Google Dialogflow Plugin

PostedMarch 15, 2021

UpdatedMarch 17, 2021

Byuniadmin

1. Overview

This guide describes how to configure and use the Google Dialogflow (GDF) plugin to the UniMRCP server. The document is intended for users having a certain knowledge of Google Dialogflow and UniMRCP.

1.1 Installation

For installation instructions, use one of the guides below.

RPM Package Installation (Red Hat / Cent OS)
Deb Package Installation (Debian / Ubuntu)

1.2 Applicable Versions

Instructions provided in this guide are applicable to the following versions.

UniMRCP 1.5.0 and above
UniMRCP GDF Plugin 1.0.0 and above

2. Supported Features

This is a brief check list of the features currently supported by the UniMRCP server running with the GDF plugin.

2.1 MRCP Methods

DEFINE-GRAMMAR
RECOGNIZE
START-INPUT-TIMERS
STOP
SET-PARAMS
GET-PARAMS

2.2 MRCP Events

RECOGNITION-COMPLETE
START-OF-INPUT

2.3 MRCP Header Fields

Input-Type
No-Input-Timeout
Recognition-Timeout
Speech-Complete-Timeout
Speech-Incomplete-Timeout
Waveform-URI
Media-Type
Completion-Cause
Confidence-Threshold
Start-Input-Timers
DTMF-Interdigit-Timeout
DTMF-Term-Timeout
DTMF-Term-Char
Save-Waveform
Speech-Language
Cancel-If-Queue
Sensitivity-Level

2.4 Grammars

Built-in speech, event and DTMF grammars
SRGS XML (limited support)

2.5 Results

NLSML
JSON

3. Configuration Format

The configuration file of the GDF plugin is located in /opt/unimrcp/conf/umsgdf.xml. The configuration file is written in XML.

3.1 Document

The root element of the XML document must be <umsgdf>.

Attributes

Name	Unit	Description
license-file	File path	Specifies the license file. File name may include patterns containing ‘*’ sign. If multiple files match the pattern, the most recent one gets used.
gapp-credentials-file	File path	Specifies the Google Application Credentials file to use. File name may include patterns containing ‘*’ sign. If multiple files match the pattern, the most recent one gets used.

Parent

None.

Children

Name	Unit	Description
<streaming-recognition>	String	Specifies parameters of streaming recognition employed via gRPC.
<results>	String	Specifies parameters of recognition results set in RECOGNITION-COMPLETE events.
<builtin-grammars>	String	Contains a list of built-in grammars.
<speech-contexts>	String	Contains a list of speech contexts.
<speech-dtmf-input-detector>	String	Specifies parameters of the speech and DTMF input detector.
<utterance-manager>	String	Specifies parameters of the utterance manager.
<rdr-manager>	String	Specifies parameters of the Recognition Details Record (RDR) manager.
<monitoring-agent>	String	Specifies parameters of the monitoring manager.
<license-server>	String	Specifies parameters used to connect to the license server. The use of the license server is optional.

Example

This is an example of a bare document.

< umsgdf license-file="umsgdf_*.lic" gapp-credentials-file="*.json">
</ umsgdf>

3.2 Streaming Recognition

This element specifies parameters of streaming recognition.

Attributes

Name	Unit	Description
language	String	Specifies the default language to use, if not set by the client. For a list of supported languages, visit https://cloud.google.com/speech/docs/languages
single-utterance	Boolean	Specifies whether to detect a single spoken utterance or perform continuous recognition. Available since GDF 1.13.0.
interim-results	Boolean	Specifies whether to request interim results or not.
start-of-input	String	Specifies the source of start of input event sent to the client (use “service-originated” for an event originated based on a first-received interim result and “internal” for an event determined by plugin). Available since GDF 1.4.0.
max-alternatives	Integer	Specifies the maximum number of speech recognition result alternatives to be returned. Can be overridden by client by means of the header field N-Best-List-Length.
project-id	String	Specifies a project ID associated to the corresponding Dialogflow agent.
skip-unsupported-grammars	Boolean	Specifies whether to skip or raise an error while referencing a malformed or not supported grammar. Available since GDF 1.5.0.
skip-empty-results	Boolean	Specifies whether to implicitly initiate a new gRPC request if the current one completes with an empty result. Available since GDF 1.14.0.
transcription-grammar	String	Specifies the name of the built-in speech transcription grammar. The grammar can be referenced as builtin:speech/transcribe or builtin:grammar/transcribe, where transcribe is the default value of this parameter. Available since GDF 1.5.0.
generate-output-audio	Boolean	Specifies whether to enable generation of output audio. Available since GDF 1.12.0.
word-info	Boolean	Specifies whether to return word-level time offset information. Can be overridden by client. Available since GDF 1.15.0.
model	String	Specifies the domain-specific model, if used. Can be overridden by client. Available since GDF 1.15.0.
model-variant	String	Specifies the variant of the specified speech model, if used. Can be overridden by client. Available since GDF 1.15.0.
environment	String	Specifies the custom environment, if used. Can be overridden by client. Available since GDF 1.15.0.
http-proxy	String	Specifies the URI of HTTP proxy, if used. Available since GDF 1.10.0.
stream-creation-timeout	Time interval [msec]	Specifies how long to wait for gRPC stream creation. If timeout is set 0, no timer is used. Otherwise, if timeout is elapsed, gRPC stream creation is cancelled. Available since GDF 1.14.0.
inter-result-timeout	Time interval

