1 | const {EventEmitter} = require('events');
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2 |
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3 | const VolumeEffect = require('./effects/VolumeEffect');
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4 |
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5 | /**
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6 | * Name of event that indicates playback has ended.
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7 | * @const {string}
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8 | */
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9 | const ON_ENDED = 'ended';
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10 |
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11 | class SoundPlayer extends EventEmitter {
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12 | /**
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13 | * Play sounds that stop without audible clipping.
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14 | *
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15 | * @param {AudioEngine} audioEngine - engine to play sounds on
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16 | * @param {object} data - required data for sound playback
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17 | * @param {string} data.id - a unique id for this sound
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18 | * @param {ArrayBuffer} data.buffer - buffer of the sound's waveform to play
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19 | * @constructor
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20 | */
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21 | constructor (audioEngine, {id, buffer}) {
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22 | super();
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23 |
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24 | /**
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25 | * Unique sound identifier set by AudioEngine.
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26 | * @type {string}
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27 | */
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28 | this.id = id;
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29 |
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30 | /**
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31 | * AudioEngine creating this sound player.
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32 | * @type {AudioEngine}
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33 | */
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34 | this.audioEngine = audioEngine;
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35 |
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36 | /**
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37 | * Decoded audio buffer from audio engine for playback.
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38 | * @type {AudioBuffer}
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39 | */
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40 | this.buffer = buffer;
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41 |
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42 | /**
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43 | * Output audio node.
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44 | * @type {AudioNode}
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45 | */
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46 | this.outputNode = null;
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47 |
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48 | /**
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49 | * VolumeEffect used to fade out playing sounds when stopping them.
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50 | * @type {VolumeEffect}
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51 | */
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52 | this.volumeEffect = null;
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53 |
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54 |
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55 | /**
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56 | * Target engine, effect, or chain this player directly connects to.
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57 | * @type {AudioEngine|Effect|EffectChain}
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58 | */
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59 | this.target = null;
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60 |
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61 | /**
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62 | * Internally is the SoundPlayer initialized with at least its buffer
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63 | * source node and output node.
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64 | * @type {boolean}
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65 | */
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66 | this.initialized = false;
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67 |
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68 | /**
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69 | * Is the sound playing or starting to play?
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70 | * @type {boolean}
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71 | */
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72 | this.isPlaying = false;
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73 |
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74 | /**
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75 | * Timestamp sound is expected to be starting playback until. Once the
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76 | * future timestamp is reached the sound is considered to be playing
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77 | * through the audio hardware and stopping should fade out instead of
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78 | * cutting off playback.
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79 | * @type {number}
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80 | */
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81 | this.startingUntil = 0;
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82 |
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83 | /**
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84 | * Rate to play back the audio at.
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85 | * @type {number}
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86 | */
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87 | this.playbackRate = 1;
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88 |
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89 | // handleEvent is a EventTarget api for the DOM, however the
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90 | // web-audio-test-api we use uses an addEventListener that isn't
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91 | // compatable with object and requires us to pass this bound function
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92 | // instead
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93 | this.handleEvent = this.handleEvent.bind(this);
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94 | }
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95 |
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96 | /**
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97 | * Is plaback currently starting?
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98 | * @type {boolean}
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99 | */
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100 | get isStarting () {
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101 | return this.isPlaying && this.startingUntil > this.audioEngine.currentTime;
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102 | }
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103 |
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104 | /**
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105 | * Handle any event we have told the output node to listen for.
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106 | * @param {Event} event - dom event to handle
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107 | */
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108 | handleEvent (event) {
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109 | if (event.type === ON_ENDED) {
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110 | this.onEnded();
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111 | }
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112 | }
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113 |
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114 | /**
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115 | * Event listener for when playback ends.
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116 | */
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117 | onEnded () {
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118 | this.emit('stop');
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119 |
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120 | this.isPlaying = false;
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121 | }
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122 |
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123 | /**
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124 | * Create the buffer source node during initialization or secondary
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125 | * playback.
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126 | */
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127 | _createSource () {
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128 | if (this.outputNode !== null) {
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129 | this.outputNode.removeEventListener(ON_ENDED, this.handleEvent);
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130 | this.outputNode.disconnect();
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131 | }
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132 |
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133 | this.outputNode = this.audioEngine.audioContext.createBufferSource();
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134 | this.outputNode.playbackRate.value = this.playbackRate;
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135 | this.outputNode.buffer = this.buffer;
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136 |
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137 | this.outputNode.addEventListener(ON_ENDED, this.handleEvent);
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138 |
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139 | if (this.target !== null) {
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140 | this.connect(this.target);
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141 | }
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142 | }
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143 |
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144 | /**
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145 | * Initialize the player for first playback.
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146 | */
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147 | initialize () {
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148 | this.initialized = true;
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149 |
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150 | this._createSource();
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151 | }
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152 |
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153 | /**
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154 | * Connect the player to the engine or an effect chain.
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155 | * @param {object} target - object to connect to
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156 | * @returns {object} - return this sound player
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157 | */
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158 | connect (target) {
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159 | if (target === this.volumeEffect) {
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160 | this.outputNode.disconnect();
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161 | this.outputNode.connect(this.volumeEffect.getInputNode());
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162 | return;
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163 | }
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164 |
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165 | this.target = target;
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166 |
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167 | if (!this.initialized) {
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168 | return;
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169 | }
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170 |
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171 | if (this.volumeEffect === null) {
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172 | this.outputNode.disconnect();
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173 | this.outputNode.connect(target.getInputNode());
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174 | } else {
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175 | this.volumeEffect.connect(target);
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176 | }
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177 |
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178 | return this;
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179 | }
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180 |
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181 | /**
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182 | * Teardown the player.
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183 | */
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184 | dispose () {
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185 | if (!this.initialized) {
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186 | return;
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187 | }
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188 |
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189 | this.stopImmediately();
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190 |
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191 | if (this.volumeEffect !== null) {
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192 | this.volumeEffect.dispose();
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193 | this.volumeEffect = null;
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194 | }
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195 |
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196 | this.outputNode.disconnect();
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197 | this.outputNode = null;
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198 |
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199 | this.target = null;
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200 |
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201 | this.initialized = false;
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202 | }
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203 |
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204 | /**
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205 | * Take the internal state of this player and create a new player from
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206 | * that. Restore the state of this player to that before its first playback.
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207 | *
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208 | * The returned player can be used to stop the original playback or
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209 | * continue it without manipulation from the original player.
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210 | *
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211 | * @returns {SoundPlayer} - new SoundPlayer with old state
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212 | */
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213 | take () {
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214 | if (this.outputNode) {
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215 | this.outputNode.removeEventListener(ON_ENDED, this.handleEvent);
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216 | }
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217 |
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218 | const taken = new SoundPlayer(this.audioEngine, this);
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219 | taken.playbackRate = this.playbackRate;
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220 | if (this.isPlaying) {
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221 | taken.startingUntil = this.startingUntil;
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222 | taken.isPlaying = this.isPlaying;
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223 | taken.initialized = this.initialized;
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224 | taken.outputNode = this.outputNode;
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225 | taken.outputNode.addEventListener(ON_ENDED, taken.handleEvent);
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226 | taken.volumeEffect = this.volumeEffect;
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227 | if (taken.volumeEffect) {
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228 | taken.volumeEffect.audioPlayer = taken;
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229 | }
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230 | if (this.target !== null) {
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231 | taken.connect(this.target);
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232 | }
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233 |
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234 | this.emit('stop');
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235 | taken.emit('play');
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236 | }
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237 |
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238 | this.outputNode = null;
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239 | this.volumeEffect = null;
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240 | this.initialized = false;
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241 | this.startingUntil = 0;
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242 | this.isPlaying = false;
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243 |
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244 | return taken;
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245 | }
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246 |
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247 | /**
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248 | * Start playback for this sound.
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249 | *
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250 | * If the sound is already playing it will stop playback with a quick fade
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251 | * out.
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252 | */
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253 | play () {
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254 | if (this.isStarting) {
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255 | this.emit('stop');
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256 | this.emit('play');
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257 | return;
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258 | }
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259 |
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260 | if (this.isPlaying) {
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261 | this.stop();
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262 | }
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263 |
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264 | if (this.initialized) {
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265 | this._createSource();
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266 | } else {
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267 | this.initialize();
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268 | }
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269 |
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270 | this.outputNode.start();
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271 |
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272 | this.isPlaying = true;
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273 |
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274 | const {currentTime, DECAY_DURATION} = this.audioEngine;
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275 | this.startingUntil = currentTime + DECAY_DURATION;
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276 |
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277 | this.emit('play');
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278 | }
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279 |
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280 | /**
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281 | * Stop playback after quickly fading out.
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282 | */
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283 | stop () {
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284 | if (!this.isPlaying) {
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285 | return;
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286 | }
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287 |
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288 | // always do a manual stop on a taken / volume effect fade out sound
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289 | // player take will emit "stop" as well as reset all of our playing
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290 | // statuses / remove our nodes / etc
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291 | const taken = this.take();
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292 | taken.volumeEffect = new VolumeEffect(taken.audioEngine, taken, null);
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293 |
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294 | taken.volumeEffect.connect(taken.target);
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295 | // volumeEffect will recursively connect to us if it needs to, so this
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296 | // happens too:
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297 | // taken.connect(taken.volumeEffect);
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298 |
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299 | taken.finished().then(() => taken.dispose());
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300 |
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301 | taken.volumeEffect.set(0);
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302 | const {currentTime, DECAY_DURATION} = this.audioEngine;
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303 | taken.outputNode.stop(currentTime + DECAY_DURATION);
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304 | }
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305 |
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306 | /**
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307 | * Stop immediately without fading out. May cause audible clipping.
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308 | */
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309 | stopImmediately () {
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310 | if (!this.isPlaying) {
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311 | return;
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312 | }
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313 |
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314 | this.outputNode.stop();
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315 |
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316 | this.isPlaying = false;
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317 | this.startingUntil = 0;
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318 |
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319 | this.emit('stop');
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320 | }
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321 |
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322 | /**
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323 | * Return a promise that resolves when the sound next finishes.
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324 | * @returns {Promise} - resolves when the sound finishes
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325 | */
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326 | finished () {
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327 | return new Promise(resolve => {
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328 | this.once('stop', resolve);
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329 | });
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330 | }
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331 |
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332 | /**
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333 | * Set the sound's playback rate.
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334 | * @param {number} value - playback rate. Default is 1.
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335 | */
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336 | setPlaybackRate (value) {
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337 | this.playbackRate = value;
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338 |
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339 | if (this.initialized) {
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340 | this.outputNode.playbackRate.value = value;
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341 | }
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342 | }
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343 | }
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344 |
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345 | module.exports = SoundPlayer;
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