前言
此博客是基于华为云中的DFCNN_Transformer的教程进行的学习和实践。本文将介绍一个结合了深度全卷积网络（DFCNN）和Transformer的模型——DFCNN-Transformer，旨在提高中文语音识别的准确性和效率。
注意：
该代码主要改进之处为将原先的TensorFlow-1.13.1版本的代码改进为TensorFlow-2.0+版本。以方便大家进行代码的实践。
所需数据已放在博客中，可自行下载。
1.定义声学模型和获取数据的函数
首先加载需要的python库
import numpy as np
import scipy.io.wavfile as wav
import matplotlib.pyplot as plt
import keras
import tensorflow as tf
tf.compat.v1.disable_eager_execution()
tf.compat.v1.logging.set_verbosity(tf.compat.v1.logging.ERROR)
from keras.layers import Input, Conv2D, BatchNormalization, MaxPooling2D
from keras.layers import Reshape, Dense, Dropout, Lambda
from keras.optimizers import Adam
from keras import backend as K
from keras.models import Model
import os
os.environ['TF_CPP_MIN_LOG_LEVEL'] = '2'
import warnings
warnings.filterwarnings("ignore")
定义声学模型
定义层函数：
- conv2d(size): 定义一个带有ReLU激活函数的二维卷积层，使用正态分布初始化权重。
- norm(x): 定义一个批量归一化层，并将其应用于输入x。
- maxpool(x): 定义一个最大池化层，并将其应用于输入x。
- dense(units, activation=“relu”): 定义一个全连接（Dense）层，带有ReLU（或指定）激活函数。
- cnn_cell(size, x, pool=True): 这是一个自定义的卷积单元，包含两个卷积层和一个可选的最大池化层。
CTC损失函数：
- ctc_lambda(args): 这是一个用于计算CTC（Connectionist Temporal Classification）损失的lambda函数。CTC损失通常用于处理序列到序列的映射问题，特别是在语音识别任务中。
声学模型类：
- acoustic_model(vocab_size):这是一个定义声学模型的类。在初始化时，它接受一个词汇表大小vocab_size作为参数，并初始化了一些模型参数和层。
在_model_init方法中：
- 首先定义了模型的输入层，然后连续应用了几个cnn_cell定义的卷积单元。
- 注意到在最后的两个cnn_cell调用中，设置了pool=False来避免最大池化。
- 通过Reshape层将特征图展平，并通过两个带有dropout的Dense层进一步处理。
- 最后，定义了一个输出层，使用softmax激活函数来生成词汇表中每个单词的概率分布。
_ctc_init 方法：
定义了三个额外的输入层：labels、input_length和label_length，这些都是CTC损失函数所需要的。然后，使用Lambda层来应用之前定义的ctc_lambda函数，计算CTC损失。最后，创建了一个新的模型self.ctc_model，该模型将这四个输入（标签、原始输入、输入长度和标签长度）作为输入，并将CTC损失作为输出。
opt_init 方法：
创建了一个Adam优化器实例，并使用它来编译self.ctc_model。注意，在定义损失函数时，使用了一个lambda函数，该函数简单地返回了由Lambda层计算出的CTC损失。这是因为在Lambda层中，已经指定了如何计算损失，所以在这里只需要将输出作为损失即可。
#定义卷积层
def conv2d(size):
return Conv2D(size, (3,3), use_bias=True, activation='relu',
padding='same', kernel_initializer='he_normal')
#定义BN层
def norm(x):
return BatchNormalization(axis=-1)(x)
#定义最大池化层
def maxpool(x):
return MaxPooling2D(pool_size=(2,2), strides=None, padding="valid")(x)
#定义dense层
def dense(units, activation="relu"):
return Dense(units, activation=activation, use_bias=True,
kernel_initializer='he_normal')
#两个卷积层加一个最大池化层的组合
def cnn_cell(size, x, pool=True):
x = norm(conv2d(size)(x))
x = norm(conv2d(size)(x))
if pool:
x = maxpool(x)
return x
#CTC损失函数
def ctc_lambda(args):
labels, y_pred, input_length, label_length = args
y_pred = y_pred[:, :, :]
return K.ctc_batch_cost(labels, y_pred, input_length, label_length)
#组合声学模型
class acoustic_model():
def __init__(self,vocab_size):
self.vocab_size = vocab_size
self.learning_rate = 0.0008
self.is_training = True
self._model_init()
if self.is_training:
self._ctc_init()
self.opt_init()
def _model_init(self):
self.inputs = Input(name='the_inputs', shape=(None, 200, 1))
self.h1 = cnn_cell(32, self.inputs)
self.h2 = cnn_cell(64, self.h1)
self.h3 = cnn_cell(128, self.h2)
self.h4 = cnn_cell(128, self.h3, pool=False)
self.h5 = cnn_cell(128, self.h4, pool=False)
# 200 / 8 * 128 = 3200
self.h6 = Reshape((-1, 3200))(self.h5)
self.h6 = Dropout(0.2)(self.h6)
self.h7 = dense(256)(self.h6)
self.h7 = Dropout(0.2)(self.h7)
