Amazon Polly: Turning Text into Lifelike Speech

In a world where digital interactions are increasingly conversational, giving your applications a voice can dramatically improve user engagement and accessibility. Amazon Polly is a cloud service that converts text into lifelike speech, allowing you to create talking applications and build entirely new categories of speech-enabled products with ease.

What is Amazon Polly?

Amazon Polly is a fully managed Text-to-Speech (TTS) service that uses advanced deep learning technologies to synthesize speech that sounds natural and human-like. Instead of building a complex speech synthesis engine from scratch, developers can send text to Polly's simple API and get back high-quality audio in a stream or as a standard file format like MP3.

The service is designed for a broad range of use cases, from creating audio versions of written content to providing dynamic voice prompts in call centers and giving a voice to IoT devices.

How It Works: A Simple API for Speech

The core workflow for using Amazon Polly is straightforward:

1. Provide Text: You send the text you want to synthesize to the Polly API. This can be plain text or text marked up with SSML for more control.

2. Select a Voice: You choose from a vast portfolio of voices across dozens of languages and regional accents.

3. Synthesize Speech: Polly's engine synthesizes the text into an audio stream.

4. Receive Audio: Your application receives the audio and can either play it back to the user in real-time or save it for future use.

Key Features of Amazon Polly

Polly is more than just a simple text-to-audio converter. It offers a rich set of features that provide fine-grained control and produce exceptionally high-quality speech.

A World of Voices: Standard vs. Neural TTS

This is one of Polly's most important features. You can choose between two types of voice technologies:

• Standard Voices: These use traditional concatenative TTS technology, where speech is constructed by piecing together recordings of a human voice. The result is clear and understandable.

• Neural Voices (NTTS): This newer technology produces a significant leap in speech quality. NTTS voices are more expressive and sound far more natural and human, with realistic intonation and cadence. Some neural voices even come with distinct speaking styles, such as a "Newscaster" or "Conversational" style, making them ideal for any user-facing application.

Fine-Grained Control with SSML

For ultimate control over the speech output, Polly supports the Speech Synthesis Markup Language (SSML). SSML is a standard XML-based markup language that allows you to modify various aspects of the speech. With SSML tags, you can:

• Add pauses of specific durations.

• Change the speaking rate, pitch, and volume.

• Emphasize specific words or phrases.

• Provide phonetic pronunciations for words.

Customizing Pronunciation with Lexicons

Every business has unique terminology—company names, acronyms, or specific jargon. With Custom Vocabularies (Lexicons), you can upload a file that tells Polly exactly how to pronounce these specific words, ensuring your brand is always represented correctly.

Synchronizing Speech with Animation using Speech Marks

Polly can generate metadata, known as Speech Marks, alongside the audio. This metadata provides timestamps for when each word, sentence, and SSML tag begins and ends in the audio stream. This feature is crucial for developers who need to synchronize visuals—such as an avatar's lip movements or highlighting text as it's being read—with the generated speech.

Common Use Cases and Applications

• Content Creation & Publishing: Automatically convert news articles, blog posts, or even entire books into audio format for podcasts and audiobooks.

• E-Learning: Create audio versions of educational materials, provide voice guidance in training applications, and build talking educational tools.

• Contact Centers: Power Interactive Voice Response (IVR) systems with a clear, friendly, and natural-sounding voice to guide customers.

• Accessibility: Make applications more accessible to individuals with visual impairments or reading disabilities by providing a text-to-speech option.

• Internet of Things (IoT): Give a voice to smart devices, appliances, and in-car navigation systems for a more intuitive user experience.