What?

This is a ffmpeg wrapper that will take in multiple audio files and combines them into a single file. Silent gaps will be put between the parts so that every new part starts from full second and there is at least 1 second pause between every part. The final file will be exported in mp3, ogg, ac3, m4a and caf(IMA-ADPCM) to support as many devices as possible. This tool will also generate a JSON file that is compatible with Howler.js or zynga/jukebox framework.

Why?

iOS, Windows Phone and some Android phones have very limited HTML5 audio support. They only support playing single file at a time and loading in new files requires user interaction and has a big latency. To overcome this there is a technique to combine all audio into single file and only play/loop certain parts of that file. zynga/jukebox is a audio framework that uses this technique. digitalfruit/limejs is a HTML5 game framework that includes Jukebox and lets you add audio to your games using audio sprites.

###Installation

npm install -g audiosprite

You can install FFmpeg and the ogg codecs on OSX using brew:

brew install ffmpeg --with-theora --with-libogg --with-libvorbis

Hints for Windows users

• You need to install Node.js
• Use Git Bash instead of Command Line or Powershell
• Download ffmpeg and include it in your path export PATH=$PATH:path/to/ffmpeg/bin
• IMA-ADPCM(the fastest iPhone format) will only be generated if you are using OSX.

###Usage

> audiosprite --help
info: Usage: audiosprite [options] file1.mp3 file2.mp3 *.wav
info: Options:
  --output, -o      Name for the output files.                                   [default: "output"]
  --path, -u        Path for files to be used on final JSON.                     [default: ""]
  --export, -e      Limit exported file types. Comma separated extension list.   [default: "ogg,m4a,mp3,ac3"]
  --format, -f      Format of the output JSON file (jukebox, howler, createjs).  [default: "jukebox"]
  --log, -l         Log level (debug, info, notice, warning, error).             [default: "info"]
  --autoplay, -a    Autoplay sprite name.                                        [default: null]
  --loop            Loop sprite name, can be passed multiple times.              [default: null]
  --silence, -s     Add special "silence" track with specified duration.         [default: 0]
  --gap, -g         Silence gap between sounds (in seconds).                     [default: 1]
  --minlength, -m   Minimum sound duration (in seconds).                         [default: 0]
  --bitrate, -b     Bit rate. Works for: ac3, mp3, mp4, m4a, ogg.                [default: 128]
  --vbr, -v         VBR [0-9]. Works for: mp3. -1 disables VBR.                  [default: -1]
  --samplerate, -r  Sample rate.                                                 [default: 44100]
  --channels, -c    Number of channels (1=mono, 2=stereo).                       [default: 1]
  --rawparts, -p    Include raw slices(for Web Audio API) in specified formats.  [default: ""]
  --help, -h        Show this help message.


> audiosprite --autoplay bg_loop --output mygameaudio bg_loop.wav *.mp3
info: File added OK file=bg_loop.wav
info: 1.25s silence gap added OK
info: File added OK file=click.mp3
info: 1.70s silence gap added OK
info: Exported caf OK file=mygameaudio.caf
info: Exported ac3 OK file=mygameaudio.ac3
info: Exported mp3 OK file=mygameaudio.mp3
info: Exported m4a OK file=mygameaudio.m4a
info: Exported ogg OK file=mygameaudio.ogg
info: Exported json OK file=mygameaudio.json
info: All done


> cat mygameaudio.json
{
  "resources": [
    "mygameaudio.caf",
    "mygameaudio.ac3",
    "mygameaudio.mp3",
    "mygameaudio.m4a",
    "mygameaudio.ogg"
  ],
  "spritemap": {
    "bg_loop": {
      "start": 0,
      "end": 3.75,
      "loop": true
    },
    "click": {
      "start": 5,
      "end": 5.3,
      "loop": false
    }
  },
  "autoplay": "bg_loop"
}

###API Usage

var audiosprite = require('audiosprite')

var files = ['file1.mp3', 'file2.mp3']
var opts = {output: 'result'}

audiosprite(files, opts, function(err, obj) {
  if (err) return console.error(err)

  console.log(JSON.stringify(obj, null, 2))
})

####Setting autoplay track

You can use --autoplay option to set a track that will start playing automatically. This track is then marked as autoplay and looping in the JSON. This syntax is Jukebox framework specific.

####Custom silent track

On some cases starting and pausing a file has bigger latency than just setting playhead position. You may get better results if your file is always playing. --silence <duration> option will generate extra track named silence that you can play instead of pausing the file.

####Usage with zynga/jukebox framework.

Generated JSON file can be passed straight into jukebox.Player constructor. Check out Jukebox documentation/demos for more info.

var settings = {/* JSON generated by audiosprite*/};
...
// This part needs to be in user event callback.
var myPlayer = new jukebox.Player(settings);
...
myPlayer.play('click');

####Usage with digitalfruit/limejs framework.

First generate LimeJS asset from the JSON file that you can require inside your code.

> bin/lime.py gensoy path/to/mygameaudio.json

Then use AudioMap class to play the file.

goog.require('lime.audio.AudioMap');
goog.require('lime.ASSETS.mygameaudio.json');

var audio = new lime.audio.AudioMap(lime.ASSETS.mygameaudio.json);
...
audio.play('click');

Don't forget to use the --rawparts=mp3 option to benefit from the LimeJS feature to automatically switch to Web Audio API when it's supported by the client.