[Freeswitch-users] Stopping TTS when play_and_detect_speech gets MRCP START-OF-INPUT

mayamatakeshi mayamatakeshi at gmail.com
Thu Mar 18 07:46:41 UTC 2021

On Thu, Mar 18, 2021 at 3:59 PM mayamatakeshi <mayamatakeshi at gmail.com>

> On Thu, Mar 18, 2021 at 12:23 PM mayamatakeshi <mayamatakeshi at gmail.com>
> wrote:
>> On Wed, Mar 17, 2021 at 6:52 PM mayamatakeshi <mayamatakeshi at gmail.com>
>> wrote:
>>> Hi,
>>> I'm trying play_and_detect_speech with an ESL app but START-OF-INPUT
>>> doesn't interrupt the TTS being played.
>>> Is this expected?
>>> (
>>> https://freeswitch.org/confluence/display/FREESWITCH/mod_dptools%3A+play_and_detect_speech
>>> is not clear about it)
>>> Or maybe I need to set some channel variable for this to work.
>> Hi,
>> My app is a fork of https://github.com/plivo/plivoframework
>> I debugged FS code and found the cause of the problem:
>> I verified that the DETECTED_SPEECH events (including the one
>> with Speech-Type begin-speaking) were not being fired.
>> This was because my app was not setting this variable:
>>   https://freeswitch.org/confluence/display/FREESWITCH/fire_asr_events
>> Then I set fire_asr_events=true
>> but still the prompt didn't get interrupted by speech.
>> Then I checked how FS code was fetching (dequeuing) events and I realized
>> it checks for divert_events.
>> Then I changed my app to send
>>   divert_events off
>> in the ESL socket
>> and after that it worked and FS stopped the prompt upon speech start.
>> However, it is not stopping the prompt when a DTMF digit is received (it
>> was already this way before I did the changes).
>> So things are better but still there is something amiss.
> OK. I found the reason:
> I was using 'playback_terminators=any'
> which reading the FS code shows will result in:
>   terminators = "1234567890*#"
> But I was sending DTMF 'a' so it was not causing the prompt to be
> terminated.
> Then I changed my test script to send '1' instead and then this caused the
> prompt to terminate.
> However, this also terminated the speech detection operation as FS sent
> STOP to the MRCP server.
> And the reason is because differently from begin-speaking, a terminator
> will set the operation as done (switch_ivr_async.c):
>                       } else if (!strcasecmp(speech_type,
> "begin-speaking")) {
> switch_log_printf(SWITCH_CHANNEL_SESSION_LOG(session), SWITCH_LOG_INFO,
> "(%s) START OF SPEECH\n", switch_channel_get_name(channel));
>                           return SWITCH_STATUS_BREAK;
>                       }
>                       if (terminators && strchr(terminators, dtmf->digit))
> {
> switch_log_printf(SWITCH_CHANNEL_SESSION_LOG(session), SWITCH_LOG_DEBUG,
> "(%s) ACCEPT TERMINATOR %c\n", switch_channel_get_name(channel),
> dtmf->digit);
>                           switch_channel_set_variable_printf(channel,
>                           state->result =
> switch_core_session_sprintf(session, "DIGIT: %c", dtmf->digit);
>                           state->done = PLAY_AND_DETECT_DONE;
>                           return SWITCH_STATUS_BREAK;
>                       }
> This might be OK for someone but in my case  there is another issue that
> the termination of the speech detection is not notified to my app via ESL.
> I am hoping to solve this by leaving the DTMF collection to be done by the
> MRCP server but currently the MRCP server I'm using (UniMRCP) doesn't
> report START-OF-INPUT for DTMF (I only get the RECOGNITION-COMPLETE after
> all digits are input). (my use case is to allow the user to speak some
> number sequence or dial it).

checking again, there is some specific condition that causes UniMRCP to not
send the START-OF-INPUT.
I'm not sure what it is yet but it may be by design or following something
in the protocol that I am not aware of.

> So I will switch to use detect_speech instead of play_and_detect_speech.
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