self.outputs = dense(self.vocab_size, activation='softmax')(self.h7)
self.model = Model(inputs=self.inputs, outputs=self.outputs)
def _ctc_init(self):
self.labels = Input(name='the_labels', shape=[None], dtype='float32')
self.input_length = Input(name='input_length', shape=[1], dtype='int64')
self.label_length = Input(name='label_length', shape=[1], dtype='int64')
self.loss_out = Lambda(ctc_lambda, output_shape=(1,), name='ctc')\
([self.labels, self.outputs, self.input_length, self.label_length])
self.ctc_model = Model(inputs=[self.labels, self.inputs,
self.input_length, self.label_length], outputs=self.loss_out)
def opt_init(self):
opt = tf.keras.optimizers.legacy.Adam(learning_rate = self.learning_rate, beta_1 = 0.9, beta_2 = 0.999, decay = 0.01, epsilon = 10e-8)
self.ctc_model.compile(loss={'ctc': lambda y_true, output: output}, optimizer=opt)
acoustic = acoustic_model(vocab_size=50)
获取数据
compute_fbank 函数：该函数旨在从WAV文件中提取特征。
get_data 类：该类用于管理数据集，包括WAV文件列表、对应的拼音和汉字标签。
from scipy.fftpack import fft
# 获取信号的时频图
def compute_fbank(file):
x=np.linspace(0, 400 - 1, 400, dtype = np.int64)
w = 0.54 - 0.46 * np.cos(2 * np.pi * (x) / (400 - 1) )
fs, wavsignal = wav.read(file)
time_window = 25
window_length = fs / 1000 * time_window
wav_arr = np.array(wavsignal)
wav_length = len(wavsignal)
range0_end = int(len(wavsignal)/fs*1000 - time_window) // 10
data_input = np.zeros((range0_end, 200), dtype = np.float)
data_line = np.zeros((1, 400), dtype = np.float)
for i in range(0, range0_end):
p_start = i * 160
p_end = p_start + 400
data_line = wav_arr[p_start:p_end]
data_line = data_line * w
data_line = np.abs(fft(data_line))
data_input[i]=data_line[0:200]
data_input = np.log(data_input + 1)
return data_input
class get_data():
def __init__(self):
self.data_path = './speech_recognition/data/'
self.data_length = 20
self.batch_size = 1
self.source_init()
def source_init(self):
self.wav_lst = []
self.pin_lst = []
self.han_lst = []
with open('speech_recognition/data.txt', 'r', encoding='utf8') as f:
data = f.readlines()
for line in data:
wav_file, pin, han = line.split('\t')
self.wav_lst.append(wav_file)
self.pin_lst.append(pin.split(' '))
self.han_lst.append(han.strip('\n'))
if self.data_length:
self.wav_lst = self.wav_lst[:self.data_length]
self.pin_lst = self.pin_lst[:self.data_length]
self.han_lst = self.han_lst[:self.data_length]
self.acoustic_vocab = self.acoustic_model_vocab(self.pin_lst)
self.pin_vocab = self.language_model_pin_vocab(self.pin_lst)
self.han_vocab = self.language_model_han_vocab(self.han_lst)
def get_acoustic_model_batch(self):
_list = [i for i in range(len(self.wav_lst))]
while 1:
for i in range(len(self.wav_lst) // self.batch_size):
wav_data_lst = []
label_data_lst = []
begin = i * self.batch_size
end = begin + self.batch_size
sub_list = _list[begin:end]
for index in sub_list:
fbank = compute_fbank(self.data_path + self.wav_lst[index])
pad_fbank = np.zeros((fbank.shape[0] // 8 * 8 + 8, fbank.shape[1]))
pad_fbank[:fbank.shape[0], :] = fbank
label = self.pin2id(self.pin_lst[index], self.acoustic_vocab)
label_ctc_len = self.ctc_len(label)
if pad_fbank.shape[0] // 8 >= label_ctc_len:
wav_data_lst.append(pad_fbank)
