node-alsa-cardinfo

A native module using N-API for determining the playback and/or capture capabilities of ALSA audio devices.

Useful when determining which parameters to pass to, for example, arecord or aplay.

This module depends on 'libasound-dev'.

Usage

Install and use as follows:
$ npm install node-alsa-cardinfo --save

Add require statement:
const cardInfo = require('node-alsa-cardinfo');

There are two methods, one for listing the available audio interfaces and one for getting the details about a specific device

LIST

The list gets a list of available audio devices as and array of objects. It does not take any parameters.

Return values

An array of objects will be returned like so:
If the device is input-only or output-only, the object will have a paramter io which will be set to either "Input", "Output" or "Bidirectional".

[ { name: 'null',
    desc:
     'Discard all samples (playback) or generate zero samples (capture)',
     io: 'Bidirectional' },
  { name: 'default:CARD=Device',
    desc: 'USB PnP Sound Device, USB Audio\nDefault Audio Device',
     io: 'Bidirectional' },
  { name: 'sysdefault:CARD=Device',
    desc: 'USB PnP Sound Device, USB Audio\nDefault Audio Device',
     io: 'Bidirectional' },
...
  { name: 'hw:CARD=ALSA,DEV=1',
    desc:
     'bcm2835 ALSA, bcm2835 IEC958/HDMI\nDirect hardware device without any conversions',
    io: 'Output' },
  { name: 'plughw:CARD=ALSA,DEV=0',
    desc:
     'bcm2835 ALSA, bcm2835 ALSA\nHardware device with all software conversions',
    io: 'Output' },
  { name: 'plughw:CARD=ALSA,DEV=1',
    desc:
     'bcm2835 ALSA, bcm2835 IEC958/HDMI\nHardware device with all software conversions',
    io: 'Output' } ]

GET

The get returns the details about a specific device as an object. e.g.
let info = cardInfo.get('hw:0,0',cardInfo.PLAYBACK);
let info = cardInfo.get('default', 1);
let info = cardInfo.get();

It takes two optional parameters which correspond to the card name (e.g. hw:0,0 or default) and the device direction ( whether the device is a playback or capture device).
The card name will default to hw if not specified and the device direction defaults to playback (0 or cardInfo.PLAYBACK).

Return values

If the device name requested is valid, an object will be returned of the form:

{ cardNum: 0,
  devNum: 0,
  subDevNum: 0,
  id: 'USB Audio',
  name: 'USB Audio',
  subName: 'subdevice #0',
  deviceType: 'HW',
  accessTypes: [ 'MMAP_INTERLEAVED', 'RW_INTERLEAVED' ],
  sampleFormats: [ 'S16_LE', 'S32_LE' ],
  channels: [ 2, 4, 6, 8 ],
  sampleRates: [ 44100, 48000, 96000, 192000 ] }

For more information on the returned values, consult the alsaaudio documentation.

If there is an error, an object with error and errorDetails properties will be returned, e.g.
{ error: 'cannot open device: hw:0,0 - Device or resource busy',
   errorDetails: 'pcm_hw.c:1590(snd_pcm_hw_open) open \'hw:0,0\' failed (16)' }