连续语音识别：语言模型

简介
针对不同的任何，可能需要不同的语言模型，从而提高语音识别系统的识别率，而srilm是一个非常好用的开源语言模型训练工具；具体介绍可上srilm官网查询。

常用命令

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ngram-count -text train.txt -lm train
iconv -f GBK -t utf-8 train

srilm 安装

官网中 http://www.speech.sri.com/projects/srilm/download.html 填写相关信息后即可免费下载源码.
下载后解压
按照INSTALL文件说明 修改Makefile文件中SRILM变量
SRILM = /home/vrgroup/Desktop/srilm-1.7.1
执行如下命令进行编译

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/home/vrgroup/Desktop/srilm-1.7.1# make World

生成bin lib include lib 三个文件夹
其中bin中就包含了需要用到的工具

训练英文语言模型

直接对REDEME文件进行语言模型建模。生成test文件。该文件即为语言模型

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/home/vrgroup/Desktop/srilm-1.7.1# bin/i686-m64/ngram-count -text README -lm test
warning: discount coeff 1 is out of range: 0
warning: count of count 8 is zero -- lowering maxcount
warning: count of count 7 is zero -- lowering maxcount
warning: count of count 6 is zero -- lowering maxcount
warning: count of count 5 is zero -- lowering maxcount
warning: count of count 4 is zero -- lowering maxcount
warning: discount coeff 1 is out of range: 0
warning: count of count 8 is zero -- lowering maxcount
warning: count of count 7 is zero -- lowering maxcount
warning: count of count 6 is zero -- lowering maxcount
warning: count of count 5 is zero -- lowering maxcount
warning: count of count 4 is zero -- lowering maxcount
warning: count of count 3 is zero -- lowering maxcount
warning: discount coeff 1 is out of range: 0
/home/vrgroup/Desktop/srilm-1.7.1# vim test
#test 文件内容如下所示

\data\
ngram 1=63
ngram 2=84
ngram 3=4

\1-grams:
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-0.7829502	</s>
-99	<s>	-1.125891
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\2-grams:
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-0.30103	19:35:49 stolcke
-0.30103	2009/12/02 19:35:49
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\3-grams:
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\end\

这是一个ARPA-MIT LM 格式的三元语言模型文件 第一个浮点数表示概率(log10),后面的浮点数表示back-off权重(log10).back-off权重主要用于平滑概率为0的数据.具体概率计算方法按照如下公式:

  • P表示 (c b a)出现的概率
  • P=p(a|b c);
  • if p(a|b c)==0 : P=backoff(c b)*p(a|b)
  • if p(a|b)==0 : P=backoff(b)*p(a)

中文语言模型训练

对于中文文本,需要先进行分词,然后才能进行词频统计来建立语言模型,HTokenize工具可以用来分词.分词后结果如下:

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/home/vrgroup/Desktop/srilm-1.7.1# iconv -f GBK -t utf-8 train.txt 
请 显示 需要 优先 处理 的 事项
请 标识 优先 处理 的 位置
请 进入 乙烯 装置 模型 定位 报警 设备 有 多处 报警
显示 设备 当前 信息 参数
切 换 安全 管 控 界面
请 给 出 复合 报警 的 相关 点 点 位 趋势 图 息 界面
请 调 出 实时 监控 画面
请 查看 复合 报警 相应 模型 图
结合 知识 库 请 分析 故障 原因 并且 给 出 处理 措施
请 进行 相应 处理 生成 故障 处理 报告 归 档 到 知识 库
请 处理 裂解 炉 燃料 油 改 燃料 气 工艺 方案 切 换
请 先 切 换 到 方案 切 换 模拟 状态
请 显示 工艺 方案 指导 规程
显示 关键 点 位 及 指标 趋势 图
观察 指标 趋势
切 换 模拟 完成
紧急 事项 处理 完成
语音 助手 主动 汇报 事故 相关 信息
了解 外 操 情况
外 操 人员 携带 防护 设备 进入 现场 勘查
调用 北 美 应急 手册
通知 人员 撤离 去 往 紧急 集合 地点
计算 消防 路线
报告 消防 支队 气 防 炼 化 医院
通知 其他 岗位 人员 增援
对 清 污 分 流 阀门 进行 确认
打开 消防 炮 消防 栓
计算 模拟 气体 扩散 影响 结果
紧急 停车
要求 上游 装置 将 酸性 气体 改 至 运行 的 其他 硫磺 收集 装置 或 气 柜
计算 气体 扩散
结果 报告 政府 部门 报告 指挥 中心
根据 堵 漏 方案 对 分 液 灌 泄 压 置换
对 现场 气体 进行 检测
形成 事故 报告
/home/vrgroup/Desktop/srilm-1.7.1#

同样命令可得到中文语言模型

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root@vrgroup-Precision-M6800:/home/vrgroup/Desktop/srilm-1.7.1# bin/i686-m64/ngram-count -text train.txt -lm train
warning: discount coeff 1 is out of range: 0
warning: count of count 8 is zero -- lowering maxcount
warning: count of count 7 is zero -- lowering maxcount
warning: count of count 6 is zero -- lowering maxcount
warning: discount coeff 3 is out of range: -0.0228311
warning: count of count 4 is zero
warning: count of count 8 is zero -- lowering maxcount
warning: count of count 7 is zero -- lowering maxcount
warning: count of count 6 is zero -- lowering maxcount
warning: count of count 5 is zero -- lowering maxcount
warning: count of count 4 is zero -- lowering maxcount
warning: count of count 3 is zero -- lowering maxcount
warning: discount coeff 1 is out of range: 0
root@vrgroup-Precision-M6800:/home/vrgroup/Desktop/srilm-1.7.1#

在HDecode中使用语言模型

训练好的模型需要进行gzip压缩才可以用于HDecode.替换掉HDecode中语言模型参数-w为train即可完成对特定语言的识别,从而提高特定领域的识别率

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/home/vrgroup/Desktop/srilm-1.7.1# gzip train
./RedisToHDecode -A -D -V -T 1 -C hdecode.hlda.cfg -H S2.hlda.MMF -y rec -t 250.0 250.0 -u 3500 -v 125.0 -s 12.0 -p -10.0 -w train -i out 64k.decode.dct xwrd.clustered.mlist test.plp

```