soundengine

Soundengine

A C++ addon for node.js that allows interacting with soundcards to e.g. play, record or process live microphone samples and send them back to the speakers. The module uses PortAudio to interact with the different host apis.

Prerequisites

Soundengine requires the shared portaudio library.

MacOS (via homebrew)

$ brew install portaudio fftw

Ubuntu (with apt-get)

$ sudo apt-get install libasound-dev libportaudio2 portaudio19-dev libfftw3-3 libfftw3-dev libfftw3-double3

Windows

...not supported yet.

Installation

$ npm i soundengine

Basic usage example

const soundengine = require('soundengine')

// Start live transmission from the default input device to the default output device at 22kHz
var engine = new soundengine.engine({sampleRate: 22050})

// Start recording
engine.startRecording()

// Apply a beep to the output when recording has stopped
engine.on('recording_stopped', () => {
    engine.beep({frequency: 300})
})

// Stop recording after 5 seconds
setTimeout(() => {
    // Stop the recording
    engine.stopRecording()

    // Playback of the recording
    engine.startPlayback()
}, 5000)

// Let the programm run forever
process.stdin.resume()

Api

Devices

To list the available devices

const soundengine = require('soundengine')
var devices = soundengine.getDevices()

Device properties

Engine options

Property	Type	Description
id	number	The device id to use in the engine options.
name	string	The device name.
defaultSampleRate	number	The default sample rate of the device.
maxInputChannels	number	The maximum supported input channels for this device.
maxOutputChannels	number	The maximum supported output channels for this device.
defaultLowInputLatency	number	See PortAudio docs
defaultLowOutputLatency	number	See PortAudio docs
defaultHighInputLatency	number	See PortAudio docs
defaultHighOutputLatency	number	See PortAudio docs

Engine methods

The engine class actually has almost all the methods of a nodejs EventEmitter to interact with the upcomming events. Furthermore these methods exist:

• loadRecording(file: string) - Loads a wave file that is then playable with startPlayback(). ⁽¹⁾
• startPlayback() - Starts playback of the last recording or loaded file.
• stopPlayback() - Stops playback.
• pausePlayback() - Pauses playback.
• isPlaying(): boolean - Returns if playback is active.
• startRecording() - Starts recording.
• stopRecording() - Stops recording.
• deleteRecording() - Deletes the recording that is currently held in memory.
• saveRecording(file: string) - Saves the recording to a wave file. ⁽²⁾
• isRecording(): boolean - Returns if recording is active.
• getRecordingSamples(): number - Return the number of total samples.
• getPlaybackPosition(): number - Returns the current sample index of the playback.
• getRecordingSampleAt(index: number): number - Returns a specific sample (between -1..1) at index.
• getPlaybackProgress(): number - Returns the relative playback progress (between 0..1).
• setPlaybackProgress(progress: number) - Sets the relative playback progress (between 0..1).
• beep(options?: beepOptions) - Applies a beep to the output.
• getVolume(): number - Returns the volume (between 0..1).
• setVolume(volume: number) - Sets the volume (between 0..1).
• getMute(): boolean - Returns if the output is muted or not.
• setMute(mute?: boolean) - Mutes or unmutes the output.
• getOptions(): engineOptions - Returns the current engine options.
• setOptions(options?: engineOptions) - Sets the engine options.
• synchronize() - Clears the internal buffer queues. If there for example is a large delay between the input and the output after initializing a new engine, calling synchronize could potentially minimize this delay.

Notes:
(1) Currently only 32bit floating point waves with the same samplerate of the current engine can be loaded (and the header will not be checked).
(2) The wave files are 32bit floating point.

Engine options

Option	Type	Default	Description
sampleRate	number	44100	Samples per second for each channel.
bufferSize	number	1024	The count of samples for each processing iteration.
inputChannels	number	1	The number of input channels.
outputChannels	number	1	The number of output channels (should equal inputChannels).
inputDevice	number	default input device	The id of the input device to use.
outputDevice	number	default output device	The id of the output device to use.
inputLatency	number	default high input latency	See PortAudio docs
outputLatency	number	default high output latency	See PortAudio docs

Beep options

Option	Type	Default	Description
duration	number	200	The duration of the applied beep in ms.
frequency	number	700	The frequency of the beep (sine wave).
level	number	1.0	The volume of the beep (between 0..1).

Engine events

EventName	Signature	Description
data	(inputBuffer: number[]): number[]	Will be called when a new inputBuffer is available to be processed and returned. Note: If the processing function takes to long to process the buffer you might experience dropouts.
info	({min: number[], max: number[]})	This event gets fired with messurements of the inputBuffer such as peaks (min) for every channel.
playback_started		Gets fired when playback started.
playback_stopped		Gets fired when playback stopped.
playback_paused		Gets fired when playback paused.
playback_progress	(progress: number)	Gets fired when playback progressed with the relative progress.
playback_finished		Gets fired when playback reached the end of the recording or loaded wave.
recording_loaded		Gets fired when the loadRecording loaded a file successfully.
recording_started		Gets fired when recording started.
recording_stopped		Gets fired when recording stopped.
recording_progress		Gets fired when recording progressed.
recording_saved		Gets fired when the recording was saved with saveRecording.
recording_deleted		Gets fired when the recording in memory was deleted.
beep_started		Gets fired when the beep method started apply a beep to the output.
beep_stopped		Gets fired when the beep method stopped apply a beep to the output.

Todos

• Implement fft stuff