Powered by Universal Speech Solutions LLC

MRCP

AWS Transcribe Plugin

Usage Guide

 

Revision: 1

Created: June 28, 2020

Last updated: June 28, 2020

Author: Arsen Chaloyan


 

Table of Contents

 

1 Overview.. 4

1.1 Installation. 4

1.2 Applicable Versions. 4

2 Supported Features. 5

2.1 MRCP Methods. 5

2.2 MRCP Events. 5

2.3 MRCP Header Fields. 5

2.4 Grammars. 6

2.5 Results. 6

3 Configuration Format 7

3.1 Document 7

3.2 Streaming Recognition. 8

3.3 Results. 10

3.4 Speech Contexts. 11

3.5 Speech Context 11

3.6 Phrase. 12

3.7 Utterance Manager 13

3.8 RDR Manager 14

3.9 Monitoring Agent 15

3.10 Usage Change Handler 16

3.11 Usage Refresh Handler 17

3.12 License Server 17

3.13 Credentials Profiles. 19

4 Configuration Steps. 20

4.1 Using Default Configuration. 20

4.2 Using with Polly. 20

4.3 Specifying AWS Credentials. 20

4.4 Specifying Recognition Language. 21

4.5 Specifying Sampling Rate. 21

4.6 Specifying Speech Input Parameters. 21

4.7 Specifying DTMF Input Parameters. 22

4.8 Specifying No-Input and Recognition Timeouts. 22

4.9 Specifying Vendor Specific Parameters. 22

4.10 Maintaining Utterances. 23

4.11 Maintaining Recognition Details Records. 24

5 Recognition Grammars and Results. 26

5.1 Using Built-in Speech Grammar 26

5.2 Using Built-in DTMF Grammars. 26

5.3 Retrieving Results. 26

6 Monitoring Usage Details. 27

6.1 Log Usage. 27

6.2 Update Usage. 27

6.3 Dump Channels. 28

7 Usage Examples. 29

7.1 Speech Recognition. 29

7.2 DTMF Recognition. 30

7.3 Speech and DTMF Recognition. 31

8 Sequence Diagram.. 33

9 References. 34

9.1 AWS Transcribe. 34

9.2 Specifications. 34

 

 

1       Overview

This guide describes how to configure and use the Amazon Web Services (AWS) Transcribe plugin to the UniMRCP server. The document is intended for users having a certain knowledge of AWS Transcribe and UniMRCP.

Asterisk / FreeSWITCH

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 1.7.0 and above

UniMRCP Transcribe 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 Transcribe 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

  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 Transcribe plugin is located in /opt/unimrcp/conf/umstranscribe.xml. The configuration file is written in XML.

3.1      Document

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

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.

credentials-file

File path

Specifies the AWS credentials file to use. File name may include patterns containing '*' sign. If multiple files match the pattern, the most recent one gets used.

credentials-provider

String

Specifies a credentials provider. If not initialized or set to custom, the custom credentials provider is used to read credentials from credentials-file. Otherwise, if set to default, the AWS default credentials provider chain is used, and credentials-file is not observer.

Otherwise, if set to sts, the AWS STS profile credentials provider is used, and credentials-file is not observer.

init-sdk

Boolean

Specifies whether to initialize AWS SDK upon loading of the plugin. Must be set to true by default. Set it to false, if another plugin using the same AWS SDK is loaded prior to this plugin.

shutdown-sdk

Boolean

Specifies whether to shut down AWS SDK upon unloading of the plugin. Must be set to true by default. Set it to false, if another plugin using the same AWS SDK is unloaded next to this plugin.

sdk-log-level

Integer

Specifies a log level of AWS SDK. If not initialized or set to 0, the SDK logs are disabled. Acceptable values are from 0 (OFF) to 6 (TRACE).

 

Parent

None.

Children

 

Name

Unit

Description

<streaming-recognition>

String

Specifies recognition parameters of streaming recognition.

<results>

String

Specifies parameters of recognition results set in RECOGNITION-COMPLETE events.

<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.

 

<umstranscribe license-file="umstranscribe_*.lic" credentials-file="*.json" credentials-provider="custom" init-sdk="true" shutdown-sdk="true">

</umstranscribe >

 

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://docs.aws.amazon.com/transcribe/latest/dg/websocket.html

single-utterance

Boolean

Specifies whether to detect a single spoken utterance or perform continuous recognition.

