Re: [LAU] Fluidsynth: map each channel to individual jack audio output

On Sun, Apr 24, 2016 at 03:13:42AM +0200, Lorenzo Sutton wrote:
> Hi all,
>
> I have also posted this on the fluid-dev list, but maybe there is some
> wisdom on LAU about it as well :)
>
> What is the current status of synth.audio-channels and
> synth.audio-groups on Linux with jack?
>
> By starting fluidsynth with something like:
>
> fluidsynth -a jack -o synth.audio-channels=4 -o synth.audio-groups=4 \
> -o audio.jack.multi=no
>
> I do get 4 pairs of jack audio outputs.
>
> However the behaviour isn't as expected at least according to this (very
> old post):
>
> https://lists.nongnu.org/archive/html/fluid-dev/2004-02/msg00027.html
>
> Ideally is there a way to have each channel routed to a separate audio
> output on jack these days? Any help appreciated.

'-o synth.audio-groups=4' fails: `fluid_settings_getint' returns 1
after `process_o_cmd_line_option' (also tested with a printf).

sh> fluidsynth -a jack -o synth.audio-groups=4 <<< settings 2>/dev/null \
    | grep audio-groups
synth.audio-groups 1

Idem with "-o synth.audio-channels=4 -o synth.audio-groups=4",
but "-G 4" works:

sh> fluidsynth -a jack -G 4 <<< settings 2>/dev/null | grep audio-groups
synth.audio-groups 4

There is a comment in `src/fluidsynth.c:594':

  /* The 'groups' setting is only relevant for LADSPA operation
   * If not given, set number groups to number of audio channels, because
   * they are the same (there is nothing between synth output and 'sound card')
   */

tested with:

sh> fluidsynth -a jack -L 4 <<< settings 2>/dev/null | grep audio-groups
synth.audio-groups 4

The follow example works (audio.jack.multi=no by default):

sh> fluidsynth -a jack -L 4
load /usr/share/sounds/sf2/FluidR3_GM.sf2
select 0 1 0 0
select 1 1 0 20
select 2 1 0 30
select 3 1 0 40
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Received on Sun Apr 24 16:15:01 2016