Add global portamento time mode setting to fix compatibility with older MIDI files

.gitignore

@@ -1,5 +1,6 @@
 .DS_Store
 build/
+install/
 
 CMakeCache.txt
 CMakeFiles
@@ -40,3 +41,4 @@ install_manifest.txt
 # ProjectFiles
 *.pro.user*
 *.user
+*.vscode

doc/fluidsettings.xml

@@ -315,6 +315,21 @@ Developers:
             <desc>
                 The polyphony defines how many voices can be played in parallel. A note event produces one or more voices. Its good to set this to a value which the system can handle and will thus limit FluidSynth's CPU usage. When FluidSynth runs out of voices it will begin terminating lower priority voices for new note events.</desc>
         </setting>
+        <setting>
+            <name>portamento-time</name>
+            <type>str</type>
+            <def>auto</def>
+            <realtime/>
+            <vals>auto, linear, xg-gs</vals>
+            <desc>
+                This setting was introduced in 2.5.0 to specify how to handle portamento time CC MSB and LSB.
+                <ul>
+                    <li>'linear' - portamento time is 14 bits wide and calculated as <code>CC5 * 128 + CC37</code> in milliseconds (this was fluidsynth's behavior before this setting was introduced).</li>
+                    <li>'xg-gs' - portamento time is 7 bits wide, using only CC5, which is mapped onto a concave curve ranging from 0s to 480s. The exact mapping was derived through listening tests and may be subject to change between different versions of fluidsynth. This setting should be used for older MIDI files, like Descent Game08.</li>
+                    <li>'auto' - the synth starts in 'xg-gs' mode. If it detects a CC37 on any MIDI channel, it switches to 'linear' mode.</li>
+                </ul>
+            </desc>
+        </setting>
         <setting>
             <name>reverb.active</name>
             <type>bool</type>

doc/recent_changes.txt

@@ -7,6 +7,7 @@
 - fluid_mod_get_transform() now receives a <code>const</code> argument
 - fluid_version_str() now returns a <code>const</code> char array
 - An API for manipulating fluid_sfont_t specific default modulators has been added: fluid_sfont_get_default_mod() and fluid_sfont_set_default_mod()
+- Support for specifying a synth-wide mode to interpret portamento time has been added, see #fluid_portamento_time_mode, fluid_synth_get_portamento_time_mode(), fluid_synth_set_portamento_time_mode() and setting "synth.portamento-time"
 
 \section NewIn2_4_5 What's new in 2.4.5?
 - In order to use the sdl3 audio driver, the downstream application is responsible for calling <code>SDL_Init()</code> and <code>SDL_Quit()</code>, just like it was practice for the sdl2 audio driver. Fluidsynth may raise a warning if this isn't done, see \ref CreatingAudioDriver

include/fluidsynth/synth.h

@@ -538,6 +538,27 @@ FLUIDSYNTH_API int fluid_synth_set_breath_mode(fluid_synth_t *synth,
 FLUIDSYNTH_API int fluid_synth_get_breath_mode(fluid_synth_t *synth,
         int chan, int  *breathmode);
 /** @} Breath Mode */
+
+/** @name Portamento Time Mode
+ * @{
+ */
+
+/**
+ * Indicates the portamento time mode the synthesizer is set to
+ */
+enum fluid_portamento_time_mode
+{
+    FLUID_PORTAMENTO_TIME_MODE_AUTO,     /**< Auto mode - Start with 7-bit MSB, switch to 14-bit when LSB seen */
+    FLUID_PORTAMENTO_TIME_MODE_XG_GS,    /**< XG/GS mode - Always use 7-bit MSB only */
+    FLUID_PORTAMENTO_TIME_MODE_LINEAR,   /**< Linear mode - Always use 14-bit MSB+LSB */
+    FLUID_PORTAMENTO_TIME_MODE_LAST      /**< @internal Value defines the count of portamento time modes
+                                           @warning This symbol is not part of the public API and ABI
+                                           stability guarantee and may change at any time! */
+};
+
+FLUIDSYNTH_API int fluid_synth_set_portamento_time_mode(fluid_synth_t *synth, int mode);
+FLUIDSYNTH_API int fluid_synth_get_portamento_time_mode(fluid_synth_t *synth, int *mode);
+/** @} Portamento Time Mode */
 /** @} MIDI Channel Setup */
 