label_data_lst.append(label)
pad_wav_data, input_length = self.wav_padding(wav_data_lst)
pad_label_data, label_length = self.label_padding(label_data_lst)
inputs = {'the_inputs': pad_wav_data,
'the_labels': pad_label_data,
'input_length': input_length,
'label_length': label_length,
}
outputs = {'ctc': np.zeros(pad_wav_data.shape[0], )}
yield inputs, outputs
def get_language_model_batch(self):
batch_num = len(self.pin_lst) // self.batch_size
for k in range(batch_num):
begin = k * self.batch_size
end = begin + self.batch_size
input_batch = self.pin_lst[begin:end]
label_batch = self.han_lst[begin:end]
max_len = max([len(line) for line in input_batch])
input_batch = np.array(
[self.pin2id(line, self.pin_vocab) + [0] * (max_len - len(line)) for line in input_batch])
label_batch = np.array(
[self.han2id(line, self.han_vocab) + [0] * (max_len - len(line)) for line in label_batch])
yield input_batch, label_batch
def pin2id(self, line, vocab):
return [vocab.index(pin) for pin in line]
def han2id(self, line, vocab):
return [vocab.index(han) for han in line]
def wav_padding(self, wav_data_lst):
wav_lens = [len(data) for data in wav_data_lst]
wav_max_len = max(wav_lens)
wav_lens = np.array([leng // 8 for leng in wav_lens])
new_wav_data_lst = np.zeros((len(wav_data_lst), wav_max_len, 200, 1))
for i in range(len(wav_data_lst)):
new_wav_data_lst[i, :wav_data_lst[i].shape[0], :, 0] = wav_data_lst[i]
return new_wav_data_lst, wav_lens
def label_padding(self, label_data_lst):
label_lens = np.array([len(label) for label in label_data_lst])
max_label_len = max(label_lens)
new_label_data_lst = np.zeros((len(label_data_lst), max_label_len))
for i in range(len(label_data_lst)):
new_label_data_lst[i][:len(label_data_lst[i])] = label_data_lst[i]
return new_label_data_lst, label_lens
def acoustic_model_vocab(self, data):
vocab = []
for line in data:
line = line
for pin in line:
if pin not in vocab:
vocab.append(pin)
vocab.append('_')
return vocab
def language_model_pin_vocab(self, data):
vocab = ['<PAD>']
for line in data:
for pin in line:
if pin not in vocab:
vocab.append(pin)
return vocab
def language_model_han_vocab(self, data):
vocab = ['<PAD>']
for line in data:
line = ''.join(line.split(' '))
for han in line:
if han not in vocab:
vocab.append(han)
return vocab
def ctc_len(self, label):
add_len = 0
label_len = len(label)
for i in range(label_len - 1):
if label[i] == label[i + 1]:
add_len += 1
return label_len + add_len
2.训练声学模型
准备训练参数及数据
为了本示例演示效果，参数batch_size在此仅设置为1，参数data_length在此仅设置为20。
若进行完整训练，则应注释data_args.data_length = 20，并调高batch_size。
train_data = get_data()
vocab_size = len(train_data.acoustic_vocab)
acoustic = acoustic_model(vocab_size)
if os.path.exists('/speech_recognition/acoustic_model/model.h5'):
print('加载声学模型')
acoustic.ctc_model.load_weights('./speech_recognition/acoustic_model/model.h5')
epochs = 20
batch_num = len(train_data.wav_lst) // train_data.batch_size
print("开始训练！")
for k in range(epochs):
print('第', k+1, '个epoch')
batch = train_data.get_acoustic_model_batch()
acoustic.ctc_model.fit_generator(batch, steps_per_epoch=batch_num, epochs=1)
print("\n训练完成，保存模型")
acoustic.ctc_model.save_weights('./speech_recognition/acoustic_model/model.h5')
