Added option to normalize log mel per batch or sequence

neural_networks.py

@@ -657,6 +657,8 @@ def __init__(self, options,inp_dim):
         self._nr_of_filters = int(options['logmelfb_nr_filt'])
         self._stft_window_size = int(options['logmelfb_stft_window_size'])
         self._stft_window_shift = int(options['logmelfb_stft_window_shift'])
+        self._normalization_mode = options['logmelfb_normalization_mode']
+        assert self._normalization_mode in ['batch', 'sequence', 'none']
         self._use_cuda = strtobool(options['use_cuda'])
         self.out_dim = self._nr_of_filters
         self._mspec = torchaudio.transforms.MelSpectrogram(
@@ -674,6 +676,18 @@ def _safe_log(inp, epsilon=1e-20):
                 eps = eps.cuda()
             log_inp = torch.log10(torch.max(inp, eps.expand_as(inp)))
             return log_inp
+        def _normalize_features(data, normalization_mode, eps=1e-6):
+            if self._normalization_mode in ['none']:
+                return data 
+            if self._normalization_mode in ['batch']:
+                norm_axis = (0, 1)
+            elif self._normalization_mode in ['sequence']:
+                norm_axis = (0)
+            mean = data.mean(norm_axis, keepdim=True)
+            std = data.std(norm_axis, keepdim=True)
+            out = (data - mean) / (std.clamp(min=eps))
+            return out
+
         assert x.shape[-1] == 1, 'Multi channel time signal processing not suppored yet'
         x_reshape_for_stft = torch.squeeze(x, -1).transpose(0, 1)
         if self._use_cuda:
@@ -691,7 +705,8 @@ def _safe_log(inp, epsilon=1e-20):
         x_power_stft_reshape_for_filterbank_mult = x_power_stft.transpose(1, 2)
         mel_spec = self._mspec.fm(x_power_stft_reshape_for_filterbank_mult).transpose(0, 1)
         log_mel_spec = _safe_log(mel_spec)
-        out = log_mel_spec 
+        norm_log_mel_spec = _normalize_features(log_mel_spec, self._normalization_mode)
+        out = norm_log_mel_spec 
         return out
 
 class channel_averaging(nn.Module):

proto/logMelFb.proto

@@ -2,5 +2,6 @@
 logmelfb_nr_filt=int
 logmelfb_stft_window_size=int
 logmelfb_stft_window_shift=int
+logmelfb_normalization_mode=str