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).

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.

alternatives-below-threshold

Boolean

Specifies whether to return speech recognition result alternatives with the confidence score below the confidence threshold.

skip-unsupported-grammars

Boolean

Specifies whether to skip or raise an error while referencing a malformed or not supported grammar.

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.

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 defaults to 0 (disabled).

region

String

Specifies the AWS region.

vocabulary-name

String

Specifies an optional custom vocabulary.

https://docs.aws.amazon.com/transcribe/latest/dg/how-vocabulary.html

 

Parent

<umstranscribe>

Children

None.

Example

This is an example of streaming recognition element.

 

<streaming-recognition

language="en-US"

single-utterance="true"

interim-results="true"

skip-unsupported-grammars="true"

transcription-grammar="transcribe"

region=""

vocabulary-name=""

/>

3.3      Results

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

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.

confidence-format

String

Specifies the format of the confidence score to be returned (use "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)

 

Parent

<umstranscribe>

Children

None.

Example

This is an example of results element.

 

<results

format="standard"

indent="0"

confidence-format="auto"

/>

3.4      Speech Contexts

This element specifies a list of speech contexts.

Attributes

None.

Parent

<umstranscribe>

Children

<speech-context>

Example

The example below defines two speech contexts booking and directory.

 

<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-context id="directory" enable="true">

<phrase>call Steve</phrase>

<phrase>call John</phrase>

<phrase>dial 5</phrase>

<phrase>dial 6</phrase>

</speech-context>

</speech-contexts>

 

3.5      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.

language

String

The language the phrases are defined for.

scope

String

Specifies a scope of the speech context, which can be set to either hint or strict.

 

Parent

<speech-contexts>

Children

<phrase>

Example

This is an example of speech context element.

 

<speech-context id="directory" enable="true">

<phrase>call Steve</phrase>

<phrase>call John</phrase>

<phrase>dial 5</phrase>

<phrase>dial 6</phrase>

</speech-context>

 

3.6      Phrase

This element specifies a phrase in the speech context.

Attributes

 

Name

Unit

Description

tag

String

Specifies an optional arbitrary string identifier to be returned as an instance in the NLSML result, if the transcription result matches the phrase.

 

Parent

<speech-context>

Children

None.

 

This is an example of a speech context with phrases having tags specified.

 

<speech-context id="boolean" speech-complete="true" scope="strict" enable="true">

<phrase tag="true">yes</phrase>

<phrase tag="true">sure</phrase>

<phrase tag="true">correct</phrase>

<phrase tag="false">no</phrase>

<phrase tag="false">not sure</phrase>

<phrase tag="false">incorrect </phrase>

</speech-context>

 

3.7        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 'umstranscribe-', 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.

 

Parent

<umstranscribe>

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=""

/>

3.8        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 'umstranscribe-', 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.

 

Parent

<umstranscribe>

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=""

/>

3.9        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

<umstranscribe>

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="umstranscribe-channels.status"/>

</usage-refresh-handler >

 

</monitoring-agent>

 

3.10  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="umstranscribe-usage.status"/>

<dump-channels enable="false" status-file="umstranscribe-channels.status"/>

</usage-change-handler>

3.11  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="umstranscribe-usage.status"/>

<dump-channels enable="false" status-file="umstranscribe-channels.status"/>

</usage-refresh-handler>

 

3.12  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.

http-proxy-address

String

Specifies the IP address or host name of the HTTP proxy server, if used.

http-proxy-port

Integer

Specifies the port number of the HTTP proxy server, if used.

 

Parent

<umstranscribe>

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

 

3.13  Credentials Profiles

This element specifies a set of credentials profiles.

Attributes

None.

Parent

<umstranscribe>

Children

<credential-profile>

Example

This is an example of credentials profiles.

 

<credentials-profiles>

<credentials-profile name="default" duration="60" />

<credentials-profile name="dev" duration="60" />

<credentials-profile name="prod" duration="60" />

</credentials-profiles>

 

 

 

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      Using with Polly

This section must be skipped if the Transcribe plugin is used without the Polly plugin. However, in case both Polly and Transcribe plugins are loaded into the same instance of UniMRCP server, then the plugins need to be configured in a certain way to ensure the AWS SDK is initialized and shutdown only once.

