Play only one audio file at a time

src/components/views/messages/MAudioBody.tsx

@@ -23,6 +23,7 @@ import AudioPlayer from "../audio_messages/AudioPlayer";
 import { IMediaEventContent } from "../../../customisations/models/IMediaEventContent";
 import MFileBody from "./MFileBody";
 import { IBodyProps } from "./IBodyProps";
+import { PlaybackManager } from "../../../voice/PlaybackManager";
 
 interface IState {
     error?: Error;
@@ -62,7 +63,7 @@ export default class MAudioBody extends React.PureComponent<IBodyProps, IState>
         const waveform = content?.["org.matrix.msc1767.audio"]?.waveform?.map(p => p / 1024);
 
         // We should have a buffer to work with now: let's set it up
-        const playback = new Playback(buffer, waveform);
+        const playback = PlaybackManager.instance.createPlaybackInstance(buffer, waveform);
         playback.clockInfo.populatePlaceholdersFrom(this.props.mxEvent);
         this.setState({ playback });
 

src/voice/ManagedPlayback.ts

@@ -0,0 +1,37 @@
+/*
+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.
+*/
+
+import { DEFAULT_WAVEFORM, Playback } from "./Playback";
+import { PlaybackManager } from "./PlaybackManager";
+
+/**
+ * A managed playback is a Playback instance that is guided by a PlaybackManager.
+ */
+export class ManagedPlayback extends Playback {
+    public constructor(private manager: PlaybackManager, buf: ArrayBuffer, seedWaveform = DEFAULT_WAVEFORM) {
+        super(buf, seedWaveform);
+    }
+
+    public async play(): Promise<void> {
+        this.manager.playOnly(this);
+        return super.play();
+    }
+
+    public destroy() {
+        this.manager.destroyPlaybackInstance(this);
+        super.destroy();
+    }
+}

src/voice/Playback.ts

@@ -32,7 +32,7 @@ export enum PlaybackState {
 
 export const PLAYBACK_WAVEFORM_SAMPLES = 39;
 const THUMBNAIL_WAVEFORM_SAMPLES = 100; // arbitrary: [30,120]
-const DEFAULT_WAVEFORM = arraySeed(0, PLAYBACK_WAVEFORM_SAMPLES);
+export const DEFAULT_WAVEFORM = arraySeed(0, PLAYBACK_WAVEFORM_SAMPLES);
 
 function makePlaybackWaveform(input: number[]): number[] {
     // First, convert negative amplitudes to positive so we don't detect zero as "noisy".

src/voice/PlaybackClock.ts

@@ -132,6 +132,10 @@ export class PlaybackClock implements IDestroyable {
 
     public flagStop() {
         this.stopped = true;
+
+        // Reset the clock time now so that the update going out will trigger components
+        // to check their seek/position information (alongside the clock).
+        this.clipStart = this.context.currentTime;
     }
 
     public syncTo(contextTime: number, clipTime: number) {

src/voice/PlaybackManager.ts

@@ -0,0 +1,54 @@
+/*
+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.
+*/
+
+import { DEFAULT_WAVEFORM, Playback } from "./Playback";
+import { ManagedPlayback } from "./ManagedPlayback";
+
+/**
+ * Handles management of playback instances to ensure certain functionality, like
+ * one playback operating at any one time.
+ */
+export class PlaybackManager {
+    private static internalInstance: PlaybackManager;
+
+    private instances: ManagedPlayback[] = [];
+
+    public static get instance(): PlaybackManager {
+        if (!PlaybackManager.internalInstance) {
+            PlaybackManager.internalInstance = new PlaybackManager();
+        }
+        return PlaybackManager.internalInstance;
+    }
+
+    /**
+     * Stops all other playback instances. If no playback is provided, all instances
+     * are stopped.
+     * @param playback Optional. The playback to leave untouched.
+     */
+    public playOnly(playback?: Playback) {
+        this.instances.filter(p => p !== playback).forEach(p => p.stop());
+    }
+
+    public destroyPlaybackInstance(playback: ManagedPlayback) {
+        this.instances = this.instances.filter(p => p !== playback);
+    }
+
+    public createPlaybackInstance(buf: ArrayBuffer, waveform = DEFAULT_WAVEFORM): Playback {
+        const instance = new ManagedPlayback(this, buf, waveform);
+        this.instances.push(instance);
+        return instance;
+    }
+}