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1. 写在前面

  上一篇文章中，对MRCP Server的开发进行了介绍，下面讲解如何通过配置让FreeSWITCH能够与MRCP Server进行对接，获得电话呼叫的语音识别结果。

2. MRCP Server 配置与测试

2.1 MRCP Server 配置

cd /usr/local/unimrcp/conf
vim unimrcpserver.xml

  以下xml只展示了需要进行调整的部分，将*.so的名称添加到配置文件中enable="true"

<!-- Factory of plugins (MRCP engines) -->
<plugin-factory><engine id="Demo-Synth-1" name="demosynth" enable="false"/><engine id="XFyun-Synth-1" name="xfyunsynth" enable="true"/><engine id="Demo-Recog-1" name="demorecog" enable="false"/><!--engine id="XFyun-Recog-1" name="xfyunrecog" enable="true"/--><engine id="Xxx-Recog-1" name="XxxRecog" enable="true"/><engine id="Demo-Verifier-1" name="demoverifier" enable="true"/><engine id="Recorder-1" name="mrcprecorder" enable="true"/>
</plugin-factory>

2.2 MRCP Server 测试

  完成配置后，启动UniMRCP Server

cd /usr/local/unimrcp/bin
./unimrcpserver -o 3

  运行结果如下图：

  启动UniMRCP Client，输入run recog进行测试。

cd /usr/local/unimrcp/bin
./unimrcpclient
>help
usage:- run [app_name] [profile_name] (run demo application)app_name is one of 'synth', 'recog', 'bypass', 'discover'profile_name is one of 'uni2', 'uni1', ...examples: run synthrun recogrun synth uni1run recog uni1- loglevel [level] (set loglevel, one of 0,1...7)- quit, exit

3. FreeSwitch 配置

3.1. 配置 mrcp profile

  创建新的 mrcp服务连接的 配置文件 xiaoi-mrcp-v2.xml

cd /usr/local/freeswitch/conf/mrcp_profiles
vim xiaoi-mrcp-v2.xml

<include><!-- UniMRCP Server MRCPv2 --><!-- 后面我们使用该配置文件，均使用 name 作为唯一标识，而不是文件名 --><profile name="xiaoi-mrcp-v2" version="2"><!-- MRCP 服务器地址 --><param name="server-ip" value="192.168.160.2"/><!-- MRCP SIP 端口号 --><param name="server-port" value="8060"/><param name="resource-location" value=""/><!-- FreeSWITCH IP、端口以及 SIP 传输方式 --><param name="client-ip" value="192.168.160.58"/><!-- 注意，当配置多个mrcp server的时候，该端口不能冲突，否则可能不可用 --><param name="client-port" value="5089"/><param name="sip-transport" value="udp"/><param name="speechsynth" value="speechsynthesizer"/><param name="speechrecog" value="speechrecognizer"/><!--param name="rtp-ext-ip" value="auto"/--><param name="rtp-ip" value="192.168.160.58"/><param name="rtp-port-min" value="4000"/><param name="rtp-port-max" value="5000"/><param name="codecs" value="PCMU PCMA L16/96/8000"/><!-- Add any default MRCP params for SPEAK requests here --><synthparams></synthparams><!-- Add any default MRCP params for RECOGNIZE requests here --><recogparams><!--param name="start-input-timers" value="false"/--></recogparams></profile>
</include>

3.2. 配置 mrcp conf

  配置/usr/local/freeswitch/conf/autoload_configs/unimrcp.conf.xml文件：

cd /usr/local/freeswitch/conf/autoload_configs
vim unimrcp.conf.xml

  配置文件如下，al-unimrcpv2为默认的，进行注释，下面配置中，只配置了xiaoi-mrcp-v2，注意，该名字与1配置的xiaoi-mrcp-v2.xml中profile name名称一致。

<configuration name="unimrcp.conf" description="UniMRCP Client"><settings><!--al-unimrcpv2 UniMRCP profile to use for TTS --><param name="default-tts-profile" value="al-unimrcpv2"/><!-- <param name="default-tts-profile" value="xiaoi-mrcp-v2"/> --><!-- UniMRCP profile to use for ASR --><!-- <param name="default-asr-profile" value="al-unimrcpv2"/> --><param name="default-asr-profile" value="xiaoi-mrcp-v2"/><!-- UniMRCP logging level to appear in freeswitch.log.  Options are:EMERGENCY|ALERT|CRITICAL|ERROR|WARNING|NOTICE|INFO|DEBUG --><param name="log-level" value="DEBUG"/><!-- Enable events for profile creation, open, and close --><param name="enable-profile-events" value="false"/><param name="max-connection-count" value="100"/><param name="offer-new-connection" value="1"/><param name="request-timeout" value="3000"/></settings><profiles><X-PRE-PROCESS cmd="include" data="../mrcp_profiles/*.xml"/></profiles></configuration>

