[Scummvm-tracker] [ScummVM :: Bugs] #15881: fix FluidSynth reverb width parameter to match actual effect width

[ScummVM :: Bugs]

#15881: fix FluidSynth reverb width parameter to match actual effect width
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Reporter:  mrbumpy409  |      Owner:  (none)
    Type:  defect      |     Status:  new
Priority:  normal      |  Component:  Audio
 Version:              |   Keywords:
    Game:              |
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 FluidSynth's internal reverb parameters all have a range of 0–1 (0–100 in
 SCUMMVM GUI) except for reverb width, which has a range of 0–100 (0–1000
 in SCUMMVM GUI). However, the actual reverb effect width of 0–100% is
 mapped to 0–1, with values above 1 only causing feedback and making the
 reverb sound monophonic, tunnel-like and extra loud.

 Therefore, it is my recommendation that the reverb width parameter should
 be changed to match the range of the other parameters, namely using only
 values 0–1 inside FluidSynth, which would be displayed as 0–100 in the
 SCUMMVM GUI.

 With this change, setting "80" in the GUI would result in 80% effect
 separation. Currently, one must set "8" in the GUI to get 80% separation,
 and the GUI slider does not offer enough granularity to set 75% width, for
 example, as non-integer values cannot be accessed.

 If this change is made, saved user values for reverb width should be
 adjusted as follows (in displayed GUI values):

 ||= Saved Value =||= Converted Value =||
 || 0–10 || 0–100 ||
 || 11–1000 || 100 ||

 Links:
 * Here is the respective bug report for FluidSynth that led to an update
 of the documentation: https://github.com/FluidSynth/fluidsynth/issues/1455
 * Here is the current documentation on the reverb width effect:
 https://www.fluidsynth.org/api/fluidsettings.xml#synth.reverb.width
 * The bug report against GeneralUser GS that brought this issue to my
 awareness: https://github.com/mrbumpy409/GeneralUser-GS/issues/13
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Ticket URL: <https://bugs.scummvm.org/ticket/15881>
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