Awesome Open Source
Awesome Open Source

Waveform Playlist

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

If you would like to help support the project please buy me a coffee using Ko-fi DONATIONS ❤️ ☕️

If you are looking for additional support or features, please consider pledging on PATREON to help the work!

npm Build Status Coverage Status

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.

Screenshot (code for picture shown can be found in ghpages/_examples/04stemtracks.html)

Screenshot (code for picture shown can be found in ghpages/_examples/13annotations.html)

Browser Support

Waveform Playlist requires webaudio in the browser to function correctly: Can I Use?


npm install waveform-playlist

  • If you want to download and run the already compiled website, navigate to folder /dist and run python -m SimpleHTTPServer 8000. The website will be available at localhost:8000/waveform-playlist.

Basic Usage

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

import WaveformPlaylist from 'waveform-playlist';

var playlist = WaveformPlaylist({
  samplesPerPixel: 3000,
  mono: true,
  waveHeight: 70,
  container: document.getElementById("playlist"),
  state: "cursor",
  colors: {
    waveOutlineColor: "#E0EFF1",
    timeColor: "grey",
    fadeColor: "black"
  controls: {
    show: false,
    width: 150,
  zoomLevels: [500, 1000, 3000, 5000]

      src: "media/audio/Vocals30.mp3",
      name: "Vocals",
      gain: 0.5
      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

  // 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,

  // enables "exclusive solo" where solo switches between tracks
  exclSolo: false,

  // 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,
    // whether to render the widget or not in the controls panel.
    widgets: {
      // Mute & solo button widget
      muteOrSolo: true,
      // Volume slider
      volume: true,
      // Stereo pan slider
      stereoPan: true,
      // Collapse track button
      collapse: true,
      // Remove track button
      remove: true,

  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
  // (cursor | select | fadein | fadeout | shift)
  state: "cursor",

  // (line | fill)
  seekStyle: "line",

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

  // Whether to automatically scroll the waveform while playing
  isAutomaticScroll: false,

  // configuration object for the annotations add on.
  annotationList: {
    // Array of annotations in [Aeneas]( JSON format
    annotations: [],

    // Whether the annotation texts will be in updateable contenteditable html elements
    editable: false,

    // User defined functions which can manipulate the loaded annotations
    controls: [
        // class names for generated <i> tag separated by '.'
        class: "fa.fa-minus",

        // title attribute for the generated <i> tag
        title: "Reduce annotation end by 0.010s",

        // function which acts on the given annotation row
        // when the corresponding <i> is clicked.
        action: (annotation, i, annotations, opts) => {
          // @param Object annotation - current annotation
          // @param Number i - index of annotation
          // @param Array annotations - array of annotations in the playlist
          // @param Object opts - configuration options available
          //      - opts.linkEndpoints

    // If false when clicking an annotation id segment
    // playback will stop after segment completion.
    isContinuousPlay: false,

    // If true annotation endpoints will remain linked when dragged
    // if they were the same value before dragging started.
    linkEndpoints: false

Track Options

  // a media path for XHR, a Blob, a File, or an AudioBuffer object.
  src: 'media/audio/BassDrums30.mp3',

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

  // volume level of the track between [0-1]
  gain: 1,

  // whether the track should initially be muted.
  muted: false,

  // whether the track should initially be soloed.
  soloed: false,

  // 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
    // (logarithmic | linear | sCurve | exponential)
    shape: 'logarithmic',

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

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

    //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,

  // custom class for unique track styling
  customClass: 'vocals',

  // custom background-color for the canvas-drawn waveform
  waveOutlineColor: '#f3f3f3',

  // 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,

  // value from -1 (full left pan) to 1 (full right pan)
  stereoPan: 0

Playlist Events

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

import EventEmitter from "event-emitter";
import WaveformPlaylist from "waveform-playlist";

var playlist = WaveformPlaylist(
    container: document.getElementById("playlist")

  // 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.
clear none Stops playout if playlist is playing, removes all tracks from 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 / fadein / fadeout / shift Changes interaction state to the state given.
fadetype logarithmic / linear / sCurve / exponential Changes playlist default fade type.
newtrack File Loads File object into the playlist.
volumechange volume, track Set volume of track to volume (0-100)
mastervolumechange volume Set a new master volume volume (0-100)
select start, end, track:optional Seek to the start time or start/end selection optionally with active track track.
startaudiorendering wav / buffer Request for a downloadable file or web Audio buffer that represent the current work
automaticscroll true/false Change property isAutomaticScroll.
continuousplay true/false Change property isContinuousPlay.
linkendpoints true/false Change property linkEndpoints.
annotationsrequest none Requests to download the annotations to a json file.
stereopan panvalue, track Set pan value of track to panvalue (-1-1)

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
mute track Mute button has been pressed for track
solo track Solo button has been pressed for track
removeTrack track Remove button has been pressed for track
changeTrackView track, opts Collapse button has been pressed for track
volumechange volume, track Volume of track has changed to volume (0-100)
mastervolumechange volume Master volume of the playlist has changed to volume (0-100)
audiorequeststatechange state, src Loading audio src (string or File) is now in state state (Number)
loadprogress percent, src Loading audio src has loaded percent percent (0-100)
audiosourcesloaded none Audio decoding has finished for all tracks
audiosourcesrendered none Tracks are rendered to the playlist
audiosourceserror err Error thrown while loading tracks
finished none Event fired when cursor ( while playing ) reaches the end (maximum duration)
audiorenderingfinished type, data Return the result of the rendering in the desired format. type can be buffer or wav and can be used to dertermine the data type. When type is wav, data is a blob object that represent the wav file.
stereopan panvalue, track Pan value of track has been changed to panvalue


npm test

Development without example changes

npm install && npm start

This will install dependencies and start the webpack server.

Development with example changes

gem install jekyll

Jekyll is needed if changes to the example pages will be done.

npm install && npm run dev

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


Originally created for the Airtime project at Sourcefabric

The annotation plugin has been sponsored by a fond Italian TED volunteer transcriber, hoping to make easier and more fun the transcription process of TEDx talks.


Wanting to see a particular feature or blog post? Consider supporting Waveform Playlist!


MIT License

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