Move src/voice to src/audio for better naming

Many of these files are used by Audio and Voice messages.

Fixes https://github.com/vector-im/element-web/issues/18131

src/audio/compat.ts

@@ -0,0 +1,82 @@
+/*
+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 { SAMPLE_RATE } from "./VoiceRecording";
+
+// @ts-ignore - we know that this is not a module. We're looking for a path.
+import decoderWasmPath from 'opus-recorder/dist/decoderWorker.min.wasm';
+import wavEncoderPath from 'opus-recorder/dist/waveWorker.min.js';
+import decoderPath from 'opus-recorder/dist/decoderWorker.min.js';
+
+export function createAudioContext(opts?: AudioContextOptions): AudioContext {
+    if (window.AudioContext) {
+        return new AudioContext(opts);
+    } else if (window.webkitAudioContext) {
+        // While the linter is correct that "a constructor name should not start with
+        // a lowercase letter", it's also wrong to think that we have control over this.
+        // eslint-disable-next-line new-cap
+        return new window.webkitAudioContext(opts);
+    } else {
+        throw new Error("Unsupported browser");
+    }
+}
+
+export function decodeOgg(audioBuffer: ArrayBuffer): Promise<ArrayBuffer> {
+    // Condensed version of decoder example, using a promise:
+    // https://github.com/chris-rudmin/opus-recorder/blob/master/example/decoder.html
+    return new Promise((resolve) => { // no reject because the workers don't seem to have a fail path
+        console.log("Decoder WASM path: " + decoderWasmPath); // so we use the variable (avoid tree shake)
+        const typedArray = new Uint8Array(audioBuffer);
+        const decoderWorker = new Worker(decoderPath);
+        const wavWorker = new Worker(wavEncoderPath);
+
+        decoderWorker.postMessage({
+            command: 'init',
+            decoderSampleRate: SAMPLE_RATE,
+            outputBufferSampleRate: SAMPLE_RATE,
+        });
+
+        wavWorker.postMessage({
+            command: 'init',
+            wavBitDepth: 24, // standard for 48khz (SAMPLE_RATE)
+            wavSampleRate: SAMPLE_RATE,
+        });
+
+        decoderWorker.onmessage = (ev) => {
+            if (ev.data === null) { // null == done
+                wavWorker.postMessage({ command: 'done' });
+                return;
+            }
+
+            wavWorker.postMessage({
+                command: 'encode',
+                buffers: ev.data,
+            }, ev.data.map(b => b.buffer));
+        };
+
+        wavWorker.onmessage = (ev) => {
+            if (ev.data.message === 'page') {
+                // The encoding comes through as a single page
+                resolve(new Blob([ev.data.page], { type: "audio/wav" }).arrayBuffer());
+            }
+        };
+
+        decoderWorker.postMessage({
+            command: 'decode',
+            pages: typedArray,
+        }, [typedArray.buffer]);
+    });
+}