Waveform Playlist

Inspired by Audacity, this project is a multiple track playlist editor written in ES2015 using the Web Audio API.

Load tracks and set cues (track cue in, cue out), fades (track fade in, fade out) and track start/end times within the playlist. I've written up some demos on github for the different audio fade types in the project.

See examples in action

(code for picture shown can be found in dist/examples/stem-tracks.html)

Try out the waveform editor!

Installation

npm install waveform-playlist

Basic Usage

Starter styles can be found in the npm package download at waveform-playlist/styles/playlist.scss

var WaveformPlaylist = require('waveform-playlist');

var playlist = WaveformPlaylist.init({
  samplesPerPixel: 3000,
  mono: false,
  waveHeight: 70,
  container: document.getElementById("playlist"),
  state: 'cursor',
  colors: {
    waveOutlineColor: '#E0EFF1',
    timeColor: 'grey',
    fadeColor: 'black'
  },
  controls: {
    show: true,
    width: 200
  },
  zoomLevels: [500, 1000, 3000, 5000]
});

playlist.load([
  {
    "src": "media/audio/Vocals30.mp3",
    "name": "Vocals"
  },
  {
    "src": "media/audio/BassDrums30.mp3",
    "name": "Drums",
    "start": 8.5,
    "fadeIn": {
      "duration": 0.5
    },
    "fadeOut": {
      "shape": "logarithmic",
      "duration": 0.5
    }
  },
  {
    "src": "media/audio/Guitar30.mp3",
    "name": "Guitar",
    "start": 23.5,
    "fadeOut": {
      "shape": "linear",
      "duration": 0.5
    },
    "cuein": 15
  }
]).then(function() {
  //can do stuff with the playlist.
});

Playlist Options

var options = {

  //webaudio api AudioContext
  ac: new (window.AudioContext || window.webkitAudioContext),

  //DOM container element REQUIRED
  container: document.getElementById("playlist"),

  //sample rate of the project. (used for correct peaks rendering)
  sampleRate: new (window.AudioContext || window.webkitAudioContext).sampleRate,

  //number of audio samples per waveform peak.
  //must be an entry in option: zoomLevels.
  samplesPerPixel: 4096,

  //whether to draw multiple channels or combine them.
  mono: true,

  //default fade curve type.
  fadeType: 'logarithmic', // (logarithmic | linear | sCurve | exponential)

  //whether or not to include the time measure.
  timescale: false,

  //control panel on left side of waveform
  controls: {
    //whether or not to include the track controls
    show: false,

    //width of controls in pixels
    width: 150
  },

  colors: {
    //color of the wave background
    waveOutlineColor: 'white',

    //color of the time ticks on the canvas
    timeColor: 'grey',

    //color of the fade drawn on canvas
    fadeColor: 'black'
  },

  //height in pixels of each canvas element a waveform is on.
  waveHeight: 128,

  //interaction state of the playlist
  state: 'cursor', // (cursor | select | fadein | fadeout | shift)

  //Array of zoom levels in samples per pixel.
  //Smaller numbers have a greater zoom in.
  zoomLevels: [512, 1024, 2048, 4096]
};

Track Options

{
  //a media path for XHR or a File object.
  "src": "media/audio/BassDrums30.mp3",

  //name that will display in the playlist control panel.
  "name": "Drums",

  //time in seconds relative to the playlist
  //ex (track will start after 8.5 seconds)
  //DEFAULT 0 - track starts at beginning of playlist
  "start": 8.5,

  //track fade in details
  "fadeIn": {
    //fade curve shape
    "shape": "logarithmic", // (logarithmic | linear | sCurve | exponential)

    //length of fade starting from the beginning of this track, in seconds.
    "duration": 0.5
  },

  //track fade out details
  "fadeOut": {
    //fade curve shape
    "shape": "logarithmic", // (logarithmic | linear | sCurve | exponential)

    //length of fade which reaches the end of this track, in seconds.
    "duration": 0.5
  }

  //where the waveform for this track should begin from
  //ex (Waveform will begin 15 seconds into this track)
  //DEFAULT start at the beginning - 0 seconds
  "cuein": 15,

  //where the waveform for this track should end
  //ex (Waveform will end at 30 second into this track)
  //DEFAULT duration of the track
  "cueout": 30,

  //interaction states allowed on this track.
  //DEFAULT - all true
  "states": {
    'cursor': true,
    'fadein': true,
    'fadeout': true,
    'select': true,
    'shift': true
  },

  //pre-selected section on track. 
  //ONLY ONE selection is permitted in a list of tracks, will take most recently set if multiple passed.
  //This track is marked as 'active'
  selected: {
    //start time of selection in seconds, relative to the playlist
    start: 5,

    //end time of selection in seconds, relative to the playlist
    end: 15
  }
}

Playlist Events

Waveform Playlist uses an instance of event-emitter to send & receive messages from the playlist.

var EventEmitter = require('event-emitter');
var WaveformPlaylist = require('waveform-playlist');

var playlist = WaveformPlaylist.init(
  {
    container: document.getElementById("playlist")
  },
  EventEmitter() //you can pass your own event emitter
);

//retrieves the event emitter the playlist is using.
var ee = playlist.getEventEmitter();

An example of using the event emitter to control the playlist can be found in /dist/js/examples/emitter.js

Events to Invoke

event	arguments	description
play	start:optional, end:optional	Starts playout of the playlist. Takes optional Number parameters in seconds start and end to play just an audio segment. start can be passed without an end to play to the end of the track.
pause	none	Pauses playout of the playlist.
stop	none	Stops playout of the playlist.
rewind	none	Stops playout if playlist is playing, resets cursor to the beginning of the playlist.
fastforward	none	Stops playout if playlist is playing, resets cursor to the end of the playlist.
record	none	Starts recording an audio track. Begins playout of other tracks in playlist if there are any.
zoomin	none	Changes zoom level to the next smallest entry (if one exists) from the array zoomLevels.
zoomout	none	Changes zoom level to the next largest entry (if one exists) from the array zoomLevels.
trim	none	Trims currently active track to the cursor selection.
statechange	(`cursor	select
fadetype	(`logarithmic	linear
newtrack	File	Loads File object into the playlist.
select	start, end, track:optional	Sets cursor selection from start to end optionally with active track track.

Events to Listen to

event	arguments	description
select	start, end, track	Cursor selection has occurred from start to end with active Track track.
timeupdate	playbackPosition	Sends current position of playout playbackPosition in seconds.
scroll	scrollLeft	Sends current position of scroll scrollLeft in seconds.
statechange	state	Sends current interaction state state.
shift	deltaTime, track	Sends deltaTime in seconds change for Track track

Tests

npm test

Development

npm start

http://localhost:8080/waveform-playlist/

This will build the jekyll site and startup the webpack dev server.

npm run jekyll:dev

This can be run to continuously build the jekyll pages as well if they are modified.

Credits

Originally created for the Airtime project at Sourcefabric

License

MIT License