(Credit: jimmy) Allow channels to change state between melodic and drum channels

fluidsynth/include/fluidsynth/synth.h

@@ -100,6 +100,15 @@ FLUIDSYNTH_API int fluid_synth_program_reset(fluid_synth_t* synth);
 FLUIDSYNTH_API int fluid_synth_system_reset(fluid_synth_t* synth);
 
 
+enum fluid_midi_channel_type
+{
+  CHANNEL_TYPE_MELODIC = 0,
+  CHANNEL_TYPE_DRUM = 1
+};
+
+int fluid_synth_set_channel_type(fluid_synth_t* synth, int chan, int type);
+
+
 /* Low level access */
 FLUIDSYNTH_API fluid_preset_t* fluid_synth_get_channel_preset(fluid_synth_t* synth, int chan);
 FLUIDSYNTH_API int fluid_synth_start(fluid_synth_t* synth, unsigned int id, 

fluidsynth/src/synth/fluid_chan.c

@@ -67,8 +67,9 @@ fluid_channel_init(fluid_channel_t* chan)
   fluid_preset_t *newpreset;
   int prognum, banknum;
 
+  chan->channel_type = (chan->channum == 9) ? CHANNEL_TYPE_DRUM : CHANNEL_TYPE_MELODIC;
   prognum = 0;
-  banknum = (chan->channum == 9)? 128 : 0; /* ?? */
+  banknum = (chan->channel_type == CHANNEL_TYPE_DRUM) ? DRUM_INST_BANK : 0;
 
   chan->sfont_bank_prog = 0 << SFONT_SHIFTVAL | banknum << BANK_SHIFTVAL
     | prognum << PROG_SHIFTVAL;
@@ -233,7 +234,7 @@ fluid_channel_set_bank_lsb(fluid_channel_t* chan, int banklsb)
   style = chan->synth->bank_select;
   if (style == FLUID_BANK_STYLE_GM ||
       style == FLUID_BANK_STYLE_GS ||
-      chan->channum == 9) //TODO: ask for channel drum mode, instead of number
+      chan->channel_type == CHANNEL_TYPE_DRUM)
       return; /* ignored */
 
   oldval = chan->sfont_bank_prog;
@@ -251,11 +252,19 @@ fluid_channel_set_bank_msb(fluid_channel_t* chan, int bankmsb)
   int oldval, newval, style;
 
   style = chan->synth->bank_select;
+
+  if (style == FLUID_BANK_STYLE_XG)
+  {
+    /* XG bank (128*MSB+LSB), save MSB, do drum-channel auto-switch */
+    /* The number "120" was based on several keyboards having drums at 120 - 127, 
+       reference: http://lists.nongnu.org/archive/html/fluid-dev/2011-02/msg00003.html */
+    chan->channel_type = (120 <= bankmsb) ? CHANNEL_TYPE_DRUM : CHANNEL_TYPE_MELODIC;
+    return;
+  }
+
   if (style == FLUID_BANK_STYLE_GM ||
-      style == FLUID_BANK_STYLE_XG ||
-      chan->channum == 9) //TODO: ask for channel drum mode, instead of number
+      chan->channel_type == CHANNEL_TYPE_DRUM)
       return; /* ignored */
-  //TODO: if style == XG and bankmsb == 127, convert the channel to drum mode
 
   oldval = chan->sfont_bank_prog;
   if (style == FLUID_BANK_STYLE_GS)
@@ -263,6 +272,7 @@ fluid_channel_set_bank_msb(fluid_channel_t* chan, int bankmsb)
   else /* style == FLUID_BANK_STYLE_MMA */
       newval = (oldval & ~BANKMSB_MASKVAL) | (bankmsb << (BANK_SHIFTVAL + 7));
   chan->sfont_bank_prog = newval;
+
 }
 
 /* Get SoundFont ID, MIDI bank and/or program.  Use NULL to ignore a value. */

fluidsynth/src/synth/fluid_chan.h

@@ -74,6 +74,10 @@ struct _fluid_channel_t
    * flag indicating whether the NRPN value is absolute or not.
    */
   char gen_abs[GEN_LAST];
+
+  /* Drum channel flag, CHANNEL_TYPE_MELODIC, or CHANNEL_TYPE_DRUM. */
+  int channel_type;
+
 };
 
 fluid_channel_t* new_fluid_channel(fluid_synth_t* synth, int num);

fluidsynth/src/synth/fluid_synth.c

@@ -1876,13 +1876,13 @@ fluid_synth_program_change(fluid_synth_t* synth, int chan, int prognum)
   /* Special handling of channel 10 (or 9 counting from 0). channel
    * 10 is the percussion channel.
    *
-   * FIXME - Shouldn't hard code bank selection for channel 10.  I think this
+   * FIXME - I think this
    * is a hack for MIDI files that do bank changes in GM mode.  Proper way to
    * handle this would probably be to ignore bank changes when in GM mode. - JG
    */
   if (prognum != FLUID_UNSET_PROGRAM)
   {
-    if (channel->channum == 9)
+    if (channel->channel_type == CHANNEL_TYPE_DRUM)
       preset = fluid_synth_find_preset(synth, DRUM_INST_BANK, prognum);
     else preset = fluid_synth_find_preset(synth, banknum, prognum);
 
@@ -1893,7 +1893,7 @@ fluid_synth_program_change(fluid_synth_t* synth, int chan, int prognum)
       subst_prog = prognum;
 
       /* Melodic instrument? */
-      if (channel->channum != 9 && banknum != DRUM_INST_BANK)
+      if ((channel->channel_type != CHANNEL_TYPE_DRUM) && (DRUM_INST_BANK != banknum))
       {
         subst_bank = 0;
 
@@ -4990,3 +4990,23 @@ void fluid_synth_api_exit(fluid_synth_t* synth)
   }
   
 }
+
+
+/**
+ * Set midi channel type 
+ * @param synth FluidSynth instance
+ * @param chan MIDI channel number (0 to MIDI channel count - 1)
+ * @param type CHANNEL_TYPE_MELODIC, or CHANNEL_TYPE_DRUM
+ * @return FLUID_OK on success, FLUID_FAILED otherwise
+ * @since 1.1.3
+ */
+int fluid_synth_set_channel_type(fluid_synth_t* synth, int chan, int type)
+{
+  fluid_return_val_if_fail ((type >= CHANNEL_TYPE_MELODIC) && (type <= CHANNEL_TYPE_DRUM), FLUID_FAILED);
+  FLUID_API_ENTRY_CHAN(FLUID_FAILED);
+  
+  synth->channel[chan]->channel_type = type;
+
+  FLUID_API_RETURN(FLUID_OK);
+}
+

fluidsynth/src/synth/fluid_voice.c

@@ -1493,7 +1493,7 @@ fluid_voice_get_overflow_prio(fluid_voice_t* voice,
    * Then it is very important.
    * Also skip the released and sustained scores.
    */
-  if (voice->chan == 9){
+  if (voice->channel->channel_type == CHANNEL_TYPE_DRUM){
     this_voice_prio += score->percussion;
   } 
   else if (voice->has_noteoff) {