88 lines
4.1 KiB
TypeScript
88 lines
4.1 KiB
TypeScript
/*
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Copyright 2021 The Matrix.org Foundation C.I.C.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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import { IAmplitudePayload, ITimingPayload, PayloadEvent, WORKLET_NAME } from "./consts";
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import { percentageOf } from "../utils/numbers";
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// from AudioWorkletGlobalScope: https://developer.mozilla.org/en-US/docs/Web/API/AudioWorkletGlobalScope
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declare const currentTime: number;
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// declare const currentFrame: number;
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// declare const sampleRate: number;
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// We rate limit here to avoid overloading downstream consumers with amplitude information.
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// The two major consumers are the voice message waveform thumbnail (resampled down to an
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// appropriate length) and the live waveform shown to the user. Effectively, this controls
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// the refresh rate of that live waveform and the number of samples the thumbnail has to
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// work with.
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const TARGET_AMPLITUDE_FREQUENCY = 16; // Hz
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function roundTimeToTargetFreq(seconds: number): number {
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// Epsilon helps avoid floating point rounding issues (1 + 1 = 1.999999, etc)
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return Math.round((seconds + Number.EPSILON) * TARGET_AMPLITUDE_FREQUENCY) / TARGET_AMPLITUDE_FREQUENCY;
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}
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function nextTimeForTargetFreq(roundedSeconds: number): number {
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// The extra round is just to make sure we cut off any floating point issues
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return roundTimeToTargetFreq(roundedSeconds + (1 / TARGET_AMPLITUDE_FREQUENCY));
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}
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class MxVoiceWorklet extends AudioWorkletProcessor {
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private nextAmplitudeSecond = 0;
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private amplitudeIndex = 0;
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process(inputs, outputs, parameters) {
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const currentSecond = roundTimeToTargetFreq(currentTime);
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// We special case the first ping because there's a fairly good chance that we'll miss the zeroth
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// update. Firefox for instance takes 0.06 seconds (roughly) to call this function for the first
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// time. Edge and Chrome occasionally lag behind too, but for the most part are on time.
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//
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// When this doesn't work properly we end up producing a waveform of nulls and no live preview
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// of the recorded message.
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if (currentSecond === this.nextAmplitudeSecond || this.nextAmplitudeSecond === 0) {
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// We're expecting exactly one mono input source, so just grab the very first frame of
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// samples for the analysis.
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const monoChan = inputs[0][0];
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// The amplitude of the frame's samples is effectively the loudness of the frame. This
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// translates into a bar which can be rendered as part of the whole recording clip's
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// waveform.
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//
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// We translate the amplitude down to 0-1 for sanity's sake.
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const minVal = Math.min(...monoChan);
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const maxVal = Math.max(...monoChan);
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const amplitude = percentageOf(maxVal, -1, 1) - percentageOf(minVal, -1, 1);
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this.port.postMessage(<IAmplitudePayload>{
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ev: PayloadEvent.AmplitudeMark,
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amplitude: amplitude,
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forIndex: this.amplitudeIndex++,
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});
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this.nextAmplitudeSecond = nextTimeForTargetFreq(currentSecond);
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}
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// We mostly use this worklet to fire regular clock updates through to components
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this.port.postMessage(<ITimingPayload>{ ev: PayloadEvent.Timekeep, timeSeconds: currentTime });
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// We're supposed to return false when we're "done" with the audio clip, but seeing as
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// we are acting as a passive processor we are never truly "done". The browser will clean
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// us up when it is done with us.
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return true;
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}
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}
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registerProcessor(WORKLET_NAME, MxVoiceWorklet);
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export default null; // to appease module loaders (we never use the export)
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