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 Table of Contents (click to expand)


0. About

The FreeSWITCH Speech Phrase Management architecture provides a consistent framework for the management of language dependent voice prompting without the need to dig into the applications source code. A single application developed using the framework will work with the current languages implemented or new languages in the future.

1. Features

  • Multilingual Support
  • No Source Code required to modify prompts
  • Ability to select prompts using pattern matching in XML
  • Integrated support for voice and TTS in the same application
  • Custom phrases can be added at any time
  • Switch voice libraries with one setting
  • Only load the code for the languages you want to support (less code bloat).

2. Overview

There are several ways to speak prompts in FreeSWITCH, but the Speech Phrase Management sub-system provides the most features and flexibility.

2.1 Language modules

Prompts are defined outside the application and can be modified to suit the specific implementation or language. When amounts, dates, numbers, or letters are enunciated, the proper phrases to assemble and the ordering of those phrases is determined by the mod_say_xx module (where xx stands for a two-letter language code, such as en ).

Because different languages assemble the same phrases differently (and even use different words depending upon the type of object being referred to), a helper application is needed to do the job properly. This is the job of the mod_say_xx (e.g., mod_say_en, mod_say_fr) module. Within this module are the necessary functions speak time, money, counts, spell letters, and digits.

In order to support the English version (mod_say_en), the code expects certain prompt directories to exist in your base voice file path (for example at /var/sounds/freeswitch/en; see sounds_dir and sound_prefix in Global Variables).

Basic sounds should be installed during a vanilla install (at /usr/share/freeswitch/sounds on Debian 9), but, just in case, here are all the available sounds:

https://github.com/access-news/freeswitch-sounds

2.2 Configuration

2.2.1 Load language modules

For each language you want to support you will need to load the appropriate mod_say_xx module in conf/autoload_configs/modules.conf.xml. (See Modules.)

Language Activation
<load module="mod_say_en"/>

2.3 Specify phrase directories

See 3 Phrase primer section below to read more on phrases.

Also specify the location of language-specific phrase directories for each language in conf/freeswitch.xml (e.g., "de" for German):

Language Configuration
 <X-PRE-PROCESS cmd="include" data="lang/de/*.xml"/>

See 6. Configuration files in Default Configuration.

3. Phrase primer

The phrases section in conf/freeswitch.xml defines the construction and enunciation of phrases in various languages. 

TODO By Tomas Bajarunas:

add optional name attribute for macros:

<macros name="optional_macros_name">
...

</macros>

I think that name later can be used when using phrases like this in dialplan:

<action application="playback" data="phrase:MyPhrase@optional_macros_name" />


from other phrases:

<action function="phrase" phrase="MyPhrase@optional_macro_name" data="some:data" />

3.1 Phrase macros

3.1.1 macros tag

The following XML snippet illustrates the structure to define phrase macros:

Phrases
<section name="phrases" description="Speech Phrase Management">
  <macros>
  ...
  </macros>
</section>

All prompts should be defined in this section.

3.1.2 language tag

The <macros> section is then sub-divided into languages as follows.

Language tags
<language name="en" sound_path="/var/sounds/phrases/en" tts_engine="cepstral" tts_voice="david">
  <!-- macros -->
</language>

Where

  • name - Defines the specific language these prompts belong to.
    In the above example it is en , that will cause the mod_say_en module to be used to enunciate any constructed phrases (like money, date, time, etc.)
  • sound_path - The base path to the voice files for this language.
  • tts_engine - The text-to-speech engine to use for any TTS spoken.
  • tts_voice - The specific voice to use for TTS.

See TTS page for available engines and voices.

3.1.3 macro tag

Within the language there are one or more macros defined:

Macros
<macro name="msgcount">
  <!-- inputs -->
</macro>

3.1.4 input tag

Macros
<macro name="msgcount">
  <input pattern="^\d+$">
    <!-- match and nomatch tags -->
  </input>
</macro>

pattern is a PCRE-compatible regular expression to match on the second argument to the phrase application (i.e., the actual data to speak).

