enable midi -> audio (#83)

fluidsynth.py

@@ -618,6 +618,16 @@ class fluid_midi_router_t(Structure):
                                     ('rule', c_void_p, 1),
                                     ('type', c_int, 1))
 
+# fluid file renderer
+new_fluid_file_renderer = cfunc('new_fluid_file_renderer', c_void_p,
+                                ('synth', c_void_p, 1))
+
+delete_fluid_file_renderer = cfunc('delete_fluid_file_renderer', None,
+                                   ('renderer', c_void_p, 1))
+
+fluid_file_renderer_process_block = cfunc('fluid_file_renderer_process_block', c_int,
+                                          ('render', c_void_p, 1))
+
 # fluidsynth 2.x
 new_fluid_cmd_handler=cfunc('new_fluid_cmd_handler', c_void_p,
                                ('synth', c_void_p, 1),
@@ -693,6 +703,8 @@ def __init__(self, gain=0.2, samplerate=44100, channels=256, **kwargs):
         self.midi_driver = None
         self.router = None
         self.custom_router_callback = None
+    def __del__(self):
+        self.delete()
     def setting(self, opt, val):
         """change an arbitrary synth setting, type-smart"""
         if isinstance(val, (str, bytes)):
@@ -1070,7 +1082,19 @@ def play_midi_stop(self):
 
     def player_set_tempo(self, tempo_type, tempo):
         return fluid_player_set_tempo(self.player, tempo_type, tempo)
-
+
+    def midi2audio(self, midifile, audiofile = "output.wav"):
+        """Convert a midi file to an audio file"""
+        self.setting("audio.file.name", audiofile)
+        player = new_fluid_player(self.synth)
+        fluid_player_add(player, midifile.encode())
+        fluid_player_play(player)
+        renderer = new_fluid_file_renderer(self.synth)
+        while(fluid_player_get_status(player) == FLUID_PLAYER_PLAYING):
+            if(fluid_file_renderer_process_block(renderer) != FLUID_OK):
+                break
+        delete_fluid_file_renderer(renderer)
+        delete_fluid_player(player)
 
 
 class Sequencer:

test/test7.py

@@ -0,0 +1,17 @@
+import fluidsynth
+
+
+def local_file_path(file_name: str) -> str:
+    """
+    Return a file path to a file that is in the same directory as this file.
+    """
+    from os.path import dirname, join
+
+    return join(dirname(__file__), file_name)
+
+fs = fluidsynth.Synth()
+sfid = fs.sfload(local_file_path("example.sf2"))
+fs.midi2audio(local_file_path("1080-c01.mid"), local_file_path("1080-c01.wav"))
+# A Synth object can synthesize multiple files. For example:
+# fs.midi2audio(local_file_path("1080-c02.mid"), local_file_path("1080-c02.wav"))
+# fs.midi2audio(local_file_path("1080-c03.mid"), local_file_path("1080-c03.wav"))