[msec]

Specifies a timeout between interim results containing transcribed speech. If the timeout is elapsed, input is considered complete. The timeout is specified in msec and defaults to 0 (disabled). Available since GDF 1.15.0.

grpc-log-redirection

Boolean

Specifies whether to enable gRPC log redirection. Available since GDF 1.14.0.

grpc-log-verbosity

String

Specifies gRPC logging verbosity. One of DEBUG, INFO, ERROR. See GRPC_VERBOSITY for more info. Available since GDF 1.14.0.

grpc-log-trace

String

Specifies a comma separated list of tracers producing gRPC logs. Use ‘all’ to turn all tracers on. See GRPC_TRACE for more info. Available since GDF 1.14.0.

Parent

Children

None.

Example

This is an example of streaming recognition element.

<streaming-recognition single-utterance=”true” interim-results=”true” start-of-input=”service-originated” language=”en-US” max-alternatives=”1″ project-id=”” skip-unsupported-grammars=”true” transcription-grammar=”transcribe” />

3.3 Results

This element specifies parameters of recognition results set in RECOGNITION-COMPLETE events.

Availability

>= GDF 1.1.0.

Attributes

Name	Unit	Description
format	String	Specifies the format of results to be returned to the client (use “standard” for NLSML and “json” for JSON).
indent	Integer	Specifies the indent to use while composing the results.
replace-dots	Boolean	Specifies whether to replace ‘.’ with ‘_’ in the parameter names, used while composing an XML content. The parameter is observed only if the format is set to standard.
replace-dashes	Boolean	Specifies whether to replace ‘-‘ with ‘_’ in the parameter names, used while composing an XML content. The parameter is observed only if the format is set to standard. Available since GDF 1.15.0.
confidence-format	String	Specifies the format of the confidence score to be returned. The parameter is observed only if the format is set to standard. Use one of: auto for a format based on protocol version, mrcpv2 for a float value in the range of 0..1, mrcpv1 for an integer value in the range of 0..100 Available since GDF 1.7.0.
tag-format	String	Specifies the format of the instance element to be returned. The parameter is observed only if the format is set to standard. Use one of: semantics/xml for query result represented in XML [default]semantics/json for query result represented in JSONswi-semantics/xml for query result set in an inner <SWI_meaning> element represented in XMLswi-semantics/json for query result set in an inner <SWI_meaning> element represented in JSON Available since GDF 1.9.0.

Parent

Children

None.

Example

This is an example of results element.

3.4 Built-in Grammars

This element specifies a list of built-in grammars.

Availability

>= GDF 1.1.0.

Attributes

None.

Parent

Children

<builtin-grammar>

Example

The example below defines built-in boolean speech and DTMF grammars.

<builtin-grammars> <builtin-grammar mode=”speech” name=”boolean” action=”builtin.boolean” parameter-name=”option” project-id=””/> <builtin-grammar mode=”dtmf” name=”boolean” action=”builtin.boolean” parameter-name=”option” project-id=”” length=”1″ input=”event”/> </builtin-grammars>

3.5 Built-in Grammar

This element specifies a built-in grammar.

Availability

>= GDF 1.1.0.

Attributes

Name	Unit	Description
enable	Boolean	Specifies whether the speech context is enabled or disabled.
mode	String	Specifies the mode of the grammar: either “speech” or “dtmf”.
name	String	Specifies the name of the grammar being referenced in MRCP requests.
action	String	Specifies the action name to be triggered by Dialogflow.
parameter-name	String	Specifies the parameter name to be set by Dialogflow.
project-id	String	Specifies an optional project ID associated to the corresponding Dialogflow agent. If not specified, the default one is used.

Parent

<builtin-grammars>

Children

None.

Example

This is an example of built-in Boolean speech grammar.

<builtin-grammar enable=”false” mode=”speech” name=”boolean” action=”builtin.boolean” parameter-name=”option” project-id=””/>

3.6 Speech Contexts

This element specifies a list of speech contexts.

Attributes

None.

Parent

Children

<speech-context>

Example

The example below defines a speech context booking.

<speech-contexts> <speech-context id=”booking” enable=”true”> <phrase>I would like to book a flight from New York to Rome with a ticket eligible for free cancellation</phrase> <phrase>I would like to book a one-way flight from New York to Rome</phrase> </speech-context> </speech-contexts>

3.7 Speech Context

This element specifies a speech context.

