BackgroundNoise fails if len(soundf)==n_target

[lostanlen]

I have a dataset of audio clips of the same length. Half of these clips are positive (contain a bird flight call), while the other half is negative (contain only background noise). I want to augment the dataset by mixing clips together, without changing the label.

But I ran into an error in 'muda.deformers.background.sample_clip_indices'. If I understand the stack trace correctly (see below my signature), the error happens when executing start = np.random.randint(0, len(soundf) - n_target) with len(soundf) - n_target equal to zero.

I made a Gist to reproduce the bug: https://gist.github.com/lostanlen/15fe9c879fdd24fe9023fa430314cd51 It disappears when the difference in lengths is strictly larger than zero.

Is this expected behavior? It seems to me that my issue could be fixed with

if len(soundf) > n_target:
    start = np.random.randint(0, len(soundf) - n_target)
else:
    start = 0

Best, Vincent.

---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
<ipython-input-43-9ecbf36219b3> in <module>()
     39 # Create short deformer
     40 short_deformer = muda.deformers.BackgroundNoise(files=[short_noise_path])
---> 41 short_jam_transformer = next(short_deformer.transform(jam_original)) # error

/Users/vl238/miniconda3/lib/python3.5/site-packages/muda/base.py in transform(self, jam)
    142         '''
    143 
--> 144         for state in self.states(jam):
    145             yield self._transform(jam, state)
    146 

/Users/vl238/miniconda3/lib/python3.5/site-packages/muda/deformers/background.py in states(self, jam)
    154         for fname in self.files:
    155             for _ in range(self.n_samples):
--> 156                 start, stop = sample_clip_indices(fname, len(mudabox._audio['y']), mudabox._audio['sr'])
    157                 yield dict(filename=fname,
    158                            weight=np.random.uniform(low=self.weight_min,

/Users/vl238/miniconda3/lib/python3.5/site-packages/muda/deformers/background.py in sample_clip_indices(filename, n_samples, sr)
     40 
     41         # Draw a random clip
---> 42         start = np.random.randint(0, len(soundf) - n_target)
     43         stop = start + n_target
     44 

mtrand.pyx in mtrand.RandomState.randint (numpy/random/mtrand/mtrand.c:16117)()

ValueError: low >= high

[bmcfee]

Yup, that makes sense, thanks for catching it! We recently hit almost the same issue over in pumpp, so it's not too surprising. Do you have any interest in doing a PR for this?

[lostanlen]

Yes, I will write a PR later today.

[lostanlen]

On second thought, this looks more like an off-by-one error. The fix would then be:

start = np.random.randint(0, 1 + len(soundf) - n_target)

That would be a breaking change, though.

[bmcfee]

That would be a breaking change, though.

That's fine -- it's broken as is. I bumped the milestone for this to 0.2, so it's okay to not be backward-compatible with the 0.1 series.