[fluid-dev] Propose changes for drum channels support

[jimmy]

GOAL FOR THIS PATCH:
--------------------
This patch would allow the flexibility to set any individual channel to be drum 
channel, and/or unset them (revert back to melodic channel).
--------------------


Add a flag to struct:

   _fluid_channel_t 

to indicate it is a drum channel, using int type, with value:

   0:  melodic channel
   1:  drum channel
   
Previously all checking for drum channel was hard-coded to compare to the 
number 9 (i.e. chan == 9).  So even with 32, 48, 64 channels, only channel 9 
was drum channel.  The channels 25, 41, 57 could not handle drums at all, even 
though each 16 midi channels were showing up as a separate ALSA-Midi port.

XG allows multiple drum channels, some use channels 9 and 10 (8, 9 with 
zero-indexing) and FludSynth could not deal with this previously.

GM2 allows 2 drum channels 10 and 11 (9, 10 with zero-indexing).

This patch is based on somewhat dated fluidsynth.svn399.20101221 (5 week old) 
code.

Let's hear if this is a reasonable change to the code base, or not.

Jimmy

----- Patch starts below: -----
diff -rup fluidsynth.svn399.20101221/src/synth/fluid_chan.c 
fluidsynth.svn399.20101221.jnDrumChannel/src/synth/fluid_chan.c
--- fluidsynth.svn399.20101221/src/synth/fluid_chan.c   2010-12-21 
19:02:53.000000000 -0500
+++ fluidsynth.svn399.20101221.jnDrumChannel/src/synth/fluid_chan.c     
2011-01-24 12:28:01.000000000 -0500
@@ -52,6 +52,7 @@ new_fluid_channel(fluid_synth_t* synth,
 
   chan->synth = synth;
   chan->channum = num;
+  chan->is_drum_channel = (9 == num) ? 1 : 0;
   chan->preset = NULL;
   chan->tuning = NULL;
 
@@ -68,7 +69,7 @@ fluid_channel_init(fluid_channel_t* chan
   int prognum, banknum;
 
   prognum = 0;
-  banknum = (chan->channum == 9)? 128 : 0; /* ?? */
+  banknum = (chan->is_drum_channel)? 128 : 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
   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->is_drum_channel)
       return; /* ignored */
 
   oldval = chan->sfont_bank_prog;
@@ -252,10 +253,8 @@ fluid_channel_set_bank_msb(fluid_channel
 
   style = chan->synth->bank_select;
   if (style == FLUID_BANK_STYLE_GM ||
-      style == FLUID_BANK_STYLE_XG ||
-      chan->channum == 9) //TODO: ask for channel drum mode, instead of number
+      chan->is_drum_channel)
       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 +262,15 @@ fluid_channel_set_bank_msb(fluid_channel
   else /* style == FLUID_BANK_STYLE_MMA */
       newval = (oldval & ~BANKMSB_MASKVAL) | (bankmsb << (BANK_SHIFTVAL + 7));
   chan->sfont_bank_prog = newval;
+
+  /* if style == XG and bankmsb == 127, convert the channel to drum mode.
+   * How should "newval" above be calculated (same as MMA style) ???
+   * Anticipate a progChange after a bankSelect, so not much else to do here */
+  if (style == FLUID_BANK_STYLE_XG && (127 == bankmsb))
+  {
+      chan->is_drum_channel = 1;
+  }
+
 }
 
 /* Get SoundFont ID, MIDI bank and/or program.  Use NULL to ignore a value. */
diff -rup fluidsynth.svn399.20101221/src/synth/fluid_chan.h 
fluidsynth.svn399.20101221.jnDrumChannel/src/synth/fluid_chan.h
--- fluidsynth.svn399.20101221/src/synth/fluid_chan.h   2010-12-21 
19:02:53.000000000 -0500
+++ fluidsynth.svn399.20101221.jnDrumChannel/src/synth/fluid_chan.h     
2011-01-25 13:07:49.000000000 -0500
@@ -74,6 +74,21 @@ struct _fluid_channel_t
    * flag indicating whether the NRPN value is absolute or not.
    */
   char gen_abs[GEN_LAST];
+
+  /* Drum channel flag, 0 for melodic channel, 1 for drum channel.
+   * Previously, even for 32, 48, 64 channels only channel 9 can be drum, 
+   * channel 25, 41, 57 were not treated as drum channel at all, even though
+   * ALSA shows 2, 3, 4 ports (each with 16 midi channels).
+   * We can optionally initialize channel 25, 41, 57 be GM drum channel if we
+   * want for each of those 16 midi channels -- need to change channel
+   * initialization, but may break existing apps unless they explicitly set
+   * these channels. 
+   * Moreover, GM2 allows 2 drum channels 10 and 11 (9, 10 with zero-indexing).
+   * Some older XG may use drum channels 9 and 10 (8, 9 with zero-indexing).
+   * Added at end of structure, hopefully existing apps using this structure 
may
+   * still work without having to recompile for the time being. */
+  int is_drum_channel;
+
 };
 