Attributes

Name	Unit	Description
id	String	Specifies a unique string identifier of the speech context to be referenced by the MRCP client.
enable	Boolean	Specifies whether the speech context is enabled or disabled.
speech-complete	Boolean	Specifies whether to complete input as soon as an interim result matches one of the specified phrases. Available since GDF 1.6.0.
language	String	The language the phrases are defined for. Available since GDF 1.8.0.

Parent

<speech-contexts>

Children

Example

This is an example of speech context element.

<speech-context id=”booking” enable=”true”> <phrase>I would like to book a flight from New York to Rome with a ticket eligible for free cancellation</phrase> <phrase>I would like to book a one-way flight from New York to Rome</phrase> </speech-context>

3.8 Phrase

This element specifies a phrase in the speech context.

Attributes

Name	Unit	Description
weight (or boost)	Float	Specifies a positive value between 0 and 20. The value increases the probability that a specific phrase is recognized over other similar sounding phrases.

Parent

<speech-context>

Children

None.

3.9 Speech and DTMF Input Detector

This element specifies parameters of the speech and DTMF input detector.

Attributes

Name	Unit	Description
vad-mode	Integer	Specifies an operating mode of VAD in the range of [0 … 3]. Default is 1.
speech-start-timeout	Time interval [msec]	Specifies how long to wait in transition mode before triggering a start of speech input event.
speech-complete-timeout	Time interval

[msec]

Specifies how long to wait in transition mode before triggering an end of speech input event. The complete timeout is used when there is an interim result available.

speech-incomplete-timeout

Time interval [msec]

Specifies how long to wait in transition mode before triggering an end of speech input event. The incomplete timeout is used as long as there is no interim result available. Afterwards, the complete timeout is used. Available since GDF 1.2.0.

noinput-timeout

Time interval

[msec]

Specifies how long to wait before triggering a no-input event.

input-timeout

Time interval [msec]

Specifies how long to wait for input to complete.

dtmf-interdigit-timeout

Time interval

[msec]

Specifies a DTMF inter-digit timeout.

dtmf-term-timeout

Time interval [msec]

Specifies a DTMF input termination timeout.

dtmf-term-char

Character

Specifies a DTMF input termination character.

speech-leading-silence

Time interval [msec]

Specifies desired silence interval preceding spoken input.

speech-trailing-silence

Time interval

[msec]

Specifies desired silence interval following spoken input.

speech-output-period

Time interval [msec]

Specifies an interval used to send speech frames to the recognizer.

Parent

Children

None.

Example

The example below defines a typical speech and DTMF input detector having the default parameters set.

<speech-dtmf-input-detector vad-mode=”2″ speech-start-timeout=”300″ speech-complete-timeout=”1000″ speech-incomplete-timeout=”3000″ noinput-timeout=”5000″ input-timeout=”10000″ dtmf-interdigit-timeout=”5000″ dtmf-term-timeout=”10000″ dtmf-term-char=”” speech-leading-silence=”300″ speech-trailing-silence=”300″ speech-output-period=”200″ />

3.10 Utterance Manager

This element specifies parameters of the utterance manager.

Attributes

Name	Unit	Description
save-waveforms	Boolean	Specifies whether to save waveforms or not.
purge-existing	Boolean	Specifies whether to delete existing records on start-up.
max-file-age	Time interval

[min]

Specifies a time interval in minutes after expiration of which a waveform is deleted. Set 0 for infinite.

max-file-count

Integer

Specifies the max number of waveforms to store. If reached, the oldest waveform is deleted. Set 0 for infinite.

waveform-base-uri

String

Specifies the base URI used to compose an absolute waveform URI.

waveform-folder

Dir path

Specifies a folder the waveforms should be stored in.

file-prefix

String

Specifies a prefix used to compose the name of the file to be stored. Defaults to ‘umsgdf-‘, if not specified.

use-logging-tag

Boolean

Specifies whether to use the MRCP header field Logging-Tag, if present, to compose the name of the file to be stored. Available since GDF 1.14.0.

Parent

Children

None.

Example

The example below defines a typical utterance manager having the default parameters set.

<utterance-manager save-waveforms=”false” purge-existing=”false” max-file-age=”60″ max-file-count=”100″ waveform-base-uri=”http://localhost/utterances/” waveform-folder=”” />

3.11 RDR Manager

This element specifies parameters of the Recognition Details Record (RDR) manager.

Attributes

Name	Unit	Description
save-records	Boolean	Specifies whether to save recognition details records or not.
purge-existing	Boolean	Specifies whether to delete existing records on start-up.
max-file-age	Time interval

[min]

Specifies a time interval in minutes after expiration of which a record is deleted. Set 0 for infinite.

max-file-count

Integer

Specifies the max number of records to store. If reached, the oldest record is deleted. Set 0 for infinite.

record-folder

Dir path

Specifies a folder to store recognition details records in. Defaults to ${UniMRCPInstallDir}/var.

file-prefix

String

Specifies a prefix used to compose the name of the file to be stored. Defaults to ‘umsgdf-‘, if not specified.

use-logging-tag

Boolean

Specifies whether to use the MRCP header field Logging-Tag, if present, to compose the name of the file to be stored. Available since GDF 1.14.0.

