Orca Binding for Node.js

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 speech synthesis runs locally.
- Cross-Platform:
- Linux (x86_64), macOS (x86_64, arm64), and Windows (x86_64, arm64)
- Android and iOS
- Chrome, Safari, Firefox, and Edge
- Raspberry Pi (3, 4, 5)

Compatibility

- Node.js 18+
- Runs on Linux (x86_64), macOS (x86_64, arm64), Windows (x86_64, arm64), and Raspberry Pi (3, 4, 5).

Installation

``console
npm install @picovoice/orca-node
`

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

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.

Create an instance of the Orca engine:

`typescript
const { Orca } = require("@picovoice/orca-node");

const accessKey = "${ACCESS_KEY}"; // Obtained from the Picovoice Console (https://console.picovoice.ai/)

const orca = new Orca(accessKey);
`

Replace ${ACCESS_KEY} with your AccessKey obtained from Picovoice Console.

To synthesize a text stream, create an OrcaStream object and add text to it one-by-one:

`typescript
const stream = orca.streamOpen();

for (const textChunk of textGenerator()) {
const pcm = stream.synthesize(textChunk);
if (pcm !== null) {
// handle pcm
}
}
`

The textGenerator() function can be any stream generating text, for example an LLM response.
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.

To ensure smooth transitions between chunks, the stream.synthesize() function returns an audio chunk that only
includes the audio for a portion of the text that has been added.

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

`typescript
const flushedPcm = stream.flush();
if (flushedPcm !== null) {
// handle flushed pcm
}

stream.close()
`

If the complete text is known before synthesis, single synthesis mode can be used to generate speech in a single call to
Orca:

`typescript
const result = orca.synthesize("${TEXT}");

const alignments = orca.synthesizeToFile("${TEXT}", "${OUTPUT_PATH}");
`

Replace ${TEXT} with the text to be synthesized and ${OUTPUT_PATH} with the path to save the generated audio as a
single-channel 16-bit PCM WAV file.
In single synthesis mode, Orca returns metadata of the synthesized audio in the form of a list of OrcaAlignment
objects.

When done make sure to explicitly release the resources using:

`typescript
orca.release()
`

$3

Orca supports a wide range of English characters, including letters, numbers, symbols, and punctuation marks.
You can get a list of all supported characters by calling validCharacters().
Pronunciations of characters or words not supported by this list can be achieved with
custom pronunciations.

$3

Orca allows to embed 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!"

$3

Orca Streaming Text-to-Speech can synthesize speech in different languages and with a variety of voices,
each of which is characterized by a model file (.pv) located in lib/common.
The language and gender of the speaker is indicated in the file name.

To create an instance of the engine with a specific voice, use:

`typescript
const orca = new Orca(accessKey, { modelPath: "${MODEL_PATH}" });
`

and replace ${MODEL_PATH} with the path to the model file with the desired voice.

$3

Orca allows for keyword arguments to control the synthesized speech. They can be provided to the streamOpen
method or the single synthesis methods synthesize and synthesizeToFile:

- speechRate: Controls the speed of the generated speech. Valid values are within [0.7, 1.3]. A higher (lower) value
produces speech that is faster (slower). The default is 1.0.
- randomState: Sets the random state for sampling during synthesis. This can be used to ensure that the synthesized
speech is deterministic across different runs. Valid values are all non-negative integers. If not provided, a random
seed will be chosen and the synthesis process will be non-deterministic.

`typescript
const synthesizeParams = {
speechRate: 1.3,
randomState: 42,
};

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

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

$3

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

$3

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.

Demos

Orca Node.js demo package provides command-line utilities for
processing audio using Orca.