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Forbid DATA_ENTRY_LSB to modulate (#465)
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and document illegal CC modulation
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@jjceresa @derselbst
jjceresa authored and derselbst committed Nov 18, 2018
1 parent f52e4fd commit 6e9d84f
Showing 1 changed file with 61 additions and 18 deletions.
79 changes: 61 additions & 18 deletions src/synth/fluid_synth.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1318,7 +1318,7 @@ fluid_synth_damp_voices_by_sostenuto_LOCAL(fluid_synth_t *synth, int chan)
* @param mod Modulator info (values copied, passed in object can be freed immediately afterwards)
* @param mode Determines how to handle an existing identical modulator (#fluid_synth_add_mod)
* @return #FLUID_OK on success, #FLUID_FAILED otherwise
*
*
* @note Not realtime safe (due to internal memory allocation) and therefore should not be called
* from synthesis context at the risk of stalling audio output.
*/
Expand Down Expand Up @@ -1388,7 +1388,7 @@ fluid_synth_add_default_mod(fluid_synth_t *synth, const fluid_mod_t *mod, int mo
* @param synth synth instance
* @param mod The modulator to remove
* @return #FLUID_OK if a matching modulator was found and successfully removed, #FLUID_FAILED otherwise
*
*
* @note Not realtime safe (due to internal memory allocation) and therefore should not be called
* from synthesis context at the risk of stalling audio output.
*/
Expand Down Expand Up @@ -1513,7 +1513,37 @@ fluid_synth_cc(fluid_synth_t *synth, int chan, int num, int val)
FLUID_API_RETURN(result);
}

/* Local synthesis thread variant of MIDI CC set function. */
/* Local synthesis thread variant of MIDI CC set function.
Most of CC are allowed to modulate but not all. A comment describes if CC num
isn't allowed to modulate.
Following explanations should help to understand both MIDI specifications and
Soundfont specifications in regard to MIDI specs.
MIDI specs:
CC LSB (32 to 63) are LSB contributions to CC MSB (0 to 31).
It's up to the synthesizer to decide to take LSB values into account or not.
Actually Fluidsynth doesn't use CC LSB value inside fluid_voice_update_param()
(once fluid_voice_modulate() has been triggered). This is because actually
fluidsynth needs only 7 bits resolution (and not 14 bits) from these CCs.
So fluidsynth is using only 7 bit MSB (except for portamento time).
In regard to MIDI specs Fluidsynth behaves correctly.
Soundfont specs 2.01 - 8.2.1:
To deal correctly with MIDI CC (regardless if any synth will use CC MSB alone (7 bit)
or both CCs MSB,LSB (14 bits) during synthesis), SF specs recommend not making use of
CC LSB (i.e only CC MSB) in modulator sources to trigger modulation (i.e modulators
with CC LSB connected to sources inputs should be ignored).
These specifics are particularly suited for synths that use 14 bits CCs. In this case,
the MIDI transmitter sends CC LSB first followed by CC MSB. The MIDI synth receives
both CC LSB and CC MSB but only CC MSB will trigger the modulation.
This will produce correct synthesis parameters update from a correct 14 bits CC.
If in SF specs, modulator sources with CC LSB had been accepted, both CC LSB and
CC MSB will triggers 2 modulations. This leads to incorrect synthesis parameters
update followed by correct synthesis parameters update.
However, as long as fluidsynth will use only CC 7 bits resolution, it is safe to ignore
these SF recommendations on CC receive.
*/
static int
fluid_synth_cc_LOCAL(fluid_synth_t *synth, int channum, int num)
{
Expand All @@ -1525,8 +1555,11 @@ fluid_synth_cc_LOCAL(fluid_synth_t *synth, int channum, int num)

switch(num)
{
case LOCAL_CONTROL: /* not allowed to modulate (spec SF 2.01 - 8.2.1) */
break;