3.定义语言模型
使用 Transformer 结构进行语言模型的建模。
normalize 函数：实现了批量归一化（Batch Normalization），用于在训练过程中标准化神经网络的输入，使其具有零均值和单位方差。它接受输入张量inputs，并返回归一化后的输出。
embedding 函数：定义了一个词嵌入层，用于将输入的整数ID（通常代表单词或符号）转换为固定大小的密集向量（词嵌入）。
def normalize(inputs,
epsilon = 1e-8,
scope="ln",
reuse=None):
with tf.compat.v1.variable_scope(scope, reuse=reuse):
inputs_shape = inputs.get_shape()
params_shape = inputs_shape[-1:]
mean, variance = tf.compat.v1.nn.moments(inputs, [-1], keep_dims=True)
beta= tf.Variable(tf.zeros(params_shape))
gamma = tf.Variable(tf.ones(params_shape))
normalized = (inputs - mean) / ( (variance + epsilon) ** (.5) )
outputs = gamma * normalized + beta
return outputs
def embedding(inputs,
vocab_size,
num_units,
zero_pad=True,
scale=True,
scope="embedding",
reuse=None):
with tf.compat.v1.variable_scope(scope, reuse=reuse):
lookup_table = tf.compat.v1.get_variable('lookup_table',
dtype=tf.float32,
shape=[vocab_size, num_units],
initializer=tf.compat.v1.keras.initializers.glorot_normal)
if zero_pad:
lookup_table = tf.concat((tf.zeros(shape=[1, num_units]),
lookup_table[1:, :]), 0)
outputs = tf.nn.embedding_lookup(lookup_table, inputs)
if scale:
outputs = outputs * (num_units ** 0.5)
return outputs
def multihead_attention(emb,
queries,
keys,
num_units=None,
num_heads=8,
dropout_rate=0,
is_training=True,
causality=False,
scope="multihead_attention",
reuse=None):
with tf.compat.v1.variable_scope(scope, reuse=reuse):
if num_units is None:
num_units = queries.get_shape().as_list[-1]
Q = tf.compat.v1.layers.dense(queries, num_units, activation=tf.nn.relu) # (N, T_q, C)
K = tf.compat.v1.layers.dense(keys, num_units, activation=tf.nn.relu) # (N, T_k, C)
V = tf.compat.v1.layers.dense(keys, num_units, activation=tf.nn.relu) # (N, T_k, C)
Q_ = tf.concat(tf.split(Q, num_heads, axis=2), axis=0) # (h*N, T_q, C/h)
K_ = tf.concat(tf.split(K, num_heads, axis=2), axis=0) # (h*N, T_k, C/h)
V_ = tf.concat(tf.split(V, num_heads, axis=2), axis=0) # (h*N, T_k, C/h)
outputs = tf.matmul(Q_, tf.transpose(K_, [0, 2, 1])) # (h*N, T_q, T_k)
outputs = outputs / (K_.get_shape().as_list()[-1] ** 0.5)
key_masks = tf.sign(tf.abs(tf.reduce_sum(emb, axis=-1))) # (N, T_k)
key_masks = tf.tile(key_masks, [num_heads, 1]) # (h*N, T_k)
key_masks = tf.tile(tf.expand_dims(key_masks, 1), [1, tf.shape(queries)[1], 1]) # (h*N, T_q, T_k)
paddings = tf.ones_like(outputs) * (-2 ** 32 + 1)
outputs = tf.where(tf.equal(key_masks, 0), paddings, outputs) # (h*N, T_q, T_k)
if causality:
diag_vals = tf.ones_like(outputs[0, :, :]) # (T_q, T_k)
tril = tf.contrib.linalg.LinearOperatorTriL(diag_vals).to_dense() # (T_q, T_k)
masks = tf.tile(tf.expand_dims(tril, 0), [tf.shape(outputs)[0], 1, 1]) # (h*N, T_q, T_k)
paddings = tf.ones_like(masks) * (-2 ** 32 + 1)
outputs = tf.where(tf.equal(masks, 0), paddings, outputs) # (h*N, T_q, T_k)
outputs = tf.nn.softmax(outputs) # (h*N, T_q, T_k)
query_masks = tf.sign(tf.abs(tf.reduce_sum(emb, axis=-1))) # (N, T_q)
query_masks = tf.tile(query_masks, [num_heads, 1]) # (h*N, T_q)
query_masks = tf.tile(tf.expand_dims(query_masks, -1), [1, 1, tf.shape(keys)[1]]) # (h*N, T_q, T_k)
outputs *= query_masks # broadcasting. (N, T_q, C)
