SSML Builder for TypeScript

A powerful, type-safe TypeScript library for building Speech Synthesis Markup Language (SSML) documents. Create expressive text-to-speech applications with Azure Speech Service and other SSML-compliant engines.

🔗 Related Project

Generate voices using SSML documents created with this library: Check out edge-tts - A text-to-speech generator that uses the SSML documents built with this library to create natural-sounding voices with Azure Speech Service.

✨ Features

• 🎯 Type-safe API - Full TypeScript support with comprehensive type definitions
• 🔗 Fluent Interface - Chainable methods for intuitive SSML document creation
• 🎙️ Azure Speech Service Support - Complete support for Azure-specific SSML extensions
• 📝 W3C SSML 1.0 Compliant - Follows the official SSML specification
• 🛡️ Auto-escaping - Automatic XML character escaping for security
• 🎨 Expressive Speech - Support for emotions, styles, and voice effects
• 📖 Well-documented - Extensive JSDoc documentation with examples
• ⚡ Zero Dependencies - Lightweight with no external dependencies

📦 Installation

npm install @andresaya/ssml-builder

or with yarn:

yarn add @andresaya/ssml-builder

or with pnpm:

pnpm add @andresaya/ssml-builder

🚀 Quick Start

import { SSMLBuilder } from '@andresaya/ssml-builder';

const ssml = new SSMLBuilder({ lang: 'en-US' })
  .voice('en-US-AvaNeural')
    .text('Hello world! ')
    .emphasis('This is important', 'strong')
    .break('500ms')
    .text(' Thank you.')
  .build();

console.log(ssml);
// Output: <speak version="1.0" xmlns="http://www.w3.org/2001/10/synthesis" 
//         xmlns:mstts="https://www.w3.org/2001/mstts" xml:lang="en-US">
//           <voice name="en-US-AvaNeural">
//             Hello world! <emphasis level="strong">This is important</emphasis>
//             <break time="500ms"/> Thank you.
//           </voice>
//         </speak>

📚 Usage Examples

Basic Text-to-Speech

const builder = new SSMLBuilder({ lang: 'en-US' });

const ssml = builder
  .voice('en-US-AvaNeural')
    .text('Welcome to our service.')
  .build();

Multiple Voices (Conversation)

const conversation = new SSMLBuilder({ lang: 'en-US' })
  .voice('en-US-AvaNeural')
    .text('Hello Andrew, how are you?')
  .voice('en-US-AndrewNeural')
    .text('I am doing great, thank you Ava!')
  .build();

Emotional Expression (Azure)

const emotional = new SSMLBuilder({ lang: 'en-US' })
  .voice('en-US-AvaNeural')
    .expressAs('I am so happy to see you!', { 
      style: 'cheerful',
      styledegree: '2'
    })
  .build();

Pronunciation Control

const pronunciation = new SSMLBuilder({ lang: 'en-US' })
  .voice('en-US-AvaNeural')
    .text('The company ')
    .phoneme('Azure', { 
      alphabet: 'ipa', 
      ph: 'æʒər' 
    })
    .text(' provides cloud services.')
  .build();

Prosody Modifications

const prosody = new SSMLBuilder({ lang: 'en-US' })
  .voice('en-US-AvaNeural')
    .prosody('This is spoken slowly and quietly', {
      rate: 'slow',
      volume: 'soft',
      pitch: 'low'
    })
  .build();

Say-As for Formatted Text

const formatted = new SSMLBuilder({ lang: 'en-US' })
  .voice('en-US-AvaNeural')
    .text('The date is ')
    .sayAs('2025-12-31', { 
      interpretAs: 'date',
      format: 'ymd'
    })
    .text(' and the amount is ')
    .sayAs('42.50', { 
      interpretAs: 'currency',
      detail: 'USD'
    })
  .build();

Background Audio

const withMusic = new SSMLBuilder({ lang: 'en-US' })
  .backgroundAudio({
    src: 'https://example.com/music.mp3',
    volume: '0.5',
    fadein: '2000ms',
    fadeout: '1000ms'
  })
  .voice('en-US-AvaNeural')
    .text('This speech has background music.')
  .build();

