bugsmatch/js/howler.min.js

/*!
 *  howler.js v2.0.13
 *  howlerjs.com
 *
 *  (c) 2013-2018, James Simpson of GoldFire Studios
 *  goldfirestudios.com
 *
 *  MIT License
 */


'use strict';

/** Global Methods **/
/***************************************************************************/

/**
 * Create the global controller. All contained methods and properties apply
 * to all sounds that are currently playing or will be in the future.
 */
var HowlerGlobal = function () {
    this.init();
};
HowlerGlobal.prototype = {
    /**
     * Initialize the global Howler object.
     * @return {Howler}
     */
    init: function () {
        var self = this || Howler;

        // Create a global ID counter.
        self._counter = 1000;

        // Internal properties.
        self._codecs = {};
        self._howls = [];
        self._muted = false;
        self._volume = 1;
        self._canPlayEvent = 'canplaythrough';
        self._navigator = (typeof window !== 'undefined' && window.navigator) ? window.navigator : null;

        // Public properties.
        self.masterGain = null;
        self.noAudio = false;
        self.usingWebAudio = true;
        self.autoSuspend = true;
        self.ctx = null;

        // Set to false to disable the auto iOS enabler.
        self.mobileAutoEnable = true;

        // Setup the various state values for global tracking.
        self._setup();

        return self;
    },

    /**
     * Get/set the global volume for all sounds.
     * @param  {Float} vol Volume from 0.0 to 1.0.
     * @return {Howler/Float}     Returns self or current volume.
     */
    volume: function (vol) {
        var self = this || Howler;
        vol = parseFloat(vol);

        // If we don't have an AudioContext created yet, run the setup.
        if (!self.ctx) {
            setupAudioContext();
        }

        if (typeof vol !== 'undefined' && vol >= 0 && vol <= 1) {
            self._volume = vol;

            // Don't update any of the nodes if we are muted.
            if (self._muted) {
                return self;
            }

            // When using Web Audio, we just need to adjust the master gain.
            if (self.usingWebAudio) {
                self.masterGain.gain.setValueAtTime(vol, Howler.ctx.currentTime);
            }

            // Loop through and change volume for all HTML5 audio nodes.
            for (var i = 0; i < self._howls.length; i++) {
                if (!self._howls[i]._webAudio) {
                    // Get all of the sounds in this Howl group.
                    var ids = self._howls[i]._getSoundIds();

                    // Loop through all sounds and change the volumes.
                    for (var j = 0; j < ids.length; j++) {
                        var sound = self._howls[i]._soundById(ids[j]);

                        if (sound && sound._node) {
                            sound._node.volume = sound._volume * vol;
                        }
                    }
                }
            }

            return self;
        }

        return self._volume;
    },

    /**
     * Handle muting and unmuting globally.
     * @param  {Boolean} muted Is muted or not.
     */
    mute: function (muted) {
        var self = this || Howler;

        // If we don't have an AudioContext created yet, run the setup.
        if (!self.ctx) {
            setupAudioContext();
        }

        self._muted = muted;

        // With Web Audio, we just need to mute the master gain.
        if (self.usingWebAudio) {
            self.masterGain.gain.setValueAtTime(muted ? 0 : self._volume, Howler.ctx.currentTime);
        }

        // Loop through and mute all HTML5 Audio nodes.
        for (var i = 0; i < self._howls.length; i++) {
            if (!self._howls[i]._webAudio) {
                // Get all of the sounds in this Howl group.
                var ids = self._howls[i]._getSoundIds();

                // Loop through all sounds and mark the audio node as muted.
                for (var j = 0; j < ids.length; j++) {
                    var sound = self._howls[i]._soundById(ids[j]);

                    if (sound && sound._node) {
                        sound._node.muted = (muted) ? true : sound._muted;
                    }
                }
            }
        }

        return self;
    },

    /**
     * Unload and destroy all currently loaded Howl objects.
     * @return {Howler}
     */
    unload: function () {
        var self = this || Howler;

        for (var i = self._howls.length - 1; i >= 0; i--) {
            self._howls[i].unload();
        }

        // Create a new AudioContext to make sure it is fully reset.
        if (self.usingWebAudio && self.ctx && typeof self.ctx.close !== 'undefined') {
            self.ctx.close();
            self.ctx = null;
            setupAudioContext();
        }

        return self;
    },

    /**
     * Check for codec support of specific extension.
     * @param  {String} ext Audio file extention.
     * @return {Boolean}
     */
    codecs: function (ext) {
        return (this || Howler)._codecs[ext.replace(/^x-/, '')];
    },

    /**
     * Setup various state values for global tracking.
     * @return {Howler}
     */
    _setup: function () {
        var self = this || Howler;

        // Keeps track of the suspend/resume state of the AudioContext.
        self.state = self.ctx ? self.ctx.state || 'running' : 'running';

        // Automatically begin the 30-second suspend process
        self._autoSuspend();

        // Check if audio is available.
        if (!self.usingWebAudio) {
            // No audio is available on this system if noAudio is set to true.
            if (typeof Audio !== 'undefined') {
                try {
                    var test = new Audio();

                    // Check if the canplaythrough event is available.
                    if (typeof test.oncanplaythrough === 'undefined') {
                        self._canPlayEvent = 'canplay';
                    }
                } catch (e) {
                    self.noAudio = true;
                }
            } else {
                self.noAudio = true;
            }
        }

        // Test to make sure audio isn't disabled in Internet Explorer.
        try {
            var test = new Audio();
            if (test.muted) {
                self.noAudio = true;
            }
        } catch (e) { }

        // Check for supported codecs.
        if (!self.noAudio) {
            self._setupCodecs();
        }

        return self;
    },

    /**
     * Check for browser support for various codecs and cache the results.
     * @return {Howler}
     */
    _setupCodecs: function () {
        var self = this || Howler;
        var audioTest = null;

        // Must wrap in a try/catch because IE11 in server mode throws an error.
        try {
            audioTest = (typeof Audio !== 'undefined') ? new Audio() : null;
        } catch (err) {
            return self;
        }

        if (!audioTest || typeof audioTest.canPlayType !== 'function') {
            return self;
        }

        var mpegTest = audioTest.canPlayType('audio/mpeg;').replace(/^no$/, '');

        // Opera version <33 has mixed MP3 support, so we need to check for and block it.
        var checkOpera = self._navigator && self._navigator.userAgent.match(/OPR\/([0-6].)/g);
        var isOldOpera = (checkOpera && parseInt(checkOpera[0].split('/')[1], 10) < 33);

        self._codecs = {
            mp3: !!(!isOldOpera && (mpegTest || audioTest.canPlayType('audio/mp3;').replace(/^no$/, ''))),
            mpeg: !!mpegTest,
            opus: !!audioTest.canPlayType('audio/ogg; codecs="opus"').replace(/^no$/, ''),
            ogg: !!audioTest.canPlayType('audio/ogg; codecs="vorbis"').replace(/^no$/, ''),
            oga: !!audioTest.canPlayType('audio/ogg; codecs="vorbis"').replace(/^no$/, ''),
            wav: !!audioTest.canPlayType('audio/wav; codecs="1"').replace(/^no$/, ''),
            aac: !!audioTest.canPlayType('audio/aac;').replace(/^no$/, ''),
            caf: !!audioTest.canPlayType('audio/x-caf;').replace(/^no$/, ''),
            m4a: !!(audioTest.canPlayType('audio/x-m4a;') || audioTest.canPlayType('audio/m4a;') || audioTest.canPlayType('audio/aac;')).replace(/^no$/, ''),
            mp4: !!(audioTest.canPlayType('audio/x-mp4;') || audioTest.canPlayType('audio/mp4;') || audioTest.canPlayType('audio/aac;')).replace(/^no$/, ''),
            weba: !!audioTest.canPlayType('audio/webm; codecs="vorbis"').replace(/^no$/, ''),
            webm: !!audioTest.canPlayType('audio/webm; codecs="vorbis"').replace(/^no$/, ''),
            dolby: !!audioTest.canPlayType('audio/mp4; codecs="ec-3"').replace(/^no$/, ''),
            flac: !!(audioTest.canPlayType('audio/x-flac;') || audioTest.canPlayType('audio/flac;')).replace(/^no$/, '')
        };

        return self;
    },

    /**
     * Mobile browsers will only allow audio to be played after a user interaction.
     * Attempt to automatically unlock audio on the first user interaction.
     * Concept from: http://paulbakaus.com/tutorials/html5/web-audio-on-ios/
     * @return {Howler}
     */
    _enableMobileAudio: function () {
        var self = this || Howler;

        // Only run this on mobile devices if audio isn't already eanbled.
        var isMobile = /iPhone|iPad|iPod|Android|BlackBerry|BB10|Silk|Mobi/i.test(self._navigator && self._navigator.userAgent);
        var isTouch = !!(('ontouchend' in window) || (self._navigator && self._navigator.maxTouchPoints > 0) || (self._navigator && self._navigator.msMaxTouchPoints > 0));
        if (self._mobileEnabled || !self.ctx || (!isMobile && !isTouch)) {
            return;
        }

        self._mobileEnabled = false;

        // Some mobile devices/platforms have distortion issues when opening/closing tabs and/or web views.
        // Bugs in the browser (especially Mobile Safari) can cause the sampleRate to change from 44100 to 48000.
        // By calling Howler.unload(), we create a new AudioContext with the correct sampleRate.
        if (!self._mobileUnloaded && self.ctx.sampleRate !== 44100) {
            self._mobileUnloaded = true;
            self.unload();
        }

        // Scratch buffer for enabling iOS to dispose of web audio buffers correctly, as per:
        // http://stackoverflow.com/questions/24119684
        self._scratchBuffer = self.ctx.createBuffer(1, 1, 22050);

        // Call this method on touch start to create and play a buffer,
        // then check if the audio actually played to determine if
        // audio has now been unlocked on iOS, Android, etc.
        var unlock = function () {
            // Fix Android can not play in suspend state.
            Howler._autoResume();

            // Create an empty buffer.
            var source = self.ctx.createBufferSource();
            source.buffer = self._scratchBuffer;
            source.connect(self.ctx.destination);

            // Play the empty buffer.
            if (typeof source.start === 'undefined') {
                source.noteOn(0);
            } else {
                source.start(0);
            }

            // Calling resume() on a stack initiated by user gesture is what actually unlocks the audio on Android Chrome >= 55.
            if (typeof self.ctx.resume === 'function') {
                self.ctx.resume();
            }

            // Setup a timeout to check that we are unlocked on the next event loop.
            source.onended = function () {
                source.disconnect(0);

                // Update the unlocked state and prevent this check from happening again.
                self._mobileEnabled = true;
                self.mobileAutoEnable = false;

                // Remove the touch start listener.
                document.removeEventListener('touchstart', unlock, true);
                document.removeEventListener('touchend', unlock, true);
            };
        };

        // Setup a touch start listener to attempt an unlock in.
        document.addEventListener('touchstart', unlock, true);
        document.addEventListener('touchend', unlock, true);

        return self;
    },

    /**
     * Automatically suspend the Web Audio AudioContext after no sound has played for 30 seconds.
     * This saves processing/energy and fixes various browser-specific bugs with audio getting stuck.
     * @return {Howler}
     */
    _autoSuspend: function () {
        var self = this;

        if (!self.autoSuspend || !self.ctx || typeof self.ctx.suspend === 'undefined' || !Howler.usingWebAudio) {
            return;
        }

        // Check if any sounds are playing.
        for (var i = 0; i < self._howls.length; i++) {
            if (self._howls[i]._webAudio) {
                for (var j = 0; j < self._howls[i]._sounds.length; j++) {
                    if (!self._howls[i]._sounds[j]._paused) {
                        return self;
                    }
                }
            }
        }

        if (self._suspendTimer) {
            clearTimeout(self._suspendTimer);
        }

