The World Wide Web Consortium (W3C) created Speech Synthesis Markup Language (SSML) as an XML-based markup language to assist in generating natural-sounding synthesized speech. The Plivo Speak XML element supports the generation of SSML-based speech, powered by Amazon Polly. It supports 27 languages and more than 40 voices, and allows developers to  control pronunciation, pitch, and volume. Here‘s how SSML appears within Plivo Speak XML elements: 
<Response>
    <Speak voice="MAN">Go Green, Go Plivo</Speak> //Basic Text-to-Speech
    <Speak voice="Polly.Joey">
        <emphasis level="moderate">Go Green, Go Plivo</emphasis> //Text-to-Speech using SSML
    </Speak>
</Response>
To synthesize SSML speech on Plivo, specify one of the Amazon Polly voices in the voice attribute of Plivo’s <Speak> XML tag. Note that Polly voices must be namespaced with a Polly prefix. For example: 
<Response>
    <Speak voice="Polly.Joey">
        <emphasis level="moderate">Go Green, Go Plivo</emphasis>
    </Speak>
</Response>

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SSML tags

You can use these SSML tags within Plivo XML.
SSML TagActionDescription
<break>Add a pauseUse this tag to include a pause in the speech.
<emphasis>Emphasize wordsUse this tag to change the rate and voice of the speech.
<lang>Specify another language for specific wordsUse this tag to set the natural language of the text.
<p>Add a pause between paragraphsUse this tag to represent a paragraph.
<phoneme>Use phonetic pronunciationUse this tag to set phonetic pronunciation for specific text.
<prosody>Control volume, speaking rate, and pitchUse this tag to modify the volume, speaking rate, and pitch of the tagged text.
<s>Add a pause between sentencesUse this tag to represent a sentence. This adds a strong break before and after the tag.
<say-as>Control how special types of words are spokenUse this tag to describe how to interpret the text.
<sub>Pronounce acronyms and abbreviationsUse this tag to pronounce the specified words or phrases as different words or phrases.
<w>Improve pronunciation by specifying parts of speechUse this tag to customize the pronunciation of words by specifying the part of speech they are.
Note: Plivo doesn’t support these Amazon Polly-specific tags in Plivo XML:
  • <amazon:auto-breaths>
  • <amazon:effect name=“drc”>
  • <amazon:effect phonation=“soft”>
  • <amazon:effect vocal-tract-length>
  • <amazon: effect name=“whispered”>

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SSML voices

Plivo supports these Amazon Polly voices for use with Plivo XML:
LanguageFemaleMale
Australian English (en-AU)Polly.NicolePolly.Russell
Brazilian Portuguese (pt-BR)Polly.VitóriaPolly.Ricardo
Canadian French (fr-CA)Polly.Chantal-
Danish (da-DK)Polly.NajaPolly.Mads
Dutch (nl-NL)Polly.LottePolly.Ruben
French (fr-FR)Polly.Lea Polly.Celine
 Polly.Mathieu-
German (de-DE)Polly.VickiPolly.Hans
 Polly.Marlene-
Hindi (hi-IN)Polly.Aditi-
Icelandic (is-IS)Polly.DoraPolly.Karl
Indian English (en-IN)Polly.Raveena -
 Polly.Aditi-
Italian (it-IT)Polly.CarlaPolly.Giorgio
Japanese (ja-JP)Polly.MizukiPolly.Takumi
Korean (ko-KR)Polly.Seoyeon-
Mandarin Chinese (cmn-CN)Polly.Zhiyu-
Norwegian (nb-NO)Polly.Liv-
Polish (pl-PL)Polly.EwaPolly.Jacek
 Polly.MajaPolly.Jan
Portuguese - Iberic (pt-PT)Polly.InesPolly.Cristiano
Romanian (ro-RO)Polly.Carmen-
Russian (ru-RU)Polly.TatyanaPolly.Maxim
Spanish - Castilian (es-ES)Polly.ConchitaPolly.Enrique
Spanish - Mexican (es-MX)Polly.Mia-
US - Spanish (es-US)Polly.PenelopePolly.Miguel
 Polly.Lupe-Standard-
Swedish (sv-SE)Polly.Astrid-
Turkish (tr-TR)Polly.Filiz-
UK English (en-GB)Polly.AmyPolly.Brian
 Polly.Emma-
US English (en-US)Polly.JoannaPolly.Matthew
 Polly.SalliPolly.Justin
 Polly.KendraPolly.Joey
 Polly.Kimberly-
 Polly.Ivy-
Welsh (cy-GB)Polly.Gwyneth-
Welsh English (en-GB-WLS)-Polly.Geraint

