add resample warning

test/torchaudio_unittest/functional/functional_impl.py

@@ -9,7 +9,7 @@
 from parameterized import parameterized
 from scipy import signal
 
-from torchaudio_unittest.common_utils import TestBaseMixin, get_sinusoid, nested_params
+from torchaudio_unittest.common_utils import TestBaseMixin, get_sinusoid, nested_params, get_whitenoise
 
 
 class Functional(TestBaseMixin):
@@ -259,6 +259,24 @@ def test_mask_along_axis_iid_preserve(self, mask_param, mask_value, axis):
 
             self.assertEqual(specgrams, specgrams_copy)
 
+    def test_resample_no_warning(self):
+        sample_rate = 44100
+        waveform = get_whitenoise(sample_rate=sample_rate)
+
+        with warnings.catch_warnings(record=True) as w:
+            warnings.simplefilter("always")
+            F.resample(waveform, sample_rate, sample_rate / 2)
+        assert len(w) == 0
+
+    def test_resample_warning(self):
+        sample_rate = 44100
+        waveform = get_whitenoise(sample_rate=sample_rate)
+
+        with warnings.catch_warnings(record=True) as w:
+            warnings.simplefilter("always")
+            F.resample(waveform, sample_rate, 5512.5)
+        assert len(w) == 1
+
 
 class FunctionalComplex(TestBaseMixin):
     complex_dtype = None

torchaudio/functional/functional.py

@@ -1373,6 +1373,16 @@ def resample(
 
     assert orig_freq > 0.0 and new_freq > 0.0
 
+    if not (int(orig_freq) == orig_freq and int(new_freq) == new_freq):
+        warnings.warn(
+            "Non-integer frequencies are cast to integers and may result in poor resampling quality."
+            "The algorithm is dependent on the integer ratio between `orig_freq` and `new_freq`,"
+            "so please manually convert frequencies to integer values that maintain the ratio"
+            "prior to passing them into the function"
+            "Example: To downsample a 44100 hz waveform by a factor of 8, you can use"
+            "`orig_freq=8` and `new_freq=1` instead of `orig_freq=44100` and `new_freq=5512.5`"
+        )
+
     orig_freq = int(orig_freq)
     new_freq = int(new_freq)
     gcd = math.gcd(orig_freq, new_freq)