        // If no sound has played after 30 seconds, suspend the context.
        self._suspendTimer = setTimeout(function () {
            if (!self.autoSuspend) {
                return;
            }

            self._suspendTimer = null;
            self.state = 'suspending';
            self.ctx.suspend().then(function () {
                self.state = 'suspended';

                if (self._resumeAfterSuspend) {
                    delete self._resumeAfterSuspend;
                    self._autoResume();
                }
            });
        }, 30000);

        return self;
    },

    /**
     * Automatically resume the Web Audio AudioContext when a new sound is played.
     * @return {Howler}
     */
    _autoResume: function () {
        var self = this;

        if (!self.ctx || typeof self.ctx.resume === 'undefined' || !Howler.usingWebAudio) {
            return;
        }

        if (self.state === 'running' && self._suspendTimer) {
            clearTimeout(self._suspendTimer);
            self._suspendTimer = null;
        } else if (self.state === 'suspended') {
            self.ctx.resume().then(function () {
                self.state = 'running';

                // Emit to all Howls that the audio has resumed.
                for (var i = 0; i < self._howls.length; i++) {
                    self._howls[i]._emit('resume');
                }
            });

            if (self._suspendTimer) {
                clearTimeout(self._suspendTimer);
                self._suspendTimer = null;
            }
        } else if (self.state === 'suspending') {
            self._resumeAfterSuspend = true;
        }

        return self;
    }
};

// Setup the global audio controller.
var Howler = new HowlerGlobal();

/** Group Methods **/
/***************************************************************************/

/**
 * Create an audio group controller.
 * @param {Object} o Passed in properties for this group.
 */
var Howl = function (o) {
    var self = this;

    // Throw an error if no source is provided.
    if (!o.src || o.src.length === 0) {
        console.error('An array of source files must be passed with any new Howl.');
        return;
    }

    self.init(o);
};
Howl.prototype = {
    /**
     * Initialize a new Howl group object.
     * @param  {Object} o Passed in properties for this group.
     * @return {Howl}
     */
    init: function (o) {
        var self = this;

        // If we don't have an AudioContext created yet, run the setup.
        if (!Howler.ctx) {
            setupAudioContext();
        }

        // Setup user-defined default properties.
        self._autoplay = o.autoplay || false;
        self._format = (typeof o.format !== 'string') ? o.format : [o.format];
        self._html5 = o.html5 || false;
        self._muted = o.mute || false;
        self._loop = o.loop || false;
        self._pool = o.pool || 5;
        self._preload = (typeof o.preload === 'boolean') ? o.preload : true;
        self._rate = o.rate || 1;
        self._sprite = o.sprite || {};
        self._src = (typeof o.src !== 'string') ? o.src : [o.src];
        self._volume = o.volume !== undefined ? o.volume : 1;
        self._xhrWithCredentials = o.xhrWithCredentials || false;

        // Setup all other default properties.
        self._duration = 0;
        self._state = 'unloaded';
        self._sounds = [];
        self._endTimers = {};
        self._queue = [];
        self._playLock = false;

        // Setup event listeners.
        self._onend = o.onend ? [{ fn: o.onend }] : [];
        self._onfade = o.onfade ? [{ fn: o.onfade }] : [];
        self._onload = o.onload ? [{ fn: o.onload }] : [];
        self._onloaderror = o.onloaderror ? [{ fn: o.onloaderror }] : [];
        self._onplayerror = o.onplayerror ? [{ fn: o.onplayerror }] : [];
        self._onpause = o.onpause ? [{ fn: o.onpause }] : [];
        self._onplay = o.onplay ? [{ fn: o.onplay }] : [];
        self._onstop = o.onstop ? [{ fn: o.onstop }] : [];
        self._onmute = o.onmute ? [{ fn: o.onmute }] : [];
        self._onvolume = o.onvolume ? [{ fn: o.onvolume }] : [];
        self._onrate = o.onrate ? [{ fn: o.onrate }] : [];
        self._onseek = o.onseek ? [{ fn: o.onseek }] : [];
        self._onresume = [];

        // Web Audio or HTML5 Audio?
        self._webAudio = Howler.usingWebAudio && !self._html5;

        // Automatically try to enable audio on iOS.
        if (typeof Howler.ctx !== 'undefined' && Howler.ctx && Howler.mobileAutoEnable) {
            Howler._enableMobileAudio();
        }

        // Keep track of this Howl group in the global controller.
        Howler._howls.push(self);

        // If they selected autoplay, add a play event to the load queue.
        if (self._autoplay) {
            self._queue.push({
                event: 'play',
                action: function () {
                    self.play();
                }
            });
        }

        // Load the source file unless otherwise specified.
        if (self._preload) {
            self.load();
        }

        return self;
    },

    /**
     * Load the audio file.
     * @return {Howler}
     */
    load: function () {
        var self = this;
        var url = null;

        // If no audio is available, quit immediately.
        if (Howler.noAudio) {
            self._emit('loaderror', null, 'No audio support.');
            return;
        }

        // Make sure our source is in an array.
        if (typeof self._src === 'string') {
            self._src = [self._src];
        }

        // Loop through the sources and pick the first one that is compatible.
        for (var i = 0; i < self._src.length; i++) {
            var ext, str;

            if (self._format && self._format[i]) {
                // If an extension was specified, use that instead.
                ext = self._format[i];
            } else {
                // Make sure the source is a string.
                str = self._src[i];
                if (typeof str !== 'string') {
                    self._emit('loaderror', null, 'Non-string found in selected audio sources - ignoring.');
                    continue;
                }

                // Extract the file extension from the URL or base64 data URI.
                ext = /^data:audio\/([^;,]+);/i.exec(str);
                if (!ext) {
                    ext = /\.([^.]+)$/.exec(str.split('?', 1)[0]);
                }

                if (ext) {
                    ext = ext[1].toLowerCase();
                }
            }

            // Log a warning if no extension was found.
            if (!ext) {
                console.warn('No file extension was found. Consider using the "format" property or specify an extension.');
            }

            // Check if this extension is available.
            if (ext && Howler.codecs(ext)) {
                url = self._src[i];
                break;
            }
        }

        if (!url) {
            self._emit('loaderror', null, 'No codec support for selected audio sources.');
            return;
        }
        self._src = url;
        self._state = 'loading';

        // If the hosting page is HTTPS and the source isn't,
        // drop down to HTML5 Audio to avoid Mixed Content errors.
        if (window.location.protocol === 'https:' && url.slice(0, 5) === 'http:') {
            self._html5 = true;
            self._webAudio = false;
        }

        // Create a new sound object and add it to the pool.
        new Sound(self);

        // Load and decode the audio data for playback.
        if (self._webAudio) {
            console.log('loadBuffer')
            loadBuffer(self);
        }

        return self;
    },

    /**
     * Play a sound or resume previous playback.
     * @param  {String/Number} sprite   Sprite name for sprite playback or sound id to continue previous.
     * @param  {Boolean} internal Internal Use: true prevents event firing.
     * @return {Number}          Sound ID.
     */
    play: function (sprite, internal) {
        var self = this;
        var id = null;

        // Determine if a sprite, sound id or nothing was passed
        if (typeof sprite === 'number') {
            id = sprite;
            sprite = null;
        } else if (typeof sprite === 'string' && self._state === 'loaded' && !self._sprite[sprite]) {
            // If the passed sprite doesn't exist, do nothing.
            return null;
        } else if (typeof sprite === 'undefined') {
            // Use the default sound sprite (plays the full audio length).
            sprite = '__default';

            // Check if there is a single paused sound that isn't ended.
            // If there is, play that sound. If not, continue as usual.
            var num = 0;
            for (var i = 0; i < self._sounds.length; i++) {
                if (self._sounds[i]._paused && !self._sounds[i]._ended) {
                    num++;
                    id = self._sounds[i]._id;
                }
            }

            if (num === 1) {
                sprite = null;
            } else {
                id = null;
            }
        }

        // Get the selected node, or get one from the pool.
        var sound = id ? self._soundById(id) : self._inactiveSound();

        // If the sound doesn't exist, do nothing.
        if (!sound) {
            return null;
        }

        // Select the sprite definition.
        if (id && !sprite) {
            sprite = sound._sprite || '__default';
        }

        // If the sound hasn't loaded, we must wait to get the audio's duration.
        // We also need to wait to make sure we don't run into race conditions with
        // the order of function calls.
        if (self._state !== 'loaded') {
            // Set the sprite value on this sound.
            sound._sprite = sprite;

            // Makr this sounded as not ended in case another sound is played before this one loads.
            sound._ended = false;

            // Add the sound to the queue to be played on load.
            var soundId = sound._id;
            self._queue.push({
                event: 'play',
                action: function () {
                    self.play(soundId);
                }
            });

            return soundId;
        }

        // Don't play the sound if an id was passed and it is already playing.
        if (id && !sound._paused) {
            // Trigger the play event, in order to keep iterating through queue.
            if (!internal) {
                self._loadQueue('play');
            }

            return sound._id;
        }

        // Make sure the AudioContext isn't suspended, and resume it if it is.
        if (self._webAudio) {
            Howler._autoResume();
        }

        // Determine how long to play for and where to start playing.
        var seek = Math.max(0, sound._seek > 0 ? sound._seek : self._sprite[sprite][0] / 1000);
        var duration = Math.max(0, ((self._sprite[sprite][0] + self._sprite[sprite][1]) / 1000) - seek);
        var timeout = (duration * 1000) / Math.abs(sound._rate);

        // Update the parameters of the sound
        sound._paused = false;
        sound._ended = false;
        sound._sprite = sprite;
        sound._seek = seek;
        sound._start = self._sprite[sprite][0] / 1000;
        sound._stop = (self._sprite[sprite][0] + self._sprite[sprite][1]) / 1000;
        sound._loop = !!(sound._loop || self._sprite[sprite][2]);
        // Begin the actual playback.
        var node = sound._node;
        if (self._webAudio) {
            // Fire this when the sound is ready to play to begin Web Audio playback.
            var playWebAudio = function () {
                self._refreshBuffer(sound);

                // Setup the playback params.
                var vol = (sound._muted || self._muted) ? 0 : sound._volume;
                node.gain.setValueAtTime(vol, Howler.ctx.currentTime);
                sound._playStart = Howler.ctx.currentTime;

                // Play the sound using the supported method.
                if (typeof node.bufferSource.start === 'undefined') {
                    sound._loop ? node.bufferSource.noteGrainOn(0, seek, 86400) : node.bufferSource.noteGrainOn(0, seek, duration);
                } else {
                    sound._loop ? node.bufferSource.start(0, seek, 86400) : node.bufferSource.start(0, seek, duration);
                }

                // Start a new timer if none is present.
                if (timeout !== Infinity) {
                    self._endTimers[sound._id] = setTimeout(self._ended.bind(self, sound), timeout);
                }

                if (!internal) {
                    setTimeout(function () {
                        self._emit('play', sound._id);
                    }, 0);
                }
            };

            if (Howler.state === 'running') {
                playWebAudio();
            } else {
                self.once('resume', playWebAudio);

                // Cancel the end timer.
                self._clearTimer(sound._id);
            }
        } else {
            // Fire this when the sound is ready to play to begin HTML5 Audio playback.
            var playHtml5 = function () {
                node.currentTime = seek;
                node.muted = sound._muted || self._muted || Howler._muted || node.muted;
                node.volume = sound._volume * Howler.volume();
                node.playbackRate = sound._rate;

