Fix auglib.transform.PinkNoise for odd samples (#24)

* Fix auglib.transform.PinkNoise for odd samples

* Add comment to code

* Fix linter

* Update test

* Add test for shape

auglib/core/transform.py

@@ -3261,16 +3261,20 @@ def _pink_noise(self, samples: int) -> np.ndarray:
         def psd(f):
             return 1 / np.where(f == 0, float("inf"), np.sqrt(f))
 
-        white_noise = np.fft.rfft(np.random.randn(samples))
+        # Add extra sample
+        # to ensure correct length for odd samples
+        length = samples + 1
+
+        white_noise = np.fft.rfft(np.random.randn(length))
 
         # Normalized pink noise shape
-        pink_shape = psd(np.fft.rfftfreq(samples))
+        pink_shape = psd(np.fft.rfftfreq(length))
         pink_shape = pink_shape / np.sqrt(np.mean(pink_shape**2))
 
         white_noise_shaped = white_noise * pink_shape
         pink_noise = np.fft.irfft(white_noise_shaped)
 
-        return np.atleast_2d(pink_noise)
+        return np.atleast_2d(pink_noise[:samples])
 
 
 class Prepend(Base):

tests/test_transform_pink_noise.py

@@ -74,3 +74,19 @@ def test_pink_noise(duration, sampling_rate, gain_db, snr_db):
     assert noise.shape == expected_noise.shape
     assert noise.dtype == expected_noise.dtype
     np.testing.assert_almost_equal(noise, expected_noise)
+
+
+@pytest.mark.parametrize(
+    "signal",
+    [
+        # Odd,
+        # compare https://github.com/audeering/auglib/issues/23
+        np.ones((1, 30045)),
+        # Even
+        np.ones((1, 200)),
+    ],
+)
+def test_pink_noise_odd_and_even_samples(signal):
+    transform = auglib.transform.PinkNoise()
+    augmented_signal = transform(signal)
+    assert signal.shape == augmented_signal.shape