Fixed issue related to negative duration and step

audio.py

@@ -105,12 +105,14 @@ def map_to_wav(song_map: pd.DataFrame, out_file: str, velocity: int=50) -> prett
   Returns:
   pretty_midi.PrettyMIDI: PrettyMIDI object containing the song's representation.
   """
-    
+
+  # Get song map as dataframe
   contracted_map = tf.squeeze(song_map)
   song_map_T = contracted_map.numpy().T
   notes = pd.DataFrame(song_map_T, columns=["pitch", "step", "duration"]).mul(_SCALING_FACTORS, axis=1)
   notes["pitch"] = notes["pitch"].astype('int32').clip(1, 127)
 
+  # Instantiate PrettyMIDI object and append notes
   pm = pretty_midi.PrettyMIDI()
   instrument = pretty_midi.Instrument(
       program=pretty_midi.instrument_name_to_program(
@@ -118,6 +120,11 @@ def map_to_wav(song_map: pd.DataFrame, out_file: str, velocity: int=50) -> prett
 
   prev_start = 0
   for i, note in notes.iterrows():
+    # The VAE might generate notes with negative step and duration,
+    # and we therefore need to make sure to skip these anomalies
+    if (note['step'] < 0 or note['duration'] < 0):
+        continue
+      
     start = float(prev_start + note['step'])
     end = float(start + note['duration'])
     note = pretty_midi.Note(
@@ -130,7 +137,9 @@ def map_to_wav(song_map: pd.DataFrame, out_file: str, velocity: int=50) -> prett
     prev_start = start
 
   pm.instruments.append(instrument)
-  if (out_file):
+
+  # If a path was specified, save as midi file
+  if out_file:
       pm.write(out_file)
   return pm