 

src/synth/fluid_chan.c

@@ -86,7 +86,7 @@ fluid_channel_init(fluid_channel_t *chan)
     /*---*/
     chan->key_mono_sustained = INVALID_NOTE; /* No previous mono note sustained */
     chan->legatomode = FLUID_CHANNEL_LEGATO_MODE_MULTI_RETRIGGER;		/* Default mode */
-    chan->portamentomode = FLUID_CHANNEL_PORTAMENTO_MODE_LEGATO_ONLY;	/* Default mode */
+    chan->portamentomode = FLUID_CHANNEL_PORTAMENTO_MODE_EACH_NOTE;	/* Default mode */
     /*--- End of poly/mono initialization --------------------------------------*/
 
     chan->channel_type = (chan->channum == 9) ? CHANNEL_TYPE_DRUM : CHANNEL_TYPE_MELODIC;
@@ -758,3 +758,69 @@ void fluid_channel_set_override_gen_default(fluid_channel_t *chan, int gen, flui
     chan->override_gen_default[gen].flags = GEN_SET;
     chan->override_gen_default[gen].val = val;
 }
+
+/* Calculate portamento time in milliseconds considering the synthesizer's portamento time mode */
+unsigned int fluid_channel_portamentotime_with_mode(fluid_channel_t *chan, enum fluid_portamento_time_mode time_mode, int lsb_seen, int fromkey, int tokey)
+{
+    int msb = fluid_channel_get_cc(chan, PORTAMENTO_TIME_MSB);
+    int lsb = fluid_channel_get_cc(chan, PORTAMENTO_TIME_LSB);
+    int res;
+    fluid_real_t tmp;
+    static const int Max = 480*1000; /*ms*/
+
+    /* Use 7-bit MSB initially, switch to 14-bit if LSB has been seen */
+    if(time_mode == FLUID_PORTAMENTO_TIME_MODE_AUTO)
+    {
+        if(lsb_seen)
+        {
+            time_mode = FLUID_PORTAMENTO_TIME_MODE_LINEAR;
+        }
+        else
+        {
+            time_mode = FLUID_PORTAMENTO_TIME_MODE_XG_GS;
+        }
+    }
+
+    switch(time_mode)
+    {
+        case FLUID_PORTAMENTO_TIME_MODE_XG_GS:
+            // Produce a curve similar to:
+            /*
+                CC 5 value  Portamento time
+                ----------  ---------------
+                    0            0.000 s
+                    1            0.006 s
+                    2            0.023 s
+                    4            0.050 s
+                    8            0.110 s
+                    16           0.250 s
+                    32           0.500 s
+                    64           2.060 s
+                    80           4.200 s
+                    96           8.400 s
+                    112         19.500 s
+                    116         26.700 s
+                    120         40.000 s
+                    124         80.000 s
+                    127        480.000 s
+            */
+            // Tests were performed by John Novak
+            // https://github.com/dosbox-staging/dosbox-staging/pull/2705
+            tmp = fluid_concave(msb);
+            res = (fluid_real_t)(Max/2 * 2.5) * tmp * fluid_concave(128 * tmp) + 400 * fluid_convex(msb * (fluid_real_t)(1/4.0));
+            res = res < Max ? res : Max;
+            // Apply a similar scaling hack as SpessaSynth to fix Descent Game08, it's unclear why exactly
+            // https://github.com/spessasus/spessasynth_core/blob/5a8730a80f8c0b74733ec193a968b36e2a0c0aee/src/synthesizer/audio_engine/engine_methods/portamento_time.ts#L84-87
+            // https://github.com/FluidSynth/fluidsynth/pull/1656#issuecomment-3355759938
+            res = (unsigned int)(res * abs(tokey - fromkey) / 36.0f + 0.5f);
+            return res;
+
+        case FLUID_PORTAMENTO_TIME_MODE_LINEAR:
+            /* Always use 14-bit MSB+LSB */
+            return msb * 128 + lsb;
+
+        default:
+            FLUID_LOG(FLUID_ERR, "THIS SHOULD NEVER HAPPEN! unknown portamento time mode %d", time_mode);
+    }
+    return 0;
+}

src/synth/fluid_chan.h

@@ -192,8 +192,6 @@ fluid_real_t fluid_channel_get_key_pitch(fluid_channel_t *chan, int key);
   ((chan)->tuning_prog)
 #define fluid_channel_set_tuning_prog(chan, prog) \
   ((chan)->tuning_prog = (prog))
-#define fluid_channel_portamentotime(_c) \
-    ((_c)->cc[PORTAMENTO_TIME_MSB] * 128 + (_c)->cc[PORTAMENTO_TIME_LSB])
 #define fluid_channel_portamento(_c)			((_c)->cc[PORTAMENTO_SWITCH] >= 64)
 #define fluid_channel_breath_msb(_c)			((_c)->cc[BREATH_MSB] > 0)
 #define fluid_channel_clear_portamento(_c)		((_c)->cc[PORTAMENTO_CTRL] = INVALID_NOTE)
@@ -286,8 +284,10 @@ void fluid_channel_cc_breath_note_on_off(fluid_channel_t *chan, int value);
 int fluid_channel_get_override_gen_default(fluid_channel_t *chan, int gen, fluid_real_t *val);
 void fluid_channel_set_override_gen_default(fluid_channel_t *chan, int gen, fluid_real_t val);
 
