Re: [fluid-dev] Fluidsynth internal structures

[Josh Green]

On Sun, 2009-02-01 at 12:23 -0800, jimmy wrote:
> Hi folks,
> 
> I know Miguel(???) was working on a reimplementation of FS using CPP.  Plus, 
> some folks here are looking to modularize FS.  You may want to use some kind 
> of dictionary, or table look up for some of the structures (objects) used in 
> FS.  Hopefully for a more efficient and a little faster real-time look up.
> 
> For what it's worth, I have been tracing through some of the FS code and find 
> that the structure:
> 
>    fluid_sfont_t
> 
> can be a virtual pointer to a font structure of type:
> 
>    fluid_defsfont_t
> 
> which contains a pointer to a "preset" structure:
> 
>    fluid_preset_t
> 
> There is a preset for each prog_num in each soundbank(s) of a soundfont.  As 
> used in
> 
>    fluid_defsfont.c : fluid_defsfont_get_preset()
> 
> The fluid_preset_t is a link-list structure pointing to the next 
> fluid_preset_t structure.  Basically, that function walks through consecutive 
> presets:
> 
>    preset for bank 0 prog 0
>    preset for bank 0 prog 1
>    preset for bank 0 prog 2
>    . . .
>    preset for bank 0 prog 128
> 
> follow by presets for any additional instrument bank(s), and drum bank 128.  
> This lookup is used for every prog_change.
> 
> That's a simple and straigh forward way to implement the system using linear 
> link-list, but can be very inefficient for look up time.
> 
> Best regards,
> 
> Jimmy
> 

Indeed, but that is only during program change time, which isn't as
critical as note-on time.  As we have been discussing, FluidSynth will
likely move to using libInstPatch for instrument management, which does
things a bit differently and in a more optimized fashion (in particular
for the note-on case).
        Josh