Disable sustain/sostenuto pedals after last MIDI event

[topaz]

While working with a larger set of MIDI files with the changes in #1159, I discovered that for some of the files, fluid_synth_get_active_voice_count(player->synth) never goes to zero (at least, not after as long as I was willing to wait for it, maybe 15-30 seconds). This causes the player to appear to terminate automatically on some songs bug hang indefinitely on others.

In an attempt to prevent that situation, this PR changes the post-MIDI-events player logic in #1159 from "wait until fluid_synth_get_active_voice_count(player->synth) is zero, then wait until FLUID_PLAYER_STOP_GRACE_MS have elapsed" to instead "wait until either fluid_synth_get_active_voice_count(player->synth) or FLUID_PLAYER_STOP_GRACE_MS have elapsed".

[derselbst]

I discovered that for some of the files, fluid_synth_get_active_voice_count(player->synth) never goes to zero

Oh really? Sounds like a bug. Could you provide an example MIDI where you've observed that?

[topaz]

Sure! I'm using a recent commit on master (89a2c4b4) that includes my change in #1159.

Just for fun, add a debug line at src/midi/fluid_midi.c line 2184:

        /* Once we've run out of MIDI events, keep playing until no voices are active */
        if(status == FLUID_PLAYER_DONE && fluid_synth_get_active_voice_count(player->synth) > 0)
        {
            printf("waiting for zero voices; voices active: %d\n", fluid_synth_get_active_voice_count(player->synth));
            status = FLUID_PLAYER_PLAYING;
        }

Then, I tried to fast-render jtbach.mid using the FluidSynth-provided SF2 file sf2/VintageDreamsWaves-v2.sf2:

path/to/fluidsynth -F tmp path/to/sf2/VintageDreamsWaves-v2.sf2 path/to/jtbach.mid

(Realtime-render does the same thing if you wait for the song to end, and other SF2 files also seem to do the same thing.)

When I do this, it eventually just repeatedly spams:

waiting for zero voices; voices active: 34

[derselbst]

Ok thanks! The problem is that MIDI channel 0 activates the sustain pedal pretty much at the end of the track, but doesn't disable it, causing some notes to keep playing in sustain forever. Therefore I would suggest the following more straightforward fix:

        /* Once we've run out of MIDI events, keep playing until no voices are active */
        if(status == FLUID_PLAYER_DONE && fluid_synth_get_active_voice_count(player->synth) > 0)
        {
            int i;
            /* disable hold pedals on all channels to release any playing voices */
            for(i = 0; i < synth->midi_channels; i++)
            {
                fluid_synth_cc(player->synth, i, SUSTAIN_SWITCH, 0);
                fluid_synth_cc(player->synth, i, SOSTENUTO_SWITCH, 0);
            }
            status = FLUID_PLAYER_PLAYING;
        }

It worked fine with the MIDI you provided. You might want to test a few more.

[topaz]

I've made the change you recommended (with a twist; it only applies the pedal changes once). This change seems to work on all of the files I have to test with. The 2000ms extra for reverb still seems like overkill to me, but I'm running with default reverb settings.

[sonarqubecloud]

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[derselbst]

Great, thanks!