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Character limit

To ensure quick synthesis, Plivo caps the length of text that can be synthesized in one <Speak> tag at 3,000 characters.

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Pricing

Support for SSML-based speech synthesis is currently in beta and free for all Plivo users. We expect to eventually charge for text-to-speech on the basis of the number of characters synthesized.

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SSML support in Plivo Server SDKs

SSML tags are supported in all of our Server SDKs.

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Example

This example use the Joey voice for US English (en-US). Use the <Speak voice> tag to specify the voice for your text.

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say-as

The say-as tag describes how to interpret the text. 
from flask import Flask, Response, request, url_for
from plivo import plivoxml

app = Flask(__name__)

@app.route("/ssml/", methods=["GET", "POST"])
def ssml():
    element = plivoxml.ResponseElement()
    response = (
        element.add(
            plivoxml.SpeakElement(content="The date is", voice="Polly.Joey", language="en-US")
            .add_say_as("20200626", interpret_as="date")
        )
        .to_string(False)
    )
    print(response)
    return Response(response, mimetype="text/xml")

if __name__ == "__main__":
    app.run(host="0.0.0.0", debug=True)
The rendered XML document would be: 
<Response>
    <Speak voice="Polly.Joey">The date is
      <say-as interpret-as="date">20200626</say-as>
    </Speak>
</Response>

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w

The w tag lets you customize the pronunciation of a word by specifying its part of speech. 
from flask import Flask, Response, request, url_for
from plivo import plivoxml

app = Flask(__name__)

@app.route("/ssml/", methods=["GET", "POST"])
def ssml():
    element = plivoxml.ResponseElement()
    response = (
        element.add(
            plivoxml.SpeakElement(content="The word", voice="Polly.Joey", language="en-US")
            .add_say_as("read", interpret_as="characters")
            .add_s("may be interpreted as either the present simple form")
            .add_w("read", role="amazon:VB")
            .add_s("or the past participle form")
            .add_w("read", role="amazon:VBD")
        )
        .to_string(False)
    )
    print(response)
    return Response(response, mimetype="text/xml")

if __name__ == "__main__":
    app.run(host="0.0.0.0", debug=True)
The rendered XML document would be: 
<Response>
    <Speak voice="Polly.Joey">The word
      <say-as interpret-as="characters">read</say-as>
      <s>
          may be interpreted as either the present simple form
      </s>
      <w role="amazon:VB">read</w>
      <s>or the past participle form</s>
      <w role="amazon:VBD">read</w>
    </Speak>
</Response>

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More examples

<Response>
    <Speak>I can speak in a 
      <prosody pitch="high">higher pitched voice</prosody>
      , or I can speak 
      <prosody pitch="low">in a lower pitched voice</prosody>
    </Speak>
</Response>

<Response>
    <Speak>I can speak 
      <prosody rate="x-slow">really slowly</prosody>
      , or  I can speak 
      <prosody rate="x-fast">really fast</prosody>
    </Speak>
</Response>

<Response>
    <Speak>I can also speak 
      <prosody volume="x-loud">very loudly</prosody>
      , or I can speak <prosody volume="x-soft">very quietly</prosody>. 
    </Speak>
</Response>