 

<umspolly license-file="umspolly_*.lic" credentials-file="aws.credentials" init-sdk="true" shutdown-sdk="false">

<umstranscribe license-file="umstranscribe_*.lic" credentials-file="aws.credentials" init-sdk="false" shutdown-sdk="true">

 

4.3      Specifying AWS Credentials

IAM User

By default, the plugin uses credentials of an IAM user to consume AWS services. The procedure how to set up the credentials is documented in the installation guide. No further action is required if the IAM user is supposed to be used.

 

Default Credentials Provider Chain

The plugin can be configured to use the AWS default credentials provider chain, which in turn allows to derive an IAM role set on an instance UniMRCP server is running on. The behavior is controlled by the configuration attribute credentials-provider, which is supposed to be set to default to use the default credentials provider chain.

 

<umstranscribe license-file="umstranscribe_*.lic" credentials-file="aws.credentials" credentials-provider="default" sdk="true" shutdown-sdk="true">

 

Note, if the attribute credentials-provider is not set to custom, the attribute credentials-file is not observed.

STS Profile Credentials Provider

 

Since 1.4.0, the plugin can be configured to use the AWS STS profile credentials provider to assume a role. The behavior is controlled by the configuration attribute credentials-provider, which is supposed to be set to sts to use STSProfileCredentialsProvider.

 

<umstranscribe license-file="umstranscribe_*.lic" credentials-file="aws.credentials" credentials-provider="sts" sdk="true" shutdown-sdk="true">

 

4.4      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 umstranscribe.xml is used. The parameter defaults to en-US.

4.5      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 to stream audio data to the service.

4.6      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.

         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

 

4.7      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.

4.8      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.

4.9      Specifying Vendor Specific Parameters

The following parameters can optionally be specified by the MRCP client in SET-PARAMS, DEFINE-GRAMMAR and RECOGNIZE requests via the MRCP header field Vendor-Specific-Parameters.

Name

Unit

Description

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).

alternatives-below-threshold

Boolean

Specifies whether to return speech recognition result alternatives with the confidence score below the confidence threshold.

single-utterance

Boolean

Specifies whether to detect a single spoken utterance or perform continuous recognition.

speech-start-timeout

Time interval [msec]

Specifies how long to wait in transition mode before triggering a start of speech input event.

interim-result-timeout

Time interval [msec]

Specifies a timeout between interim results containing transcribed speech. If the timeout is elapsed, input is considered complete.

 

All the vendor-specific parameters can also be specified at the grammar-level via a built-in or SRGS XML grammar.

 

The following example demonstrates the use of a built-in grammar with the vendor-specific parameters alternatives-below-threshold and speech-start-timeout set to true and 100 correspondingly.

 

builtin:speech/transcribe?alternatives-below-threshold=true;speech-start-timeout=100

 

The following example demonstrates the use of an SRGS XML grammar with the vendor-specific parameters alternatives-below-threshold and speech-start-timeout set to true and 100 correspondingly.

 

<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"/>

<meta name="alternatives-below-threshold" content="true"/>

<meta name="speech-start-timeout" content="100"/>

<rule id="transcribe">

<one-of ><item>blank</item></one-of>

</rule>

</grammar>

 

4.10Maintaining 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 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.

4.11  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 Grammar

A pre-set built-in speech grammar can be referenced by the MRCP client in a RECOGNIZE request as follows:

 

builtin:speech/transcribe

 

5.2      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

 

5.3      Retrieving Results

Results received from the 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 umstranscribe.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 NLSML representation of received results.

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 received results.

 

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.

         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] Transcribe Usage: 0/0/2

 

6.2      Update Usage

The action update-usage writes the following data to a status file umstranscribe-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.

         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.

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 umstranscribe-channels.status, located by default in the directory ${UniMRCPInstallDir}/var/status.

 

7       Usage Examples

7.1      Speech Recognition

This example demonstrates how to reference a built-in speech transcription grammar in a RECOGNIZE request.