                // Mobile browsers will throw an error if this is called without user interaction.
                try {
                    var play = node.play();

                    // Support older browsers that don't support promises, and thus don't have this issue.
                    if (typeof Promise !== 'undefined' && play instanceof Promise) {
                        // Implements a lock to prevent DOMException: The play() request was interrupted by a call to pause().
                        self._playLock = true;

                        // Releases the lock and executes queued actions.
                        var runLoadQueue = function () {
                            self._playLock = false;
                            if (!internal) {
                                self._emit('play', sound._id);
                            }
                        };
                        play.then(runLoadQueue, runLoadQueue);
                    } else if (!internal) {
                        self._emit('play', sound._id);
                    }

                    // Setting rate before playing won't work in IE, so we set it again here.
                    node.playbackRate = sound._rate;

                    // If the node is still paused, then we can assume there was a playback issue.
                    if (node.paused) {
                        self._emit('playerror', sound._id, 'Playback was unable to start. This is most commonly an issue ' +
                            'on mobile devices where playback was not within a user interaction.');
                        return;
                    }

                    // Setup the end timer on sprites or listen for the ended event.
                    if (sprite !== '__default' || sound._loop) {
                        self._endTimers[sound._id] = setTimeout(self._ended.bind(self, sound), timeout);
                    } else {
                        self._endTimers[sound._id] = function () {
                            // Fire ended on this audio node.
                            self._ended(sound);

                            // Clear this listener.
                            node.removeEventListener && node.removeEventListener('ended', self._endTimers[sound._id], false);
                        };
                        node.removeEventListener && node.addEventListener('ended', self._endTimers[sound._id], false);
                    }
                } catch (err) {
                    self._emit('playerror', sound._id, err);
                }
            };

            var playWX = function () {
                node.loop = self._loop;
                console.log("播放",node.src)
                node.play();
            }

            // Play immediately if ready, or wait for the 'canplaythrough'e vent.
            var loadedNoReadyState = (window && window.ejecta) || (!node.readyState && Howler._navigator.isCocoonJS);
            if (node.readyState >= 3 || loadedNoReadyState) {
                playHtml5();
            } else {
                playWX();
                var listener = function () {
                    // Begin playback.
                    playHtml5();

                    // Clear this listener.
                    node.removeEventListener && node.removeEventListener(Howler._canPlayEvent, listener, false);
                };
                node.addEventListener && node.addEventListener(Howler._canPlayEvent, listener, false);

                // Cancel the end timer.
                self._clearTimer(sound._id);
            }
        }

        return sound._id;
    },

    /**
     * Pause playback and save current position.
     * @param  {Number} id The sound ID (empty to pause all in group).
     * @return {Howl}
     */
    pause: function (id) {
        var self = this;

        // If the sound hasn't loaded or a play() promise is pending, add it to the load queue to pause when capable.
        if (self._state !== 'loaded' || self._playLock) {
            self._queue.push({
                event: 'pause',
                action: function () {
                    self.pause(id);
                }
            });

            return self;
        }

        // If no id is passed, get all ID's to be paused.
        var ids = self._getSoundIds(id);

        for (var i = 0; i < ids.length; i++) {
            // Clear the end timer.
            self._clearTimer(ids[i]);

            // Get the sound.
            var sound = self._soundById(ids[i]);

            if (sound && !sound._paused) {
                // Reset the seek position.
                sound._seek = self.seek(ids[i]);
                sound._rateSeek = 0;
                sound._paused = true;

                // Stop currently running fades.
                self._stopFade(ids[i]);

                if (sound._node) {
                    if (self._webAudio) {
                        // Make sure the sound has been created.
                        if (!sound._node.bufferSource) {
                            continue;
                        }

                        if (typeof sound._node.bufferSource.stop === 'undefined') {
                            sound._node.bufferSource.noteOff(0);
                        } else {
                            sound._node.bufferSource.stop(0);
                        }

                        // Clean up the buffer source.
                        self._cleanBuffer(sound._node);
                    } else if (!isNaN(sound._node.duration) || sound._node.duration === Infinity) {
                        sound._node.pause();
                    }
                }
            }

            // Fire the pause event, unless `true` is passed as the 2nd argument.
            if (!arguments[1]) {
                self._emit('pause', sound ? sound._id : null);
            }
        }

        return self;
    },

    /**
     * Stop playback and reset to start.
     * @param  {Number} id The sound ID (empty to stop all in group).
     * @param  {Boolean} internal Internal Use: true prevents event firing.
     * @return {Howl}
     */
    stop: function (id, internal) {
        var self = this;

        // If the sound hasn't loaded, add it to the load queue to stop when capable.
        if (self._state !== 'loaded') {
            self._queue.push({
                event: 'stop',
                action: function () {
                    self.stop(id);
                }
            });

            return self;
        }

        // If no id is passed, get all ID's to be stopped.
        var ids = self._getSoundIds(id);

        for (var i = 0; i < ids.length; i++) {
            // Clear the end timer.
            self._clearTimer(ids[i]);

            // Get the sound.
            var sound = self._soundById(ids[i]);

            if (sound) {
                // Reset the seek position.
                sound._seek = sound._start || 0;
                sound._rateSeek = 0;
                sound._paused = true;
                sound._ended = true;

                // Stop currently running fades.
                self._stopFade(ids[i]);

                if (sound._node) {
                    if (wx) {
                        sound._node.stop();
                    } else if (self._webAudio) {
                        // Make sure the sound's AudioBufferSourceNode has been created.
                        if (sound._node.bufferSource) {
                            if (typeof sound._node.bufferSource.stop === 'undefined') {
                                sound._node.bufferSource.noteOff(0);
                            } else {
                                sound._node.bufferSource.stop(0);
                            }

                            // Clean up the buffer source.
                            self._cleanBuffer(sound._node);
                        }
                    } else if (!isNaN(sound._node.duration) || sound._node.duration === Infinity) {
                        try {
                            // sound._node.currentTime = sound._start || 0;
                        } catch (e) {
                            console.log(e)
                        }

                        sound._node.pause();
                    }
                }

                if (!internal) {
                    self._emit('stop', sound._id);
                }
            }
        }

        return self;
    },

    /**
     * Mute/unmute a single sound or all sounds in this Howl group.
     * @param  {Boolean} muted Set to true to mute and false to unmute.
     * @param  {Number} id    The sound ID to update (omit to mute/unmute all).
     * @return {Howl}
     */
    mute: function (muted, id) {
        var self = this;

        // If the sound hasn't loaded, add it to the load queue to mute when capable.
        if (self._state !== 'loaded') {
            self._queue.push({
                event: 'mute',
                action: function () {
                    self.mute(muted, id);
                }
            });

            return self;
        }

        // If applying mute/unmute to all sounds, update the group's value.
        if (typeof id === 'undefined') {
            if (typeof muted === 'boolean') {
                self._muted = muted;
            } else {
                return self._muted;
            }
        }

        // If no id is passed, get all ID's to be muted.
        var ids = self._getSoundIds(id);

        for (var i = 0; i < ids.length; i++) {
            // Get the sound.
            var sound = self._soundById(ids[i]);

            if (sound) {
                sound._muted = muted;

                // Cancel active fade and set the volume to the end value.
                if (sound._interval) {
                    self._stopFade(sound._id);
                }

                if (self._webAudio && sound._node) {
                    sound._node.gain.setValueAtTime(muted ? 0 : sound._volume, Howler.ctx.currentTime);
                } else if (sound._node) {
                    sound._node.muted = Howler._muted ? true : muted;
                }

                self._emit('mute', sound._id);
            }
        }

        return self;
    },

    /**
     * Get/set the volume of this sound or of the Howl group. This method can optionally take 0, 1 or 2 arguments.
     *   volume() -> Returns the group's volume value.
     *   volume(id) -> Returns the sound id's current volume.
     *   volume(vol) -> Sets the volume of all sounds in this Howl group.
     *   volume(vol, id) -> Sets the volume of passed sound id.
     * @return {Howl/Number} Returns self or current volume.
     */
    volume: function () {
        var self = this;
        var args = arguments;
        var vol, id;

        // Determine the values based on arguments.
        if (args.length === 0) {
            // Return the value of the groups' volume.
            return self._volume;
        } else if (args.length === 1 || args.length === 2 && typeof args[1] === 'undefined') {
            // First check if this is an ID, and if not, assume it is a new volume.
            var ids = self._getSoundIds();
            var index = ids.indexOf(args[0]);
            if (index >= 0) {
                id = parseInt(args[0], 10);
            } else {
                vol = parseFloat(args[0]);
            }
        } else if (args.length >= 2) {
            vol = parseFloat(args[0]);
            id = parseInt(args[1], 10);
        }

        // Update the volume or return the current volume.
        var sound;
        if (typeof vol !== 'undefined' && vol >= 0 && vol <= 1) {
            // If the sound hasn't loaded, add it to the load queue to change volume when capable.
            if (self._state !== 'loaded') {
                self._queue.push({
                    event: 'volume',
                    action: function () {
                        self.volume.apply(self, args);
                    }
                });

                return self;
            }

            // Set the group volume.
            if (typeof id === 'undefined') {
                self._volume = vol;
            }

            // Update one or all volumes.
            id = self._getSoundIds(id);
            for (var i = 0; i < id.length; i++) {
                // Get the sound.
                sound = self._soundById(id[i]);

                if (sound) {
                    sound._volume = vol;

                    // Stop currently running fades.
                    if (!args[2]) {
                        self._stopFade(id[i]);
                    }

                    if (self._webAudio && sound._node && !sound._muted) {
                        sound._node.gain.setValueAtTime(vol, Howler.ctx.currentTime);
                    } else if (sound._node && !sound._muted) {
                        sound._node.volume = vol * Howler.volume();
                    }

                    self._emit('volume', sound._id);
                }
            }
        } else {
            sound = id ? self._soundById(id) : self._sounds[0];
            return sound ? sound._volume : 0;
        }

        return self;
    },

    /**
     * Fade a currently playing sound between two volumes (if no id is passsed, all sounds will fade).
     * @param  {Number} from The value to fade from (0.0 to 1.0).
     * @param  {Number} to   The volume to fade to (0.0 to 1.0).
     * @param  {Number} len  Time in milliseconds to fade.
     * @param  {Number} id   The sound id (omit to fade all sounds).
     * @return {Howl}
     */
    fade: function (from, to, len, id) {
        var self = this;

        // If the sound hasn't loaded, add it to the load queue to fade when capable.
        if (self._state !== 'loaded') {
            self._queue.push({
                event: 'fade',
                action: function () {
                    self.fade(from, to, len, id);
                }
            });

            return self;
        }

        // Set the volume to the start position.
        self.volume(from, id);

        // Fade the volume of one or all sounds.
        var ids = self._getSoundIds(id);
        for (var i = 0; i < ids.length; i++) {
            // Get the sound.
            var sound = self._soundById(ids[i]);

            // Create a linear fade or fall back to timeouts with HTML5 Audio.
            if (sound) {
                // Stop the previous fade if no sprite is being used (otherwise, volume handles this).
                if (!id) {
                    self._stopFade(ids[i]);
                }

                // If we are using Web Audio, let the native methods do the actual fade.
                if (self._webAudio && !sound._muted) {
                    var currentTime = Howler.ctx.currentTime;
                    var end = currentTime + (len / 1000);
                    sound._volume = from;
                    sound._node.gain.setValueAtTime(from, currentTime);
                    sound._node.gain.linearRampToValueAtTime(to, end);
                }

                self._startFadeInterval(sound, from, to, len, ids[i], typeof id === 'undefined');
            }
        }

        return self;
    },

    /**
     * Starts the internal interval to fade a sound.
     * @param  {Object} sound Reference to sound to fade.
     * @param  {Number} from The value to fade from (0.0 to 1.0).
     * @param  {Number} to   The volume to fade to (0.0 to 1.0).
     * @param  {Number} len  Time in milliseconds to fade.
     * @param  {Number} id   The sound id to fade.
     * @param  {Boolean} isGroup   If true, set the volume on the group.
     */
    _startFadeInterval: function (sound, from, to, len, id, isGroup) {
        var self = this;
        var vol = from;
        var diff = to - from;
        var steps = Math.abs(diff / 0.01);
        var stepLen = Math.max(4, (steps > 0) ? len / steps : len);
        var lastTick = Date.now();

        // Store the value being faded to.
        sound._fadeTo = to;

        // Update the volume value on each interval tick.
        sound._interval = setInterval(function () {
            // Update the volume based on the time since the last tick.
            var tick = (Date.now() - lastTick) / len;
            lastTick = Date.now();
            vol += diff * tick;

            // Make sure the volume is in the right bounds.
            vol = Math.max(0, vol);
            vol = Math.min(1, vol);

            // Round to within 2 decimal points.
            vol = Math.round(vol * 100) / 100;

            // Change the volume.
            if (self._webAudio) {
                sound._volume = vol;
            } else {
                self.volume(vol, sound._id, true);
            }

            // Set the group's volume.
            if (isGroup) {
                self._volume = vol;
            }

            // When the fade is complete, stop it and fire event.
            if ((to < from && vol <= to) || (to > from && vol >= to)) {
                clearInterval(sound._interval);
                sound._interval = null;
                sound._fadeTo = null;
                self.volume(to, sound._id);
                self._emit('fade', sound._id);
            }
        }, stepLen);
    },

    /**
     * Internal method that stops the currently playing fade when
     * a new fade starts, volume is changed or the sound is stopped.
     * @param  {Number} id The sound id.
     * @return {Howl}
     */
    _stopFade: function (id) {
        var self = this;
        var sound = self._soundById(id);

        if (sound && sound._interval) {
            if (self._webAudio) {
                sound._node.gain.cancelScheduledValues(Howler.ctx.currentTime);
            }

            clearInterval(sound._interval);
            sound._interval = null;
            self.volume(sound._fadeTo, id);
            sound._fadeTo = null;
            self._emit('fade', id);
        }

        return self;
    },

    /**
     * Get/set the loop parameter on a sound. This method can optionally take 0, 1 or 2 arguments.
     *   loop() -> Returns the group's loop value.
     *   loop(id) -> Returns the sound id's loop value.
     *   loop(loop) -> Sets the loop value for all sounds in this Howl group.
     *   loop(loop, id) -> Sets the loop value of passed sound id.
     * @return {Howl/Boolean} Returns self or current loop value.
     */
    loop: function () {
        var self = this;
        var args = arguments;
        var loop, id, sound;

        // Determine the values for loop and id.
        if (args.length === 0) {
            // Return the grou's loop value.
            return self._loop;
        } else if (args.length === 1) {
            if (typeof args[0] === 'boolean') {
                loop = args[0];
                self._loop = loop;
            } else {
                // Return this sound's loop value.
                sound = self._soundById(parseInt(args[0], 10));
                return sound ? sound._loop : false;
            }
        } else if (args.length === 2) {
            loop = args[0];
            id = parseInt(args[1], 10);
        }

        // If no id is passed, get all ID's to be looped.
        var ids = self._getSoundIds(id);
        for (var i = 0; i < ids.length; i++) {
            sound = self._soundById(ids[i]);

            if (sound) {
                sound._loop = loop;
                if (self._webAudio && sound._node && sound._node.bufferSource) {
                    sound._node.bufferSource.loop = loop;
                    if (loop) {
                        sound._node.bufferSource.loopStart = sound._start || 0;
                        sound._node.bufferSource.loopEnd = sound._stop;
                    }
                }
            }
        }

        return self;
    },

    /**
     * Get/set the playback rate of a sound. This method can optionally take 0, 1 or 2 arguments.
     *   rate() -> Returns the first sound node's current playback rate.
     *   rate(id) -> Returns the sound id's current playback rate.
     *   rate(rate) -> Sets the playback rate of all sounds in this Howl group.
     *   rate(rate, id) -> Sets the playback rate of passed sound id.
     * @return {Howl/Number} Returns self or the current playback rate.
     */
    rate: function () {
        var self = this;
        var args = arguments;
        var rate, id;

        // Determine the values based on arguments.
        if (args.length === 0) {
            // We will simply return the current rate of the first node.
            id = self._sounds[0]._id;
        } else if (args.length === 1) {
            // First check if this is an ID, and if not, assume it is a new rate value.
            var ids = self._getSoundIds();
            var index = ids.indexOf(args[0]);
            if (index >= 0) {
                id = parseInt(args[0], 10);
            } else {
                rate = parseFloat(args[0]);
            }
        } else if (args.length === 2) {
            rate = parseFloat(args[0]);
            id = parseInt(args[1], 10);
        }

        // Update the playback rate or return the current value.
        var sound;
        if (typeof rate === 'number') {
            // If the sound hasn't loaded, add it to the load queue to change playback rate when capable.
            if (self._state !== 'loaded') {
                self._queue.push({
                    event: 'rate',
                    action: function () {
                        self.rate.apply(self, args);
                    }
                });

                return self;
            }

            // Set the group rate.
            if (typeof id === 'undefined') {
                self._rate = rate;
            }

            // Update one or all volumes.
            id = self._getSoundIds(id);
            for (var i = 0; i < id.length; i++) {
                // Get the sound.
                sound = self._soundById(id[i]);

                if (sound) {
                    // Keep track of our position when the rate changed and update the playback
                    // start position so we can properly adjust the seek position for time elapsed.
                    sound._rateSeek = self.seek(id[i]);
                    sound._playStart = self._webAudio ? Howler.ctx.currentTime : sound._playStart;
                    sound._rate = rate;

                    // Change the playback rate.
                    if (self._webAudio && sound._node && sound._node.bufferSource) {
                        sound._node.bufferSource.playbackRate.setValueAtTime(rate, Howler.ctx.currentTime);
                    } else if (sound._node) {
                        sound._node.playbackRate = rate;
                    }

                    // Reset the timers.
                    var seek = self.seek(id[i]);
                    var duration = ((self._sprite[sound._sprite][0] + self._sprite[sound._sprite][1]) / 1000) - seek;
                    var timeout = (duration * 1000) / Math.abs(sound._rate);

                    // Start a new end timer if sound is already playing.
                    if (self._endTimers[id[i]] || !sound._paused) {
                        self._clearTimer(id[i]);
                        self._endTimers[id[i]] = setTimeout(self._ended.bind(self, sound), timeout);
                    }

                    self._emit('rate', sound._id);
                }
            }
        } else {
            sound = self._soundById(id);
            return sound ? sound._rate : self._rate;
        }

        return self;
    },

    /**
     * Get/set the seek position of a sound. This method can optionally take 0, 1 or 2 arguments.
     *   seek() -> Returns the first sound node's current seek position.
     *   seek(id) -> Returns the sound id's current seek position.
     *   seek(seek) -> Sets the seek position of the first sound node.
     *   seek(seek, id) -> Sets the seek position of passed sound id.
     * @return {Howl/Number} Returns self or the current seek position.
     */
    seek: function () {
        var self = this;
        var args = arguments;
        var seek, id;

        // Determine the values based on arguments.
        if (args.length === 0) {
            // We will simply return the current position of the first node.
            id = self._sounds[0]._id;
        } else if (args.length === 1) {
            // First check if this is an ID, and if not, assume it is a new seek position.
            var ids = self._getSoundIds();
            var index = ids.indexOf(args[0]);
            if (index >= 0) {
                id = parseInt(args[0], 10);
            } else if (self._sounds.length) {
                id = self._sounds[0]._id;
                seek = parseFloat(args[0]);
            }
        } else if (args.length === 2) {
            seek = parseFloat(args[0]);
            id = parseInt(args[1], 10);
        }

        // If there is no ID, bail out.
        if (typeof id === 'undefined') {
            return self;
        }

        // If the sound hasn't loaded, add it to the load queue to seek when capable.
        if (self._state !== 'loaded') {
            self._queue.push({
                event: 'seek',
                action: function () {
                    self.seek.apply(self, args);
                }
            });

            return self;
        }

        // Get the sound.
        var sound = self._soundById(id);

        if (sound) {
            if (typeof seek === 'number' && seek >= 0) {
                // Pause the sound and update position for restarting playback.
                var playing = self.playing(id);
                if (playing) {
                    self.pause(id, true);
                }

                // Move the position of the track and cancel timer.
                sound._seek = seek;
                sound._ended = false;
                self._clearTimer(id);

                // Restart the playback if the sound was playing.
                if (playing) {
                    self.play(id, true);
                }

                // Update the seek position for HTML5 Audio.
                if (!self._webAudio && sound._node) {
                    sound._node.currentTime = seek;
                }

                // Wait for the play lock to be unset before emitting (HTML5 Audio).
                if (playing && !self._webAudio) {
                    var emitSeek = function () {
                        if (!self._playLock) {
                            self._emit('seek', id);
                        } else {
                            setTimeout(emitSeek, 0);
                        }
                    };
                    setTimeout(emitSeek, 0);
                } else {
                    self._emit('seek', id);
                }
            } else {
                if (self._webAudio) {
                    var realTime = self.playing(id) ? Howler.ctx.currentTime - sound._playStart : 0;
                    var rateSeek = sound._rateSeek ? sound._rateSeek - sound._seek : 0;
                    return sound._seek + (rateSeek + realTime * Math.abs(sound._rate));
                } else {
                    return sound._node.currentTime;
                }
            }
        }

        return self;
    },

    /**
     * Check if a specific sound is currently playing or not (if id is provided), or check if at least one of the sounds in the group is playing or not.
     * @param  {Number}  id The sound id to check. If none is passed, the whole sound group is checked.
     * @return {Boolean} True if playing and false if not.
     */
    playing: function (id) {
        var self = this;

        // Check the passed sound ID (if any).
        if (typeof id === 'number') {
            var sound = self._soundById(id);
            return sound ? !sound._paused : false;
        }

        // Otherwise, loop through all sounds and check if any are playing.
        for (var i = 0; i < self._sounds.length; i++) {
            if (!self._sounds[i]._paused) {
                return true;
            }
        }

        return false;
    },

    /**
     * Get the duration of this sound. Passing a sound id will return the sprite duration.
     * @param  {Number} id The sound id to check. If none is passed, return full source duration.
     * @return {Number} Audio duration in seconds.
     */
    duration: function (id) {
        var self = this;
        var duration = self._duration;

        // If we pass an ID, get the sound and return the sprite length.
        var sound = self._soundById(id);
        if (sound) {
            duration = self._sprite[sound._sprite][1] / 1000;
        }

        return duration;
    },

    /**
     * Returns the current loaded state of this Howl.
     * @return {String} 'unloaded', 'loading', 'loaded'
     */
    state: function () {
        return this._state;
    },

    /**
     * Unload and destroy the current Howl object.
     * This will immediately stop all sound instances attached to this group.
     */
    unload: function () {
        var self = this;

        // Stop playing any active sounds.
        var sounds = self._sounds;
        for (var i = 0; i < sounds.length; i++) {
            // Stop the sound if it is currently playing.
            if (!sounds[i]._paused) {
                self.stop(sounds[i]._id);
            }

            // Remove the source or disconnect.
            if (!self._webAudio) {
                // Set the source to 0-second silence to stop any downloading (except in IE).
                var checkIE = /MSIE |Trident\//.test(Howler._navigator && Howler._navigator.userAgent);
                if (!checkIE) {
                    sounds[i]._node.src = 'data:audio/wav;base64,UklGRigAAABXQVZFZm10IBIAAAABAAEARKwAAIhYAQACABAAAABkYXRhAgAAAAEA';
                }

                // Remove any event listeners.
                sounds[i]._node.removeEventListener('error', sounds[i]._errorFn, false);
                sounds[i]._node.removeEventListener(Howler._canPlayEvent, sounds[i]._loadFn, false);
            }

            // Empty out all of the nodes.
            delete sounds[i]._node;

            // Make sure all timers are cleared out.
            self._clearTimer(sounds[i]._id);
        }

        // Remove the references in the global Howler object.
        var index = Howler._howls.indexOf(self);
        if (index >= 0) {
            Howler._howls.splice(index, 1);
        }

        // Delete this sound from the cache (if no other Howl is using it).
        var remCache = true;
        for (i = 0; i < Howler._howls.length; i++) {
            if (Howler._howls[i]._src === self._src) {
                remCache = false;
                break;
            }
        }

        if (cache && remCache) {
            delete cache[self._src];
        }

        // Clear global errors.
        Howler.noAudio = false;

        // Clear out `self`.
        self._state = 'unloaded';
        self._sounds = [];
        self = null;

        return null;
    },

    /**
     * Listen to a custom event.
     * @param  {String}   event Event name.
     * @param  {Function} fn    Listener to call.
     * @param  {Number}   id    (optional) Only listen to events for this sound.
     * @param  {Number}   once  (INTERNAL) Marks event to fire only once.
     * @return {Howl}
     */
    on: function (event, fn, id, once) {
        var self = this;
        var events = self['_on' + event];

        if (typeof fn === 'function') {
            events.push(once ? { id: id, fn: fn, once: once } : { id: id, fn: fn });
        }

        return self;
    },

    /**
     * Remove a custom event. Call without parameters to remove all events.
     * @param  {String}   event Event name.
     * @param  {Function} fn    Listener to remove. Leave empty to remove all.
     * @param  {Number}   id    (optional) Only remove events for this sound.
     * @return {Howl}
     */
    off: function (event, fn, id) {
        var self = this;
        var events = self['_on' + event];
        var i = 0;

        // Allow passing just an event and ID.
        if (typeof fn === 'number') {
            id = fn;
            fn = null;
        }

        if (fn || id) {
            // Loop through event store and remove the passed function.
            for (i = 0; i < events.length; i++) {
                var isId = (id === events[i].id);
                if (fn === events[i].fn && isId || !fn && isId) {
                    events.splice(i, 1);
                    break;
                }
            }
        } else if (event) {
            // Clear out all events of this type.
            self['_on' + event] = [];
        } else {
            // Clear out all events of every type.
            var keys = Object.keys(self);
            for (i = 0; i < keys.length; i++) {
                if ((keys[i].indexOf('_on') === 0) && Array.isArray(self[keys[i]])) {
                    self[keys[i]] = [];
                }
            }
        }

        return self;
    },

    /**
     * Listen to a custom event and remove it once fired.
     * @param  {String}   event Event name.
     * @param  {Function} fn    Listener to call.
     * @param  {Number}   id    (optional) Only listen to events for this sound.
     * @return {Howl}
     */
    once: function (event, fn, id) {
        var self = this;

        // Setup the event listener.
        self.on(event, fn, id, 1);

        return self;
    },

    /**
     * Emit all events of a specific type and pass the sound id.
     * @param  {String} event Event name.
     * @param  {Number} id    Sound ID.
     * @param  {Number} msg   Message to go with event.
     * @return {Howl}
     */
    _emit: function (event, id, msg) {
        var self = this;
        var events = self['_on' + event];

        // Loop through event store and fire all functions.
        for (var i = events.length - 1; i >= 0; i--) {
            // Only fire the listener if the correct ID is used.
            if (!events[i].id || events[i].id === id || event === 'load') {
                setTimeout(function (fn) {
                    fn.call(this, id, msg);
                }.bind(self, events[i].fn), 0);

                // If this event was setup with `once`, remove it.
                if (events[i].once) {
                    self.off(event, events[i].fn, events[i].id);
                }
            }
        }

        // Pass the event type into load queue so that it can continue stepping.
        self._loadQueue(event);

        return self;
    },

    /**
     * Queue of actions initiated before the sound has loaded.
     * These will be called in sequence, with the next only firing
     * after the previous has finished executing (even if async like play).
     * @return {Howl}
     */
    _loadQueue: function (event) {
        var self = this;

        if (self._queue.length > 0) {
            var task = self._queue[0];

            // Remove this task if a matching event was passed.
            if (task.event === event) {
                self._queue.shift();
                self._loadQueue();
            }

            // Run the task if no event type is passed.
            if (!event) {
                task.action();
            }
        }

        return self;
    },

    /**
     * Fired when playback ends at the end of the duration.
     * @param  {Sound} sound The sound object to work with.
     * @return {Howl}
     */
    _ended: function (sound) {
        var self = this;
        var sprite = sound._sprite;

        // If we are using IE and there was network latency we may be clipping
        // audio before it completes playing. Lets check the node to make sure it
        // believes it has completed, before ending the playback.
        if (!self._webAudio && sound._node && !sound._node.paused && !sound._node.ended && sound._node.currentTime < sound._stop) {
            setTimeout(self._ended.bind(self, sound), 100);
            return self;
        }

        // Should this sound loop?
        var loop = !!(sound._loop || self._sprite[sprite][2]);

        // Fire the ended event.
        self._emit('end', sound._id);

        // Restart the playback for HTML5 Audio loop.
        if (!self._webAudio && loop) {
            self.stop(sound._id, true).play(sound._id);
        }

        // Restart this timer if on a Web Audio loop.
        if (self._webAudio && loop) {
            self._emit('play', sound._id);
            sound._seek = sound._start || 0;
            sound._rateSeek = 0;
            sound._playStart = Howler.ctx.currentTime;

            var timeout = ((sound._stop - sound._start) * 1000) / Math.abs(sound._rate);
            self._endTimers[sound._id] = setTimeout(self._ended.bind(self, sound), timeout);
        }

        // Mark the node as paused.
        if (self._webAudio && !loop) {
            sound._paused = true;
            sound._ended = true;
            sound._seek = sound._start || 0;
            sound._rateSeek = 0;
            self._clearTimer(sound._id);

            // Clean up the buffer source.
            self._cleanBuffer(sound._node);

            // Attempt to auto-suspend AudioContext if no sounds are still playing.
            Howler._autoSuspend();
        }

        // When using a sprite, end the track.
        if (!self._webAudio && !loop) {
            self.stop(sound._id, true);
        }

        return self;
    },

    /**
     * Clear the end timer for a sound playback.
     * @param  {Number} id The sound ID.
     * @return {Howl}
     */
    _clearTimer: function (id) {
        var self = this;

        if (self._endTimers[id]) {
            // Clear the timeout or remove the ended listener.
            if (typeof self._endTimers[id] !== 'function') {
                clearTimeout(self._endTimers[id]);
            } else {
                var sound = self._soundById(id);
                if (sound && sound._node) {
                    sound._node.removeEventListener('ended', self._endTimers[id], false);
                }
            }

            delete self._endTimers[id];
        }

        return self;
    },

    /**
     * Return the sound identified by this ID, or return null.
     * @param  {Number} id Sound ID
     * @return {Object}    Sound object or null.
     */
    _soundById: function (id) {
        var self = this;

        // Loop through all sounds and find the one with this ID.
        for (var i = 0; i < self._sounds.length; i++) {
            if (id === self._sounds[i]._id) {
                return self._sounds[i];
            }
        }

        return null;
    },

    /**
     * Return an inactive sound from the pool or create a new one.
     * @return {Sound} Sound playback object.
     */
    _inactiveSound: function () {
        var self = this;

        self._drain();

        // Find the first inactive node to recycle.
        for (var i = 0; i < self._sounds.length; i++) {
            if (self._sounds[i]._ended) {
                return self._sounds[i].reset();
            }
        }

        // If no inactive node was found, create a new one.
        return new Sound(self);
    },

    /**
     * Drain excess inactive sounds from the pool.
     */
    _drain: function () {
        var self = this;
        var limit = self._pool;
        var cnt = 0;
        var i = 0;

        // If there are less sounds than the max pool size, we are done.
        if (self._sounds.length < limit) {
            return;
        }

        // Count the number of inactive sounds.
        for (i = 0; i < self._sounds.length; i++) {
            if (self._sounds[i]._ended) {
                cnt++;
            }
        }

        // Remove excess inactive sounds, going in reverse order.
        for (i = self._sounds.length - 1; i >= 0; i--) {
            if (cnt <= limit) {
                return;
            }

            if (self._sounds[i]._ended) {
                // Disconnect the audio source when using Web Audio.
                if (self._webAudio && self._sounds[i]._node) {
                    self._sounds[i]._node.disconnect(0);
                }

                // Remove sounds until we have the pool size.
                self._sounds.splice(i, 1);
                cnt--;
            }
        }
    },

    /**
     * Get all ID's from the sounds pool.
     * @param  {Number} id Only return one ID if one is passed.
     * @return {Array}    Array of IDs.
     */
    _getSoundIds: function (id) {
        var self = this;

        if (typeof id === 'undefined') {
            var ids = [];
            for (var i = 0; i < self._sounds.length; i++) {
                ids.push(self._sounds[i]._id);
            }

            return ids;
        } else {
            return [id];
        }
    },

    /**
     * Load the sound back into the buffer source.
     * @param  {Sound} sound The sound object to work with.
     * @return {Howl}
     */
    _refreshBuffer: function (sound) {
        var self = this;

        // Setup the buffer source for playback.
        sound._node.bufferSource = Howler.ctx.createBufferSource();
        sound._node.bufferSource.buffer = cache[self._src];

        // Connect to the correct node.
        if (sound._panner) {
            sound._node.bufferSource.connect(sound._panner);
        } else {
            sound._node.bufferSource.connect(sound._node);
        }

        // Setup looping and playback rate.
        sound._node.bufferSource.loop = sound._loop;
        if (sound._loop) {
            sound._node.bufferSource.loopStart = sound._start || 0;
            sound._node.bufferSource.loopEnd = sound._stop;
        }
        sound._node.bufferSource.playbackRate.setValueAtTime(sound._rate, Howler.ctx.currentTime);

        return self;
    },

    /**
     * Prevent memory leaks by cleaning up the buffer source after playback.
     * @param  {Object} node Sound's audio node containing the buffer source.
     * @return {Howl}
     */
    _cleanBuffer: function (node) {
        var self = this;

        if (Howler._scratchBuffer && node.bufferSource) {
            node.bufferSource.onended = null;
            node.bufferSource.disconnect(0);
            try { node.bufferSource.buffer = Howler._scratchBuffer; } catch (e) { }
        }
        node.bufferSource = null;

        return self;
    }
};

/** Single Sound Methods **/
/***************************************************************************/

/**
 * Setup the sound object, which each node attached to a Howl group is contained in.
 * @param {Object} howl The Howl parent group.
 */
var Sound = function (howl) {
    this._parent = howl;
    this.init();
};
Sound.prototype = {
    /**
     * Initialize a new Sound object.
     * @return {Sound}
     */
    init: function () {
        var self = this;
        var parent = self._parent;

        // Setup the default parameters.
        self._muted = parent._muted;
        self._loop = parent._loop;
        self._volume = parent._volume;
        self._rate = parent._rate;
        self._seek = 0;
        self._paused = true;
        self._ended = true;
        self._sprite = '__default';