For example, using the example below, the above macro pattern will match "130".

    <action application="phrase" data="msgcount,130"/>

Using regexes, you can filter for specific conditions, and even "scrub" the data to ensure it is in the proper layout.

Within macro  all input patterns will be tested for possible matches, unless the break action is used.

See 3.2 Phrase macro actions section below.

3.1.4.1 Example

To achieve proper pluralization, you may define multiple input patterns, and use different prompts for each, such as "You have 2 messages" versus "You have 1 message".

Macros
<macro name="msgcount">
  <input pattern="^\d+$">
    <!-- ... plural prompt ... -->
  </input>
  <input pattern="^\d$">
    <!-- ... singular prompt ... -->
  </input>
</macro>

3.1.5 match and nomatch tags

Within a input tag there are one or more match and nomatch tags.

Macros
<macro name="msgcount">
  <input pattern="^\d+$">
    <match>
      <!-- actions -->
    </match>
    <nomatch>
      <!-- actions -->
    </nomatch>
  </input>
</macro>

These define the actions to take if the input pattern is matched (or not matched).

3.1.5.1 Example
<macro name="tts-timeleft">
  <input pattern="(\d+):(\d+)">
    <match>
      <!-- Speak the time in the format: -->
      <action function="speak-text" data="You have $1 minutes, $2 seconds remaining $strftime(%Y-%m-%d)"/>
    </match>
    <nomatch>
      <!-- The input wasn't in the format of 12:34 (or similar), hence: -->
      <action function="speak-text" data="That input was invalid."/>
    </nomatch>
  </input>
</macro>

3.1.6 action tag

Within a match and nomatch tag there are one or more actions.

Matches and No matches
<action function="execute" data="sleep(1000)"/>
<action function="play-file" data="vm-youhave.wav"/>
<action function="say" data="$1" method="pronounced" type="items"/>

These define the specific actions to take when this macro is applied. It usually consist of calling the say application, passing the parsed data to be spoken.

The possible actions are described in 3.2 Phrase macro actions section below.

 3.2 Phrase macro actions

Syntax
<action function=[phrase_macro_action] data=[arguments] [other_properties] />

Where phrase_macro_action can be:

phrase_macro_action Description
execute

Calls the FreeSWITCH execute API (you can execute any other API's).

TODO What is the execute API?

play-file

Play a specific audio file or play a macro in the form phrase:macro_name

say

Use the pre-recorded sound files to read or say various things like dates, times, digits, etc.

Requires the type and method properties whose values correspond to the say_type and say_method input values of mod_dptools:say. See 1. Syntax section there.

speak-textSpeak some text using the TTS engine.
break

Stop parsing any more input patterns.

See 3.1.4 input tag section.


3. Usage

3.1 From XML Dialplan

3.1.1 Selecting the language

The language to use is selected by setting the default_language variable (see Channel Variables Catalog) to the specific language code you want.

Language selection
<!-- select English as the default language -->
<action application="set" data="default_language=en"/>

If you specify a specific language to use in the API call (see below methods), it will override the default_language channel variable setting.

This is to support prompts that should be spoken in a particular language regardless of the users default language selection.

3.1.2 Playing prompts from the dialplan

The phrase application will call the say API using the phrases defined in the phrases section of your conf/freeswitch.xml file.

Invoke phrases in the Dialplan
<action application="phrase" data="msgcount:10"/>
<action application="phrase" data="spell-phonetic:abc.012345 6789def#*"/>
<action application="phrase" data="spell:${caller_id_name}"/>

The data field passes two parameters:

  • phrase macro name to use
    The macro names are arbitrary but should be meaningful for documentation purposes.

  • data (i.e., arguments) to pass to the macro
    The data can be a literal as in the first two examples above or a string variable as in the third example.

The playback  application can also be used in same way as "phrase" application.

