Naudiodon LAME MP3

A Node.js addon that provides a wrapper around the PortAudio library, enabling an application to record and play audio with cross platform support. With this library, you can create node.js streams that can be piped to or from other streams, such as files and network connections. This library supports back-pressure.

This is a fork of node-portaudio, refactored by:

• changing from an event model to a stream model;
• linking to the v8 libraries through the Native Abstractions for Node.js (NAN) library to enable more portability between node versions.
• adding in local copies of libraries so that portaudio does not have to be installed preemptively.
• adding mp3 support

Little of the original remains but I am very grateful for Joe Ferner for the inspiration and framework to get started.

This library has been tested on MacOS X 10.13, Windows 10, Linux Ubuntu Trusty and Raspbian Jessie (armhf architecture). Compiled mp3 libraries have only been tested on MacOS 10.13.

Note: This is a server side library. It is not intended as a means to play and record audio via a browser.

Installation

Install Node.js for your platform. This software has been developed against the long term stable (LTS) release. For ease of installation with other node packages, this package includes a copy of the dependent PortAudio library and so has no prerequisites.

Naudiodon is designed to be required to use from your own application to provide async processing. For example:

npm install --save naudiodon

For Raspberry Pi users, please note that this library is not intended for use with the internal sound card. Please use an external USB sound card or GPIO breakout board such as the Pi-DAC+ Full-HD Audio Card.

Using naudiodon

Listing devices

To get list of supported devices, call the getDevices() function.

const portAudio = require('naudiodon');

console.log(portAudio.getDevices());

An example of the output is:

[ { id: 0,
    name: 'Built-in Microph',
    maxInputChannels: 2,
    maxOutputChannels: 0,
    defaultSampleRate: 44100,
    defaultLowInputLatency: 0.00199546485260771,
    defaultLowOutputLatency: 0.01,
    defaultHighInputLatency: 0.012154195011337868,
    defaultHighOutputLatency: 0.1,
    hostAPIName: 'Core Audio' },
  { id: 1,
    name: 'Built-in Input',
    maxInputChannels: 2,
    maxOutputChannels: 0,
    defaultSampleRate: 44100,
    defaultLowInputLatency: 0.00199546485260771,
    defaultLowOutputLatency: 0.01,
    defaultHighInputLatency: 0.012154195011337868,
    defaultHighOutputLatency: 0.1,
    hostAPIName: 'Core Audio' },
  { id: 2,
    name: 'Built-in Output',
    maxInputChannels: 0,
    maxOutputChannels: 2,
    defaultSampleRate: 44100,
    defaultLowInputLatency: 0.01,
    defaultLowOutputLatency: 0.002108843537414966,
    defaultHighInputLatency: 0.1,
    defaultHighOutputLatency: 0.012267573696145125,
    hostAPIName: 'Core Audio' } ]

Note that the device id parameter index value can be used as to specify which device to use for playback or recording with optional parameter deviceId.

Playing audio

Playing audio involves streaming audio data to an instance of AudioOutput.

const fs = require('fs');
const portAudio = require('naudiodon');

// Create an instance of AudioOutput, which is a WriteableStream
var ao = new portAudio.AudioOutput({
  channelCount: 2,
  sampleFormat: portAudio.SampleFormat16Bit,
  sampleRate: 48000,
  deviceId : -1, // Use -1 or omit the deviceId to select the default device
});

// handle errors from the AudioOutput
ao.on('error', err => console.error(err));

// Create a stream to pipe into the AudioOutput
// Note that this does not strip the WAV header so a click will be heard at the beginning
var rs = fs.createReadStream('steam_48000.wav');

// setup to close the output stream at the end of the read stream
rs.on('end', () => ao.end());

// Start piping data and start streaming
rs.pipe(ao);
ao.start();

Recording audio

Recording audio invovles reading from an instance of AudioInput.

const fs = require('fs');
const portAudio = require('../index.js');

// Create an instance of AudioInput, which is a ReadableStream
const ai = new portAudio.AudioInput({
  channelCount: 2,
  sampleFormat: portAudio.SampleFormat16Bit,
  sampleRate: 44100
  deviceId : -1 // Use -1 or omit the deviceId to select the default device
  bitRate: 320, // kbps
  lameQuality: 2, // Valid values: 2, 5, 7
});

// handle errors from the AudioInput
ai.on('error', err => console.error(err));

// Create a write stream to write out to a raw audio file
const ws = fs.createWriteStream('rawAudio.raw');

//Start streaming
ai.pipe(ws);
ai.start();

Note that this produces a raw audio file - wav headers would be required to create a wav file. However this basic example produces a file may be read by audio software such as Audacity, using the sample rate and format parameters set when establishing the stream.

To stop the recording, call ai.quit(). For example:

process.on('SIGINT', () => {
  console.log('Received SIGINT. Stopping recording.');
  ai.quit();
});

MP3

naudiodon-lame adds new properties to set in portAudio.AudioInput method: bitRate and lameQuality.

• bitRate: default value: 192
• lameQuality: default value: 5

lameQuality - internal algorithm selection. In a nutshell: Selecting cheap or expensive algorithms for decoding.:

| Value | Description | | ------------- | ------------- | | 2 | near-best quality, not too slow | | 5 | good quality, fast | | 7 | ok quality, really fast |

Troubleshooting

Linux - No Default Device Found

Ensure that when you compile portaudio that the configure scripts says "ALSA" yes.

Mac - Carbon Component Manager

You may see or have seen the following message during initilisation of the audio library on MacOS:

WARNING:  140: This application, or a library it uses, is using the deprecated Carbon Component Manager
for hosting Audio Units. Support for this will be removed in a future release. Also, this makes the host
incompatible with version 3 audio units. Please transition to the API's in AudioComponent.h.

A locally compiled version of the portaudio library is now included with the latest version of naudiodon that uses more up-to-date APIs from Apple. The portaudio team are aware of this issue.

Status, support and further development

Optimisation is still required for use with lower specification devices, such as Raspberry Pis.

Although the architecture of naudiodon is such that it could be used at scale in production environments, development is not yet complete. In its current state, it is recommended that this software is used in development environments and for building prototypes. Future development will make this more appropriate for production use.

Contributions can be made via pull requests and will be considered by the author on their merits. Enhancement requests and bug reports should be raised as github issues. For support, please contact Streampunk Media.

License

This software is released under the Apache 2.0 license. Copyright 2017 Streampunk Media Ltd.

This software uses libraries from the PortAudio project. The license terms for PortAudio are stated to be an MIT license. Streampunk Media are grateful to Ross Bencina and Phil Burk for their excellent library.