fluid_synth_noteoff() return value

[nandlab]

Hello everyone,

in the documentation it says about the fluid_synth_noteoff() return value:

FLUID_OK on success, FLUID_FAILED otherwise (may just mean that no voices matched the note off event)

Now, is there a way to distinguish between "no voices matched the note off event" and an actual error?

I am writing a C++ wrapper around fluidsynth and I am always checking the return codes of the libfluidsynth functions. If it is FLUID_FAILED (-1), I am throwing an exception.

void fluid_synth_auto::noteoff(int chan, int key) const {
    if (fluid_synth_noteoff(ptr, chan, key)) {
        throw fluid_exception();
    }
}

In my program, if a note faded out after a note_on, and I call noteoff, it throws an exception, which is unexpected.

How do I handle the return value of noteoff correctly?

[derselbst]

Currently there is no way to distinguish. By default, noteoff() returns FLUID_FAILED, unless it found a matching voice, in which case it returns FLUID_OK from here:

fluidsynth/src/synth/fluid_synth_monopoly.c

Line 594 in b580a11

status = FLUID_OK;

On the other hand, the only real errors that could occur during noteoff are:

• synth is NULL
• key is out of range
• chan is out of range
• chan specifies a channel that has been disabled due to a previous call to fluid_synth_set_basic_channel()

You can easily avoid the first three error sources. Not sure if you're using the basic channels feature; if not, you can ignore that as well. Then you know that FLUID_FAILED is because it didn't match a voice.

A more explicit way of doing it would be to lookup all voices with fluid_synth_get_voicelist () and search for voices playing on that channel with that particular key which are in state ON. If there are no ON voices, fluid_synth_noteoff will give you a FLUID_FAILED when called afterwards. However, this lookup can only be safely done when called from synth context.

[nandlab]

Thanks for extensive reply! I do not use basic channels, so I can avoid these error sources. But I think, as an improvement, the return value could be more detailed here (e.g. FLUID_OK, FLUID_NO_VOICE_MATCH and FLUID_FAILED).