        // Generate a unique ID for this sound.
        self._id = ++Howler._counter;

        // Add itself to the parent's pool.
        parent._sounds.push(self);

        // Create the new node.
        self.create();

        return self;
    },

    /**
     * Create and setup a new sound object, whether HTML5 Audio or Web Audio.
     * @return {Sound}
     */
    create: function () {
        var self = this;
        var parent = self._parent;
        var volume = (Howler._muted || self._muted || self._parent._muted) ? 0 : self._volume;

        if (parent._webAudio) {
            // Create the gain node for controlling volume (the source will connect to this).
            self._node = (typeof Howler.ctx.createGain === 'undefined') ? Howler.ctx.createGainNode() : Howler.ctx.createGain();
            self._node.gain.setValueAtTime(volume, Howler.ctx.currentTime);
            self._node.paused = true;
            self._node.connect(Howler.masterGain);
        } else {
            if (wx.createInnerAudioContext) {
                self._node = wx.createInnerAudioContext();
                // Listen for errors (http://dev.w3.org/html5/spec-author-view/spec.html#mediaerror).
                self._errorFn = self._errorListener.bind(self);
                self._node.onError(self._errorFn);

                // Listen for 'canplaythrough' event to let us know the sound is ready.
                self._loadFn = self._loadListener.bind(self);
                self._node.onCanplay(self._loadFn);

                // Setup the new audio node.
                self._node.src = parent._src;
                self._node.loop = self._loop;
                self._node.preload = 'auto';
                self._node.volume = volume * Howler.volume();

                // wx.downloadFile({
                //     url: parent._src,
                //     success: function (res) {
                //         if (res.statusCode === 200) {
                //             console.log(self._node, res.tempFilePath)
                //         }
                //     }
                // })


                // Begin loading the source.
                // self._node.load();


            } else {
                self._node = new Audio();

                // Listen for errors (http://dev.w3.org/html5/spec-author-view/spec.html#mediaerror).
                self._errorFn = self._errorListener.bind(self);
                self._node.addEventListener('error', self._errorFn, false);

                // Listen for 'canplaythrough' event to let us know the sound is ready.
                self._loadFn = self._loadListener.bind(self);
                self._node.addEventListener(Howler._canPlayEvent, self._loadFn, false);

                // Setup the new audio node.
                self._node.src = parent._src;
                self._node.preload = 'auto';
                self._node.volume = volume * Howler.volume();

                // Begin loading the source.
                self._node.load();
            }


        }

        return self;
    },

    /**
     * Reset the parameters of this sound to the original state (for recycle).
     * @return {Sound}
     */
    reset: function () {
        var self = this;
        var parent = self._parent;

        // Reset all of the parameters of this sound.
        self._muted = parent._muted;
        self._loop = parent._loop;
        self._volume = parent._volume;
        self._rate = parent._rate;
        self._seek = 0;
        self._rateSeek = 0;
        self._paused = true;
        self._ended = true;
        self._sprite = '__default';

        // Generate a new ID so that it isn't confused with the previous sound.
        self._id = ++Howler._counter;

        return self;
    },

    /**
     * HTML5 Audio error listener callback.
     */
    _errorListener: function () {
        var self = this;

        // Fire an error event and pass back the code.
        self._parent._emit('loaderror', self._id, self._node.error ? self._node.error.code : 0);

        // Clear the event listener.
        self._node.removeEventListener && self._node.removeEventListener('error', self._errorFn, false);
        self._node.offError && self._node.offError(self._errorFn);
    },

    /**
     * HTML5 Audio canplaythrough listener callback.
     */
    _loadListener: function () {
        var self = this;
        var parent = self._parent;

        // Round up the duration to account for the lower precision in HTML5 Audio.
        parent._duration = Math.ceil(self._node.duration * 10) / 10;

        // Setup a sprite if none is defined.
        if (Object.keys(parent._sprite).length === 0) {
            parent._sprite = { __default: [0, parent._duration * 1000] };
        }

        if (parent._state !== 'loaded') {
            parent._state = 'loaded';
            parent._emit('load');
            parent._loadQueue();
        }

        // Clear the event listener.
        self._node.removeEventListener && self._node.removeEventListener(Howler._canPlayEvent, self._loadFn, false);
        self._node.offCanplay && self._node.offCanplay(self._loadFn);
    }
};

/** Helper Methods **/
/***************************************************************************/

var cache = {};

/**
 * Buffer a sound from URL, Data URI or cache and decode to audio source (Web Audio API).
 * @param  {Howl} self
 */
var loadBuffer = function (self) {
    var url = self._src;

    // Check if the buffer has already been cached and use it instead.
    if (cache[url]) {
        // Set the duration from the cache.
        self._duration = cache[url].duration;

        // Load the sound into this Howl.
        loadSound(self);

        return;
    }
    if (wx.createInnerAudioContext) {
        var audio = wx.createInnerAudioContext();
        audio.src = url
        cache[self._src] = audio;
    } else if (/^data:[^;]+;base64,/.test(url)) {
        // Decode the base64 data URI without XHR, since some browsers don't support it.
        var data = atob(url.split(',')[1]);
        var dataView = new Uint8Array(data.length);
        for (var i = 0; i < data.length; ++i) {
            dataView[i] = data.charCodeAt(i);
        }

        decodeAudioData(dataView.buffer, self);
    } else {
        // Load the buffer from the URL.
        var xhr = new XMLHttpRequest();
        xhr.open('GET', url, true);
        xhr.withCredentials = self._xhrWithCredentials;
        xhr.responseType = 'arraybuffer';
        xhr.onload = function () {
            // Make sure we get a successful response back.
            var code = (xhr.status + '')[0];
            if (code !== '0' && code !== '2' && code !== '3') {
                self._emit('loaderror', null, 'Failed loading audio file with status: ' + xhr.status + '.');
                return;
            }

            decodeAudioData(xhr.response, self);
        };
        xhr.onerror = function () {
            // If there is an error, switch to HTML5 Audio.
            if (self._webAudio) {
                self._html5 = true;
                self._webAudio = false;
                self._sounds = [];
                delete cache[url];
                self.load();
            }
        };
        safeXhrSend(xhr);
    }
};

/**
 * Send the XHR request wrapped in a try/catch.
 * @param  {Object} xhr XHR to send.
 */
var safeXhrSend = function (xhr) {
    try {
        xhr.send();
    } catch (e) {
        xhr.onerror();
    }
};

/**
 * Decode audio data from an array buffer.
 * @param  {ArrayBuffer} arraybuffer The audio data.
 * @param  {Howl}        self
 */
var decodeAudioData = function (arraybuffer, self) {
    // Decode the buffer into an audio source.
    Howler.ctx.decodeAudioData(arraybuffer, function (buffer) {
        if (buffer && self._sounds.length > 0) {
            cache[self._src] = buffer;
            loadSound(self, buffer);
        }
    }, function () {
        self._emit('loaderror', null, 'Decoding audio data failed.');
    });
};

/**
 * Sound is now loaded, so finish setting everything up and fire the loaded event.
 * @param  {Howl} self
 * @param  {Object} buffer The decoded buffer sound source.
 */
var loadSound = function (self, buffer) {
    // Set the duration.
    if (buffer && !self._duration) {
        self._duration = buffer.duration;
    }

    // Setup a sprite if none is defined.
    if (Object.keys(self._sprite).length === 0) {
        self._sprite = { __default: [0, self._duration * 1000] };
    }

    // Fire the loaded event.
    if (self._state !== 'loaded') {
        self._state = 'loaded';
        self._emit('load');
        self._loadQueue();
    }
};

/**
 * Setup the audio context when available, or switch to HTML5 Audio mode.
 */
var setupAudioContext = function () {
    // Check if we are using Web Audio and setup the AudioContext if we are.
    try {
        if (typeof AudioContext !== 'undefined') {
            Howler.ctx = new AudioContext();
        } else if (typeof webkitAudioContext !== 'undefined') {
            Howler.ctx = new webkitAudioContext();
        } else {
            Howler.usingWebAudio = false;
        }
    } catch (e) {
        Howler.usingWebAudio = false;
    }

    // Check if a webview is being used on iOS8 or earlier (rather than the browser).
    // If it is, disable Web Audio as it causes crashing.
    var iOS = (/iP(hone|od|ad)/.test(Howler._navigator && Howler._navigator.platform));
    var appVersion = Howler._navigator && Howler._navigator.appVersion.match(/OS (\d+)_(\d+)_?(\d+)?/);
    var version = appVersion ? parseInt(appVersion[1], 10) : null;
    if (iOS && version && version < 9) {
        var safari = /safari/.test(Howler._navigator && Howler._navigator.userAgent.toLowerCase());
        if (Howler._navigator && Howler._navigator.standalone && !safari || Howler._navigator && !Howler._navigator.standalone && !safari) {
            Howler.usingWebAudio = false;
        }
    }

    // Create and expose the master GainNode when using Web Audio (useful for plugins or advanced usage).
    if (Howler.usingWebAudio) {
        Howler.masterGain = (typeof Howler.ctx.createGain === 'undefined') ? Howler.ctx.createGainNode() : Howler.ctx.createGain();
        Howler.masterGain.gain.setValueAtTime(Howler._muted ? 0 : 1, Howler.ctx.currentTime);
        Howler.masterGain.connect(Howler.ctx.destination);
    }

    // Re-run the setup on Howler.
    Howler._setup();
};

// Add support for AMD (Asynchronous Module Definition) libraries such as require.js.
if (typeof define === 'function' && define.amd) {
    define([], function () {
        return {
            Howler: Howler,
            Howl: Howl
        };
    });
}

// Add support for CommonJS libraries such as browserify.
if (typeof exports !== 'undefined') {
    exports.Howler = Howler;
    exports.Howl = Howl;
}

// Define globally in case AMD is not available or unused.
if (typeof window !== 'undefined') {
    window.HowlerGlobal = HowlerGlobal;
    window.Howler = Howler;
    window.Howl = Howl;
    window.Sound = Sound;
} else if (typeof global !== 'undefined') { // Add to global in Node.js (for testing, etc).
    global.HowlerGlobal = HowlerGlobal;
    global.Howler = Howler;
    global.Howl = Howl;
    global.Sound = Sound;
}



/*!
 *  Spatial Plugin - Adds support for stereo and 3D audio where Web Audio is supported.
 *  
 *  howler.js v2.0.13
 *  howlerjs.com
 *
 *  (c) 2013-2018, James Simpson of GoldFire Studios
 *  goldfirestudios.com
 *
 *  MIT License
 */



'use strict';

// Setup default properties.
HowlerGlobal.prototype._pos = [0, 0, 0];
HowlerGlobal.prototype._orientation = [0, 0, -1, 0, 1, 0];

/** Global Methods **/
/***************************************************************************/

/**
 * Helper method to update the stereo panning position of all current Howls.
 * Future Howls will not use this value unless explicitly set.
 * @param  {Number} pan A value of -1.0 is all the way left and 1.0 is all the way right.
 * @return {Howler/Number}     Self or current stereo panning value.
 */
HowlerGlobal.prototype.stereo = function (pan) {
    var self = this;

    // Stop right here if not using Web Audio.
    if (!self.ctx || !self.ctx.listener) {
        return self;
    }

    // Loop through all Howls and update their stereo panning.
    for (var i = self._howls.length - 1; i >= 0; i--) {
        self._howls[i].stereo(pan);
    }

    return self;
};

/**
 * Get/set the position of the listener in 3D cartesian space. Sounds using
 * 3D position will be relative to the listener's position.
 * @param  {Number} x The x-position of the listener.
 * @param  {Number} y The y-position of the listener.
 * @param  {Number} z The z-position of the listener.
 * @return {Howler/Array}   Self or current listener position.
 */
HowlerGlobal.prototype.pos = function (x, y, z) {
    var self = this;

