manual/include/osc58-querying-ardour.html

<p>
  In order to make a custom controller that knows what strips Ardour
  has, the controller needs to be able to query Ardour for that
  information. These set of commands are for smarter control surfaces
  That have the logic to figure out what to do with the information.
  These are not of value for mapped controllers like touchOSC and
  friends. The controller will need to send these queries to ardour
  as often as it needs this information. It may well make sense to use
  regular feedback for things that need to be updated often such as
  position or metering.
  Here are the commands used to query Ardour: (added in Ardour 5.5)
</p>

<table class="dl">
  <tr><th><kbd class="osc">/strip/list</kbd></th>
  <td>Ask for a list of strips</td></tr>
  <tr><th><kbd class="osc">/strip/sends <em>ssid</em></kbd></th>
  <td>Asks for a list of sends on the strip <em>ssid</em></td></tr>
  <tr><th><kbd class="osc">/strip/receives <em>ssid</em></kbd></th>
  <td>Asks for a list of tracks that have sends to the strip <em>ssid</em> points to</td></tr>
  <tr><th><kbd class="osc">/strip/plugin/list <em>ssid</em></kbd></th>
  <td>Asks for a list of plug-ins for strip <em>ssid.</em></td></tr>
  <tr><th><kbd class="osc">/plugin/descriptor <em>ssid</em> <em>piid</em></kbd></th>
  <td>Asks for a list of descriptors for plug-in <em>piid</em> on strip <em>ssid</em></td></tr>
</table>

<h3>A list of strips</h3>

<p>
  <code>/strip/list</code> asks Ardour for a list of strips that the
  current session has. Ardour replies with a message for each
  strip with the following information:
  <ul>
    <li>Strip type - One of:</li>
    <ul>
		<li>AT - Audio Track</li>
		<li>MT - MIDI Track</li>
		<li>B - Audio Bus</li>
		<li>MB - MIDI bus</li>
		<li>AX - Aux bus</li>
		<li>V - VCA</li>
    </ul>
    <li>Strip name</li>
    <li>Number of inputs</li>
    <li>Number of outputs</li>
    <li>Muted</li>
    <li>Soloed</li>
    <li>Ssid (strip number)</li>
    <li>Record enabled</li>
  </ul>
  After all the strip messages have been sent, one final message is
  sent with:
  <ul>
    <li>The text <code>end_route_list</code></li>
    <li>The session frame rate</li>
    <li>The last frame number of the session</li>
    <li>Monitor section present</li>
  </ul>
</p>
<p class="note">
	The <code>/set_surface</code> should be set before this is called. That way
	The right set of strips will be sent in return (though the default is good
	for most uses) and feedback will start correctly.
</p>
<p>
  If the surface is using <code>/strip/list</code>, the surface needs to know
  if the strips have changed. This would be true if a strip gets moved, created or
  deleted. When this happens Ardour sends <code>/strip/list</code> to the surfaces
  that have previously requested a <code>/strip/list</code>. This lets the
  surface know that it's list of strips is no longer valid.
</p>
<p class="note">A bus will not have a record enable and so a bus message
  will have one less parameter than a track. It is the controllers
  responsability to deal with this.
</p>

<h3>A list of sends</h3>
<p>
  <code>/strip/sends <em>ssid</em></code> asks Ardour for a list of
  sends for strip number ssid. The reply is sent back to the
  controller as one message with the following information:
  <ul>
    <li>Ssid that information is for</li>
    <li>Each send's information:</li>
    <ul>
      <li>The send's target bus ssid</li>
      <li>The send's target bus name</li>
      <li>The send id for this strip</li>
      <li>The send gain as a fader possition</li>
      <li>The Send's enable state</li>
    </ul>
  </ul>
</p>
<p>
  The controller can tell how many sends there are from the number of
  parameters as each send has 5 parameters and there is one extra for
  ssid.
</p>

<h3>A list if tracks that send audio to a bus</h3>
<p>
  <code>/strip/receives <em>ssid</em></code> will return a list of
  tracks that have sends to the bus at the ssid. The reply will
  contain the following information for each track conntected to this
  bus:
  <ul>
    <li>The ssid of the track sending</li>
    <li>The name of the sending track</li>
    <li>The id of the send at that track</li>
    <li>It's gain in fader possition</li>
    <li>The send's enable state</li>
  </ul>
</p>

<h3>A list of plug-ins for strip</h3>
<p>
  <code>/strip/plugin/list <em>ssid</em></code> will return a list of
  plug-ins that strip ssid has. The reply will contain the following
  information:
  <ul>
    <li>Ssid that information is for</li>
    <li>Each plugin's information:</li>
    <ul>
      <li>The plug-in's id</li>
      <li>The plug-in's name</li>
    </ul>
  </ul>
</p>

<h3>A list of a plug-in's parameters</h3>
<p>
  <code>/plugin/descriptor <em>ssid</em> <em>piid</em></code> will
  return the plug-in parameters for ppid plug-in on the ssid strip. The
  reply will contain the following information:
  <ul>
    <li>Ssid of the strip the plug-in is in</li>
    <li>The plug-in id for the plug-in</li>
    <li>The plug-in's name</li>
    <li>Information about each parameter</li>
    <ul>
      <li>The parameter id</li>
      <li>The parameter's name</li>
      <li>A bitset of flags (see below)</li>
      <li>Data type</li>
      <li>Minimum value</li>
      <li>Maximum value</li>
      <li>The number of scale points</li>
      <li>zero or more scale points of one value and one string each</li>
      <li>The current parameter value</li>
    </ul>
  </ul>
</p>
<p>
  The flag bitset above has been defined as (from lsb):
  <ul>
    <li>0&mdash;enumeration</li>
    <li>1&mdash;integer step</li>
    <li>2&mdash;logarithmic</li>
    <li>3&mdash;max unbound</li>
    <li>4&mdash;min unbound</li>
    <li>5&mdash;sample rate dependent</li>
    <li>6&mdash;toggled</li>
    <li>7&mdash;controllable</li>
  </ul>
</p>
<p>
	While this seems complex, it is really not that bad. Minimum,
	maximum and value will in most cases give you all you need.
</p>