  注意，完成配置后，不能直接 F6 reloadxml 需要重启FreeSWITCH才生效

systemctl restart freeswitch

3.3. 配置拨号任务

  在/usr/local/freeswitch/conf/dialplan/default.xml里新增如下配置：

<extension name="unimrcp"><condition field="destination_number" expression="^5001$"><action application="answer"/><action application="lua" data="asr.lua"/></condition>
</extension>

  lua脚本存放地址及内容，可根据需要调整：

cd /usr/local/freeswitch/scripts
vim asr.lua

session:answer()--freeswitch.consoleLog("INFO", "Called extension is '".. argv[1]"'\n")
welcome = "ivr/ivr-welcome_to_freeswitch.wav"
menu = "ivr/ivr-this_ivr_will_let_you_test_features.wav"
--
grammar = "hello"
no_input_timeout = 80000
recognition_timeout = 80000
confidence_threshold = 0.2
--
session:streamFile(welcome)
--freeswitch.consoleLog("INFO", "Prompt file is \n")
tryagain = 1while (tryagain == 1) do
--session:execute("play_and_detect_speech",menu .. "detect:unimrcp {start-input-timers=false,no-input-timeout=" .. no_input_timeout .. ",recognition-timeout=" .. recognition_timeout .. "}" .. grammar)xml = session:getVariable('detect_speech_result')
--if (xml == nil) thenfreeswitch.consoleLog("CRIT","Result is 'nil'\n")tryagain = 0elsefreeswitch.consoleLog("CRIT","Result is '" .. xml .. "'\n")tryagain = 0end
end
session:hangup()

  从上面的lua脚本能看出，会加载grammar语法文件，在/usr/local/freeswitch/grammar目录新增hello.gram语法文件，可以为空语法文件须满足语音识别语法规范1.0标准（简称 SRGS1.0），该语法文件 ASR 引擎在进行识别时可以使用。

<!-- grammar  hello.gram -->
<?xml version="1.0" encoding="utf-8" ?>
<grammar version="1.0" xml:lang="zh-cn" root="digit" tag- format="semantics/1.0" mode="continuous" xmlns="http://www.w3.org/2001/06/grammar"><!-- 这些都是必不可少的,做一个假配置--><rule id="digit"><one-of><item>one</item><item>two</item></one-of></rule>
</grammar>

4. 效果测试

  完成以上配置后，使用sip软电话，拨打配置的号码5001，在fs端fs_cli查看log

2021-05-19 14:43:37.981898 [DEBUG] apt_task.c:265 () Signal Message to [MRCP Client] [0x7f6500023ec0;2;3]
2021-05-19 14:43:37.981898 [DEBUG] apt_poller_task.c:251 () Wait for Messages [MRCPv2ConnectionAgent]
2021-05-19 14:43:37.981898 [DEBUG] apt_task.c:337 () Process Message [MRCP Client] [0x7f6500023ec0;2;3]
2021-05-19 14:43:37.981898 [INFO] mrcp_client_session.c:516 (ASR-13) Raise App MRCP Event ASR-13 <ea2c920254a0462d>
2021-05-19 14:43:37.981898 [DEBUG] mod_unimrcp.c:3675 (ASR-13) RECOGNITION COMPLETE, Completion-Cause: 000
2021-05-19 14:43:37.981898 [DEBUG] mod_unimrcp.c:3684 (ASR-13) Recognition result is not null-terminated.  Appending null terminator.
2021-05-19 14:43:37.981898 [DEBUG] mod_unimrcp.c:2733 (ASR-13) ASR adding result headers
2021-05-19 14:43:37.981898 [DEBUG] mod_unimrcp.c:2628 (ASR-13) result:<?xml version="1.0"?>
<result><interpretation confidence="99"><instance><engineName>Xxx</engineName><engineStartTime></engineStartTime><result>喂喂喂讲话.</result><beginTime></beginTime><endTime></endTime></instance><input mode="speech">喂喂喂讲话.</input></interpretation>
</result>

  后续开发中，使用mod_event_socket的内连模式，对fs事件进行监听，在play_and_detect_speech 应用执行完成的事件CHANNEL_EXECUTE_COMPLETE中就能获取到语音识别结果。

  socket 连接命令与监听命令如下：

nc 127.0.0.1 8021
auth ClueCon
event plain CHANNEL_EXECUTE_COMPLETE

  监听事件的结果如下（便于查看，进行了URL解码，省略了该事件的部分细节内容）

Content-Length: 9403
Content-Type: text/event-plainEvent-Name: CHANNEL_EXECUTE_COMPLETE
Core-UUID: 6f535b68-8025-4727-a210-70c2278501f9
FreeSWITCH-Hostname: freeswitch-seat
FreeSWITCH-Switchname: freeswitch-seat
FreeSWITCH-IPv4: 192.168.160.58
FreeSWITCH-IPv6: ::1
......
variable_current_application: play_and_detect_speech
variable_playback_last_offset_pos: 29760
variable_playback_seconds: 3
variable_playback_ms: 3970
variable_playback_samples: 31765
variable_detect_speech_result: <?xml version="1.0"?>
<result><interpretation confidence="99"><instance><engineName>Xxx</engineName><engineStartTime></engineStartTime><result>喂喂喂讲话.</result><beginTime></beginTime><endTime></endTime></instance><input mode="speech">喂喂喂讲话.</input></interpretation>
</result>
variable_current_application_response: DONE
Application: play_and_detect_speech
Application-Data: ivr/ivr-this_ivr_will_let_you_test_features.wavdetect:unimrcp {start-input-timers=false,no-input-timeout=80000,recognition-timeout=80000}hello
Application-Response: DONE
Application-UUID: 7f56ddc1-2d8f-4a2c-aae1-a236749f8133

技术参考资料
https://github.com/wangkaisine/mrcp-plugin-with-freeswitch