AUDIO: Optimise default fluidsynth configuration paramenters

[ccawley2011]

Originally from libretro/scummvm#108

Regarding the FluidSynth changes, I got the new values from here: https://forums.scummvm.org/viewtopic.php?t=11632

To quote the forum post:

The FluidSynth reverb, while not as good as the old Live!/Audigy hardware reverbs (which were quite good), can still sound decent with the right settings. I have no idea how to change this in ScummVM, but I have found the following FluidSynth settings to sound much better:

Reverb:

Room: 0.61
Damp: 0.23
Width: 0.76
Level: 0.57

Chorus:

N: 3
Level: 1.2
Speed: 0.3
Depth: 8

This gives a much more spacious sound, as opposed to the "stuffy room" that seems to be FluidSynth's default.

I basically tested these settings with every (!) game, and it was indeed a huge improvement.

In addition, the reverbWidth setting in ScummVM master is handled internally as an int. This is a bug, which means the value can never be adjusted correctly - it should be a double, like all the other parameters.

[criezy]

I am not sure about using custom defaults (different from the fluidsynth default) as I am guessing what is best will be subjective. But I am not really opposed to it either.

However shouldn't our GUI respect the documented value range for each setting? You change the max for the reverb width to 1, but the fluidsynth documentation indicates that the valid range is [0, 100], with a default at 0.5 (http://www.fluidsynth.org/api/fluidsettings.xml#synth.reverb.width). The chorus level is another one with a discrepancy (documented maximum of 10, but we use 2). We are also still using the old chorus depth range (the upper bound was increased from 21 to 256 one year ago: FluidSynth/fluidsynth@fd7db02).

[neuromancer]

@coderabbitai review

[coderabbitai]

Walkthrough

Walkthrough

The changes primarily focus on enhancing the audio effects in the application by modifying the default values of various parameters related to reverb and chorus effects. The type of the reverbWidth variable has also been changed from int to double for more precise control.

Changes

File Path	Change Summary
.../fluidsynth.cpp	The type of the reverbWidth variable has been changed from int to double in the MidiDriver_FluidSynth::open function.
.../commandLine.cpp	Default values for parameters fluidsynth_chorus_level, fluidsynth_reverb_roomsize, fluidsynth_reverb_damping, fluidsynth_reverb_width, and fluidsynth_reverb_level have been adjusted in the registerDefaults function.
.../fluidsynth-dialog.cpp	Default values for sliders and labels related to reverb and chorus effects in the FluidSynthSettingsDialog class have been modified.

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[bluegr]

These settings have been updated in 2023 (two years after this PR) with commit f1abbff - hence the conflicts in all the files that this PR touches.

The updated settings are set to value ranges and defaults used by the current FluidSynth version 2.3.4.

Since basically every setting has been updated, there's no point in keeping this PR around. If we do find that the suggested settings improve the sound output, a new PR can be opened