LADSPA plugins in Liquidsoap

LADSPA is a standard that allows software audio processors and effects to be plugged into a wide range of audio synthesis and recording packages.

If enabled, Liquidsoap supports LADSPA plugins. In this case, installed plugins are detected at run-time and are all available in Liquidsoap under a name of the form: ladspa.plugin, for instance ladspa.karaoke, ladspa.flanger, etc.

The full list of those operators can be found using liquidsoap --list-functions | grep '^ladspa.'. Also, as usual, liquidsoap -h ladspa.plugin returns a detailed description of each LADSPA operator, including its parameters and their ranges. For instance, liquidsoap -h ladspa.flanger starts with:

Flanger by Steve Harris <steve(at)plugin.org.uk>.

Type: (?id : string?, ?delay_base : {float}, ?feedback : {float},
 ?lfo_frequency : {float}, ?max_slowdown : {float},
 source(audio=pcm('a), 'b)) -> source(audio=pcm('a), 'b)

For advanced users, it is worth noting that the parameters associated with LADSPA operators are getters, for instance max_slowdown : {float} in the above: they accept either a float or a function returning a float. This means that those parameters may be dynamically changed while running a liquidsoap script.