Audio Output
Node.js Quick Start

Platforms

• Linux (x86_64)
• macOS (x86_64, arm64)
• Windows (x86_64)
• Raspberry Pi (3, 4, 5)

Requirements

• Node.js 16+
• npm

Quick Start

Setup

1. Install Node.js.

2. Install the pvspeaker-node npm package:

npm install @picovoice/pvspeaker-node

Usage

Initialize and start PvSpeaker:

const { PvSpeaker } = require("@picovoice/pvspeaker-node");

const sampleRate = 22050;
const bitsPerSample = 16;
const speaker = new PvSpeaker(sampleRate, bitsPerSample);

speaker.start()

Write PCM data to the speaker:

function getNextAudioFrame(): ArrayBuffer {
  //
}

const writtenLength = speaker.write(getNextAudioFrame())

Note: the write() method only writes as much PCM data as the internal circular buffer can currently fit, and returns the number of samples that were successfully written.

When all frames have been written, run flush() to wait for all buffered PCM data (i.e. previously buffered via write()) to be played:

speaker.flush()

Note: calling flush() with PCM data as an argument will both write that PCM data and wait for all buffered PCM data to finish.

function getRemainingAudioFrames(): ArrayBuffer {
  //
}

speaker.flush(getRemainingAudioFrames())

To stop the audio output device, run stop():

speaker.stop()

Once you are done (i.e. no longer need PvSpeaker to write and/or play PCM), free the resources acquired by PvSpeaker by calling release(). You do not have to call stop() before release():

speaker.release()

Selecting an Audio Device

To get a list of available audio devices:

const devices = PvSpeaker.getAvailableDevices()

The index of the device in the returned list can be used in the constructor() to select that device for audio output:

const sampleRate = 22050;
const bitsPerSample = 16;
const deviceIndex = 2;

const speaker = new PvSpeaker(sampleRate, bitsPerSample, { deviceIndex });

Demo

For the PvSpeaker Node.js SDK, we offer a demo application that demonstrates how use PvSpeaker to play audio from an audio file (.wav).

Setup

Install the PvSpeaker demo package:

npm install -g @picovoice/pvspeaker-node-demo

This package installs command-line utilities for the PvSpeaker Node.js demo.

Usage

Use the --help flag to see the usage options for the demo:

pvspeaker-node-demo --help

Run the following to see what devices are available for audio playback:

pvspeaker-node-demo --show_audio_devices

Run the demo with the desired audio device (or -1 for the default one) and an input file path:

pvspeaker-node-demo --audio_device_index ${DEVICE_INDEX} --input_wav_path ${INPUT_WAV_PATH}

For more information about our PvSpeaker demo for Node.js, head over to our GitHub repository.

Resources