ear-pipe

Pipe audio streams to your ears

Dan Motzenbecker, MIT License

@dcmotz

Concept

ear-pipe is a duplex stream that allows you to pipe any streaming audio data to your ears (by default), handling any decoding automatically for most formats. You can also leverage this built-in decoding by specifying an output encoding and pipe the output stream somewhere else.

Installation

ear-pipe relies on the cross-platform audio utility SoX, so make sure that's installed first.

$ npm install --save ear-pipe

Usage

var EarPipe = require('ear-pipe'),
    ep      = new EarPipe(/* <type>, <bitrate>, <transcode-type> */);

When arguments are omitted (e.g. ep = new EarPipe;), the type defaults to 'mp3', the bitrate defaults to 16, and the third argument is null indicating that the pipe destination is your ears rather than a transcoded stream.

If your input encoding isn't mp3, make sure you set it to one of the formats supported by SoX:

8svx aif aifc aiff aiffc al amb au avr cdda cdr cvs cvsd cvu dat dvms f32 f4 f64
f8 fssd gsm gsrt hcom htk ima ircam la lpc lpc10 lu maud mp2 mp3 nist prc raw s1
s16 s2 s24 s3 s32 s4 s8 sb sf sl sln smp snd sndr sndt sou sox sph sw txw u1 u16
u2 u24 u3 u32 u4 u8 ub ul uw vms voc vox wav wavpcm wve xa

Examples

HTTP Stream

Let's pipe some number station audio to our ears right as it comes off the wire:

http.get(
  'http://ia700500.us.archive.org/12/items/ird059/tcp_d1_06_the_lincolnshire_poacher_mi5_irdial.mp3',
  function(res) { res.pipe(new EarPipe) });

If your connection and speakers work, you should hear it as it downloads.

Nondeterministic DJ Set

Let's send multiple audio streams to the same ear-pipe:

var ep      = new EarPipe,
    telstar = fs.createReadStream('./telstar.mp3'),
    cream   = fs.createReadStream('./cream.mp3');

http.get('http://127.0.0.1/sirens.mp3', function(res) { res.pipe(ep) });
telstar.pipe(ep);
cream.pipe(ep);

Since only one chunk passes through at a time, this DJ set should have plenty of cuts.

Transcode

Since we're decoding the audio on the fly, we can specify that we'd like to use that output for another destination besides our ears:

// null arguments mean defaults, true implies default output encoding (wav)
var ep    = new EarPipe(null, null, true),
    hotel = fs.createReadStream('./hotel.mp3');

hotel.pipe(ep).pipe(fs.createWriteStream('./hotel.wav'));

Or pipe to another process:

var ep      = new EarPipe('wav'),
    epTrans = new EarPipe(null, null, true),
    audio   = someStreamingNetworkData();

audio.pipe(epTrans).pipe(ep);
epTrans.pipe(anotherStreamingAudioConsumer);

Killing

Kill an ear-pipe instance by calling its kill() method. If you're interested in the underlying SoX process, access an instance's .process property.