/* CC omnioff, omnion, mono, poly */
/* not allowed to modulate (spec SF 2.01 - 8.2.1) */
case POLY_OFF:
case POLY_ON:
case OMNI_OFF:
Expand Down Expand Up @@ -1581,18 +1614,18 @@ fluid_synth_cc_LOCAL(fluid_synth_t *synth, int channum, int num)

return FLUID_FAILED;

case LEGATO_SWITCH:
case LEGATO_SWITCH: /* not allowed to modulate */
/* handles Poly/mono commutation on Legato pedal On/Off.*/
fluid_channel_cc_legato(chan, value);
break;

case PORTAMENTO_SWITCH:
case PORTAMENTO_SWITCH: /* not allowed to modulate */
/* Special handling of the monophonic list */
/* Invalids the most recent note played in a staccato manner */
fluid_channel_invalid_prev_note_staccato(chan);
break;

case SUSTAIN_SWITCH:
case SUSTAIN_SWITCH: /* not allowed to modulate */

/* Release voices if Sustain switch is released */
if(value < 64) /* Sustain is released */
Expand All @@ -1602,7 +1635,7 @@ fluid_synth_cc_LOCAL(fluid_synth_t *synth, int channum, int num)

break;

case SOSTENUTO_SWITCH:
case SOSTENUTO_SWITCH: /* not allowed to modulate */

/* Release voices if Sostetuno switch is released */
if(value < 64) /* Sostenuto is released */
Expand All @@ -1617,28 +1650,31 @@ fluid_synth_cc_LOCAL(fluid_synth_t *synth, int channum, int num)

break;

case BANK_SELECT_MSB:
case BANK_SELECT_MSB: /* not allowed to modulate (spec SF 2.01 - 8.2.1) */
fluid_channel_set_bank_msb(chan, value & 0x7F);
break;

case BANK_SELECT_LSB:
case BANK_SELECT_LSB: /* not allowed to modulate (spec SF 2.01 - 8.2.1) */
fluid_channel_set_bank_lsb(chan, value & 0x7F);
break;

case ALL_NOTES_OFF:
case ALL_NOTES_OFF: /* not allowed to modulate (spec SF 2.01 - 8.2.1) */
fluid_synth_all_notes_off_LOCAL(synth, channum);
break;

case ALL_SOUND_OFF:
case ALL_SOUND_OFF: /* not allowed to modulate (spec SF 2.01 - 8.2.1) */
fluid_synth_all_sounds_off_LOCAL(synth, channum);
break;

case ALL_CTRL_OFF:
case ALL_CTRL_OFF: /* not allowed to modulate (spec SF 2.01 - 8.2.1) */
fluid_channel_init_ctrl(chan, 1);
fluid_synth_modulate_voices_all_LOCAL(synth, channum);
break;

case DATA_ENTRY_MSB:
case DATA_ENTRY_LSB: /* not allowed to modulate (spec SF 2.01 - 8.2.1) */
break;

case DATA_ENTRY_MSB: /* not allowed to modulate (spec SF 2.01 - 8.2.1) */
{
int data = (value << 7) + fluid_channel_get_cc(chan, DATA_ENTRY_LSB);

Expand Down Expand Up @@ -1698,13 +1734,13 @@ fluid_synth_cc_LOCAL(fluid_synth_t *synth, int channum, int num)
break;
}

case NRPN_MSB:
case NRPN_MSB: /* not allowed to modulate (spec SF 2.01 - 8.2.1) */
fluid_channel_set_cc(chan, NRPN_LSB, 0);
chan->nrpn_select = 0;
chan->nrpn_active = 1;
break;

case NRPN_LSB:
case NRPN_LSB: /* not allowed to modulate (spec SF 2.01 - 8.2.1) */

/* SontFont 2.01 NRPN Message (Sect. 9.6, p. 74) */
if(fluid_channel_get_cc(chan, NRPN_MSB) == 120)
Expand All @@ -1730,8 +1766,8 @@ fluid_synth_cc_LOCAL(fluid_synth_t *synth, int channum, int num)
chan->nrpn_active = 1;
break;

case RPN_MSB:
case RPN_LSB:
case RPN_MSB: /* not allowed to modulate (spec SF 2.01 - 8.2.1) */
case RPN_LSB: /* not allowed to modulate (spec SF 2.01 - 8.2.1) */
chan->nrpn_active = 0;
break;

Expand All @@ -1741,7 +1777,14 @@ fluid_synth_cc_LOCAL(fluid_synth_t *synth, int channum, int num)

/* fall-through */
default:
return fluid_synth_modulate_voices_LOCAL(synth, channum, 1, num);
/* CC lsb shouldn't allowed to modulate (spec SF 2.01 - 8.2.1) */
/* However, as long fluidsynth will use only CC 7 bits resolution, it
is safe to ignore these SF recommendations on CC receive. See
explanations above */
/* if (! (32 <= num && num <= 63)) */
{
return fluid_synth_modulate_voices_LOCAL(synth, channum, 1, num);
}
}

return FLUID_OK;
Expand Down

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