Parent

Children

None.

Example

The example below defines a typical utterance manager having the default parameters set.

<rdr-manager save-records=”false” purge-existing=”false” max-file-age=”60″ max-file-count=”100″ waveform-folder=”” />

3.12 Monitoring Agent

This element specifies parameters of the monitoring agent.

Attributes

Name	Unit	Description
refresh-period	Time interval

[sec]

Specifies a time interval in seconds used to periodically refresh usage details. See <usage-refresh-handler>.

Parent

Children

<usage-change-handler>

<usage-refresh-handler>

Example

The example below defines a monitoring agent with usage change and refresh handlers.

<monitoring-agent refresh-period=”60″> <usage-change-handler> <log-usage enable=”true” priority=”NOTICE”/> </usage-change-handler> <usage-refresh-handler> <dump-channels enable=”true” status-file=”umsgdf-channels.status”/> </usage-refresh-handler > </monitoring-agent>

3.13 Usage Change Handler

This element specifies an event handler called on every usage change.

Attributes

None.

Parent

<monitoring-agent>

Children

<log-usage>

<update-usage>

<dump-channels>

Example

This is an example of the usage change event handler.

<usage-change-handler> <log-usage enable=”true” priority=”NOTICE”/> <update-usage enable=”false” status-file=”umsgdf-usage.status”/> <dump-channels enable=”false” status-file=”umsgdf-channels.status”/> </usage-change-handler>

3.14 Usage Refresh Handler

This element specifies an event handler called periodically to update usage details.

Attributes

None.

Parent

<monitoring-agent>

Children

<log-usage>

<update-usage>

<dump-channels>

Example

This is an example of the usage change event handler.

<usage-refresh-handler> <log-usage enable=”true” priority=”NOTICE”/> <update-usage enable=”false” status-file=”umsgdf-usage.status”/> <dump-channels enable=”false” status-file=”umsgdf-channels.status”/> </usage-refresh-handler>

3.15 License Server

This element specifies parameters used to connect to the license server.

Attributes

Name	Unit	Description
enable	Boolean	Specifies whether the use of license server is enabled or not. If enabled, the license-file attribute is not honored.
server-address	String	Specifies the IP address or host name of the license server.
certificate-file	File path	Specifies the client certificate used to connect to the license server. File name may include patterns containing a ‘*’ sign. If multiple files match the pattern, the most recent one gets used.
ca-file	File path	Specifies the certificate authority used to validate the license server.
channel-count	Integer	Specifies the number of channels to check out from the license server. If not specified or set to 0, either all available channels or a pool of channels will be checked based on the configuration of the license server.

Parent

Children

None.

Example

The example below defines a typical configuration which can be used to connect to a license server located, for example, at 10.0.0.1.

<license-server enable=”true” server-address=”10.0.0.1″ certificate-file=”unilic_client_*.crt” ca-file=”unilic_ca.crt” />

For further reference to the license server, visit

http://unimrcp.org/licserver

4. Configuration Steps

This section outlines common configuration steps.

4.1 Using Default Configuration

The default configuration should be sufficient for the general use.

4.2 Specifying Dialogflow Agent

A Dialogflow agent is associated by the corresponding Google Project ID.

https://dialogflow.com/docs/agents#settings

The Project ID is specified in the configuration file umsgdf.xml by the parameter project-id in the element <streaming-recognition>. For example:

<streaming-recognition interim-results=”true” start-of-input=”service-originated” language=”en-US” max-alternatives=”1″ project-id=“abcdefgh-ijklmn-123456” />

The Project ID can also be specified per individual MRCP RECOGNIZE request as a query input attribute to the built-in speech grammar. For example:

builtin:speech/transcribe?projectid=abcdefgh-ijklmn-123456

Since GDF 1.7.0 release, the Project ID can also be specified per individual MRCP RECOGNIZE request via the header field Vendor-Specific-Parameters. For example:

Vendor-Specific-Parameters: projectid=abcdefgh-ijklmn-123456

Since GDF 1.8.0 release, the Project ID can also be specified in SRGS XML grammar by means of predefined metadata. For example:

4.3 Specifying Recognition Language

Recognition language can be specified by the client per MRCP session by means of the header field Speech-Language set in a SET-PARAMS or RECOGNIZE request. Otherwise, the parameter language set in the configuration file umsgdf.xml is used. The parameter defaults to en-US.

For supported languages and their corresponding codes, visit the following link.

https://cloud.google.com/speech/docs/languages

Since GDF 1.8.0, the recognition language can also be set by the attribute xml:lang specified in the SRGS grammar.

<?xml version=”1.0″ encoding=”UTF-8″?> <grammar mode=”voice” root=”transcribe” version=”1.0″ xml:lang=”en-AU” xmlns=”http://www.w3.org/2001/06/grammar”> <meta name=”scope” content=”builtin”/> <rule id=”transcribe”><one-of/></rule> </grammar>

4.4 Specifying Sampling Rate

Sampling rate is determined based on the SDP negotiation. Refer to the configuration guide of the UniMRCP server on how to specify supported encodings and sampling rates to be used in communication between the client and server.

