Re: [fluid-dev] Thread safety

[josh]

Quoting jimmy <address@hidden>:
> Here's my my comments on special effects  processing (SFX, for short  
>  here) in sound synthesis.  But since Midi allow for some live   
> manipulation of some paramenters, it may allow for per channel   
> manipulation, too?
>
> I guess one way to describe it is how many "SFX processors" can be   
> used concurrently in a chained sequence.  JackRack is one such   
> implementation where each plugin is 1 SFX processor.  Each of these   
> SFX processor parameters can change in real-time.  I would love to   
> have SFX processing for individual Midi channel (individual solo   
> instrument pan, sustain, delayed echo, vibrato...), or all channels   
> combined audio signal (like reverb, delayed echo, pitch shift).  But  
>  I guess individual solo instruments with SFX could be simulated by   
> running in a separate instance of FS.
>
> So if per channel SFX is possible, please do allow for ways to   
> specify which channel(s) these SFX processors should work on.  You   
> may also want to allow users to define/specify, or loaded-on-the-fly  
>  (maybe some sample code to use) these SFX processors from   
> configuration files, and let parameters be changed in real-time.
>
> The simplest case is 0, or 1 SFX processor.  More complicated are 2,  
>  3, or more sound effects chained together, but too many of these   
> chained together will introduce audio lags of some sort.
>
> Of course, you can impose or set a limit on the number of SFX   
> processors, i.e 3 max per voice/channel, 8 total...  Or if no   
> specific SFX limit is imposed, at least give a word of warning so   
> people don't have wild ideas that they can chain 5-10 SFX per   
> channel for 32 channels... or 100 SFX together and still get   
> real-time response on 1-2 core CPU's, or that the audio would sound   
> like anything we can still recognize.
>
> Jimmy


Hello Jimmy,

That isn't really on the topic of threads, but..  FluidSynth has  
support for SoundFont modulators, which allow for almost any effect  
parameter of an instrument to be controlled by MIDI controllers as  
well as things like velocity, aftertouch, etc.  One improvement that  
could be added to FluidSynth would be session modulators, which apply  
to the session, rather than having to edit the SoundFont.  This has  
been supported by Swami for some time now.  Just need to add a method  
for doing this in stand alone FluidSynth (shell commands, etc).  In  
addition FluidSynth supports parameter changes using NRPN data, as  
defined by the SoundFont standard.  This is on a per channel basis.

FluidSynth also has some LADSPA code for adding effects chains to MIDI  
channels.  I think this code is in a rather poor state though and  
suffers from stability issues and might be completely broken at this  
point, since I don't think anyone is using it.  Getting this stuff to  
work again is on the TODO list.

Regards,

Josh