Re: [fluid-dev] Some Questions About FluidSynth MIDI Player

[Josh Green]

Hello Peter,

My guess is that the FluidSynth MIDI file playback sequencer probably
wont live up to your expectations.  I'm not real familiar with the
internals of it myself, since I'm not the original author, only a mere
maintainer ;)  I could likely know the answers to these questions fairly
quickly, were I to do some research on the code.  I can do this at some 
point, if you decide you still want to use FluidSynth for your project.

As for the audio mixing..  I still suspect some internal clipping
issues, but have not put in the time to verify this.  All audio mixing
is done using floating point calculations and in the case of 16 bit
playback, is converted from the range +/- 1.0 to signed 16 bit.
Anything outside of this range gets clipped.  The synth gain parameter
is what keeps this from happening, but can be somewhat of a hassle to
get right, especially when Reverb and/or Chorus are enabled.

Hope this answered some of your questions.  I haven't had as much time
to put into FluidSynth as I would have liked, as I've been devoting most
of my time to Swami, which uses FluidSynth.  When Swami 2.0 is ready for
release (target date is the end of this year), then I'll put more of my
efforts into FluidSynth and thus improve Swami as well.

Best regards,
        Josh

On Tue, 2008-09-30 at 19:09 +1000, Zegelin Peter wrote:
> Hi,
> 
>       I have been playing with fluidSynth under MacOSX for a few days now  
> and am seriously thinking that it may be suitable for a new commercial  
> product of mine. However I do have a couple of questions, mainly to do  
> with the midi player part of fluidSynth.
> 
> 1. I really need to be able to adjust the playback speed of the file.  
> I notice that there is a fluid_player_set_midi_tempo function but it  
> isn't well documented. Is this the correct place to adjust the  
> playback rate?
> 
> 2. Is it possible to stop the player in the middle of a song, move the  
> current playback position either forward or backwards and then start  
> again? Are all the controllers set to their correct values for that  
> position before playback begins?
> 
> 3. Is it possible to get the player to issue events to an external  
> device rather than through the internal synth?
> 
> 4. Does looping work?
> 
> My last question has to do with the synth itself. From reading some of  
> the mailing list it seems that reverb, chorus and gain don't work as  
> well as they should and I have heard the occasional crackle myself.  
> Switching chorus and reverb off helped a lot but it is still  
> noticeable on some files. I am a complete novice here but I am  
> wondering if it would be possible to modify fluidsynth so that the  
> internal mixer was bypassed and the unmixed sound data was sent to the  
> fluid_core_audio_callback. This data could then be sent to OSX's built  
> in CoreAudio  mixers and AudioUnits to do the processing, thus  
> avoiding the problem. I am not even sure if this makes sense but I  
> thought I'd ask!
> 
> Anyway - many thanks for a very nice piece of software.
> 
> Peter
> 
> 
> 
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