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

2.1 MRCP Methods

ü SPEAK

ü STOP

ü PAUSE

ü RESUME

ü BARGE-IN-OCCURRED

ü SET-PARAMS

ü GET-PARAMS

2.2 MRCP Events

ü SPEECH-MARKER

ü SPEAK-COMPLETE

2.3 MRCP Header Fields

ü Kill-On-Barge-In

ü Completion-Cause

ü Voice-Gender

ü Voice-Name

ü Prosody-Rate

ü Prosody-Volume

ü Speech-Language

ü Logging-Tag

ü Cache-Control

2.4 Speech Data

ü Plain text (text/plain)

ü SSML (application/ssml+xml or application/synthesis+ssml)

3 Supported Voices

The list of voices supported by AWS Polly is dynamically populated by the plugin on initial loading via an API call.

All the supported voices are listed in the following page:

https://docs.aws.amazon.com/polly/latest/dg/voicelist.html

4 Configuration Format

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

4.1 Document

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

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. Available since 1.3.0. Otherwise, if set to sts, the AWS STS profile credentials provider is used, and credentials-file is not observer. Available since 1.4.0.
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. Available since 1.1.0.
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. Available since 1.1.0.
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). Available since 1.4.0.

Parent

None.

Children

Name	Unit	Description
<synth-settings>	String	Specifies synthesis parameters.
<waveform-manager>	String	Specifies parameters of the waveform manager.
<sdr-manager>	String	Specifies parameters of the Synthesis Details Record (SDR) 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.

</ umspolly>

4.2 Synthesis Settings

This element specifies synthesis parameters.

Attributes

Name	Unit	Description
language	String	Specifies the default language to use, if not set by the client.
bypass-ssml	Boolean	Specifies whether transparently bypass or parse received content in order to determine voice parameters set in SSML.
voice-name	String	Specifies the default voice name. Can be overridden by client.
voice-gender	String	Specifies the default voice gender. Can be overridden by client.
voice-engine	String	Specifies the default voice engine (standard or neural). Can be overridden by client via vendor-specific parameters. Available since 1.5.0.
prosody-pitch	String	Specifies the default prosody pitch. Use either labels (x-low, low, medium, high, x-high) or an absolute value (600 Hz) or relative changes from the default pitch (+80 Hz or -20 Hz). Can be overridden by client in SSML. Available since 1.6.0.
prosody-rate	String	Specifies the default prosody rate. Use either labels (x-slow, slow, medium, fast, x-fast) or relative changes from the default rate as a percentage (+10% or -20%) or numeric values as a multiplier where 1 indicates no change. Can be overridden by client. Available since 1.6.0.
prosody-duration	String	Specifies the default prosody duration. Can be overridden by client in SSML. Available since 1.6.0.
prosody-volume	String	Specifies the default prosody volume. Use either labels (silent, x-soft, soft, medium, loud, x-loud) or relative changes from the default volume as a percentage (+10% or -20%) or numeric values in the range from 0 to 100. Can be overridden by client. Available since Azure SS 1.11.0.
thread-pool-size	Integer	Specifies the size of the executor thread pool provided by AWS SDK.
region	String	Specifies the AWS region.
proxy-host	String	Specifies the host name of HTTP proxy, if used. Available since 1.4.0.
proxy-port	Integer	Specifies the port number of HTTP proxy, if used. Available since 1.4.0.
proxy-username	String	Specifies the username employed for HTTP proxy authentication, if used. Available since 1.4.0.
proxy-password	String	Specifies the password employed for HTTP proxy authentication, if used. Available since 1.4.0.
caching	Boolean	Specifies whether to enable caching of synthesized waveforms. Available since 1.6.0.

Parent

Children

None.

Example

This is an example of synthesis parameters.

<synth-settings

language="en-US"

bypass-ssml="true"

voice-name=""

voice-gender=""

thread-pool-size="1"

region=""

4.3 Waveform Manager

This element specifies parameters of the waveform 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-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 'umspolly-', 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 1.5.0.

Parent

Children

None.

Example

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

<waveform-manager

save-waveforms="false"

purge-existing="false"

max-file-age="60"

max-file-count="100"

waveform-folder=""

4.4 SDR Manager

This element specifies parameters of the Synthesis Details Record (SDR) 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 'umspolly-', 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 1.5.0.

Parent

Children

None.

Example

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

<sdr-manager

save-records="false"

purge-existing="false"

max-file-age="60"

max-file-count="100"

waveform-folder=""

4.5 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="umspolly-channels.status"/>

</usage-refresh-handler >

</monitoring-agent>

4.6 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="umspolly-usage.status"/>

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

</usage-change-handler>

4.7 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="umspolly-usage.status"/>

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

</usage-refresh-handler>

4.8 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. Available since 1.4.0.
http-proxy-port	Integer	Specifies the port number of the HTTP proxy server, if used. Available since 1.4.0.

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

5 Configuration Steps

This section outlines common configuration steps.

5.1 Using Default Configuration

The default configuration should be sufficient for the general use.

5.2 Using with Lex

This section must be skipped if the Polly plugin is used without the Lex plugin. However, in case both Polly and Lex 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">

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

5.3 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

Since 1.3.0, 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.

Note, if the attribute credentials-provider is set to default, 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.

Since 1.7.0, different AWS credentials profiles can be configured per UniMRCP server profile. The profiles can also be created and referenced on-demand by the MRCP client via the header field Vendor-Specific-Parameters. The following parameters can be specified.

