src/python/melodyparser.py

   1 notesChars = ['A', 'B', 'C', 'D', 'E', 'F', 'G']
   2 pauseChar = 'P'
   3
   4 def window(iterable, size=2):
   5         i = iter(iterable)
   6         win = []
   7         for e in range(0, size):
   8                 win.append(next(i))
   9         yield win
  10         for e in i:
  11                 win = win[1:] + [e]
  12                 yield win
  13
  14 def parseMelody(melodyString, bpm=120, transposeBySemitones=0):
  15         # parse string to python list
  16         tokenizedNotes = melodyString.split(' ')
  17         operations = []
  18         for token, nextToken in window(tokenizedNotes + [None], 2):
  19                 if token.startswith(pauseChar):
  20                         # Token is a pause operation, use frequency 0
  21                         operations.append([0, getDurationInMs(bpm, token[1:])])
  22                 elif token.startswith(tuple(notesChars)):
  23                         # Token is a note; next token will be duration of this note
  24                         frequency = getFrequency(token, transposeBySemitones)
  25                         duration = getDurationInMs(bpm, nextToken)
  26                         operations.append([frequency, duration])
  27                 else:
  28                         continue
  29         # turn list into C-style array string
  30         arrayString = generateArrayString(operations)
  31         return arrayString
  32
  33 def getFrequency(note, transposeBy=0, A4=440):
  34         # example note: A#5, meaning: 5th octave A sharp
  35         notes = ['A', 'A#', 'B', 'C', 'C#', 'D', 'D#', 'E', 'F', 'F#', 'G', 'G#']
  36         octave = int(note[2]) if len(note) == 3 else int(note[1])
  37         keyNumber = notes.index(note[0:-1])
  38         if keyNumber < 3:
  39                 keyNumber = keyNumber + 12 + ((octave - 1) * 12) + 1
  40         else:
  41                 keyNumber = keyNumber + ((octave - 1) * 12) + 1
  42         keyNumber += transposeBy
  43         return int(A4 * 2 ** ((keyNumber - 49) / 12))
  44
  45 def getDurationInMs(bpm, duration):
  46         return int((1000 * (60 * 4 / bpm)) / float(duration))
  47
  48 def generateArrayString(melodyArray):
  49         # generate C-style array string from python list
  50         elements = []
  51         for element in melodyArray:
  52                 elements.append("{" + str(element[0]) + "," + str(element[1]) + "}")
  53         return "{" + ','.join(elements) + "}"
  54
  55 def parse(melodyOrRTTTL):
  56         # If | in melody it is original notes|bpm|transpose format
  57         if ('|' in melodyOrRTTTL):
  58                 defineValue = melodyOrRTTTL.split("|")
  59                 transposeBySemitones = int(defineValue[2]) if len(defineValue) > 2 else 0
  60                 return parseMelody(defineValue[0].strip(), int(defineValue[1]), transposeBySemitones)
  61         # Else assume RTTL
  62         else:
  63                 from rtttl import RTTTL
  64                 retVal = ""
  65                 tune = RTTTL(melodyOrRTTTL)
  66                 for freq, msec in tune.notes():
  67                         retVal += f"{{{freq:.0f},{msec:.0f}}},"
  68
  69                 if retVal != "":
  70                         retVal = "{" + retVal[:-1] + "}"
  71                 else:
  72                         raise ValueError("Blank RTTTL melody detected")
  73                 return retVal
  74