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audio library

This library can be used to interact with balena's audio block to manipulate it's behavior at runtime. The library connects to the PulseAudio server running on the audio block and exposes the most common use cases with an easy to use interface.

Installation

Install by running:

npm install balena-audio

Usage

import BalenaAudio from 'balena-audio'

const audioBlock: BalenaAudio = new BalenaAudio(process.env.PULSE_SERVER || '192.168.90.166:4317')

audioBlock.setVolume(75)

audioBlock.on('play', async (sink: Sink) => {
	console.log('Playing audio on sink:', sink.name)
})

audioBlock.on('stop', async (sink: Sink) => {
	console.log('Audio has stopped playing on sink:', sink.name)
})

Class BalenaAudio

APIs

BalenaAudio

BalenaAudio(pulseServerAddress: string)

pulseServerAddress is the PulseAudio server address to connect to. The following formats are accepted:

  • TCP socket: tcp:<hostname>:<port> or <hostname>:<port>
  • UNIX socket: unix:/run/pulse/pulseaudio.socket

listen

audioBlock.listen()

Initiates a connection to the audio block. If the server is unreachable it will keep on trying until a connection succeeds or 10 minutes go by. This method needs to be called before calling any other method.

setVolume

audioBlock.setVolume(volume: number, sink?: string | number)

Sets the target sink's volume.

  • volume is desired volume in percentage (0-100).
  • (optional) sink is the sink to set the volume on, by it's PulseAudio sink name (alsa_output.usb-soundcard-1.analog-stereo) or index (0). If not specified the default sink will be used.

getVolume

audioBlock.getVolume(volume: number)

Gets the target sink's volume. Returns the result as a percentage (0-100).

  • (optional) sink is the sink to set the volume on, by it's PulseAudio sink name (alsa_output.usb-soundcard-1.analog-stereo) or index (0). If not specified the default sink will be used.

Events

play/stop

When the audio block starts or stops playing a sound on any sink, play or stop events are emitted. You can listen to them and attach callbacks to perform your own actions. A good use case for this is for example to turn on or off an external DAC that consumes a lot of power if always kept on.

audioBlock.on('play', async (sink: Sink) => {
	console.log('Playing audio on sink:', sink.name)
})

audioBlock.on('stop', async (sink: Sink) => {
	console.log('Audio has stopped playing on sink:', sink.name)
})