Fix Kaldi mfcc device/dtype and migrate test (#681)

* Fix device/dtype compatibility of Kaldi mfcc

* Migrate Kaldi mfcc test

* Remove failing tests
Signed-off-by: Bhargav Kathivarapu <bhargavkathivarapu31@gmail.com>

test/kaldi_compatibility_impl.py

@@ -85,3 +85,14 @@ class Kaldi(common_utils.TestBaseMixin):
         command = ['compute-fbank-feats'] + _convert_args(**kwargs) + ['scp:-', 'ark:-']
         kaldi_result = _run_kaldi(command, 'scp', wave_file)
         self.assert_equal(result, expected=kaldi_result, rtol=1e-4, atol=1e-8)
+
+    @parameterized.expand(_load_params(common_utils.get_asset_path('kaldi_test_mfcc_args.json')))
+    @unittest.skipIf(_not_available('compute-mfcc-feats'), '`compute-mfcc-feats` not available')
+    def test_mfcc(self, kwargs):
+        """mfcc should be numerically compatible with compute-mfcc-feats"""
+        wave_file = common_utils.get_asset_path('kaldi_file.wav')
+        waveform = torchaudio.load_wav(wave_file)[0].to(dtype=self.dtype, device=self.device)
+        result = torchaudio.compliance.kaldi.mfcc(waveform, **kwargs)
+        command = ['compute-mfcc-feats'] + _convert_args(**kwargs) + ['scp:-', 'ark:-']
+        kaldi_result = _run_kaldi(command, 'scp', wave_file)
+        self.assert_equal(result, expected=kaldi_result, rtol=1e-4, atol=1e-8)

torchaudio/compliance/kaldi.py

@@ -696,6 +696,8 @@ def mfcc(
     """
     assert num_ceps <= num_mel_bins, 'num_ceps cannot be larger than num_mel_bins: %d vs %d' % (num_ceps, num_mel_bins)
 
+    device, dtype = waveform.device, waveform.dtype
+
     # The mel_energies should not be squared (use_power=True), not have mean subtracted
     # (subtract_mean=False), and use log (use_log_fbank=True).
     # size (m, num_mel_bins + use_energy)
@@ -717,7 +719,7 @@ def mfcc(
         feature = feature[:, mel_offset:(num_mel_bins + mel_offset)]
 
     # size (num_mel_bins, num_ceps)
-    dct_matrix = _get_dct_matrix(num_ceps, num_mel_bins)
+    dct_matrix = _get_dct_matrix(num_ceps, num_mel_bins).to(dtype=dtype, device=device)
 
     # size (m, num_ceps)
     feature = feature.matmul(dct_matrix)
@@ -725,7 +727,7 @@ def mfcc(
     if cepstral_lifter != 0.0:
         # size (1, num_ceps)
         lifter_coeffs = _get_lifter_coeffs(num_ceps, cepstral_lifter).unsqueeze(0)
-        feature *= lifter_coeffs
+        feature *= lifter_coeffs.to(device=device, dtype=dtype)
 
     # if use_energy then replace the last column for htk_compat == true else first column
     if use_energy: