waveplayer

An HTML5 based audio player with a waveform view.

Author: Michael Dzjaparidze

License: MIT

Table of Contents

• Requirements
• Installation
• API
  • Factory
  • Player
  • Playlist
  • View
  • Strategies
• Examples
  • Player
  • Playlist
  • View

Requirements

In order to minimise waveform drawing times it is adviced to supply waveform amplitude data yourself using either the data or JSON strategies. There exist a number of tools for extracting waveform data in JSON format from an audio file; wav2json or py-wav2json can be used for instance. It is enough to provide a single array of floating point values. If the JSON contains a collection of name / value pairs only the first name / value pair will be used.

Installation

This package is available through npm:

npm install --save waveplayer

After that the package may be directly included using a <script> tag:

<script src="path-to-waveform-js/waveplayer.js"></script>

or may be imported in your own scripts files:

import { Player, Playlist, View } from 'waveplayer';

API

The constructor of each class takes an option object as an argument. See the Options section for more information on which options are available. Some options are required (currently only the container option).

Factory

A convenience class for building player or playlist instances without having to explicitly specify any dependencies yourself.

player = Factory.createPlayer(options);

Create a new player instance.

Argument	Example	Type	Required	Description
options	{ container: '#container' }	Object	Yes	An object where each key / value pair represents a valid player or view option.

Returns

A fully initialised Player instance that can be used to load and play audio files.

playlist = Factory.createPlaylist(tracks, options);

Create a new playlist instance.

Argument	Example	Type	Required	Description
tracks	[ { url: 'path-to-audio.mp3', strategy: { type: 'data', data: [0.1, -0.4, ...] } } ]	Array<{ url: string; strategy: Strategy }>	Yes	An array of objects, where each object references an URL or path to an audio file and a strategy data object that instructs how to resolve the amplitude data associated with the audio file. See the Strategies section for more information on the available strategies and how to use them.
options	{ container: '#container' }	Object	Yes	An object where each key / value pair represents a valid player or view option.

Returns

A fully initialised Playlist instance that can be used to load and play multiple audio files in succession.

Player

player = new Player(view, options);

Create a new player instance.

Argument	Example	Type	Required	Description
view	new View([], { container: '#container' })	View	Yes	A view instance used for drawing the waveform associated with the audio file that will be loaded.
options	{ audioElement: '#audio' }	Object	No	An object where each key / value pair represents a valid player option.

Returns

A fully initialised Player instance that can be used to load and play audio files.

const player = await player.load(url, strategy);

Load an audio track using a specific strategy.

Argument	Example	Type	Required	Description
url	'path-to-audio.mp3'	string	Yes	A path or URL to an audio file
strategy	{ type: 'json', url: 'path-to-amplitude-data.json' }	Strategy	Yes	A strategy data object that instructs how to resolve the amplitude data associated with the audio file.

Returns

A promise that resolves to the player instance on which the method was called.

const player = await player.play();

Start playback of the currently loaded audio file.

Returns

A promise that resolves to the player instance on which the method was called.

const player = player.pause();

Pause playback of the currently loaded audio file.

Returns

The player instance on which the method was called.

player.destroy();

Destroy the player instance and do the appropriate clean up. This will pause audio playback, remove all internally registered event handlers, remove the HTML audio element from the DOM if it was created by the player instance, and lastly call view.destroy().

player.volume = 0.5;

Get / set the volume of the currently playing audio file.

Argument	Example	Type
volume	0.5	number

player.currentTime = 1;

Get / set the current playback time in seconds.

Argument	Example	Type
currentTime	1	number

player.duration;

Get the duration of the currently playing audio file.

player.paused;

Get the flag that checks if audio playback is currently paused.

player.view;

Get the view instance associated with the player.

player.audioElement;

Get the HTML audio element associated with the player.

Options

Option	Type	Default	Required	Description
audioElement	string | HTMLAudioElement	undefined	No	The HTML audio element associated with the player instance. If not passed in as an option when creating a new player instance it will be created internally.
preload	string	metadata	No	The value of the preload attribute of the HTML audio element. Note: will only be used when the player instance creates the HTML audio element internally.

Playlist

playlist = new Playlist(player, tracks);

Create a new playlist instance.

Argument	Example	Type	Required	Description
player	new Player(new View([], { container: '#container' }))	Player	Yes	A player instance used for playing back all the tracks / audio files that make up the playlist.
tracks	[ { url: 'path-to-audio.mp3', strategy: { type: 'data', data: [0.1, -0.4, ...] } } ]	Array<{ url: string; strategy: Strategy }>	Yes	An array of objects, where each object references an URL or path to an audio file and a strategy data object that instructs how to resolve the amplitude data associated with the audio file. See the Strategies section for more information on the available strategies and how to use them.

Returns

A fully initialised Playlist instance that can be used to load and play multiple audio files in succession.

const playlist = await playlist.prepare();

Prepare a playlist for playback. This is an alias for playlist.reset().

Returns

A promise that resolves to the playlist instance on which the method was called.

const playlist = await playlist.reset();

Reset a playlist. This will pause playback and set the first track in the playlist as the current track to play.

Returns

A promise that resolves to the playlist instance on which the method was called.

const playlist = await playlist.next(forcePlay);

Skip to the next track in the playlist.

Argument	Example	Type	Required	Description
forcePlay	true	boolean	No	This will start playback of the next track regardless if the playlist is currently paused.

Returns

A promise that resolves to the playlist instance on which the method was called.

const playlist = await playlist.previous(forcePlay);

Skip to the previous track in the playlist.

Argument	Example	Type	Required	Description
forcePlay	true	boolean	No	This will start playback of the previous track regardless if the playlist is currently paused.

Returns

A promise that resolves to the playlist instance on which the method was called.

const playlist = await playlist.select(track, forcePlay);

Select a specific track in the playlist.

Argument	Example	Type	Required	Description
track	1	number	Yes	The index of the track in the playlist that should be selected.
forcePlay	true	boolean	No	This will start playback of the selected track regardless if the playlist is currently paused.

Returns

A promise that resolves to the playlist instance on which the method was called.

playlist.destroy();

Destroy the player instance and do the appropriate clean up. This will remove all internally registered event handlers and call player.destroy().

playlist.forcePlay = true;

Get / set the flag that indicates whether playback should start after selecting another track in the playlist, regardless if the playlist is paused or not.

Argument	Example	Type
forcePlay	true	boolean

playlist.player;

Get the player instance associated with the playlist.

playlist.current;

Get the index of the currently playing track.

playlist.ended;

Get the flag that indicates whether the playlist has finished playback.

Options

Option	Type	Default	Required	Description
forcePlay	boolean	true	No	Indicates whether playback should start after selecting another track in the playlist, regardless if the playlist is paused or not.

View

view = new View(data, options);

Create a new view instance.

Argument	Example	Type	Required	Description
data	[-0.1, 0.4, ...]	Array<number>	Yes	An array of floating point values representing the amplitude of some audio file at equally spaced intervals that will be used to draw the waveform.
options	{ container: '#container' }	Object	Yes	An object where each key / value pair represents a valid view option.

Returns

A fully initialised View instance that can be used to draw the waveform associated with an audio file.

view = view.draw();

Draw the waveform on the canvas HTML element.

Returns

The view instance on which the method was called.

view = view.clear();

Clear the canvas HTML element where the waveform is drawn on.

Returns

The view instance on which the method was called.

view.destroy();

Destroy the view instance and do the appropriate clean up. This will remove all internally registered event handlers and remove the HTML canvas element from the DOM.

view.data = [-0.1, 0.4, ...];

Get / set the waveform amplitude data.

Argument	Example	Type
data	[-0.1, 0.4, ...]	Array<number>

view.progress = 0.5;

Get / set the progress of the waveform, assumed to be in the range [0-1].

Argument	Example	Type
progress	0.5	number

view.container = '#container';

Get / set the HTML container element for the view instance.

Argument	Example	Type
container	'#container'	`HTMLDivElement

view.width = 512;

Get / set the width of the drawn waveform. Setting the width only has an effect if the view instance is not operating in responsive mode.

Argument	Example	Type
width	512	number

view.height = 128;

Get / set the height of the drawn waveform.

Argument	Example	Type
height	128	number

view.barWidth = 4;

Get / set the width of a bar representing an element of the waveform.

Argument	Example	Type
barWidth	4	number

view.barGap = 1;

Get / set the width of the gap that separates consecutive bars.

Argument	Example	Type
barGap	1	number

view.responsive = true;

Get / set the flag that determines if the view instance is operating in responsive mode.

Argument	Example	Type
responsive	true	boolean

view.gradient = true;

Get / set the flag that determines if the waveform should be drawn with a gradient.

Argument	Example	Type
gradient	true	boolean

view.interact = true;

Get / set the interaction state of the view instance.

Argument	Example	Type
interact	true	boolean

view.redraw = true;

Get / set the redraw flag. This flag determines whether the waveform should be redrawn when setting one of the view properties that affects the look of the waveform (e.g. width, height, gradient).

Argument	Example	Type
redraw	true	boolean

view.canvas;

Get the HTML canvas element that is used for drawing the waveform.

Options

Option	Type	Default	Required	Description
container	string | HTMLDivElement	undefined	Yes	CSS selector or div HTML element that acts as the container for the HTML canvas element on which the waveform will be drawn.
width	integer	512	No	The width of the waveform in pixels (only relevant when the responsive option is set to false).
height	integer	128	No	The height of the waveform in pixels.
waveformColor	string	#428bca	No	The fill color of the waveform bars that have not been played back so far.
progressColor	string	#31708f	No	The fill color of the waveform bars that have been played back so far.
barGap	integer	1	No	Gap between bars in pixels.
barWidth	integer	4	No	Width of a bar in pixels.
responsive	boolean	true	No	If set to true, the width of the waveform view adapts to the width of the container element.
gradient	boolean	true	No	Indicates if the waveform should be drawn with a gradient or not.
interact	boolean	true	No	Enables / disables mouse interaction with the waveform view. This may be changed at any point after creation.
redraw	boolean	true	No	Indicates if the waveform will be redrawn when one of the view properties that affects the look of the waveform (e.g. width, height, gradient) is set.

Strategies

waveplayer v2 introduces the concept of strategies for providing amplitude data for an audio file that is used to draw waveforms. Each audio file you wish to load should reference a path / URL to the file and in addition specify how the amplitude data should be resolved. Currently, three strategies are available:

Data Strategy

Use this strategy if your waveform amplitude data is readily available in the form of an array of floating point values, assumed to be in the range [-1, 1].

Key	Value	Type	Default	Required	Description
type	'data'	string	undefined	Yes	The strategy type identifier.
data	[0.1, -0.4, ...]	Array<number>	undefined	Yes	An array of floating point values representing the amplitude of some audio file at equally spaced intervals that will be used to draw the waveform.

JSON Strategy

Use this strategy if your waveform amplitude data is stored inside a JSON file. This JSON file should either consist of a single array structure containing floating point values, assumed to be in the range [-1, 1] or key / value pairs where the value point to such an array. Currently, only the first key / value pair is used for the amplitude data. Waveform amplitude data extracted from a JSON file is cached by default

Key	Value	Type	Default	Required	Description
type	'json'	string	undefined	Yes	The strategy type identifier.
url	'path-to-amplitude-data.json'	string	undefined	Yes	A path or URL to a JSON file containing amplitude data for an audio file.
cache	true	boolean	true	No	Determines whether to use cached amplitude data (if it exists) or to extract the data from the JSON file.

WebAudio Strategy

Although convenient, this strategy is a bit experimental and if you can use either the JSON or data strategies it is generally adviced to use one of these. Use this strategy if you would like to extract the amplitude data of an audio file during runtime. Note that this could take a considerable amount of time depending on the duration of the audio file and the number of points you would like to extract. Also, not all audio file formats are supported, although MP3 and WAV should work just fine.

Key	Value	Type	Default	Required	Description
type	'webAudio'	string	undefined	Yes	The strategy type identifier.
points	1200	number	800	No	The number of equally spaced amplitude data points to extract from the audio file.
normalise	false	boolean	true	No	Determines whether to normalise the extracted data points (i.e. scale them such that the absolute maximum is 1).
logarithmic	true	boolean	true	No	Determines whether to compute the extracted data points on a logarithmic or linear scale.
cache	false	boolean	true	No	Determines whether to use cached amplitude data (if it exists) or to extract the data from the audio file.

Note: The JSON and WebAudio strategies cache amplitude data by default in order to speed up subsequent loading of the same audio files. If this is undesired behaviour you should set the "cache" flag of the relevant strategy to false.

Examples

This section discusses a few simple examples for more worked out, fully working examples see the /examples directory.

Player

Create a player instance and pass in some (optional) options:

import { Factory } from 'waveplayer';

const player = Factory.createPlayer({
    container: '#waveform',
    barWidth: 4,
    barGap: 1,
    height: 128,
});

await player.load('url-to-some-audio-file.mp3', { type: 'data', data: [0.1, -0.4, ...] });

player.play();

If you need more control or don't like factory classes for some reason you can also create a player instance explicitly:

import { Player, View } from 'waveplayer';

const player = new Player(new View([], { 'container': '#container' }), { 'audioElement': '#audio' });

Playlist

Load some audio files from a URL and start playback when loading has finished:

import { Factory } from 'waveplayer';

playlist = await Factory.createPlaylist(
    [{ url: 'url-to-some-audio-file.mp3', strategy: { type: 'data', data: [0.1, -0.4, ...] } }],
    { container: '#waveform' },
).prepare();

playlist.play();

Similarly to the Player class you can also create a playlist instance explicitly:

import { Player, Playlist, View } from 'waveplayer';

const playlist = new Playlist(
    new Player(new View([], { container: '#waveform' })),
    [{ url: 'url-to-some-audio-file.mp3', strategy: { type: 'json', url: 'url-to-some-amplitude-data.json' } }],
);

View

It is also possible to only use the view part of waveplayer if you are interested in the drawing of waveform data only:

import { View } from 'waveplayer';

const view = new View([0.1, -0.4, ...], { 'container': '#container' });

view.progress = 0.5;

view.draw();