mirror of
https://github.com/mozilla/DeepSpeech.git
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105 lines
3.5 KiB
Python
105 lines
3.5 KiB
Python
from __future__ import absolute_import, division, print_function
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import codecs
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import re
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import numpy as np
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from six.moves import range
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class Alphabet(object):
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def __init__(self, config_file):
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self._config_file = config_file
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self._label_to_str = []
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self._str_to_label = {}
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self._size = 0
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with codecs.open(config_file, 'r', 'utf-8') as fin:
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for line in fin:
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if line[0:2] == '\\#':
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line = '#\n'
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elif line[0] == '#':
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continue
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self._label_to_str += line[:-1] # remove the line ending
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self._str_to_label[line[:-1]] = self._size
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self._size += 1
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def string_from_label(self, label):
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return self._label_to_str[label]
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def label_from_string(self, string):
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try:
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return self._str_to_label[string]
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except KeyError as e:
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raise KeyError(
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'''ERROR: Your transcripts contain characters which do not occur in data/alphabet.txt! Use util/check_characters.py to see what characters are in your {train,dev,test}.csv transcripts, and then add all these to data/alphabet.txt.'''
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).with_traceback(e.__traceback__)
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def decode(self, labels):
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res = ''
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for label in labels:
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res += self.string_from_label(label)
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return res
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def size(self):
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return self._size
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def config_file(self):
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return self._config_file
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def text_to_char_array(original, alphabet):
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r"""
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Given a Python string ``original``, remove unsupported characters, map characters
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to integers and return a numpy array representing the processed string.
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"""
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return np.asarray([alphabet.label_from_string(c) for c in original])
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# The following code is from: http://hetland.org/coding/python/levenshtein.py
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# This is a straightforward implementation of a well-known algorithm, and thus
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# probably shouldn't be covered by copyright to begin with. But in case it is,
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# the author (Magnus Lie Hetland) has, to the extent possible under law,
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# dedicated all copyright and related and neighboring rights to this software
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# to the public domain worldwide, by distributing it under the CC0 license,
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# version 1.0. This software is distributed without any warranty. For more
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# information, see <http://creativecommons.org/publicdomain/zero/1.0>
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def levenshtein(a, b):
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"Calculates the Levenshtein distance between a and b."
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n, m = len(a), len(b)
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if n > m:
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# Make sure n <= m, to use O(min(n,m)) space
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a, b = b, a
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n, m = m, n
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current = list(range(n+1))
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for i in range(1, m+1):
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previous, current = current, [i]+[0]*n
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for j in range(1, n+1):
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add, delete = previous[j]+1, current[j-1]+1
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change = previous[j-1]
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if a[j-1] != b[i-1]:
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change = change + 1
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current[j] = min(add, delete, change)
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return current[n]
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# Validate and normalize transcriptions. Returns a cleaned version of the label
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# or None if it's invalid.
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def validate_label(label):
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# For now we can only handle [a-z ']
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if re.search(r"[0-9]|[(<\[\]&*{]", label) is not None:
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return None
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label = label.replace("-", "")
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label = label.replace("_", "")
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label = label.replace(".", "")
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label = label.replace(",", "")
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label = label.replace("?", "")
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label = label.replace("\"", "")
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label = label.strip()
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label = label.lower()
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return label if label else None
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