Loud clicks on rapid ModEnv FilterFc changes

[spessasus]

FluidSynth version

Execute fluidsynth --version and provide the output.
2.4.0

Describe the bug

The attached preset Echo Drops will audibly click when the notes are played rapidly. See the video below:

2024-11-06.23-00-03.mp4

Expected behavior

No clicks, like in polyphone.

Steps to reproduce

1. Load the attached soundfont
2. Play a short note
3. Hear clicks

echo_drops.sf2.zip
IMPORTANT: Remove .zip extension. This is just .sf2 file, not an archive!!

Additional context

Definitely related to #1415 and #1417 , but this one is:

• not a distortion like Christian's report
• not related to AWE NRPNs like derselbst's report
• this is the filter clicking with modEnv release set to the minimum value.

So this is a new bug report. If it is similar enough to the two bugs mentioned above, feel free to close it.

[spessasus]

The fix I implemented for this was to copy the volEnv code:

fluidsynth/src/synth/fluid_voice.c

Lines 37 to 38 in d2c56ca

	/* min vol envelope release (to stop clicks) in SoundFont timecents */
	#define FLUID_MIN_VOLENVRELEASE -7200.0f /* ~16ms */

Fluid should to that for modEnv too IMO. Not noticeable and should fix the issue.

[derselbst]

Thanks, I have added a test for this here https://github.com/FluidSynth/fluidsynth/tree/iir-tests/test/manual/iir_filter .

By reverting #1345 the clicks are no longer audible. I will therefore close this issue as duplicate in favor of the other two already open issues. I currently disagree that adjusting the minimum modEnvRelease would be a feasible fix.