From 9c2d44805d2c7238bd0c339daf3b11006c1e471c Mon Sep 17 00:00:00 2001
From: Travis Ralston <travpc@gmail.com>
Date: Mon, 29 Mar 2021 21:59:31 -0600
Subject: [PATCH] Revert "Avoid use of deprecated APIs, instead using an
 AudioWorklet"

This reverts commit 5c685dcf35fbe8c896f22882a6843dc0cc0b835d.
---
 src/voice/VoiceRecorder.ts  | 30 ++++++++++++++----------------
 src/voice/mxVoiceWorklet.js | 35 -----------------------------------
 2 files changed, 14 insertions(+), 51 deletions(-)
 delete mode 100644 src/voice/mxVoiceWorklet.js

diff --git a/src/voice/VoiceRecorder.ts b/src/voice/VoiceRecorder.ts
index 319a6c3a37..50497438ca 100644
--- a/src/voice/VoiceRecorder.ts
+++ b/src/voice/VoiceRecorder.ts
@@ -16,7 +16,6 @@ limitations under the License.
 
 import * as Recorder from 'opus-recorder';
 import encoderPath from 'opus-recorder/dist/encoderWorker.min.js';
-import mxVoiceWorkletPath from './mxVoiceWorklet';
 import {MatrixClient} from "matrix-js-sdk/src/client";
 import CallMediaHandler from "../CallMediaHandler";
 import {SimpleObservable} from "matrix-widget-api";
@@ -37,7 +36,7 @@ export class VoiceRecorder {
     private recorderSource: MediaStreamAudioSourceNode;
     private recorderStream: MediaStream;
     private recorderFFT: AnalyserNode;
-    private recorderWorklet: AudioWorkletNode;
+    private recorderProcessor: ScriptProcessorNode;
     private buffer = new Uint8Array(0);
     private mxc: string;
     private recording = false;
@@ -71,20 +70,18 @@ export class VoiceRecorder {
         // it makes the time domain less than helpful.
         this.recorderFFT.fftSize = 64;
 
-        await this.recorderContext.audioWorklet.addModule(mxVoiceWorkletPath);
-        this.recorderWorklet = new AudioWorkletNode(this.recorderContext, "mx-voice-worklet");
+        // We use an audio processor to get accurate timing information.
+        // The size of the audio buffer largely decides how quickly we push timing/waveform data
+        // out of this class. Smaller buffers mean we update more frequently as we can't hold as
+        // many bytes. Larger buffers mean slower updates. For scale, 1024 gives us about 30Hz of
+        // updates and 2048 gives us about 20Hz. We use 1024 to get as close to perceived realtime
+        // as possible. Must be a power of 2.
+        this.recorderProcessor = this.recorderContext.createScriptProcessor(1024, CHANNELS, CHANNELS);
 
         // Connect our inputs and outputs
         this.recorderSource.connect(this.recorderFFT);
-        this.recorderSource.connect(this.recorderWorklet);
-        this.recorderWorklet.connect(this.recorderContext.destination);
-
-        // Dev note: we can't use `addEventListener` for some reason. It just doesn't work.
-        this.recorderWorklet.port.onmessage = (ev) => {
-            if (ev.data['ev'] === 'proc') {
-                this.tryUpdateLiveData(ev.data['timeMs']);
-            }
-        };
+        this.recorderSource.connect(this.recorderProcessor);
+        this.recorderProcessor.connect(this.recorderContext.destination);
 
         this.recorder = new Recorder({
             encoderPath, // magic from webpack
@@ -131,7 +128,7 @@ export class VoiceRecorder {
         return this.mxc;
     }
 
-    private tryUpdateLiveData = (timeMillis: number) => {
+    private tryUpdateLiveData = (ev: AudioProcessingEvent) => {
         if (!this.recording) return;
 
         // The time domain is the input to the FFT, which means we use an array of the same
@@ -153,7 +150,7 @@ export class VoiceRecorder {
 
         this.observable.update({
             waveform: translatedData,
-            timeSeconds: timeMillis / 1000,
+            timeSeconds: ev.playbackTime,
         });
     };
 
@@ -169,6 +166,7 @@ export class VoiceRecorder {
         }
         this.observable = new SimpleObservable<IRecordingUpdate>();
         await this.makeRecorder();
+        this.recorderProcessor.addEventListener("audioprocess", this.tryUpdateLiveData);
         await this.recorder.start();
         this.recording = true;
     }
@@ -180,7 +178,6 @@ export class VoiceRecorder {
 
         // Disconnect the source early to start shutting down resources
         this.recorderSource.disconnect();
-        this.recorderWorklet.disconnect();
         await this.recorder.stop();
 
         // close the context after the recorder so the recorder doesn't try to
@@ -192,6 +189,7 @@ export class VoiceRecorder {
 
         // Finally do our post-processing and clean up
         this.recording = false;
+        this.recorderProcessor.removeEventListener("audioprocess", this.tryUpdateLiveData);
         await this.recorder.close();
 
         return this.buffer;
diff --git a/src/voice/mxVoiceWorklet.js b/src/voice/mxVoiceWorklet.js
deleted file mode 100644
index a74f5c17c9..0000000000
--- a/src/voice/mxVoiceWorklet.js
+++ /dev/null
@@ -1,35 +0,0 @@
-/*
-Copyright 2021 The Matrix.org Foundation C.I.C.
-
-Licensed under the Apache License, Version 2.0 (the "License");
-you may not use this file except in compliance with the License.
-You may obtain a copy of the License at
-
-    http://www.apache.org/licenses/LICENSE-2.0
-
-Unless required by applicable law or agreed to in writing, software
-distributed under the License is distributed on an "AS IS" BASIS,
-WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-See the License for the specific language governing permissions and
-limitations under the License.
-*/
-
-class MxVoiceWorklet extends AudioWorkletProcessor {
-    constructor() {
-        super();
-
-        this._timeStart = 0;
-    }
-
-    process(inputs, outputs, parameters) {
-        const now = (new Date()).getTime();
-        if (this._timeStart === 0) {
-            this._timeStart = now;
-        }
-
-        this.port.postMessage({ev: 'proc', timeMs: now - this._timeStart});
-        return true;
-    }
-}
-
-registerProcessor('mx-voice-worklet', MxVoiceWorklet);