 fluid_channel_t* new_fluid_channel(fluid_synth_t* synth, int num);
diff -rup fluidsynth.svn399.20101221/src/synth/fluid_synth.c 
fluidsynth.svn399.20101221.jnDrumChannel/src/synth/fluid_synth.c
--- fluidsynth.svn399.20101221/src/synth/fluid_synth.c  2010-12-21 
19:02:53.000000000 -0500
+++ fluidsynth.svn399.20101221.jnDrumChannel/src/synth/fluid_synth.c    
2011-01-25 13:12:11.000000000 -0500
@@ -51,7 +51,6 @@ static int fluid_synth_sysex_midi_tuning
                                           int len, char *response,
                                           int *response_len, int 
avail_response,
                                           int *handled, int dryrun);
-static int fluid_synth_all_notes_off_LOCAL(fluid_synth_t* synth, int chan);
 static int fluid_synth_all_sounds_off_LOCAL(fluid_synth_t* synth, int chan);
 static int fluid_synth_system_reset_LOCAL(fluid_synth_t* synth);
 static int fluid_synth_modulate_voices_LOCAL(fluid_synth_t* synth, int chan,
@@ -1875,14 +1874,10 @@ fluid_synth_program_change(fluid_synth_t
 
   /* 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
-   * 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->is_drum_channel)
       preset = fluid_synth_find_preset(synth, DRUM_INST_BANK, prognum);
     else preset = fluid_synth_find_preset(synth, banknum, prognum);
 
@@ -1893,7 +1888,7 @@ fluid_synth_program_change(fluid_synth_t
       subst_prog = prognum;
 
       /* Melodic instrument? */
-      if (channel->channum != 9 && banknum != DRUM_INST_BANK)
+      if ((! channel->is_drum_channel) && banknum != DRUM_INST_BANK)
       {
         subst_bank = 0;
 
@@ -4990,3 +4985,40 @@ void fluid_synth_api_exit(fluid_synth_t*
   }
   
 }
+
+
+/**
+ * Set a midi channel to drum mode.
+ * @param synth FluidSynth instance
+ * @param chan MIDI channel number (0 to MIDI channel count - 1)
+ * @return FLUID_OK on success, FLUID_FAILED otherwise
+ */
+int
+fluid_synth_set_drum_channel(fluid_synth_t* synth, int chan)
+{
+  fluid_return_val_if_fail (synth != NULL, FLUID_FAILED);
+  fluid_return_val_if_fail (chan >= 0 && chan < synth->midi_channels, 
FLUID_FAILED);
+
+  synth->channel[chan]->is_drum_channel = 1;
+  /* reset channel, or just leave it for prog_change to deal with soundbank 
??? */
+
+  FLUID_API_RETURN(FLUID_OK);
+}
+
+
+/**
+ * Unset a midi channel from drum mode, GM2 allows 2 channels to be 
drum-channel.
+ * @param synth FluidSynth instance
+ * @param chan MIDI channel number (0 to MIDI channel count - 1)
+ * @return FLUID_OK on success, FLUID_FAILED otherwise
+ */
+int
+fluid_synth_unset_drum_channel(fluid_synth_t* synth, int chan)
+{
+  fluid_return_val_if_fail (synth != NULL, FLUID_FAILED);
+  fluid_return_val_if_fail (chan >= 0 && chan < synth->midi_channels, 
FLUID_FAILED);
+
+  synth->channel[chan]->is_drum_channel = 0;
+  
+  FLUID_API_RETURN(FLUID_OK);
+}
diff -rup fluidsynth.svn399.20101221/src/synth/fluid_synth.h 
fluidsynth.svn399.20101221.jnDrumChannel/src/synth/fluid_synth.h
--- fluidsynth.svn399.20101221/src/synth/fluid_synth.h  2010-12-21 
19:02:53.000000000 -0500
+++ fluidsynth.svn399.20101221.jnDrumChannel/src/synth/fluid_synth.h    
2011-01-23 13:42:24.000000000 -0500
@@ -230,4 +230,7 @@ void fluid_synth_api_exit(fluid_synth_t*
 
 void fluid_synth_settings(fluid_settings_t* settings);
 
+int fluid_synth_set_drum_channel(fluid_synth_t* synth, int chan);
+int fluid_synth_unset_drum_channel(fluid_synth_t* synth, int chan);
+
 #endif  /* _FLUID_SYNTH_H */
diff -rup fluidsynth.svn399.20101221/src/synth/fluid_voice.c 
fluidsynth.svn399.20101221.jnDrumChannel/src/synth/fluid_voice.c
--- fluidsynth.svn399.20101221/src/synth/fluid_voice.c  2010-12-21 
19:02:53.000000000 -0500
+++ fluidsynth.svn399.20101221.jnDrumChannel/src/synth/fluid_voice.c    
2011-01-23 12:19:21.000000000 -0500
@@ -1493,7 +1493,7 @@ fluid_voice_get_overflow_prio(fluid_voic
    * Then it is very important.
    * Also skip the released and sustained scores.
    */
-  if (voice->chan == 9){
+  if (voice->channel->is_drum_channel){
     this_voice_prio += score->percussion;
   } 
   else if (voice->has_noteoff) {
----- Patch ended above -----