Example LADSPA line without this plugins

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(padsp) listplugins
(padsp) analyseplugin cmt.so amp_mono
gst-launch-1.0 -e filesrc location="$myfile" ! decodebin ! audioconvert ! audioresample ! "audio/x-raw,format=S16LE,rate=48000,channels=1" ! wavenc ! filesink location="testin.wav"
(padsp) applyplugin testin.wav testout.wav cmt.so amp_mono 2
gst-launch-1.0 playbin uri=file://"$PWD"/testout.wav

Decode any audio file into wav with the format expected for the specific ladspa plugin to be applied, apply the ladspa filter and play it.

Now with this plugin:

Example LADSPA line with this plugins

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gst-launch-1.0 autoaudiosrc ! ladspa-cmt-so-amp-mono gain=2 ! ladspa-caps-so-plate ! ladspa-tap-echo-so-tap-stereo-echo l-delay=500 r-haas-delay=500 ! tee name=myT myT. ! queue ! autoaudiosink myT. ! queue ! audioconvert ! goom ! videoconvert ! xvimagesink pixel-aspect-ratio=3/4

Get audio input, filter it through CAPS Plate and TAP Stereo Echo, play it and show a visualization (recommended hearphones).

In case you wonder the plugin naming scheme, quoting ladspa.h: "Plugin types should be identified by file and label rather than by index or plugin name, which may be changed in new plugin versions." This is really the best way then, and so it is less prone to conflicts.

Also it is worth noting that LADSPA provides a control in and out interface, on top of the audio in and out one, so some parameters are readable too.

You can see the listing of plugins available with:

Inspecting the plugins list

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gst-inspect ladspa

List available LADSPA plugins on gstreamer.

You can see the parameters of any plugin with:

Inspecting the plugins

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gst-inspect ladspa-retro-flange-1208-so-retroflange

List details of the plugin, parameters, range and defaults included.

The elements categorize in:

Example Filter/Effect/Audio/LADSPA line with this plugins

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gst-launch-1.0 filesrc location="$myfile" ! decodebin ! audioconvert ! audioresample ! ladspa-calf-so-reverb decay-time=15 high-frq-damp=20000 room-size=5 diffusion=1 wet-amount=2 dry-amount=2 pre-delay=50 bass-cut=20000 treble-cut=20000 ! ladspa-tap-echo-so-tap-stereo-echo l-delay=500 r-haas-delay=500 ! autoaudiosink

Decode any audio file, filter it through Calf Reverb LADSPA then TAP Stereo Echo, and play it.

Example Source/Audio/LADSPA line with this plugins

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gst-launch-1.0 ladspasrc-sine-so-sine-fcac frequency=220 amplitude=100 ! audioconvert ! autoaudiosink

Generate a sine wave with Sine Oscillator (Freq:control, Amp:control) and play it.

Example Source/Audio/LADSPA line with this plugins

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gst-launch-1.0 ladspasrc-caps-so-click bpm=240 volume=1 ! autoaudiosink

Generate clicks with CAPS Click - Metronome at 240 beats per minute and play it.

Example Source/Audio/LADSPA line with this plugins

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gst-launch-1.0 ladspasrc-random-1661-so-random-fcsc-oa ! ladspa-cmt-so-amp-mono gain=1.5 ! ladspa-caps-so-plate ! tee name=myT myT. ! queue ! autoaudiosink myT. ! queue ! audioconvert ! wavescope ! videoconvert ! autovideosink

Generate random wave, filter it trhough Mono Amplifier and Versatile Plate Reverb, and play, while showing, it.

Example Sink/Audio/LADSPA line with this plugins

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gst-launch-1.0 autoaudiosrc ! ladspa-cmt-so-amp-mono gain=2 ! ladspa-caps-so-plate ! ladspa-tap-echo-so-tap-stereo-echo l-delay=500 r-haas-delay=500 ! tee name=myT myT. ! audioconvert ! audioresample ! queue ! ladspasink-cmt-so-null-ai myT. ! audioconvert ! audioresample ! queue ! goom ! videoconvert ! xvimagesink pixel-aspect-ratio=3/4

Get audio input, filter it trhough Mono Amplifier, CAPS Plate LADSPA and TAP Stereo Echo, explicitily anulate audio with Null (Audio Output), and play a visualization (recommended hearphones).

struct GstLADSPA

struct GstLADSPA {
  GstLADSPAClass *klass;

  LADSPA_Handle *handle;
  gboolean activated;
  unsigned long rate;

  struct
  {
    struct
    {
      LADSPA_Data *in;
      LADSPA_Data *out;
    } control;

    struct
    {
      LADSPA_Data **in;
      LADSPA_Data **out;
    } audio;
  } ports;
};