outputs = tf.compat.v1.layers.dropout(outputs, rate=dropout_rate, training=tf.convert_to_tensor(is_training))
outputs = tf.matmul(outputs, V_) # ( h*N, T_q, C/h)
outputs = tf.concat(tf.split(outputs, num_heads, axis=0), axis=2) # (N, T_q, C)
outputs += queries
outputs = normalize(outputs) # (N, T_q, C)
return outputs
def feedforward(inputs,
num_units=[2048, 512],
scope="multihead_attention",
reuse=None):
with tf.compat.v1.variable_scope(scope, reuse=reuse):
params = {"inputs": inputs, "filters": num_units[0], "kernel_size": 1,
"activation": tf.nn.relu, "use_bias": True}
outputs = tf.compat.v1.layers.conv1d(**params)
params = {"inputs": outputs, "filters": num_units[1], "kernel_size": 1,
"activation": None, "use_bias": True}
outputs = tf.compat.v1.layers.conv1d(**params)
outputs += inputs
outputs = normalize(outputs)
return outputs
#定义 label_smoothing层¶
def label_smoothing(inputs, epsilon=0.1):
K = inputs.get_shape().as_list()[-1] # number of channels
return ((1-epsilon) * inputs) + (epsilon / K)
# 组合语言模型
class language_model():
def __init__(self, input_vocab_size, label_vocab_size):
self.graph = tf.Graph()
with self.graph.as_default():
self.is_training = True
self.hidden_units = 512
self.input_vocab_size = input_vocab_size
self.label_vocab_size = label_vocab_size
self.num_heads = 8
self.num_blocks = 6
self.max_length = 100
self.learning_rate = 0.0003
self.dropout_rate = 0.2
self.x = tf.compat.v1.placeholder(tf.int32, shape=(None, None))
self.y = tf.compat.v1.placeholder(tf.int32, shape=(None, None))
self.emb = embedding(self.x, vocab_size=self.input_vocab_size, num_units=self.hidden_units, scale=True,
scope="enc_embed")
self.enc = self.emb + embedding(
tf.tile(tf.expand_dims(tf.range(tf.shape(self.x)[1]), 0), [tf.shape(self.x)[0], 1]),
vocab_size=self.max_length, num_units=self.hidden_units, zero_pad=False, scale=False, scope="enc_pe")
self.enc = tf.compat.v1.layers.dropout(self.enc,
rate=self.dropout_rate,
training=tf.convert_to_tensor(self.is_training))
for i in range(self.num_blocks):
with tf.compat.v1.variable_scope("num_blocks_{}".format(i)):
self.enc = multihead_attention(emb=self.emb,
queries=self.enc,
keys=self.enc,
num_units=self.hidden_units,
num_heads=self.num_heads,
dropout_rate=self.dropout_rate,
is_training=self.is_training,
causality=False)
self.outputs = feedforward(self.enc, num_units=[4 * self.hidden_units, self.hidden_units])
self.logits = tf.compat.v1.layers.dense(self.outputs, self.label_vocab_size)
self.preds = tf.compat.v1.to_int32(tf.argmax(self.logits, axis=-1))
self.istarget = tf.compat.v1.to_float(tf.not_equal(self.y, 0))
self.acc = tf.reduce_sum(tf.compat.v1.to_float(tf.equal(self.preds, self.y)) * self.istarget) / (
tf.reduce_sum(self.istarget))
tf.summary.scalar('acc', self.acc)
if self.is_training:
self.y_smoothed = label_smoothing(tf.one_hot(self.y, depth=self.label_vocab_size))
self.loss = tf.compat.v1.nn.softmax_cross_entropy_with_logits_v2(logits=self.logits,
labels=self.y_smoothed)
self.mean_loss = tf.reduce_sum(self.loss * self.istarget) / (tf.reduce_sum(self.istarget))
self.global_step = tf.Variable(0, name='global_step', trainable=False)
self.optimizer = tf.compat.v1.train.AdamOptimizer(learning_rate=self.learning_rate, beta1=0.9,