The native sampling rate with the linear16 audio encoding is used in gRPC streaming to the Google Dialogflow service.

4.5 Specifying Speech Input Parameters

While the default parameters specified for the speech input detector are sufficient for the general use, various parameters can be adjusted to better suit a particular requirement.

speech-start-timeout

This parameter is used to trigger a start of speech input. The shorter is the timeout, the sooner a START-OF-INPUT event is delivered to the client. However, a short timeout may also lead to a false positive.

speech-complete-timeout

This parameter is used to trigger an end of speech input. The shorter is the timeout, the shorter is the response time. However, a short timeout may also lead to a false positive.

Note that both events, an expiration of the speech complete timeout and an END-OF-SINGLE-UTTERANCE response delivered from the Google Dialogflow service, are monitored to trigger an end of speech input, on whichever comes first basis. In order to rely solely on an event delivered from the speech service, the parameter speech-complete-timeout needs to be set to a higher value.

vad-mode

This parameter is used to specify an operating mode of the Voice Activity Detector (VAD) within an integer range of [0 … 3]. A higher mode is more aggressive and, as a result, is more restrictive in reporting speech. The parameter can be overridden per MRCP session by setting the header field Sensitivity-Level in a SET-PARAMS or RECOGNIZE request. The following table shows how the Sensitivity-Level is mapped to the vad-mode.

Sensitivity-Level	Vad-Mode
[0.00 … 0.25)	0
[0.25 … 0.50)	1
[0.50 … 0.75)	2
[0.75 … 1.00]	3

4.6 Specifying DTMF Input Parameters

While the default parameters specified for the DTMF input detector are sufficient for the general use, various parameters can be adjusted to better suit a particular requirement.

dtmf-interdigit-timeout

This parameter is used to set an inter-digit timeout on DTMF input. The parameter can be overridden per MRCP session by setting the header field DTMF-Interdigit-Timeout in a SET-PARAMS or RECOGNIZE request.

dtmf-term-timeout

This parameter is used to set a termination timeout on DTMF input and is in effect when dtmf-term-char is set and there is a match for an input grammar. The parameter can be overridden per MRCP session by setting the header field DTMF-Term-Timeout in a SET-PARAMS or RECOGNIZE request.

dtmf-term-char

This parameter is used to set a character terminating DTMF input. The parameter can be overridden per MRCP session by setting the header field DTMF-Term-Char in a SET-PARAMS or RECOGNIZE request.

4.7 Specifying No-Input and Recognition Timeouts

noinput-timeout

This parameter is used to trigger a no-input event. The parameter can be overridden per MRCP session by setting the header field No-Input-Timeout in a SET-PARAMS or RECOGNIZE request.

input-timeout

This parameter is used to limit input (recognition) time. The parameter can be overridden per MRCP session by setting the header field Recognition-Timeout in a SET-PARAMS or RECOGNIZE request.

4.8 Specifying Speech Recognition Mode

Single Utterance Mode

By default, if the configuration parameter single-utterance is set to true, recognition is performed in the single utterance mode.

Continuous Recognition Mode

In the continuous speech recognition mode, when the configuration parameter single-utterance is set to false, recognition is terminated upon an expiration of the speech complete timeout.

Since GDF 1.13.0, the parameter single-utterance can be specified by the MRCP client per individual MRCP RECOGNIZE request as a query input attribute to the built-in speech grammar. For example:

builtin:speech/transcribe?single-utterance=false

Since GDF 1.13.0 release, the parameter single-utterance can also be specified in SRGS XML grammar by means of predefined metadata. For example:

4.9 Specifying Dialogflow Query Parameters

The optional Dialogflow QueryParameters can be specified by setting individual name/value parameters in the header field Vendor-Specific-Parameters. For example, the following header field specifies the timeZone, and geoLocation parameters.

Vendor-Specific-Parameters: timeZone=Europe/Paris; geoLocation={“latitude”: 48.85,”longitude”: ‎2.29}

Since GDF 1.9.0, query parameters can also be specified as input attributes to the built-in speech grammar. For example:

builtin:speech/transcribe?timeZone=Europe/Paris;geoLocation={“latitude”: 48.85,”longitude”: 2.29}

Since GDF 1.9.0, query parameters can also be specified in a tag element of an SRGS XML grammar. For example:

<grammar mode=”voice” root=”transcribe” version=”1.0″ xml:lang=”en-US” xmlns=”http://www.w3.org/2001/06/grammar”> <meta name=”scope” content=”builtin”/> <tag> {“timeZone“:”Europe/Paris”,”geoLocation“:{“latitude”: 48.85,”longitude”: 2.29}} </tag> <rule id=”main”> <one-of/ > </rule> </grammar>

4.10 Specifying Dialogflow Session ID

By default, the Dialogflow session identifier is maintained internally by the plugin based on the MRCP session identifier.