Structured Content

const structured = new SSMLBuilder({ lang: 'en-US' })
  .voice('en-US-AvaNeural')
    .paragraph(p => p
      .sentence(s => s
        .text('First sentence in the paragraph.')
      )
      .sentence(s => s
        .text('Second sentence with ')
        .emphasis('emphasis', 'strong')
        .text('.')
      )
    )
  .build();

Multilingual Support

const multilingual = new SSMLBuilder({ lang: 'en-US' })
  .voice('en-US-AvaMultilingualNeural')
    .text('Hello! ')
    .lang('es-ES', lang => lang
      .text('¡Hola! ')
    )
    .lang('fr-FR', lang => lang
      .text('Bonjour!')
    )
  .build();

🎯 API Reference

SSMLBuilder

The main builder class for creating SSML documents.

const builder = new SSMLBuilder(options: SSMLOptions);

Options

• lang (required): Language/locale code (e.g., 'en-US', 'es-ES')
• version (optional): SSML version (default: '1.0')
• xmlns (optional): XML namespace
• xmlnsMstts (optional): Microsoft TTS namespace

Methods

• .voice(name: string, effect?: string) - Add a voice element
• .backgroundAudio(options: BackgroundAudioOptions) - Add background audio
• .voiceConversion(url: string) - Add voice conversion (Azure preview)
• .build() - Generate the final SSML XML string

VoiceBuilder

Builder for voice elements with various speech modifications.

Methods

• .text(text: string) - Add plain text
• .audio(src: string, fallback?: string) - Add audio file
• .bookmark(mark: string) - Add bookmark for tracking
• .break(options?: BreakOptions | string) - Add pause
• .emphasis(text: string, level?: EmphasisLevel) - Add emphasis
• .expressAs(text: string, options: ExpressAsOptions) - Add emotional expression (Azure)
• .lang(locale: string, callback: Function) - Switch language
• .lexicon(uri: string) - Reference pronunciation lexicon
• .paragraph(callback: Function) - Add paragraph
• .phoneme(text: string, options: PhonemeOptions) - Specify pronunciation
• .prosody(text: string, options: ProsodyOptions) - Modify speech characteristics
• .sayAs(text: string, options: SayAsOptions) - Interpret formatted text
• .sentence(callback: Function) - Add sentence
• .silence(options: SilenceOptions) - Add silence (Azure)
• .sub(original: string, alias: string) - Text substitution

🛠️ Advanced Features

Custom Voice Profiles (Azure)

const customVoice = new SSMLBuilder({ lang: 'en-US' })
  .voice('en-US-AvaNeural')
    .ttsEmbedding('custom-profile-id', 'Custom voice text')
  .build();

Viseme Generation (Azure)

const withViseme = new SSMLBuilder({ lang: 'en-US' })
  .voice('en-US-AvaNeural')
    .viseme('redlips_front')
    .text('Text for lip-sync animation')
  .build();

Audio Duration Control (Azure)

const timedAudio = new SSMLBuilder({ lang: 'en-US' })
  .voice('en-US-AvaNeural')
    .audioDuration('10s')
    .text('This will be adjusted to last exactly 10 seconds.')
  .build();

📖 Documentation

Full API documentation is available at https://andresayac.github.io/ssml-builder

Generate documentation locally:

npm run docs

🧪 Testing

Run the test suite:

npm test

Run tests with coverage:

npm run test:coverage

🏗️ Building

Build the library:

npm run build

🤝 Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

1. Fork the repository
2. Create your feature branch (git checkout -b feature/AmazingFeature)
3. Commit your changes (git commit -m 'Add some AmazingFeature')
4. Push to the branch (git push origin feature/AmazingFeature)
5. Open a Pull Request

📝 License

This project is licensed under the MIT License - see the LICENSE file for details.

🙏 Acknowledgments

• Azure Speech Service for comprehensive SSML support
• W3C SSML Specification for the standard
• All contributors who have helped improve this library

🔗 Links

• GitHub Repository
• NPM Package
• Documentation
• Issues

📊 Project Status

This library is actively maintained. If you encounter any issues or have feature requests, please open an issue on GitHub.

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Made with ❤️ by andresayac