+/* Portamento time calculation with mode support */
+unsigned int fluid_channel_portamentotime_with_mode(fluid_channel_t *chan, enum fluid_portamento_time_mode time_mode, int lsb_seen, int, int);
+
 #ifdef __cplusplus
 }
 #endif
-
 #endif /* _FLUID_CHAN_H */

src/synth/fluid_synth.c

@@ -131,13 +131,15 @@ static int fluid_synth_set_important_channels(fluid_synth_t *synth, const char *
 
 static void fluid_synth_process_awe32_nrpn_LOCAL(fluid_synth_t *synth, int chan, int gen, int data, int data_lsb);
 
+static int fluid_parse_portamento_time_str(const char* value);
+
 /* Callback handlers for real-time settings */
 static void fluid_synth_handle_gain(void *data, const char *name, double value);
 static void fluid_synth_handle_polyphony(void *data, const char *name, int value);
 static void fluid_synth_handle_device_id(void *data, const char *name, int value);
 static void fluid_synth_handle_overflow(void *data, const char *name, double value);
-static void fluid_synth_handle_important_channels(void *data, const char *name,
-        const char *value);
+static void fluid_synth_handle_important_channels(void *data, const char *name, const char *value);
+static void fluid_synth_handle_portamento_mode(void *data, const char *name, const char *value);
 static void fluid_synth_handle_reverb_chorus_num(void *data, const char *name, double value);
 static void fluid_synth_handle_reverb_chorus_int(void *data, const char *name, int value);
 
@@ -261,6 +263,11 @@ void fluid_synth_settings(fluid_settings_t *settings)
 
     fluid_settings_register_int(settings, "synth.dynamic-sample-loading", 0, 0, 1, FLUID_HINT_TOGGLED);
     fluid_settings_register_int(settings, "synth.note-cut", 0, 0, 2, 0);
+
+    fluid_settings_register_str(settings, "synth.portamento-time", "auto", 0);
+    fluid_settings_add_option(settings, "synth.portamento-time", "auto");
+    fluid_settings_add_option(settings, "synth.portamento-time", "xg-gs");
+    fluid_settings_add_option(settings, "synth.portamento-time", "linear");
 }
 
 /**
@@ -766,6 +773,8 @@ new_fluid_synth(fluid_settings_t *settings)
                                 fluid_synth_handle_reverb_chorus_num, synth);
     fluid_settings_callback_num(settings, "synth.chorus.speed",
                                 fluid_synth_handle_reverb_chorus_num, synth);
+    fluid_settings_callback_str(settings, "synth.portamento-time",
+                                fluid_synth_handle_portamento_mode, synth);
 
     /* do some basic sanity checking on the settings */
 
@@ -848,6 +857,29 @@ new_fluid_synth(fluid_settings_t *settings)
 
     synth->fromkey_portamento = INVALID_NOTE;		/* disable portamento */
 
+    /* Initialize portamento time mode */
+    {
+        char *portamento_mode_str;
+        if(fluid_settings_dupstr(settings, "synth.portamento-time", &portamento_mode_str) == FLUID_OK)
+        {
+            int res = fluid_parse_portamento_time_str(portamento_mode_str);
+            if(res == FLUID_FAILED)
+            {
+                synth->portamento_time_mode = FLUID_PORTAMENTO_TIME_MODE_AUTO;
+            }
+            else
+            {
+                synth->portamento_time_mode = res;
+            }
+            FLUID_FREE(portamento_mode_str);
+        }
+        else
+        {
+            synth->portamento_time_mode = FLUID_PORTAMENTO_TIME_MODE_AUTO;
+        }
+        synth->portamento_time_has_seen_lsb = 0; /* Start in xg-gs mode for auto */
+    }
+
     fluid_atomic_int_set(&synth->ticks_since_start, 0);
     synth->tuning = NULL;
     fluid_private_init(synth->tuning_iter);
@@ -2040,6 +2072,13 @@ fluid_synth_cc_LOCAL(fluid_synth_t *synth, int channum, int num)
         fluid_channel_cc_breath_note_on_off(chan, value);
 
     /* fall-through */
+    case PORTAMENTO_TIME_LSB:
+        /* Track LSB reception for auto portamento mode */
+        if(num == PORTAMENTO_TIME_LSB && synth->portamento_time_mode == FLUID_PORTAMENTO_TIME_MODE_AUTO)
+        {
+            synth->portamento_time_has_seen_lsb = 1;
+        }
+        /* fall-through */
     default:
         /* 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
@@ -2823,6 +2862,12 @@ fluid_synth_system_reset_LOCAL(fluid_synth_t *synth)
     fluid_synth_update_mixer(synth, fluid_rvoice_mixer_reset_reverb, 0, 0.0f);
     fluid_synth_update_mixer(synth, fluid_rvoice_mixer_reset_chorus, 0, 0.0f);
 