However, since GDF 1.8.0, the session (dialog) identifier can be specified by the MRCP client per individual MRCP RECOGNIZE request as a query input attribute to the built-in speech grammar. For example:

builtin:speech/transcribe?dialogid=123456

Since GDF 1.8.0 release, the session (dialog) identifier can also be specified in SRGS XML grammar by means of predefined metadata. For example:

4.11 Specifying Dialogflow Environment

Since GDF 1.15.0 release, separate Dialogflow environments are supported and can be specified in the configuration file umsgdf.xml by the parameter environment in the element <streaming-recognition>. For example:

<streaming-recognition interim-results=”true” start-of-input=”service-originated” language=”en-US” max-alternatives=”1″ environment=“production” />

The environment can also be specified per individual MRCP RECOGNIZE request as a query input attribute to the built-in speech grammar. For example:

builtin:speech/transcribe?environment=testing

The environment can also be specified in SRGS XML grammar by means of predefined metadata. For example:

4.12 Specifying Dialogflow Model

Since GDF 1.15.0 release, domain-specific models and model variants are supported and can be specified in the configuration file umsgdf.xml by the parameters model and model-variant in the element <streaming-recognition>. For example:

<streaming-recognition interim-results=”true” start-of-input=”service-originated” language=”en-US” max-alternatives=”1″ model=“phone_call” model-variant=“USE_ENHANCED” />

The model and model variant can also be specified per individual MRCP RECOGNIZE request as a query input attribute to the built-in speech grammar. For example:

builtin:speech/transcribe?model=phone_call;model-variant=USE_ENHANCED

The model and model variant can also be specified in SRGS XML grammar by means of predefined metadata. For example:

4.13 Maintaining Utterances

Saving of utterances is not required for regular operation and is disabled by default. However, enabling this functionality allows to save utterances sent to the Google Dialogflow service and later listen to them offline.

The relevant settings can be specified via the element utterance-manager.

save-waveforms

Utterances can optionally be recorded and stored if the configuration parameter save-waveforms is set to true. The parameter can be overridden per MRCP session by setting the header field Save-Waveforms in a SET-PARAMS or RECOGNIZE request.

purge-existing

This parameter specifies whether to delete existing waveforms on start-up.

max-file-age

This parameter specifies a time interval in minutes after expiration of which a waveform is deleted. If set to 0, there is no expiration time specified.

max-file-count

This parameter specifies the maximum number of waveforms to store. If the specified number is reached, the oldest waveform is deleted. If set to 0, there is no limit specified.

waveform-base-uri

This parameter specifies the base URI used to compose an absolute waveform URI returned in the header field Waveform-Uri in response to a RECOGNIZE request.

waveform-folder

This parameter specifies a path to the directory used to store waveforms in. The directory defaults to ${UniMRCPInstallDir}/var.

4.14 Maintaining Recognition Details Records

Producing of recognition details records (RDR) is not required for regular operation and is disabled by default. However, enabling this functionality allows to store details of each recognition attempt in a separate file and analyze them later offline. The RDRs ate stored in the JSON format.

The relevant settings can be specified via the element rdr-manager.

save-records

This parameter specifies whether to save recognition details records or not.

purge-existing

This parameter specifies whether to delete existing records on start-up.

max-file-age

This parameter specifies a time interval in minutes after expiration of which a record is deleted. If set to 0, there is no expiration time specified.

max-file-count

This parameter specifies the maximum number of records to store. If the specified number is reached, the oldest record is deleted. If set to 0, there is no limit specified.

record-folder

This parameter specifies a path to the directory used to store records in. The directory defaults to ${UniMRCPInstallDir}/var.

5. Recognition Grammars and Results

5.1 Using Built-in Speech Contexts

Pre-set built-in speech contexts can be referenced by the MRCP client in a RECOGNIZE request as follows:

builtin:speech/$id

Where $id is a unique string identifier of built-in speech context.

As a result, the Dialogflow QueryInput parameter is initialized to InputAudioConfig.

Speech contexts are defined in the configuration file umsgdf.xml. A speech context is assigned a unique string identifier and holds a list of phrases which can optionally be passed to the Google Dialogflow service to improve the recognition accuracy.

Below is a definition of a sample speech context booking:

<speech-context id=”booking”> <phrase> I would like to book a flight from New York to Rome with a ticket eligible for free cancellation</phrase> <phrase> I would like to book a one-way flight from New York to Rome</phrase> </speech-context>

Which can be referenced in a RECOGNIZE request as follows:

builtin:speech/booking

Since GDF 1.6.0, the prefixes builtin:speech and builtin:grammar can be used interchangeably as follows:

builtin:grammar/booking

For generic speech transcription, having no speech contexts defined, a pre-set identifier transcribe must be used.

builtin:speech/transcribe

The name of the identifier transcribe can be changed from the configuration file umsgdf.xml, since GDF 1.6.0.

Since GDF 1.8.0, a speech context can be referenced by means metadata in SRGS XML grammar. For example, the following SRGS grammar references a built-in speech context booking.

Where the root rule name identifies a speech context.