    // Stop right here if not using Web Audio.
    if (!self.ctx || !self.ctx.listener) {
        return self;
    }

    // Set the defaults for optional 'y' & 'z'.
    y = (typeof y !== 'number') ? self._pos[1] : y;
    z = (typeof z !== 'number') ? self._pos[2] : z;

    if (typeof x === 'number') {
        self._pos = [x, y, z];

        if (typeof self.ctx.listener.positionX !== 'undefined') {
            self.ctx.listener.positionX.setTargetAtTime(self._pos[0], Howler.ctx.currentTime, 0.1);
            self.ctx.listener.positionY.setTargetAtTime(self._pos[1], Howler.ctx.currentTime, 0.1);
            self.ctx.listener.positionZ.setTargetAtTime(self._pos[2], Howler.ctx.currentTime, 0.1);
        } else {
            self.ctx.listener.setPosition(self._pos[0], self._pos[1], self._pos[2]);
        }
    } else {
        return self._pos;
    }

    return self;
};

/**
 * Get/set the direction the listener is pointing in the 3D cartesian space.
 * A front and up vector must be provided. The front is the direction the
 * face of the listener is pointing, and up is the direction the top of the
 * listener is pointing. Thus, these values are expected to be at right angles
 * from each other.
 * @param  {Number} x   The x-orientation of the listener.
 * @param  {Number} y   The y-orientation of the listener.
 * @param  {Number} z   The z-orientation of the listener.
 * @param  {Number} xUp The x-orientation of the top of the listener.
 * @param  {Number} yUp The y-orientation of the top of the listener.
 * @param  {Number} zUp The z-orientation of the top of the listener.
 * @return {Howler/Array}     Returns self or the current orientation vectors.
 */
HowlerGlobal.prototype.orientation = function (x, y, z, xUp, yUp, zUp) {
    var self = this;

    // Stop right here if not using Web Audio.
    if (!self.ctx || !self.ctx.listener) {
        return self;
    }

    // Set the defaults for optional 'y' & 'z'.
    var or = self._orientation;
    y = (typeof y !== 'number') ? or[1] : y;
    z = (typeof z !== 'number') ? or[2] : z;
    xUp = (typeof xUp !== 'number') ? or[3] : xUp;
    yUp = (typeof yUp !== 'number') ? or[4] : yUp;
    zUp = (typeof zUp !== 'number') ? or[5] : zUp;

    if (typeof x === 'number') {
        self._orientation = [x, y, z, xUp, yUp, zUp];

        if (typeof self.ctx.listener.forwardX !== 'undefined') {
            self.ctx.listener.forwardX.setTargetAtTime(x, Howler.ctx.currentTime, 0.1);
            self.ctx.listener.forwardY.setTargetAtTime(y, Howler.ctx.currentTime, 0.1);
            self.ctx.listener.forwardZ.setTargetAtTime(z, Howler.ctx.currentTime, 0.1);
            self.ctx.listener.upX.setTargetAtTime(x, Howler.ctx.currentTime, 0.1);
            self.ctx.listener.upY.setTargetAtTime(y, Howler.ctx.currentTime, 0.1);
            self.ctx.listener.upZ.setTargetAtTime(z, Howler.ctx.currentTime, 0.1);
        } else {
            self.ctx.listener.setOrientation(x, y, z, xUp, yUp, zUp);
        }
    } else {
        return or;
    }

    return self;
};

/** Group Methods **/
/***************************************************************************/

/**
 * Add new properties to the core init.
 * @param  {Function} _super Core init method.
 * @return {Howl}
 */
Howl.prototype.init = (function (_super) {
    return function (o) {
        var self = this;

        // Setup user-defined default properties.
        self._orientation = o.orientation || [1, 0, 0];
        self._stereo = o.stereo || null;
        self._pos = o.pos || null;
        self._pannerAttr = {
            coneInnerAngle: typeof o.coneInnerAngle !== 'undefined' ? o.coneInnerAngle : 360,
            coneOuterAngle: typeof o.coneOuterAngle !== 'undefined' ? o.coneOuterAngle : 360,
            coneOuterGain: typeof o.coneOuterGain !== 'undefined' ? o.coneOuterGain : 0,
            distanceModel: typeof o.distanceModel !== 'undefined' ? o.distanceModel : 'inverse',
            maxDistance: typeof o.maxDistance !== 'undefined' ? o.maxDistance : 10000,
            panningModel: typeof o.panningModel !== 'undefined' ? o.panningModel : 'HRTF',
            refDistance: typeof o.refDistance !== 'undefined' ? o.refDistance : 1,
            rolloffFactor: typeof o.rolloffFactor !== 'undefined' ? o.rolloffFactor : 1
        };

        // Setup event listeners.
        self._onstereo = o.onstereo ? [{ fn: o.onstereo }] : [];
        self._onpos = o.onpos ? [{ fn: o.onpos }] : [];
        self._onorientation = o.onorientation ? [{ fn: o.onorientation }] : [];

        // Complete initilization with howler.js core's init function.
        return _super.call(this, o);
    };
})(Howl.prototype.init);

/**
 * Get/set the stereo panning of the audio source for this sound or all in the group.
 * @param  {Number} pan  A value of -1.0 is all the way left and 1.0 is all the way right.
 * @param  {Number} id (optional) The sound ID. If none is passed, all in group will be updated.
 * @return {Howl/Number}    Returns self or the current stereo panning value.
 */
Howl.prototype.stereo = function (pan, id) {
    var self = this;

    // Stop right here if not using Web Audio.
    if (!self._webAudio) {
        return self;
    }

    // If the sound hasn't loaded, add it to the load queue to change stereo pan when capable.
    if (self._state !== 'loaded') {
        self._queue.push({
            event: 'stereo',
            action: function () {
                self.stereo(pan, id);
            }
        });

        return self;
    }

    // Check for PannerStereoNode support and fallback to PannerNode if it doesn't exist.
    var pannerType = (typeof Howler.ctx.createStereoPanner === 'undefined') ? 'spatial' : 'stereo';

    // Setup the group's stereo panning if no ID is passed.
    if (typeof id === 'undefined') {
        // Return the group's stereo panning if no parameters are passed.
        if (typeof pan === 'number') {
            self._stereo = pan;
            self._pos = [pan, 0, 0];
        } else {
            return self._stereo;
        }
    }

    // Change the streo panning of one or all sounds in group.
    var ids = self._getSoundIds(id);
    for (var i = 0; i < ids.length; i++) {
        // Get the sound.
        var sound = self._soundById(ids[i]);

        if (sound) {
            if (typeof pan === 'number') {
                sound._stereo = pan;
                sound._pos = [pan, 0, 0];

                if (sound._node) {
                    // If we are falling back, make sure the panningModel is equalpower.
                    sound._pannerAttr.panningModel = 'equalpower';

                    // Check if there is a panner setup and create a new one if not.
                    if (!sound._panner || !sound._panner.pan) {
                        setupPanner(sound, pannerType);
                    }

                    if (pannerType === 'spatial') {
                        if (typeof sound._panner.positionX !== 'undefined') {
                            sound._panner.positionX.setValueAtTime(pan, Howler.ctx.currentTime);
                            sound._panner.positionY.setValueAtTime(0, Howler.ctx.currentTime);
                            sound._panner.positionZ.setValueAtTime(0, Howler.ctx.currentTime);
                        } else {
                            sound._panner.setPosition(pan, 0, 0);
                        }
                    } else {
                        sound._panner.pan.setValueAtTime(pan, Howler.ctx.currentTime);
                    }
                }

                self._emit('stereo', sound._id);
            } else {
                return sound._stereo;
            }
        }
    }

    return self;
};

/**
 * Get/set the 3D spatial position of the audio source for this sound or group relative to the global listener.
 * @param  {Number} x  The x-position of the audio source.
 * @param  {Number} y  The y-position of the audio source.
 * @param  {Number} z  The z-position of the audio source.
 * @param  {Number} id (optional) The sound ID. If none is passed, all in group will be updated.
 * @return {Howl/Array}    Returns self or the current 3D spatial position: [x, y, z].
 */
Howl.prototype.pos = function (x, y, z, id) {
    var self = this;

    // Stop right here if not using Web Audio.
    if (!self._webAudio) {
        return self;
    }

    // If the sound hasn't loaded, add it to the load queue to change position when capable.
    if (self._state !== 'loaded') {
        self._queue.push({
            event: 'pos',
            action: function () {
                self.pos(x, y, z, id);
            }
        });

        return self;
    }

    // Set the defaults for optional 'y' & 'z'.
    y = (typeof y !== 'number') ? 0 : y;
    z = (typeof z !== 'number') ? -0.5 : z;

    // Setup the group's spatial position if no ID is passed.
    if (typeof id === 'undefined') {
        // Return the group's spatial position if no parameters are passed.
        if (typeof x === 'number') {
            self._pos = [x, y, z];
        } else {
            return self._pos;
        }
    }

    // Change the spatial position of one or all sounds in group.
    var ids = self._getSoundIds(id);
    for (var i = 0; i < ids.length; i++) {
        // Get the sound.
        var sound = self._soundById(ids[i]);

        if (sound) {
            if (typeof x === 'number') {
                sound._pos = [x, y, z];

                if (sound._node) {
                    // Check if there is a panner setup and create a new one if not.
                    if (!sound._panner || sound._panner.pan) {
                        setupPanner(sound, 'spatial');
                    }

                    if (typeof sound._panner.positionX !== 'undefined') {
                        sound._panner.positionX.setValueAtTime(x, Howler.ctx.currentTime);
                        sound._panner.positionY.setValueAtTime(y, Howler.ctx.currentTime);
                        sound._panner.positionZ.setValueAtTime(z, Howler.ctx.currentTime);
                    } else {
                        sound._panner.setOrientation(x, y, z);
                    }
                }

                self._emit('pos', sound._id);
            } else {
                return sound._pos;
            }
        }
    }

    return self;
};

/**
 * Get/set the direction the audio source is pointing in the 3D cartesian coordinate
 * space. Depending on how direction the sound is, based on the `cone` attributes,
 * a sound pointing away from the listener can be quiet or silent.
 * @param  {Number} x  The x-orientation of the source.
 * @param  {Number} y  The y-orientation of the source.
 * @param  {Number} z  The z-orientation of the source.
 * @param  {Number} id (optional) The sound ID. If none is passed, all in group will be updated.
 * @return {Howl/Array}    Returns self or the current 3D spatial orientation: [x, y, z].
 */
Howl.prototype.orientation = function (x, y, z, id) {
    var self = this;

    // Stop right here if not using Web Audio.
    if (!self._webAudio) {
        return self;
    }

    // If the sound hasn't loaded, add it to the load queue to change orientation when capable.
    if (self._state !== 'loaded') {
        self._queue.push({
            event: 'orientation',
            action: function () {
                self.orientation(x, y, z, id);
            }
        });

        return self;
    }

    // Set the defaults for optional 'y' & 'z'.
    y = (typeof y !== 'number') ? self._orientation[1] : y;
    z = (typeof z !== 'number') ? self._orientation[2] : z;

    // Setup the group's spatial orientation if no ID is passed.
    if (typeof id === 'undefined') {
        // Return the group's spatial orientation if no parameters are passed.
        if (typeof x === 'number') {
            self._orientation = [x, y, z];
        } else {
            return self._orientation;
        }
    }