+    /* Reset auto portamento mode tracking */
+    if(synth->portamento_time_mode == FLUID_PORTAMENTO_TIME_MODE_AUTO)
+    {
+        synth->portamento_time_has_seen_lsb = 0;
+    }
+
     return FLUID_OK;
 }
 
@@ -8327,6 +8372,41 @@ static void fluid_synth_handle_important_channels(void *data, const char *name,
     fluid_synth_api_exit(synth);
 }
 
+static int fluid_parse_portamento_time_str(const char* value)
+{
+    int mode;
+    if(FLUID_STRCMP(value, "auto") == 0)
+    {
+        mode = FLUID_PORTAMENTO_TIME_MODE_AUTO;
+    }
+    else if(FLUID_STRCMP(value, "xg-gs") == 0)
+    {
+        mode = FLUID_PORTAMENTO_TIME_MODE_XG_GS;
+    }
+    else if(FLUID_STRCMP(value, "linear") == 0)
+    {
+        mode = FLUID_PORTAMENTO_TIME_MODE_LINEAR;
+    }
+    else
+    {
+        FLUID_LOG(FLUID_ERR, "Invalid portamento time mode '%s'. Valid modes: auto, xg-gs, linear", value);
+        mode = FLUID_FAILED;
+    }
+    return mode;
+}
+
+static void fluid_synth_handle_portamento_mode(void *data, const char *name, const char *value)
+{
+    int mode;
+    fluid_synth_t *synth = (fluid_synth_t *)data;
+
+    mode = fluid_parse_portamento_time_str(value);
+    if(mode != FLUID_FAILED)
+    {
+        fluid_synth_set_portamento_time_mode(synth, mode);
+    }
+}
+
 
 /* API legato mode *********************************************************/
 
@@ -8434,6 +8514,63 @@ int fluid_synth_get_portamento_mode(fluid_synth_t *synth, int chan,
     FLUID_API_RETURN(FLUID_OK);
 }
 
+/*  API portamento time mode ************************************************/
+
+/**
+ * Sets the global portamento time mode of the synthesizer.
+ *
+ * @param synth the synth instance.
+ * @param mode The portamento time mode as indicated by #fluid_portamento_time_mode.
+ *
+ * @return
+ * - #FLUID_OK on success.
+ * - #FLUID_FAILED
+ *   - \a synth is NULL.
+ *   - \a mode is invalid.
+ */
+int fluid_synth_set_portamento_time_mode(fluid_synth_t *synth, int mode)
+{
+    /* checks parameters first */
+    fluid_return_val_if_fail(synth != NULL, FLUID_FAILED);
+    fluid_synth_api_enter(synth);
+
+    if(mode < 0 || mode >= FLUID_PORTAMENTO_TIME_MODE_LAST)
+    {
+        FLUID_API_RETURN(FLUID_FAILED);
+    }
+
+    synth->portamento_time_mode = (enum fluid_portamento_time_mode)mode;
+
+    /* Reset auto mode tracking when mode changes */
+    synth->portamento_time_has_seen_lsb = 0;
+
+    FLUID_API_RETURN(FLUID_OK);
+}
+
+/**
+ * Gets the global portamento time mode of the synthesizer.
+ *
+ * @param synth the synth instance.
+ * @param mode the address to store the portamento time mode to.
+ *
+ * @return
+ * - #FLUID_OK on success.
+ * - #FLUID_FAILED
+ *   - \a synth is NULL.
+ *   - \a mode is NULL.
+ */
+int fluid_synth_get_portamento_time_mode(fluid_synth_t *synth, int *mode)
+{
+    /* checks parameters first */
+    fluid_return_val_if_fail(mode != NULL, FLUID_FAILED);
+    fluid_return_val_if_fail(synth != NULL, FLUID_FAILED);
+    fluid_synth_api_enter(synth);
+
+    *mode = synth->portamento_time_mode;
+
+    FLUID_API_RETURN(FLUID_OK);
+}
+
 /*  API breath mode *********************************************************/
 
 /**

src/synth/fluid_synth.h

@@ -175,6 +175,10 @@ struct _fluid_synth_t
     enum fluid_iir_filter_flags custom_filter_flags; /**< filter type of the user-defined filter currently used for all voices */
     enum fluid_msgs_note_cut msgs_note_cut_mode;
 
+    /** Portamento time mode settings */
+    enum fluid_portamento_time_mode portamento_time_mode; /**< Global portamento time mode */
+    int portamento_time_has_seen_lsb; /**< Flag to track if LSB has been seen (for auto mode) */
+
     fluid_iir_sincos_t iir_sincos_table[SINCOS_TAB_SIZE]; /**< Table of sin/cos values for IIR filter */
 };