Mod avmd
From FreeSWITCH Wiki
Contents |
Description
AVMD stands for "Advanced Voice Mail Detection" and mod_avmd is designed to detect the beep sound at the end of voicemail or answering machine greetings. This is useful in cases where you wish to leave a recorded message on the recipient's message system but don't want to have the pregnant pause that is common when using wait_for_silence.
mod_avmd (AVMD) is the second generation Voice Mail Detection, and has a number of enhancements that make it much better at determining a beep. It is intended to replace mod_vmd. It works very similar to mod_vmd with a few exceptions.
- VMD will listen for and send an event each time it thinks there is a beep. Therefore VMD may send many events while listening to a call.
- AVMD only sends one event, and then quits. However AVMD is much better at determining correct beep sounds, which means it gives back fewer false positives and more true positives than VMD.
- VDM events included frequency and duration details for the beep.
- AVMD does not. [Eric said this about not including frequency and duration in the events, “It saves resources (cpu & memory) and we didn’t need the values.”]
Warning
AVMD (and VMD) are both very CPU intensive. You need to be aware of this fact when using it. It will drastically reduce your call capacity if you do not manage it correctly. On the other hand it is a very useful tool, and if managed properly will be a great aid for calls needing to do Voice Mail Detection.
- Eric states, "You can expect about ~50 simultaneous instances on an Intel i7 920 CPU."
Usage
For best results in getting accurate detection as well a saving system resources (CPU & memory), you should do the following:
- Wait until AFTER the call has been answered before starting AVMD. In many cases you may find it best to wait a few seconds after the call is answered before starting AVMD.
- Starting AVMD before the call is answered will often result in false beeps and wastes CPU resources.
- Once you have received the AVMD event, you should explicitly stop AVMD, even though it will not return another event.
From mod_event_socket
To start the mod:
api avmd <uuid> start
To stop the mod:
api avmd <uuid> stop
To get mod_avmd events:
event plain CUSTOM avmd::beep
A useful way to start avmd a few seconds after answer. Once you get an answer event, issue this command
api sched_api +3 none avmd <uuid> start
Example Event
Event-Subclass: avmd%3A%3Abeep Event-Name: CUSTOM Core-UUID: 3395d705-6571-414d-a38c-fad8b0bdd3e9 FreeSWITCH-Hostname: tpa-es-cos-232 FreeSWITCH-IPv4: 10.50.48.232 FreeSWITCH-IPv6: %3A%3A1 Event-Date-Local: 2010-07-02%2009%3A58%3A01 Event-Date-GMT: Fri,%2002%20Jul%202010%2013%3A58%3A01%20GMT Event-Date-Timestamp: 1278079081446061 Event-Calling-File: mod_avmd.c Event-Calling-Function: avmd_process Event-Calling-Line-Number: 548 Beep-Status: stop Unique-ID: d6ff2323-d57e-4e7d-b75b-7724d81bb5d9 call-command: avmd
Lua Example
This is an example of a callback in Lua:
local human_detected = false;
local voicemail_detected = false;
function onInput(session, type, obj)
if type == "dtmf" and obj['digit'] == '1' and human_detected == false then
human_detected = true;
return "break";
end
if type == "event" and voicemail_detected == false then
voicemail_detected = true;
return "break";
end
end
session:setInputCallback("onInput");
session:execute("avmd","start");
Javascript Example
This is an example of a callback in Javascript:
function onInput(s, type, obj, arg)
{
try
{
if(type == "dtmf")
{
console_log("info", "DTMF digit: "+s.name+" ["+obj.digit+"] len ["+obj.duration+"]\n");
}
else if(type == "event" && session.getVariable("avmd_detect") == "TRUE")
{
console_log("info", "Voicemail Detected\n");
}
}
catch(e)
{
console_log("err", e + "\n");
}
return true;
}
session.answer();
session.execute("avmd", "start");
while(session.ready())
{
session.streamFile(argv[0], onInput);
}
From Dialplan
Note: all it does is set chan variable ${avmd_detect} to "TRUE" and nothing else, so don't rely on this for acting quickly if a beep is detected.
<!-- mod_avmd test extension (new mod)-->
<extension name="avmdtest">
<condition field="destination_number" expression="^(\d{10})$">
<action application="answer"/>
<action application="info"/>
<action application="avmd"/> <!-- Starts detection on the call. -->
<action application="sleep" data="25000"/>
<action application="info"/> <!-- Look for chan var "avmd_detect" here -->
<action application="avmd" data="stop"/> <!-- Stops detection on the call. -->
<action application="hangup"/>
</condition>
</extension>
Configuration
To compile it simply add this to 'modules.conf':
applications/mod_avmd
And do not forget to rebuild and install:
sudo make sure sudo make install
To have FreeSWITCH load it on startup simply add this to '/usr/local/freeswitch/conf/autoload_configs/modules.conf.xml':
<load module="mod_avmd"/>
Notes
No voicemail detection can claim to be 100% accurate. The industry standard is 80% detection. This module if used properly should exceed the standard by a very wide margin.
