Add Pathlib support for 'apply_effects_file' (#1048)

test/torchaudio_unittest/sox_effect/sox_effect_test.py

 import itertools
+from pathlib import Path
 
 from torchaudio import sox_effects
 from parameterized import parameterized
@@ -104,7 +105,7 @@ class TestSoxEffectsFile(TempDirMixin, PytorchTestCase):
         load_params("sox_effect_test_args.json"),
         name_func=lambda f, i, p: f'{f.__name__}_{i}_{p.args[0]["effects"][0][0]}',
     )
-    def test_apply_effects(self, args):
+    def test_apply_effects_str(self, args):
         """`apply_effects_file` should return identical data as sox command"""
         dtype = 'int32'
         channels_first = True
@@ -127,6 +128,29 @@ class TestSoxEffectsFile(TempDirMixin, PytorchTestCase):
         assert sr == expected_sr
         self.assertEqual(found, expected)
 
+    def test_apply_effects_path(self):
+        """`apply_effects_file` should return identical data as sox command when file path is given as a Path Object"""
+        dtype = 'int32'
+        channels_first = True
+        effects = [["hilbert"]]
+        num_channels = 2
+        input_sr = 8000
+        output_sr = 8000
+
+        input_path = self.get_temp_path('input.wav')
+        reference_path = self.get_temp_path('reference.wav')
+        data = get_wav_data(dtype, num_channels, channels_first=channels_first)
+        save_wav(input_path, data, input_sr, channels_first=channels_first)
+        sox_utils.run_sox_effect(
+            input_path, reference_path, effects, output_sample_rate=output_sr)
+
+        expected, expected_sr = load_wav(reference_path)
+        found, sr = sox_effects.apply_effects_file(
+            Path(input_path), effects, normalize=False, channels_first=channels_first)
+
+        assert sr == expected_sr
+        self.assertEqual(found, expected)
+
 
 @skipIfNoExtension
 class TestFileFormats(TempDirMixin, PytorchTestCase):

torchaudio/sox_effects/sox_effects.py

-from typing import List, Tuple
+from typing import List, Tuple, Union
+from pathlib import Path
 
 import torch
 
@@ -169,7 +170,8 @@ def apply_effects_file(
         rate and leave samples untouched.
 
     Args:
-        path (str): Path to the audio file.
+        path (str or pathlib.Path): Path to the audio file. This function also handles ``pathlib.Path`` objects, but is
+            annotated as ``str`` for TorchScript compiler compatibility.
         effects (List[List[str]]): List of effects.
         normalize (bool):
             When ``True``, this function always return ``float32``, and sample values are
@@ -247,5 +249,7 @@ def apply_effects_file(
         >>> for batch in loader:
         >>>     pass
     """
+    # Get string representation of 'path' in case Path object is passed
+    path = str(path)
     signal = torch.ops.torchaudio.sox_effects_apply_effects_file(path, effects, normalize, channels_first)
     return signal.get_tensor(), signal.get_sample_rate()