Example using "playback"
<action application="set" data="playback_terminators=#"/>
<action application="playback" data="phrase:demo_ivr_main_menu"/>
<action application="playback" data="phrase:voicemail_message_count:16:new"/>

3.2 Playing prompts from a C application

Prompts form "C"
status = switch_ivr_phrase_macro(session, "phrasename", "phrasedata", language, args);

3.3 Playing prompts from JavaScript application

Prompts from JavaScript
function sayphrase(phrase, args)
{
    console_log("sayphrase: phrase=[" + phrase + "] args=[" + args + "]\n");
    var rtn = session.execute("phrase", phrase + "," + args);
    return(rtn);
}

if (session.ready()) {
    session.answer();
    session.execute("sleep","1000");
    sayphrase("msgcount", "10");
    session.hangup();
}

4. Examples

4.1 Speaking a number


The sample dialplan extension below demonstrates speaking a number of the prompts in the "phrases" section.
Dialplan
<extension name="556"> 
   <condition field="destination_number" expression="^556$">
     <action application="answer"/>
     <action application="set" data="call_start_time=$strftime"/>
     <action application="sleep" data="500"/>
     <action application="phrase" data="spell,${caller_id_name}"/>
     <action application="sleep" data="500"/>
 
     <action application="phrase" data="spell-phonetic,abc.012345 6789def#*"/>
     <action application="sleep" data="500"/>
 
     <action application="phrase" data="saymoney,851920.11"/>
     <action application="sleep" data="500"/>
 
     <action application="phrase" data="spell,192.168.0.100"/>
     <action application="sleep" data="500"/>
 
     <action application="phrase" data="ip-addr,66.250.68.194"/>
     <action application="sleep" data="500"/>
 
     <action application="phrase" data="timespec,12:45:15"/>
     <action application="sleep" data="500"/>
 
     <action application="phrase" data="saydate,${strepoch(2006-03-23)}"/>
     <action application="sleep" data="500"/>
 
     <action application="phrase" data="saytime,${strepoch(2006-03-23 01:59)}"/>
     <action application="sleep" data="500"/>
 
     <action application="phrase" data="saydatetime,${strepoch(2006-03-23 12:34)}"/>
     <action application="sleep" data="500"/>
 
     <action application="phrase" data="msgcount,10"/>
     <action application="sleep" data="500"/>
 
     <action application="phrase" data="timeleft,3:30"/>
     <action application="sleep" data="500"/>
   </condition>
 </extension>

