2017-10-19 22:23:39 +00:00
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# FluidSynth LADSPA Interface
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The [LADSPA](http://ladspa.org/) (Linux Audio Developer's Simple Plugin API)
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binding can be used to route the FluidSynth audio output through any number
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of LADSPA plugins. As the name implies, it is only available on Linux.
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## Configuration
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To configure and compile FluidSynth with LADSPA support, make sure you have
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the LADSPA SDK (basically the ladspa.h header file) installed. Then enable
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LADSPA when calling cmake:
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2017-10-20 10:43:53 +00:00
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cmake -Denable-ladspa=1 <path-to-source>
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2017-10-19 22:23:39 +00:00
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You should see `LADSPA support: yes` in the cmake output.
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To enable the LADSPA engine, use the `synth.ladspa.active` setting when
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starting FluidSynth:
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fluidsynth -o synth.ladspa.active=1 ...
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# Signal Flow
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The LADSPA effects unit runs immediately after the internal reverb and chorus
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effects have been processed. When no plugins have been configured, the
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effects unit is dormant and uses no additional system resources.
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When at least one plugin is configured and the engine is activated, the
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rendered audio is passed into the LADSPA effects unit, each plugin is
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run in the order that they were created and the resulting audio is
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passed back into FluidSynth (and from there to the sound card or other
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output).
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# Loading and Connecting Plugins
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Currently the only way to configure the effects unit is via the FluidSynth
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shell or via a config file.
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## Example Setups
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All examples assume that your `LADSPA_PATH` environment variable points
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to the directory containing the plugin libraries (e.g. /usr/lib/ladspa).
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### Single Plugin
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The following loads the delay.so plugin library from the LADSPA SDK and
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instantiates the `delay_5s` plugin from that library. It connects the
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main left channel output from FluidSynth with the plugin input, the
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main left channel input to FluidSynth with the plugin output. It also
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sets the two control ports of the plugin to example values and starts
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the engine.
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ladspa_plugin delay.so delay_5s
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ladspa_port Input < in1_L
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ladspa_port Output > out1_L
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ladspa_port Delay = 1.0
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ladspa_port Dry/Wet = 0.5
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ladspa_start
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2017-10-20 10:43:53 +00:00
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The audible effect should be an untouched right channel and a slightly
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2017-10-19 22:23:39 +00:00
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lower volume on the left with a delay effect of 1 second on top.
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