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import numpy as np
from fairseq.data.audio.feature_transforms import (
AudioFeatureTransform,
register_audio_feature_transform,
)
@register_audio_feature_transform("global_cmvn")
class GlobalCMVN(AudioFeatureTransform):
"""Global CMVN (cepstral mean and variance normalization). The global mean
and variance need to be pre-computed and stored in NumPy format (.npz)."""
@classmethod
def from_config_dict(cls, config=None):
_config = {} if config is None else config
return GlobalCMVN(_config.get("stats_npz_path"))
def __init__(self, stats_npz_path):
self.stats_npz_path = stats_npz_path
stats = np.load(stats_npz_path)
self.mean, self.std = stats["mean"], stats["std"]
def __repr__(self):
return self.__class__.__name__ + f'(stats_npz_path="{self.stats_npz_path}")'
def __call__(self, x):
x = np.subtract(x, self.mean)
x = np.divide(x, self.std)
return x
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