Re: [fluid-dev] synth.audio-groups and LADSPA effects

[Bill Peterson]

Hi Tom - thanks for the reply. I tried to follow the LADSPA documentation's advice, but maybe I'm not understanding how synth.audio-channels and synth.audio-groups interact. Here's the command line I'm using:

sudo fluidsynth -a alsa -o midi.autoconnect=1 -o synth.ladspa.active=1 -o synth.audio-channels=1 -o synth.audio-groups=2 -f effects.txt

and effects.txt:

load /usr/share/sounds/sf2/FluidR3_GM.sf2
select 0 1 0 0 # piano
select 1 1 0 4 # rhodes
select 2 1 0 6 # harpsichord
select 3 1 0 11 # vibes
ladspa_effect dL /usr/lib/ladspa/delay.so
ladspa_effect dR /usr/lib/ladspa/delay.so
ladspa_link dL Inp Main:L1
ladspa_link dR Inp Main:R1
ladspa_link dL Out Main:L1
ladspa_link dR Out Main:R1
ladspa_start

My intent is for the delay effect to only apply to some channels (e.g. piano and harpsichord), but I hear the delay effect on all channels. Oddly, channels 1 and 3 (rhodes and harpsichord), also sound quiet, as if they're coming through the Reverb/Chorus channels only. I get the same result with synth.audio-channels=2. What am I doing wrong?

Thanks!

Bill

On Sat, Jul 25, 2020 at 8:03 AM Tom M. <tom.mbrt@googlemail.com> wrote:

> experimenting with various combinations of values synth.audio-channels and synth.audio-groups either gets me effects on all channels or none

Seems like you created the Ladspa effects on the Main:L and Main:R
ports. Have you tried explicitly specifying the subgroups as described
here?

https://github.com/FluidSynth/fluidsynth/blob/master/doc/ladspa.md#multi-channel-output


Tom