beta2=0.98, epsilon=1e-8)
self.train_op = self.optimizer.minimize(self.mean_loss, global_step=self.global_step)
tf.summary.scalar('mean_loss', self.mean_loss)
self.merged = tf.compat.v1.summary.merge_all()
print('语音模型建立完成！')
4.训练语言模型
input_vocab_size = len(train_data.pin_vocab)
label_vocab_size = len(train_data.han_vocab)
is_training = True
language = language_model(input_vocab_size,label_vocab_size)
epochs = 20
with language.graph.as_default():
saver =tf.compat.v1.train.Saver()
with tf.compat.v1.Session(graph=language.graph) as sess:
merged = tf.compat.v1.summary.merge_all()
sess.run(tf.compat.v1.global_variables_initializer())
if os.path.exists('./speech_recognition/language_model/model.meta'):
print('加载语言模型')
saver.restore(sess, './speech_recognition/language_model/model')
for k in range(epochs):
total_loss = 0
batch = train_data.get_language_model_batch()
for i in range(batch_num):
input_batch, label_batch = next(batch)
feed = {language.x: input_batch, language.y: label_batch}
cost,_ = sess.run([language.mean_loss,language.train_op], feed_dict=feed)
total_loss += cost
print('第', k+1, '个 epoch', ': average loss = ', total_loss/batch_num)
print("\n训练完成")
5.模型测试
准备解码所需字典，需和训练一致，也可以将字典保存到本地，直接进行读取
train_data = get_data()
test_data = get_data()
acoustic_model_batch = test_data.get_acoustic_model_batch()
language_model_batch = test_data.get_language_model_batch()
vocab_size = len(train_data.acoustic_vocab)
acoustic = acoustic_model(vocab_size)
acoustic.ctc_model.load_weights('./speech_recognition/acoustic_model/model.h5')
print('\n加载声学模型完成！')
tf.compat.v1.disable_v2_behavior()
input_vocab_size = len(train_data.pin_vocab)
label_vocab_size = len(train_data.han_vocab)
language = language_model(input_vocab_size,label_vocab_size)
sess = tf.compat.v1.Session(graph=language.graph)
with language.graph.as_default():
saver =tf.compat.v1.train.Saver()
with sess.as_default():
saver.restore(sess, './speech_recognition/language_model/model')
print('\n加载语言模型完成！')
def decode_ctc(num_result, num2word):
result = num_result[:, :, :]
in_len = np.zeros((1), dtype = np.int32)
in_len[0] = result.shape[1]
t = K.ctc_decode(result, in_len, greedy = True, beam_width=10, top_paths=1)
v = K.get_value(t[0][0])
v = v[0]
text = []
for i in v:
text.append(num2word[i])
return v, text
for i in range(10):
print('\n示例', i+1)
# 载入训练好的模型，并进行识别
inputs, outputs = next(acoustic_model_batch)
x = inputs['the_inputs']
y = inputs['the_labels'][0]
result = acoustic.model.predict(x, steps=1)
# 将数字结果转化为文本结果
_, text = decode_ctc(result, train_data.acoustic_vocab)
text = ' '.join(text)
text = text.replace(" _", "")
print('原文拼音：', ' '.join([train_data.acoustic_vocab[int(i)] for i in y]))
print('识别结果：', text)
with sess.as_default():
try:
_, y = next(language_model_batch)
text = text.strip('\n').split(' ')
x = np.array([train_data.pin_vocab.index(pin) for pin in text])
x = x.reshape(1, -1)
preds = sess.run(language.preds, {language.x: x})
got = ''.join(train_data.han_vocab[idx] for idx in preds[0])
print('原文汉字：', ''.join(train_data.han_vocab[idx] for idx in y[0]))
print('识别结果：', got)
except StopIteration:
break
sess.close()
5.总结
原文链接：https://bbs.huaweicloud.com/blogs/386935
具体细节内容可参考原文链接进行学习。