Phrase macro definition for the above dialplan
<section name="phrases" description="Speech Phrase Management">
   <macros>
     <language name="en" sound_path="/var/sounds/phrases/en" tts_engine="cepstral" tts_voice="david">
       <macro name="msgcount">
         <input pattern="(.*)">
           <match>
             <action function="execute" data="sleep(1000)"/>
             <action function="play-file" data="vm-youhave.wav"/>
             <action function="say" data="$1" method="pronounced" type="items"/>
           </match>
         </input>
         <input pattern="^1$">
           <match>
             <action function="play-file" data="vm-message.wav"/>
           </match>
           <nomatch>
             <action function="play-file" data="vm-messages.wav"/>
           </nomatch>
         </input>
       </macro>
       <macro name="saymoney">
         <input pattern="(.*)">
           <match>
             <action function="say" data="$1" method="pronounced" type="currency"/>
           </match>
         </input>
       </macro>
       <macro name="saydate">
         <input pattern="(.*)">
           <match>
             <action function="say" data="$1" method="pronounced" type="current_date"/>
           </match>
         </input>
       </macro>
       <macro name="ip-addr">
         <input pattern="(.*)">
           <match>
             <action function="say" data="$1" method="iterated" type="ip_address"/>
             <action function="say" data="$1" method="pronounced" type="ip_address"/>
           </match>
         </input>
       </macro>
       <macro name="saytime">
         <input pattern="(.*)">
           <match>
             <action function="say" data="$1" method="pronounced" type="current_time"/>
           </match>
         </input>
       </macro>
       <macro name="saydatetime">
         <input pattern="(.*)">
           <match>
             <action function="say" data="$1" method="pronounced" type="current_date_time"/>
           </match>
         </input>
       </macro>
       <macro name="timespec">
         <input pattern="(.*)">
           <match>
             <action function="say" data="$1" method="pronounced" type="time_measurement"/>
           </match>
         </input>
       </macro>
       <macro name="spell">
         <input pattern="(.*)">
           <match>
             <action function="say" data="$1" method="pronounced" type="name_spelled"/>
           </match>
         </input>
       </macro>
       <macro name="spell-phonetic">
         <input pattern="(.*)">
           <match>
             <action function="say" data="$1" method="pronounced" type="name_phonetic"/>
           </match>
         </input>
       </macro>
       <macro name="timeleft">
         <input pattern="(\d+):(\d+)">
           <match>
             <action function="say" data="$1:$2" method="pronounced" type="time_measurement"/>
           </match>
         </input>
       </macro>
       <macro name="tts-timeleft">
         <input pattern="(\d+):(\d+)">
           <match>
             <action function="speak-text" data="You have $1 minutes, $2 seconds remaining $strftime(%Y-%m-%d)"/>
           </match>
           <nomatch>
             <action function="speak-text" data="That input was invalid."/>
           </nomatch>
         </input>
         <input pattern="(\d+) min (\d+) sec">
           <match>
             <action function="speak-text" data="You have $1 minutes, $2 seconds remaining $strftime(%Y-%m-%d)"/>
             <action function="break"/>
           </match>
           <nomatch>
             <action function="speak-text" data="That input was invalid."/>
           </nomatch>
         </input>
       </macro>
     </language>
     <language name="fr" sound_path="/var/sounds/lang/fr/jean" tts_engine="cepstral" tts_voice="jean-pierre">
       <macro name="msgcount">
         <input pattern="(.*)">
           <match>
             <action function="play-file" data="tuas.wav"/>
             <action function="say" data="$1" method="pronounced" type="items"/>
             <action function="play-file" data="messages.wav"/>
           </match>
         </input>
       </macro>
       <macro name="timeleft">
         <input pattern="(\d+):(\d+)">
           <match>
             <action function="speak-text" data="il y a $1 minutes et de $2 secondes de restant"/>
           </match>
         </input>
       </macro>
     </language>
   </macros>
 </section>

4.2 Calling a macro from within a macro

Calling a macro from a macro
 <macro name="main_menu" pause="100">
   <input pattern="(.*)">
     <match>
       <action function="speak-text" data="Welcome to the FreeSWITCH System."/>
       <action function="play-file" data="phrase:main_menu_short"/>
     </match>
   </input>
 </macro>
 <macro name="main_menu_short" pause="100">
   <input pattern="(.*)">
     <match>
       <action function="speak-text" data="For English press 1."/>
       <action function="speak-text" data="To speak to the operator press 0."/>
     </match>
   </input>
 </macro>

5. Pitfalls

I used the following for German prompts conf/lang/de/de.xml

Pitfalls
  <include>
    <language name="de" sound-path="$${base_dir}/sounds/de/de/callie" tts-engine="cepstral" tts-voice="katrin">
      <X-PRE-PROCESS cmd="include" data="demo/demo.xml"/>
      <!--voicemail_de_tts is purely implemented with tts, we need a files based implementation too -->
      <!-- <X-PRE-PROCESS cmd="include" data="vm/tts.xml"/> -->
      <X-PRE-PROCESS cmd="include" data="vm/sounds.xml"/>  <!-- vm/tts.xml if you want to use tts and have cepstral -->
      <X-PRE-PROCESS cmd="include" data="dir/sounds.xml"/>  <!-- dir/tts.xml if you want to use tts and have cepstral -->
    </language>
  </include>
Although <X-PRE-PROCESS cmd="include" data="vm/tts.xml"/> is commented, TTS is thus being used. So delete this line completely if you need voice prompts to be played as sound files.




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