Division by NoneType in TimeStretch

[slychief]

The attempt to produce a time stretch transformation to an audio file raises a type error exception due to a division by a None type.

import jams
import muda

audiofile = "D:/temp/test.mp3"

jam = jams.JAMS()
jam = muda.jam_pack(jam)

jam = muda.core.load_jam_audio(jam, audiofile)

# this works
P = muda.deformers.PitchShift(n_semitones=5)
out_jams = list(P.transform(jam))

# this not
T = muda.deformers.TimeStretch(rate=2.0)
out_jams = list(T.transform(jam))

produces the following error

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-30-603bfe0e77bc> in <module>()
     13 
     14 T = muda.deformers.TimeStretch(rate=2.0)
---> 15 out_jams = list(T.transform(jam))

C:\Anaconda\lib\site-packages\muda-0.1.1-py2.7.egg\muda\base.pyc in transform(self, jam)
    141 
    142         for state in self.states(jam):
--> 143             yield self._transform(jam, state)
    144 
    145     @property

C:\Anaconda\lib\site-packages\muda-0.1.1-py2.7.egg\muda\base.pyc in _transform(self, jam, state)
    112 
    113         if hasattr(self, 'metadata'):
--> 114             self.metadata(jam_w.file_metadata, state)
    115 
    116         # Walk over the list of deformers

C:\Anaconda\lib\site-packages\muda-0.1.1-py2.7.egg\muda\deformers\time.pyc in metadata(metadata, state)
     40     def metadata(metadata, state):
     41         # Deform the metadata
---> 42         metadata.duration /= state['rate']
     43 
     44     @staticmethod

TypeError: unsupported operand type(s) for /=: 'NoneType' and 'float'

[bmcfee]

Aha, good catch.

It looks like the file_metadata.duration field is not getting initialized in load_jam_audio. This is an easy fix.

In the meantime, you can patch around this by setting the duration field manually after loading:

jam = muda.jam_pack(jam)

jam = muda.core.load_jam_audio(jam, audiofile)

jam.file_metadata.duration = librosa.get_duration(filename=audiofile)

# proceed as before