Add Kaldi compatibility tests for sliding_window_cmn (#560)

test/test_kaldi_compatibility.py

+"""Test suites for checking numerical compatibility against Kaldi"""
+import shutil
+import unittest
+import subprocess
+
+import kaldi_io
+import torch
+import torchaudio.functional as F
+
+
+def _exe_exists(cmd):
+    return shutil.which(cmd) is not None
+
+
+def _convert_args(**kwargs):
+    args = []
+    for key, value in kwargs.items():
+        key = '--' + key.replace('_', '-')
+        value = str(value).lower() if value in [True, False] else str(value)
+        args.append('%s=%s' % (key, value))
+    return args
+
+
+def _run_kaldi(command, input_tensor):
+    """Run provided Kaldi command, pass a tensor and get the resulting tensor
+
+    Assumption:
+        The provided Kaldi command consumes one ark and produces one ark.
+        i.e. 'ark:- ark:-'
+    """
+    process = subprocess.Popen(command, stdin=subprocess.PIPE, stdout=subprocess.PIPE)
+    kaldi_io.write_mat(process.stdin, input_tensor.numpy(), key='foo')
+    process.stdin.close()
+    result = dict(kaldi_io.read_mat_ark(process.stdout))['foo']
+    return torch.from_numpy(result.copy())  # copy supresses some torch warning
+
+
+class TestFunctional:
+    @unittest.skipUnless(_exe_exists('apply-cmvn-sliding'), '`apply-cmvn-sliding` not available')
+    def test_sliding_window_cmn(self):
+        """sliding_window_cmn should be numerically compatible with apply-cmvn-sliding"""
+        kwargs = {
+            'cmn_window': 600,
+            'min_cmn_window': 100,
+            'center': False,
+            'norm_vars': False,
+        }
+
+        tensor = torch.randn(40, 10)
+        result = F.sliding_window_cmn(tensor, **kwargs)
+        command = ['apply-cmvn-sliding'] + _convert_args(**kwargs) + ['ark:-', 'ark:-']
+        kaldi_result = _run_kaldi(command, tensor)
+        torch.testing.assert_allclose(result, kaldi_result)