5.2 Using Built-in Event Grammars

Pre-set built-in event grammars can be referenced by the MRCP client in a RECOGNIZE request as follows:

builtin:event/$id

As a result, the Dialogflow QueryInput parameter will be initialized to EventInput, an event that specifies which intent to trigger, where $id must be replaced with the event name. For example:

builtin:event/welcome

Since GDF 1.8.0, an input event can be triggered by metadata in SRGS XML grammar. The following example is equivalent to the built-in grammar above.

Where the root rule name identifies an event name.

5.3 Using Built-in DTMF Grammars

Pre-set built-in DTMF grammars can be referenced by the MRCP client in a RECOGNIZE request as follows:

builtin:dtmf/$id

As a result, the Dialogflow QueryInput parameter will be initialized to EventInput, an event that specifies which intent to trigger, where $id must be replaced with the event name. For example:

builtin:dtmf/digits

Since GDF 1.8.0, built-in DTMF digits can also be referenced by metadata in SRGS XML grammar. The following example is equivalent to the built-in grammar above.

Where the root rule name identifies a built-in DTMF grammar.

5.4 Using Dynamic Speech Contexts

The MRCP client can also dynamically specify a speech context either

in a DEFINE-GRAMMAR request by further referencing the defined speech context in a RECOGNIZE request using the session URI scheme
or inline in a RECOGNIZE request

While composing a DEFINE-GRAMMAR or RECOGNIZE request containing speech context definition, the following should be considered.

The value of the header field Content-Id must be used as a unique string identifier of the speech context being defined.
The value of the header field Content-Type must be set to application/xml.
The message body must contain a definition of the speech context, composed based on the XML format of the element <speech-context>, specified in the configuration file umsgsr.xml. Note that the unique identifier of the speech context is set based on the header field Content-Id, as opposed to the attribute Id when loading from configuration.

Since GDF 1.8.0, a dynamic speech context can be specified by means of the <one-of> construct in SRGS XML grammar. For example:

<grammar mode=”voice” root=”booking” version=”1.0″ xml:lang=”en-US” xmlns=”http://www.w3.org/2001/06/grammar”> <meta name=”scope” content=”hint“/> <rule id=”booking”> <one-of> <item> I would like to book a flight from New York to Rome with a ticket eligible for free cancellation</item> <item> I would like to book a one-way flight from New York to Rome</item> <one-of> </rule> </grammar>

5.5 Retrieving Results

Results received from the Google Dialogflow service are transformed to a certain data structure and sent to the MRCP client in a RECOGNITION-COMPLETE event. The way results are composed can be adjusted via the <results> element in the configuration file umsgdf.xml.

NLSML Format

If the format attribute is set to standard, which is the default setting, then the header filed Content-Type is set to application/x-nlsml and the body of a RECOGNITION-COMPLETE event is set to an NSLML result composed as follows.

<input>

The <input> element in an NLSML result is set to the query_text field of the QueryResult structure received in a response to the StreamingDetectIntent request.

<instance>

By default, the <instance> element in an NLSML result is set to an XML representation of the QueryResult structure received in a response to the StreamingDetectIntent request. Since GDF 1.9.0, this behavior can be adjusted via the tag-format attribute, which accepts the following values.

semantics/xml

The default setting. The QueryResult structure is represented in XML.

semantics/json

The QueryResult is represented in JSON.

swi-semantics/xml

The QueryResult structure is set in an inner <SWI_meaning> element being represented in XML.

swi-semantics/json

The QueryResult structure is set in an inner <SWI_meaning> element being represented in JSON.

JSON Format

If the format attribute is set to json, then the header filed Content-Type is set to application/json and the body of a RECOGNITION-COMPLETE event is set to a JSON representation of the QueryResult structure received in a response to the StreamingDetectIntent request.

Since GDF 1.1.3.0, the format attribute can be specified by the MRCP client per individual MRCP RECOGNIZE request as a query input attribute to the built-in speech grammar. For example:

builtin:speech/transcribe?format=json

Since GDF 1.13.0 release, the format attribute can also be specified in SRGS XML grammar by means of predefined metadata. For example:

6. Monitoring Usage Details

The number of in-use and total licensed channels can be monitored in several alternate ways. There is a set of actions which can take place on certain events. The behavior is configurable via the element monitoring-agent, which contains two event handlers: usage-change-handler and usage-refresh-handler.

While the usage-change-handler is invoked on every acquisition and release of a licensed channel, the usage-refresh-handler is invoked periodically on expiration of a timeout specified by the attribute refresh-period.

The following actions can be specified for either of the two handlers.

6.1 Log Usage

The action log-usage logs the following data in the order specified.

The number of currently in-use channels.
The maximum number of channels used concurrently. Available since GDF 1.6.0.
The total number of licensed channels.

The following is a sample log statement, indicating 0 in-use, 0 max-used and 2 total channels.

[NOTICE] GDF Usage: 0/0/2

6.2 Update Usage

The action update-usage writes the following data to a status file umsgdf-usage.status, located by default in the directory ${UniMRCPInstallDir}/var/status.

