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Features and Capabilities

This section highlights additional features and capabilities of the Voice Gateway.

SSML (Speech Synthesis Markup Language)

Using SSML allows developers to control aspects of speech synthesis such as pronunciation, volume, pitch, and rate of speech. Here's a guide on how to use SSML effectively:

Understanding SSML Basics

  • SSML is an XML-based markup language used to control text-to-speech synthesis.
  • It provides tags to control various aspects of speech synthesis, including pronunciation, prosody, volume, and more.
  • SSML is supported by many speech synthesis systems, including Amazon Polly, Google Text-to-Speech, and others.

Basic SSML Tags

  • <speak>: This is the root element of an SSML document and indicates the start and end of the speech content.
  • <break>: Inserts a pause into the speech synthesis. You can specify the duration of the pause using the time attribute.
  • <emphasis>: Emphasizes a portion of the text. You can specify the level of emphasis using the level attribute.
  • <prosody>: Modifies aspects of speech such as pitch, rate, and volume. Attributes include pitch, rate, and volume.
  • <phoneme>: Specifies the pronunciation of a word using phonetic alphabet symbols.
  • <say-as>: Indicates how a particular piece of text should be pronounced, such as numbers, dates, or currency.
  • <audio>: Embeds audio files into the speech output.

Using SSML in Code

When using SSML in your code, wrap the SSML markup within <speak> tags.

Example: 

<speak>

    Here is a number <w role='amazon:VBD'>read</w>

    as a cardinal number:

    <say-as interpret-as='cardinal'>12345</say-as>.

    Here is a word spelled out:

    <say-as interpret-as='spell-out'>hello</say-as>.

</speak>

Voice Tag Support

Support For Voice Elements in SSML

In the speak tag, follow below-mentioned steps:

  1. Empty speak tag without attributes <speak>
    1. In this case, Voice Gateway will construct voice and language elements on its own based on values supplied in Call control params.
  2. Customised speak tag with attributes <speak version="1.0" xml:lang="en-US" xmlns="W3C Speech Synthesis namespace ">
    1. In this case, Voice Gateway will send the SSML without any modifications to the TTS engine. Follow option 2 and the voice element will work.

Example: 

<speak version="1.0" xml:lang="en-US" xmlns="http://www.w3.org/2001/10/synthesis"><voice name="en-US-AvaNeural">Hi, I'm eBay's automated phone assistant. Let me know in a few words how I can help.</voice></speak>