Orca Binding for Web

Orca Streaming Text-to-Speech Engine

Made in Vancouver, Canada by Picovoice

Orca is an on-device streaming text-to-speech engine that is designed for use with LLMs, enabling zero-latency voice assistants. Orca is:

• Private; All voice processing runs locally.
• Cross-Platform:
  • Linux (x86_64), macOS (x86_64, arm64), and Windows (x86_64)
  • Android and iOS
  • Chrome, Safari, Firefox, and Edge
  • Raspberry Pi (3, 4, 5)

Compatibility

• Chrome / Edge
• Firefox
• Safari

Restrictions

IndexedDB is required to use Orca in a worker thread. Browsers without IndexedDB support (i.e. Firefox Incognito Mode) should use Orca in the main thread.

Installation

Package

Using Yarn:

yarn add @picovoice/orca-web

or using npm:

npm install --save @picovoice/orca-web

AccessKey

Orca requires a valid Picovoice AccessKey at initialization. AccessKey acts as your credentials when using Orca SDKs. You can get your AccessKey for free. Make sure to keep your AccessKey secret. Signup or Login to Picovoice Console to get your AccessKey.

Usage

For the web packages, there are two methods to initialize Orca.

Public Directory

NOTE: Due to modern browser limitations of using a file URL, this method does not work if used without hosting a server.

This method fetches the model file from the public directory and feeds it to Orca. Copy a model file for the desired voice (male or female) into the public directory:

cp ${ORCA_MODEL_FILE} ${PATH_TO_PUBLIC_DIRECTORY}

Base64

NOTE: This method works without hosting a server, but increases the size of the model file roughly by 33%.

This method uses a base64 string of the model file and feeds it to Orca. Use the built-in script pvbase64 to base64 your model file:

npx pvbase64 -i ${ORCA_MODEL_FILE} -o ${OUTPUT_DIRECTORY}/${MODEL_NAME}.js

The output will be a js file which you can import into any file of your project. For detailed information about pvbase64, run:

npx pvbase64 -h

Orca Model

Orca saves and caches your model file in IndexedDB to be used by WebAssembly. Use a different customWritePath variable to hold multiple models and set the forceWrite value to true to force re-save a model file.

Either base64 or publicPath must be set to instantiate Orca. If both are set, Orca will use the base64 model.

const orcaModel = {
  publicPath: "${MODEL_RELATIVE_PATH}",
  // or
  base64: "${MODEL_BASE64_STRING}",

  // Optionals
  customWritePath: "orca_model",
  forceWrite: false,
  version: 1,
}

Initialize Orca

Create an instance of Orca on the main thread:

const orca = await Orca.create(
  "${ACCESS_KEY}",
  orcaModel
);

Or create an instance of Orca in a worker thread:

const orca = await OrcaWorker.create(
  "${ACCESS_KEY}",
  orcaModel
);

Streaming vs. Single Synthesis

Orca supports two modes of operation: streaming and single synthesis. In the streaming synthesis mode, Orca processes an incoming text stream in real-time and generates audio in parallel. In the single synthesis mode, the complete text needs to be known in advance and is synthesized in a single call to the Orca engine.

Custom Pronunciations

Orca allows the embedding of custom pronunciations in the text via the syntax: {word|pronunciation}. The pronunciation is expressed in ARPAbet phonemes, for example:

• "This is a {custom|K AH S T AH M} pronunciation"
• "{read|R IY D} this as {read|R EH D}, please."
• "I {live|L IH V} in {Sevilla|S EH V IY Y AH}. We have great {live|L AY V} sports!"

Orca Properties

To obtain the complete set of valid characters, call .validCharacters. To retrieve the maximum number of characters allowed, call .maxCharacterLimit. The sample rate of the generated Int16Array is .sampleRate.

Usage

Streaming Synthesis

To use streaming synthesis, call streamOpen to create an OrcaStream object.

const orcaStream = await orca.streamOpen();

Then, call synthesize on orcaStream to generate speech from a stream of text:

function* textStream(): IterableIterator<string> {
  ... // yield text chunks e.g. from an LLM response
}

for (const textChunk of textStream()) {
  const pcm = await orcaStream.synthesize(textChunk);
  if (pcm !== null) {
    // handle pcm
  }
}

The OrcaStream object buffers input text until there is enough to generate audio. If there is not enough text to generate audio, null is returned.

When done, call flush to synthesize any remaining text, and close to delete the orcaStream object.

const flushedPcm = orcaStream.flush();
if (flushedPcm !== null) {
  // handle pcm
}

orcaStream.close();

Single Synthesis

To use single synthesis, simply call synthesize directly on the Orca instance. The synthesize function will send the text to the engine and return the speech audio data as an Int16Array as well as the alignments metadata.

const { pcm, alignments } = await orca.synthesize("${TEXT}");

Speech Control

Orca allows for additional arguments to control the synthesized speech. These can be provided to streamOpen or one of the single mode synthesize methods:

• speechRate: Controls the speed of the generated speech. Valid values are within [0.7, 1.3]. A higher value produces speech that is faster, and a lower value produces speech that is slower. The default value is 1.0.

const synthesizeParams = {
  speechRate: 1.3,
};

// Streaming synthesis
const OrcaStream = await orca.streamOpen(synthesizeParams);

// Single synthesis
const result = await orca.synthesize("${TEXT}", synthesizeParams);

Alignments Metadata

Along with the raw PCM or saved audio file, Orca returns metadata for the synthesized audio in single synthesis mode. The OrcaAlignment object has the following properties:

• Word: String representation of the word.
• Start Time: Indicates when the word started in the synthesized audio. Value is in seconds.
• End Time: Indicates when the word ended in the synthesized audio. Value is in seconds.
• Phonemes: An array of OrcaPhoneme objects.

The OrcaPhoneme object has the following properties:

• Phoneme: String representation of the phoneme.
• Start Time: Indicates when the phoneme started in the synthesized audio. Value is in seconds.
• End Time: Indicates when the phoneme ended in the synthesized audio. Value is in seconds.

Clean Up

Clean up used resources by Orca or OrcaWorker:

await orca.release();

Terminate (Worker only)

Terminate OrcaWorker instance:

await orca.terminate();

Demo

For example usage refer to our Web demo application.