The number of currently in-use channels.
The maximum number of channels used concurrently. Available since GDF 1.6.0.
The total number of licensed channels.
The current status of the license permit.
The license server alarm. Set to on, if the license server is not available for more than one hour; otherwise, set to off. This parameter is maintained only if the license server is used. Available since GDF 1.10.0.

The following is a sample content of the status file.

in-use channels: 0 max used channels: 0 total channels: 2 license permit: true licserver alarm: off

6.3 Dump Channels

The action dump-channels writes the identifiers of in-use channels to a status file umsgdf-channels.status, located by default in the directory ${UniMRCPInstallDir}/var/status.

7. Usage Examples

S->C:

MRCP/2.0 3043 RECOGNITION-COMPLETE 6 COMPLETE Channel-Identifier: 66122953e5be8b4a@speechrecog Completion-Cause: 000 success Waveform-Uri: <http://localhost/utterances/umsgdf-66122953e5be8b4a-6.wav>;size=35840;duration=1120 Content-Type: application/x-nlsml Content-Length: 2756 <?xml version=”1.0″?> <result> <interpretation grammar=”builtin:speech/transcribe” confidence=”1″> <instance> <query_text>two people</query_text> <action>room.reservation</action> <parameters> <duration> <amount>30</amount> <unit>min</unit> </duration> <guests>2</guests> <location> <city>Mountain View</city> </location> <time>2017-12-29T14:30:00-05:00</time> <date>2017-12-29T12:00:00-05:00</date> </parameters> <all_required_params_present>true</all_required_params_present> <fulfillment_text>Choose a room please.</fulfillment_text> <fulfillment_messages> <text> <text>Choose a room please.</text> </text> <platform>FACEBOOK</platform> </fulfillment_messages> <fulfillment_messages> <card> <title>I have these room options for you.</title> <buttons> <text>A</text> </buttons> <buttons> <text>B</text> </buttons> <buttons> <text>C</text> </buttons> </card> <platform>FACEBOOK</platform> </fulfillment_messages> <fulfillment_messages> <text> <text>Choose a room please.</text> </text> </fulfillment_messages> <output_contexts> <name>projects/abcdefgh-igklm-123456/agent/sessions/66122953e5be8b4a/contexts/roomreservation-followup</name> <lifespan_count>2</lifespan_count> <parameters> <duration_original>half an hour</duration_original> <time_original>2:30 p.m.</time_original> <guests_original>two people</guests_original> <location_original>Mountain View</location_original> <date_original>today</date_original> <guests>2</guests> <duration> <amount>30</amount> <unit>min</unit> </duration> <location> <city_object> </city_object> <city>Mountain View</city> <city_original>Mountain View</city_original> </location> <time>2017-12-29T14:30:00-05:00</time> <date>2017-12-29T12:00:00-05:00</date> </parameters> </output_contexts> <intent> <name>projects/abcdefgh-igklm-123456/agent/intents/e8f6a63e-73da-4a1a-8bfc-857183f71228</name> <display_name>room.reservation</display_name> </intent> <intent_detection_confidence>1</intent_detection_confidence> <diagnostic_info> </diagnostic_info> <language_code>en-us</language_code> </instance> <input mode=”speech”>two people</input> </interpretation> </result>

8. Sequence Diagrams

The following sequence diagrams outline common interactions between all the main components involved in a typical recognition session performed over MRCPv1 and MRCPv2 respectively.

8.1 MRCPv1

8.2 MRCPv2

9. Security Considerations

9.1 Network Connection

All the data transmitted to and received from the Google Dialogflow API is carried over a secure TLS v1.2 connection via the gRPC streaming. It is not even allowed to establish an unsecure connection to any of Google Cloud APIs in general.

Google Cloud

Microsoft Azure

Amazon Web Services

IBM Watson

Yandex Cloud

Miscellaneous

UniMRCP

Asterisk Modules

Google Dialogflow Plugin

1. Overview

1.1 Installation

1.2 Applicable Versions

2. Supported Features

2.1 MRCP Methods

2.2 MRCP Events

2.3 MRCP Header Fields

2.4 Grammars

2.5 Results

3. Configuration Format

3.1 Document

Attributes

Parent

Children

Example

3.2 Streaming Recognition

Attributes

Parent

Children

Example

3.3 Results

Availability

Attributes

Parent

Children

Example

3.4 Built-in Grammars

Availability

Attributes

Parent

Children

Example

3.5 Built-in Grammar

Availability

Attributes

Parent

Children

Example

3.6 Speech Contexts

Attributes

Parent

Children

Example

3.7 Speech Context

Attributes

Parent

Children

Example

3.8 Phrase

Attributes

Parent

Children

3.9 Speech and DTMF Input Detector

Attributes

Parent

Children

Example

3.10 Utterance Manager

Attributes

Parent

Children

Example

3.11 RDR Manager

Attributes

Parent

Children

Example

3.12 Monitoring Agent

Attributes

Parent

Children