    // Change the spatial orientation of one or all sounds in group.
    var ids = self._getSoundIds(id);
    for (var i = 0; i < ids.length; i++) {
        // Get the sound.
        var sound = self._soundById(ids[i]);

        if (sound) {
            if (typeof x === 'number') {
                sound._orientation = [x, y, z];

                if (sound._node) {
                    // Check if there is a panner setup and create a new one if not.
                    if (!sound._panner) {
                        // Make sure we have a position to setup the node with.
                        if (!sound._pos) {
                            sound._pos = self._pos || [0, 0, -0.5];
                        }

                        setupPanner(sound, 'spatial');
                    }

                    sound._panner.orientationX.setValueAtTime(x, Howler.ctx.currentTime);
                    sound._panner.orientationY.setValueAtTime(y, Howler.ctx.currentTime);
                    sound._panner.orientationZ.setValueAtTime(z, Howler.ctx.currentTime);
                }

                self._emit('orientation', sound._id);
            } else {
                return sound._orientation;
            }
        }
    }

    return self;
};

/**
 * Get/set the panner node's attributes for a sound or group of sounds.
 * This method can optionall take 0, 1 or 2 arguments.
 *   pannerAttr() -> Returns the group's values.
 *   pannerAttr(id) -> Returns the sound id's values.
 *   pannerAttr(o) -> Set's the values of all sounds in this Howl group.
 *   pannerAttr(o, id) -> Set's the values of passed sound id.
 *
 *   Attributes:
 *     coneInnerAngle - (360 by default) A parameter for directional audio sources, this is an angle, in degrees,
 *                      inside of which there will be no volume reduction.
 *     coneOuterAngle - (360 by default) A parameter for directional audio sources, this is an angle, in degrees,
 *                      outside of which the volume will be reduced to a constant value of `coneOuterGain`.
 *     coneOuterGain - (0 by default) A parameter for directional audio sources, this is the gain outside of the
 *                     `coneOuterAngle`. It is a linear value in the range `[0, 1]`.
 *     distanceModel - ('inverse' by default) Determines algorithm used to reduce volume as audio moves away from
 *                     listener. Can be `linear`, `inverse` or `exponential.
 *     maxDistance - (10000 by default) The maximum distance between source and listener, after which the volume
 *                   will not be reduced any further.
 *     refDistance - (1 by default) A reference distance for reducing volume as source moves further from the listener.
 *                   This is simply a variable of the distance model and has a different effect depending on which model
 *                   is used and the scale of your coordinates. Generally, volume will be equal to 1 at this distance.
 *     rolloffFactor - (1 by default) How quickly the volume reduces as source moves from listener. This is simply a
 *                     variable of the distance model and can be in the range of `[0, 1]` with `linear` and `[0, ∞]`
 *                     with `inverse` and `exponential`.
 *     panningModel - ('HRTF' by default) Determines which spatialization algorithm is used to position audio.
 *                     Can be `HRTF` or `equalpower`.
 *
 * @return {Howl/Object} Returns self or current panner attributes.
 */
Howl.prototype.pannerAttr = function () {
    var self = this;
    var args = arguments;
    var o, id, sound;

    // Stop right here if not using Web Audio.
    if (!self._webAudio) {
        return self;
    }

    // Determine the values based on arguments.
    if (args.length === 0) {
        // Return the group's panner attribute values.
        return self._pannerAttr;
    } else if (args.length === 1) {
        if (typeof args[0] === 'object') {
            o = args[0];

            // Set the grou's panner attribute values.
            if (typeof id === 'undefined') {
                if (!o.pannerAttr) {
                    o.pannerAttr = {
                        coneInnerAngle: o.coneInnerAngle,
                        coneOuterAngle: o.coneOuterAngle,
                        coneOuterGain: o.coneOuterGain,
                        distanceModel: o.distanceModel,
                        maxDistance: o.maxDistance,
                        refDistance: o.refDistance,
                        rolloffFactor: o.rolloffFactor,
                        panningModel: o.panningModel
                    };
                }

                self._pannerAttr = {
                    coneInnerAngle: typeof o.pannerAttr.coneInnerAngle !== 'undefined' ? o.pannerAttr.coneInnerAngle : self._coneInnerAngle,
                    coneOuterAngle: typeof o.pannerAttr.coneOuterAngle !== 'undefined' ? o.pannerAttr.coneOuterAngle : self._coneOuterAngle,
                    coneOuterGain: typeof o.pannerAttr.coneOuterGain !== 'undefined' ? o.pannerAttr.coneOuterGain : self._coneOuterGain,
                    distanceModel: typeof o.pannerAttr.distanceModel !== 'undefined' ? o.pannerAttr.distanceModel : self._distanceModel,
                    maxDistance: typeof o.pannerAttr.maxDistance !== 'undefined' ? o.pannerAttr.maxDistance : self._maxDistance,
                    refDistance: typeof o.pannerAttr.refDistance !== 'undefined' ? o.pannerAttr.refDistance : self._refDistance,
                    rolloffFactor: typeof o.pannerAttr.rolloffFactor !== 'undefined' ? o.pannerAttr.rolloffFactor : self._rolloffFactor,
                    panningModel: typeof o.pannerAttr.panningModel !== 'undefined' ? o.pannerAttr.panningModel : self._panningModel
                };
            }
        } else {
            // Return this sound's panner attribute values.
            sound = self._soundById(parseInt(args[0], 10));
            return sound ? sound._pannerAttr : self._pannerAttr;
        }
    } else if (args.length === 2) {
        o = args[0];
        id = parseInt(args[1], 10);
    }

    // Update the values of the specified sounds.
    var ids = self._getSoundIds(id);
    for (var i = 0; i < ids.length; i++) {
        sound = self._soundById(ids[i]);

        if (sound) {
            // Merge the new values into the sound.
            var pa = sound._pannerAttr;
            pa = {
                coneInnerAngle: typeof o.coneInnerAngle !== 'undefined' ? o.coneInnerAngle : pa.coneInnerAngle,
                coneOuterAngle: typeof o.coneOuterAngle !== 'undefined' ? o.coneOuterAngle : pa.coneOuterAngle,
                coneOuterGain: typeof o.coneOuterGain !== 'undefined' ? o.coneOuterGain : pa.coneOuterGain,
                distanceModel: typeof o.distanceModel !== 'undefined' ? o.distanceModel : pa.distanceModel,
                maxDistance: typeof o.maxDistance !== 'undefined' ? o.maxDistance : pa.maxDistance,
                refDistance: typeof o.refDistance !== 'undefined' ? o.refDistance : pa.refDistance,
                rolloffFactor: typeof o.rolloffFactor !== 'undefined' ? o.rolloffFactor : pa.rolloffFactor,
                panningModel: typeof o.panningModel !== 'undefined' ? o.panningModel : pa.panningModel
            };

            // Update the panner values or create a new panner if none exists.
            var panner = sound._panner;
            if (panner) {
                panner.coneInnerAngle = pa.coneInnerAngle;
                panner.coneOuterAngle = pa.coneOuterAngle;
                panner.coneOuterGain = pa.coneOuterGain;
                panner.distanceModel = pa.distanceModel;
                panner.maxDistance = pa.maxDistance;
                panner.refDistance = pa.refDistance;
                panner.rolloffFactor = pa.rolloffFactor;
                panner.panningModel = pa.panningModel;
            } else {
                // Make sure we have a position to setup the node with.
                if (!sound._pos) {
                    sound._pos = self._pos || [0, 0, -0.5];
                }

                // Create a new panner node.
                setupPanner(sound, 'spatial');
            }
        }
    }

    return self;
};

/** Single Sound Methods **/
/***************************************************************************/

/**
 * Add new properties to the core Sound init.
 * @param  {Function} _super Core Sound init method.
 * @return {Sound}
 */
Sound.prototype.init = (function (_super) {
    return function () {
        var self = this;
        var parent = self._parent;

        // Setup user-defined default properties.
        self._orientation = parent._orientation;
        self._stereo = parent._stereo;
        self._pos = parent._pos;
        self._pannerAttr = parent._pannerAttr;

        // Complete initilization with howler.js core Sound's init function.
        _super.call(this);

        // If a stereo or position was specified, set it up.
        if (self._stereo) {
            parent.stereo(self._stereo);
        } else if (self._pos) {
            parent.pos(self._pos[0], self._pos[1], self._pos[2], self._id);
        }
    };
})(Sound.prototype.init);

/**
 * Override the Sound.reset method to clean up properties from the spatial plugin.
 * @param  {Function} _super Sound reset method.
 * @return {Sound}
 */
Sound.prototype.reset = (function (_super) {
    return function () {
        var self = this;
        var parent = self._parent;

        // Reset all spatial plugin properties on this sound.
        self._orientation = parent._orientation;
        self._stereo = parent._stereo;
        self._pos = parent._pos;
        self._pannerAttr = parent._pannerAttr;

        // If a stereo or position was specified, set it up.
        if (self._stereo) {
            parent.stereo(self._stereo);
        } else if (self._pos) {
            parent.pos(self._pos[0], self._pos[1], self._pos[2], self._id);
        } else if (self._panner) {
            // Disconnect the panner.
            self._panner.disconnect(0);
            self._panner = undefined;
            parent._refreshBuffer(self);
        }

        // Complete resetting of the sound.
        return _super.call(this);
    };
})(Sound.prototype.reset);

/** Helper Methods **/
/***************************************************************************/

/**
 * Create a new panner node and save it on the sound.
 * @param  {Sound} sound Specific sound to setup panning on.
 * @param {String} type Type of panner to create: 'stereo' or 'spatial'.
 */
var setupPanner = function (sound, type) {
    type = type || 'spatial';

    // Create the new panner node.
    if (type === 'spatial') {
        sound._panner = Howler.ctx.createPanner();
        sound._panner.coneInnerAngle = sound._pannerAttr.coneInnerAngle;
        sound._panner.coneOuterAngle = sound._pannerAttr.coneOuterAngle;
        sound._panner.coneOuterGain = sound._pannerAttr.coneOuterGain;
        sound._panner.distanceModel = sound._pannerAttr.distanceModel;
        sound._panner.maxDistance = sound._pannerAttr.maxDistance;
        sound._panner.refDistance = sound._pannerAttr.refDistance;
        sound._panner.rolloffFactor = sound._pannerAttr.rolloffFactor;
        sound._panner.panningModel = sound._pannerAttr.panningModel;

        if (typeof sound._panner.positionX !== 'undefined') {
            sound._panner.positionX.setValueAtTime(sound._pos[0], Howler.ctx.currentTime);
            sound._panner.positionY.setValueAtTime(sound._pos[1], Howler.ctx.currentTime);
            sound._panner.positionZ.setValueAtTime(sound._pos[2], Howler.ctx.currentTime);
        } else {
            sound._panner.setPosition(sound._pos[0], sound._pos[1], sound._pos[2]);
        }

        if (typeof sound._panner.orientationX !== 'undefined') {
            sound._panner.orientationX.setValueAtTime(sound._orientation[0], Howler.ctx.currentTime);
            sound._panner.orientationY.setValueAtTime(sound._orientation[1], Howler.ctx.currentTime);
            sound._panner.orientationZ.setValueAtTime(sound._orientation[2], Howler.ctx.currentTime);
        } else {
            sound._panner.setOrientation(sound._orientation[0], sound._orientation[1], sound._orientation[2]);
        }
    } else {
        sound._panner = Howler.ctx.createStereoPanner();
        sound._panner.pan.setValueAtTime(sound._stereo, Howler.ctx.currentTime);
    }

    sound._panner.connect(sound._node);

    // Update the connections.
    if (!sound._paused) {
        sound._parent.pause(sound._id, true).play(sound._id, true);
    }
};

export {
    Howl,
    Howler,
    Sound
}