 

C->S:

 

MRCP/2.0 336 RECOGNIZE 1

Channel-Identifier: 6e1a2e4e54ae11e7@speechrecog

Content-Id: request1@form-level

Content-Type: text/uri-list

Cancel-If-Queue: false

No-Input-Timeout: 5000

Recognition-Timeout: 10000

Start-Input-Timers: true

Confidence-Threshold: 0.87

Save-Waveform: true

Content-Length: 25

 

builtin:speech/transcribe

 

S->C:

 

MRCP/2.0 83 1 200 IN-PROGRESS

Channel-Identifier: 6e1a2e4e54ae11e7@speechrecog

 

 

S->C:

 

MRCP/2.0 115 START-OF-INPUT 1 IN-PROGRESS

Channel-Identifier: 6e1a2e4e54ae11e7@speechrecog

Input-Type: speech

 

 

S->C:

 

MRCP/2.0 498 RECOGNITION-COMPLETE 1 COMPLETE

Channel-Identifier: 6e1a2e4e54ae11e7@speechrecog

Completion-Cause: 000 success

Waveform-Uri: <http://localhost/utterances/utter-6e1a2e4e54ae11e7-1.wav>;size=20480;duration=1280

Content-Type: application/x-nlsml

Content-Length: 214

 

<?xml version="1.0"?>

<result>

<interpretation grammar="builtin:speech/transcribe" confidence="1.00">

<instance>Book a room</instance>

<input mode="speech">Book a room</input>

</interpretation>

</result>

7.2      DTMF Recognition

This example demonstrates how to reference a built-in DTMF grammar in a RECOGNIZE request.

 

C->S:

 

MRCP/2.0 266 RECOGNIZE 1

Channel-Identifier: d26bef74091a174c@speechrecog

Content-Type: text/uri-list

Cancel-If-Queue: false

Start-Input-Timers: true

Confidence-Threshold: 0.7

Speech-Language: en-US

Dtmf-Term-Char: #

Content-Length: 19

 

builtin:dtmf/digits

 

S->C:

 

MRCP/2.0 83 1 200 IN-PROGRESS

Channel-Identifier: d26bef74091a174c@speechrecog

 

 

S->C:

 

MRCP/2.0 113 START-OF-INPUT 1 IN-PROGRESS

Channel-Identifier: d26bef74091a174c@speechrecog

Input-Type: dtmf

 

 

S->C:

 

MRCP/2.0 382 RECOGNITION-COMPLETE 1 COMPLETE

Channel-Identifier: d26bef74091a174c@speechrecog

Completion-Cause: 000 success

Content-Type: application/x-nlsml

Content-Length: 197

 

<?xml version="1.0"?>

<result>

<interpretation grammar="builtin:dtmf/digits" confidence="1.00">

<input mode="dtmf">1 2 3 4</input>

<instance>1234</instance>

</interpretation>

</result>

 

7.3      Speech and DTMF Recognition

This example demonstrates how to perform recognition by activating both speech and DTMF grammars. In this example, the user is expected to input a 4-digit pin.

 

C->S:

 

MRCP/2.0 275 RECOGNIZE 1

Channel-Identifier: 6ae0f23e1b1e3d42@speechrecog

Content-Type: text/uri-list

Cancel-If-Queue: false

Start-Input-Timers: true

Confidence-Threshold: 0.7

Speech-Language: en-US

Content-Length: 47

 

builtin:dtmf/digits?length=4

builtin:speech/transcribe

 

S->C:

 

MRCP/2.0 83 2 200 IN-PROGRESS

Channel-Identifier: 6ae0f23e1b1e3d42@speechrecog

 

 

S->C:

 

MRCP/2.0 115 START-OF-INPUT 2 IN-PROGRESS

Channel-Identifier: 6ae0f23e1b1e3d42@speechrecog

Input-Type: speech

 

 

S->C:

 

MRCP/2.0 399 RECOGNITION-COMPLETE 2 COMPLETE

Channel-Identifier: 6ae0f23e1b1e3d42@speechrecog

Completion-Cause: 000 success

Content-Type: application/x-nlsml

Content-Length: 214

 

<?xml version="1.0"?>

<result>

<interpretation grammar=" builtin:speech/transcribe" confidence="1.00">

<instance>one two three four</instance>

<input mode="speech">one two three four</input>

</interpretation>

</result>

 

8       Sequence Diagram

The following sequence diagram outlines common interactions between all the main components involved in a typical recognition session performed over MRCPv2.

9       References

9.1           AWS Transcribe

         What is Amazon Transcribe

         Using Amazon Transcribe Streaming with WebSockets

9.2           Specifications

         Speech Recognizer Resource

         NLSML Results