130 lines
3.6 KiB
JavaScript
130 lines
3.6 KiB
JavaScript
import logger from '../logger';
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import { RecordingAdapter } from './RecordingAdapter';
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/**
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* Base class for {@code AudioContext}-based recording adapters.
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*/
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export class AbstractAudioContextAdapter extends RecordingAdapter {
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/**
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* The {@code AudioContext} instance.
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*/
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_audioContext = null;
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/**
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* The {@code ScriptProcessorNode} instance.
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*/
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_audioProcessingNode = null;
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/**
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* The {@code MediaStreamAudioSourceNode} instance.
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*/
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_audioSource = null;
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/**
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* The {@code MediaStream} instance, representing the current audio device.
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*/
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_stream = null;
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/**
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* Sample rate.
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*/
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_sampleRate = 44100;
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/**
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* Constructor.
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*/
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constructor() {
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super();
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// sampleRate is browser and OS dependent.
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// Setting sampleRate explicitly is in the specs but not implemented
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// by browsers.
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// See: https://developer.mozilla.org/en-US/docs/Web/API/AudioContext/
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// AudioContext#Browser_compatibility
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// And https://bugs.chromium.org/p/chromium/issues/detail?id=432248
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this._audioContext = new AudioContext();
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this._sampleRate = this._audioContext.sampleRate;
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logger.log(`Current sampleRate ${this._sampleRate}.`);
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}
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/**
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* Sets up the audio graph in the AudioContext.
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*
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* @protected
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* @param {string} micDeviceId - The current microphone device ID.
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* @param {Function} callback - Callback function to
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* handle AudioProcessingEvents.
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* @returns {Promise}
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*/
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_initializeAudioContext(micDeviceId, callback) {
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if (typeof callback !== 'function') {
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return Promise.reject('a callback function is required.');
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}
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return this._getAudioStream(micDeviceId)
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.then(stream => {
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this._stream = stream;
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this._audioSource
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= this._audioContext.createMediaStreamSource(stream);
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this._audioProcessingNode
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= this._audioContext.createScriptProcessor(4096, 1, 1);
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this._audioProcessingNode.onaudioprocess = callback;
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logger.debug('AudioContext is set up.');
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})
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.catch(err => {
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logger.error(`Error calling getUserMedia(): ${err}`);
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return Promise.reject(err);
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});
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}
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/**
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* Connects the nodes in the {@code AudioContext} to start the flow of
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* audio data.
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*
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* @protected
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* @returns {void}
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*/
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_connectAudioGraph() {
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this._audioSource.connect(this._audioProcessingNode);
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this._audioProcessingNode.connect(this._audioContext.destination);
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}
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/**
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* Disconnects the nodes in the {@code AudioContext}.
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*
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* @protected
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* @returns {void}
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*/
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_disconnectAudioGraph() {
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this._audioProcessingNode.onaudioprocess = undefined;
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this._audioProcessingNode.disconnect();
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this._audioSource.disconnect();
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}
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/**
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* Replaces the current microphone MediaStream.
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*
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* @protected
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* @param {string} micDeviceId - New microphone ID.
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* @returns {Promise}
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*/
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_replaceMic(micDeviceId) {
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if (this._audioContext && this._audioProcessingNode) {
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return this._getAudioStream(micDeviceId).then(newStream => {
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const newSource = this._audioContext
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.createMediaStreamSource(newStream);
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this._audioSource.disconnect();
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newSource.connect(this._audioProcessingNode);
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this._stream = newStream;
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this._audioSource = newSource;
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});
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}
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return Promise.resolve();
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}
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}
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