Update README.md

README.md

@@ -117,3 +117,60 @@ def postprocess(txt, path):
 
 postprocess(txt, './result.mid')
 ```
+
+
+
+Similarlt, to convert a midi file to the text representation:
+
+```
+
+def preprocess(path):
+    # turn the midi into a custom format and write it to ./example/output.txt
+    # midi files may be broken
+    try:
+        score = symusic.Score(path, ttype='Second')
+    except Exception as e:
+        print('Ignored midi loading error:', e)
+        return ''
+    
+    # prolong notes to the end of the current pedal
+    score = score.copy()
+    for track in score.tracks:
+        notes = track.notes
+        pedals = track.pedals
+        track.pedals = []
+        j = 0
+        for i, note in enumerate(notes):
+            while j < len(pedals) and pedals[j].time + pedals[j].duration < note.time:
+                j += 1
+            if j < len(pedals) and pedals[j].time <= note.time <= pedals[j].time + pedals[j].duration:
+                # adjust the duration
+                note.duration = max(
+                    note.duration, 
+                    pedals[j].time + pedals[j].duration - note.time,
+                )
+    
+    notes = []
+    for track in score.tracks:
+        instrument = str(track.program)   # program id. `instrument` is always a string.
+        if track.is_drum:
+            instrument = 'drum'
+        for note in track.notes:
+            notes.append((note.time, note.duration, note.pitch, note.velocity, instrument))
+    # dedup
+    notes = list({
+        (time, duration, pitch): (time, duration, pitch, velocity, instrument) 
+        for time, duration, pitch, velocity, instrument in notes
+    }.values())
+    # merge channels, sort by start time. If notes start at the same time, the higher pitch comes first.
+    notes.sort(key=lambda x: (x[0], -x[2]))
+    # Translate start time to the delta time format: 
+    # ie. 'pitch duration wait', in milliseconds.
+    notes1 = []
+    
+    txt = []
+    for note in notes1:
+        txt.append(' '.join(map(str, note)))
+    txt = '\n'.join(txt)
+    return txt
+```