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

[Lorenzo Sutton]

Hi Tito,

On 24/04/16 14:15, Tito Latini wrote:
> On Sun, Apr 24, 2016 at 03:13:42AM +0200, Lorenzo Sutton wrote:

[...]
>>
>> 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
>

Thanks for testing... However I'm not really sure what to make out of 
that apart from assuming that the use case isn't directly covered by 
fluidsynth?

I imagine the easiest workaround would be starting multiple fluidsynth 
instances, maybe lowering poliphony (not sure what impact this has on 
resource consumption), possibly scripting it...

Lorenzo.