midi_synthesizer.py

from threading import Lock

import fluidsynth
import numpy as np


class MidiSynthesizer:
 def __init__(self, soundfont_path, sample_rate=44100):
 self.soundfont_path = soundfont_path
 self.sample_rate = sample_rate
 fl = fluidsynth.Synth(samplerate=float(sample_rate))
 sfid = fl.sfload(soundfont_path)
 self.devices = [[fl, sfid, False]]
 self.file_lock = Lock()

 def get_fluidsynth(self):
 for device in self.devices:
 if not device[2]:
 device[2] = True
 return device
 with self.file_lock:
 fl = fluidsynth.Synth(samplerate=float(self.sample_rate))
 sfid = fl.sfload(self.soundfont_path)
 device = [fl, sfid, True]
 self.devices.append(device)
 return device

 def release_fluidsynth(self, device):
 device[0].system_reset()
 device[0].get_samples(self.sample_rate*5) # wait for silence
 device[2] = False

 def synthesis(self, midi_opus):
 ticks_per_beat = midi_opus[0]
 event_list = []
 for track_idx, track in enumerate(midi_opus[1:]):
 abs_t = 0
 for event in track:
 abs_t += event[1]
 event_new = [*event]
 event_new[1] = abs_t
 event_list.append(event_new)
 event_list = sorted(event_list, key=lambda e: e[1])

 tempo = int((60 / 120) * 10 ** 6) # default 120 bpm
 ss = np.empty((0, 2), dtype=np.int16)
 device = self.get_fluidsynth()
 fl, sfid = device[:-1]
 last_t = 0
 for c in range(16):
 fl.program_select(c, sfid, 128 if c == 9 else 0, 0)
 for event in event_list:
 name = event[0]
 sample_len = int(((event[1] / ticks_per_beat) * tempo / (10 ** 6)) * self.sample_rate)
 sample_len -= int(((last_t / ticks_per_beat) * tempo / (10 ** 6)) * self.sample_rate)
 last_t = event[1]
 if sample_len > 0:
 sample = fl.get_samples(sample_len).reshape(sample_len, 2)
 ss = np.concatenate([ss, sample])
 if name == "set_tempo":
 tempo = event[2]
 elif name == "patch_change":
 c, p = event[2:4]
 fl.program_select(c, sfid, 128 if c == 9 else 0, p)
 elif name == "control_change":
 c, cc, v = event[2:5]
 fl.cc(c, cc, v)
 elif name == "note_on" and event[3] > 0:
 c, p, v = event[2:5]
 fl.noteon(c, p, v)
 elif name == "note_off" or (name == "note_on" and event[3] == 0):
 c, p = event[2:4]
 fl.noteoff(c, p)

 self.release_fluidsynth(device)
 if ss.shape[0] > 0:
 max_val = np.abs(ss).max()
 if max_val != 0:
 ss = (ss / max_val) * np.iinfo(np.int16).max
 ss = ss.astype(np.int16)
 return ss