DAW, such as outputs of NDI
  devices. Pre-plugins run before Ardour does any processing, post-plugins run
  after Ardour has done all processing.
</p>

<p>
  A common use case is wet recording where a number of plugins are applied
  directly to the physical input. The processed signal then can be routed to any
  number of tracks or busses in Ardour. This is a lot like doing some of the
  processing with a chain of guitar pedals, then feeding the signal to an Aux In
  port on a mixing console or an input port on a multi-effects digital
  pedalboard. The rationale for pre-processing with I/O plugins is that it's a
  more lightweight way to do it as compared to busses.
</p>

<p>
  Another use case would be loading an instance of the NDI Input plugin as a
  pre-processing plugin to be able to capture and mix sources from NDI devices,
  or loading an instance of the NDI Output plugin to send audio from Ardour over
  IP to a receiver for broadcasting.
</p>

<p>
  It's also possible to use the post-processing section to load plugins for room
  correction or signal analysis (VU meters, spectrum analyzers etc.).
</p>

<h2>Adding I/O plugins</h2>

<p>
  New I/O plugins can be added in the <kbd class="title">I/O Plugins</kbd>
  dialog (<kbd class="menu">Window &gt; I/O Plugins</kbd>).
</p>

<figure>
  <img style="width:50%;" width="50%" src="/images/io-plugins-empty-slots.png" alt="Empty slots in the I/O Plugins dialog">
  <figcaption>Empty slots in the I/O Plugins dialog</figcaption>
</figure> 

<p>
  Right-clicking opens the same menu for plugin selection available for mixer
  channel strips:
</p>

<figure>
  <img style="width:50%;" width="50%" src="/images/io-plugins-right-click-menu.png" alt="Right-click menu in the I/O Plugins dialog">
  <figcaption>Right-click menu in the I/O Plugins dialog</figcaption>
</figure> 

<p>
  Double-clicking opens the <kbd class="title">Plugin Selector</kbd> dialog.
</p>

<p>
  Once a plugin has been selected and added, it shows in either Pre- or
  Post-process section depending on your choice.
</p>

<figure>
  <img style="width:50%;" width="50%" src="/images/io-plugins-one-plugin-added.png" alt="ACE Compressor added to the pre- section">
  <figcaption>ACE Compressor added to the Pre-process section</figcaption>
</figure> 

<h2>Routing I/O plugins</h2>

<p>
  I/O plugins have the same user interface for setting input and outputs that is
  also available in mixer channel strips. The button above the plugin name opens
  a drop-down menu for quickly choosing an input port. The button below opens
  the drop-down menu for choosing the output port.
</p>

<figure>
  <img style="width:50%;" width="50%" src="/images/io-plugins-choose-output.png" alt="Choosing output for an I/O plugin">
  <figcaption>Choosing output for an I/O plugin</figcaption>
</figure> 

<p>
  Additionally, new tracks automatically connected to an I/O plugin can be
  easily created in the <kbd class="title">Recorder</kbd> window by clicking the
  <kbd class="key">+</kbd> button and then setting a new for that track.
</p>

<figure>
  <img style="width:50%;" width="50%" src="/images/io-plugins-new-track-from-io-plugin.png" alt="New track connected to an I/O plugin">
  <figcaption>New track connected to an I/O plugin</figcaption>
</figure>