Name	Unit	Description
aws-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. Available since 1.7.0.
aws-credentials-provider	String	Specifies a credentials provider. Use one of: · custom for credentials read from the specified file · default for the AWS default credentials provider chain · sts for the AWS STS profile credentials provider Available since 1.7.0.
aws-credentials-profile	String	Specifies a credentials profile to reference and/or create. Available since 1.7.0.
aws-credentials-duration	Integer	Specifies a lifetime of the credentials profile to create. Available since 1.7.0.
aws-arn-role	String	Specifies an ARN role. Available since 1.7.0.
aws-region	String	Specifies an AWS region. Available since 1.7.0.

5.4 Specifying Synthesis Language

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

5.5 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. Either 8 or 16 kHz can be used by AWS Polly API for synthesis.

5.6 Specifying Voice Parameters

Global Settings

The default voice name and gender can be specified from the configuration file umspolly.xml using the voice-name and voice-gender attributes of the synth-settings element.

MRCP Header Fields

The voice name and gender can be specified by the MRCP client in SET-PARAMS and SPEAK requests.

· Voice-Name

This is an optional parameter indicating the name of the voice to use for synthesis.

· Voice-Gender

This is an optional parameter indicating the preferred gender of the voice to use for synthesis, which can be set to either male or female or neutral.

· Voice-Engine

This is an optional parameter indicating the voice engine to use for synthesis. The parameter is supposed to be set via the header field Vendor-Specific-Parameters by using the parameter name voice-engine and value standard or neural. Available since 1.5.0.

SSML Content

The voice name and gender can also be specified using the corresponding attributes of the voice element in SSML content. In order to parse and determine the parameters, the bypass-ssml attribute of the synth-settings element must be set to false in the configuration file umspolly.xml.

5.7 Specifying Prosody Parameters

The following prosody parameters can be specified by the MRCP client in SET-PARAMS and SPEAK requests.

· Prosody-Rate

This is an optional parameter indicating the speaking rate, which can be set to one of the following labels: x-slow, slow, medium, fast, x-fast, default.

· Prosody-Volume

This is an optional parameter indicating the speaking volume, which can be set to one of the following labels: silent, x-soft, soft, medium, loud, x-loud, default.

5.8 Specifying Speech Data

Speech data can be specified by the MRCP client in SPEAK requests using one of the following content types:

· plain/text

· application/ssml+xml (or application/synthesis+ssml)

5.9 Maintaining Waveforms

Collection of waveforms is not required for regular operation and is disabled by default. However, enabling this functionality allows to save synthesized speech received from the AWS Polly service and later listen to them offline.

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

· save-waveforms

Utterances can optionally be recorded and stored if the configuration parameter save-waveforms is set to true.

· 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-folder

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

5.10 Maintaining Synthesis Details Records

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

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

· save-records

This parameter specifies whether to save synthesis 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.

5.11 Using Cache

Since 1.6.0, synthesized waveforms can be stored and re-used for consecutive speech synthesis requests, when applicable. In order to use this functionality, the attribute caching of the element synth-settings must be set to true. The attribute defaults to false.

The lifetime and size of cached records are controlled by the attributes max-file-age and max-file-count of the element waveform-manager.

The cached records are persistent and populated on initial loading, unless the attribute purge-existing of the element waveform-manager is set to true.

The following speech synthesis parameters are observed while searching for a cached record.

· language

· voice-name

· voice-gender

· sampling-rate

· prosody-pitch

· prosody-contour

· prosody-range

· prosody-rate

· prosody-duration

· prosody-volume

· content

The following cache control directives are observed while searching for a cached record.

· max-age

· min-fresh

The cache control directives can be specified by the client per individual speech synthesis request via the MRCP header field Cache-Control. By default, no cache control directives are applied.

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] Polly Usage: 0/0/2

6.2 Update Usage

The action update-usage writes the following data to a status file umspolly-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. Available since 1.2.0.

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

7 Usage Examples

7.1 SSML

This examples demonstrates how to perform speech synthesis by using a SPEAK request with an SSML content.

C->S:

MRCP/2.0 309 SPEAK 1

Channel-Identifier: 4dde51f37d1a9546@speechsynth

Content-Type: application/ssml+xml

Voice-Age: 28

Content-Length: 163

<?xml version="1.0"?>

<p>

<s>Welcome to Uni MRCP.</s>

</p>

</speak>

S->C:

MRCP/2.0 83 1 200 IN-PROGRESS

Channel-Identifier: 4dde51f37d1a9546@speechsynth

S->C:

MRCP/2.0 122 SPEAK-COMPLETE 1 COMPLETE

Channel-Identifier: 4dde51f37d1a9546@speechsynth

Completion-Cause: 000 normal

7.2 Plain Text

This examples demonstrates how to perform speech synthesis by using a SPEAK request with a plain text content.

C->S:

MRCP/2.0 155 SPEAK 1

Channel-Identifier: 85667d0efbf95345@speechsynth

Content-Type: text/plain

Voice-Age: 28

Content-Length: 20

Welcome to Uni MRCP.

S->C:

MRCP/2.0 83 1 200 IN-PROGRESS

Channel-Identifier: 85667d0efbf95345@speechsynth

S->C:

MRCP/2.0 122 SPEAK-COMPLETE 1 COMPLETE

Channel-Identifier: 85667d0efbf95345@speechsynth

Completion-Cause: 000 normal

8 Sequence Diagram

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

9 References

9.1 AWS Polly

· What is Amazon Polly

· How It Works

· API Reference

9.2 Specifications

· Speech Synthesizer Resource

· SSML