Run audio through the Web Audio API instead

This leads to more reliable frequency/timing information, and involves a whole lot less decoding.

We still maintain ongoing encoded frames to avoid having to do one giant encode at the end, as that could take long enough to be disruptive.

src/components/views/rooms/VoiceRecordComposerTile.tsx

@@ -58,8 +58,8 @@ export default class VoiceRecordComposerTile extends React.PureComponent<IProps,
         await recorder.start();
         this.props.onRecording(true);
         // TODO: @@ TravisR: Run through EQ component
-        // recorder.rawData.onUpdate((frame) => {
-        //     console.log('@@ FRAME', frame);
+        // recorder.frequencyData.onUpdate((freq) => {
+        //     console.log('@@ UPDATE', freq);
         // });
         this.setState({recorder});
     };

src/voice/VoiceRecorder.ts

@@ -20,40 +20,74 @@ import {MatrixClient} from "matrix-js-sdk/src/client";
 import CallMediaHandler from "../CallMediaHandler";
 import {SimpleObservable} from "matrix-widget-api";
 
+const CHANNELS = 1; // stereo isn't important
+const SAMPLE_RATE = 48000; // 48khz is what WebRTC uses. 12khz is where we lose quality.
+const BITRATE = 64000; // 64kbps is average for WebRTC, so we might as well use it too.
+const FREQ_SAMPLE_RATE = 4; // Target rate of frequency data. We don't need this super often.
+
+export interface IFrequencyPackage {
+    dbBars: Float32Array;
+    dbMin: number;
+    dbMax: number;
+
+    // TODO: @@ TravisR: Generalize this for a timing package?
+}
+
 export class VoiceRecorder {
-    private recorder = new Recorder({
-        encoderPath, // magic from webpack
-        mediaTrackConstraints: <MediaTrackConstraints>{
-            deviceId: CallMediaHandler.getAudioInput(),
-        },
-        encoderSampleRate: 48000, // we could go down to 12khz, but we lose quality. 48khz is a webrtc default
-        encoderApplication: 2048, // voice (default is "audio")
-        streamPages: true, // so we can have a live EQ for the user
-        encoderFrameSize: 20, // ms, we want updates fairly regularly for the UI
-        numberOfChannels: 1, // stereo isn't important for us
-        //sourceNode: instanceof MediaStreamAudioSourceNode, // TODO: @@ Travis: Use this for EQ stuff.
-        encoderBitRate: 64000, // 64kbps is average for webrtc
-        encoderComplexity: 3, // 0-10, 0 is fast and low complexity
-        resampleQuality: 3, // 0-10, 10 is slow and high quality
-    });
+    private recorder: Recorder;
+    private recorderContext: AudioContext;
+    private recorderSource: MediaStreamAudioSourceNode;
+    private recorderStream: MediaStream;
+    private recorderFreqNode: AnalyserNode;
     private buffer = new Uint8Array(0);
     private mxc: string;
     private recording = false;
-    private observable: SimpleObservable<Uint8Array>;
+    private observable: SimpleObservable<IFrequencyPackage>;
+    private freqTimerId: number;
 
     public constructor(private client: MatrixClient) {
+    }
+
+    private async makeRecorder() {
+        this.recorderStream = await navigator.mediaDevices.getUserMedia({
+            audio: {
+                // specify some audio settings so we're feeding the recorder with the
+                // best possible values. The browser will handle resampling for us.
+                sampleRate: SAMPLE_RATE,
+                channelCount: CHANNELS,
+                noiseSuppression: true, // browsers ignore constraints they can't honour
+                deviceId: CallMediaHandler.getAudioInput(),
+            },
+        });
+        this.recorderContext = new AudioContext({
+            latencyHint: "interactive",
+            sampleRate: SAMPLE_RATE, // once again, the browser will resample for us
+        });
+        this.recorderSource = this.recorderContext.createMediaStreamSource(this.recorderStream);
+        this.recorderFreqNode = this.recorderContext.createAnalyser();
+        this.recorderSource.connect(this.recorderFreqNode);
+        this.recorder = new Recorder({
+            encoderPath, // magic from webpack
+            encoderSampleRate: SAMPLE_RATE,
+            encoderApplication: 2048, // voice (default is "audio")
+            streamPages: true, // this speeds up the encoding process by using CPU over time
+            encoderFrameSize: 20, // ms, arbitrary frame size we send to the encoder
+            numberOfChannels: CHANNELS,
+            sourceNode: this.recorderSource,
+            encoderBitRate: BITRATE,
+            encoderComplexity: 3, // 0-10, 0 is fast and low complexity
+            resampleQuality: 3, // 0-10, 10 is slow and high quality
+        });
         this.recorder.ondataavailable = (a: ArrayBuffer) => {
-            // TODO: @@ TravisR: We'll have to decode each frame and convert it to an EQ to observe
             const buf = new Uint8Array(a);
             const newBuf = new Uint8Array(this.buffer.length + buf.length);
             newBuf.set(this.buffer, 0);
             newBuf.set(buf, this.buffer.length);
             this.buffer = newBuf;
-            this.observable.update(buf); // send the frame over the observable
         };
     }
 
-    public get rawData(): SimpleObservable<Uint8Array> {
+    public get frequencyData(): SimpleObservable<IFrequencyPackage> {
         if (!this.recording) throw new Error("No observable when not recording");
         return this.observable;
     }
@@ -83,7 +117,18 @@ export class VoiceRecorder {
         if (this.observable) {
             this.observable.close();
         }
-        this.observable = new SimpleObservable<Uint8Array>();
+        this.observable = new SimpleObservable<IFrequencyPackage>();
+        await this.makeRecorder();
+        this.freqTimerId = setInterval(() => {
+            if (!this.recording) return;
+            const data = new Float32Array(this.recorderFreqNode.frequencyBinCount);
+            this.recorderFreqNode.getFloatFrequencyData(data);
+            this.observable.update({
+                dbBars: data,
+                dbMin: this.recorderFreqNode.minDecibels,
+                dbMax: this.recorderFreqNode.maxDecibels,
+            });
+        }, 1000 / FREQ_SAMPLE_RATE) as any as number; // XXX: Linter doesn't understand timer environment
         return this.recorder.start().then(() => this.recording = true);
     }
 
@@ -91,12 +136,20 @@ export class VoiceRecorder {
         if (!this.recording) {
             throw new Error("No recording to stop");
         }
-        return new Promise<Uint8Array>(resolve => {
-            this.recorder.stop().then(() => {
+        // Disconnect the source early to start shutting down resources
+        this.recorderSource.disconnect();
+        return this.recorder.stop()
+            // close the context after the recorder so the recorder doesn't try to
+            // connect anything to the context (this would generate a warning)
+            .then(() => this.recorderContext.close())
+            // Now stop all the media tracks so we can release them back to the user/OS
+            .then(() => this.recorderStream.getTracks().forEach(t => t.stop()))
+            // Finally do our post-processing and clean up
+            .then(() => {
+                clearInterval(<number>this.freqTimerId);
                 this.recording = false;
                 return this.recorder.close();
-            }).then(() => resolve(this.buffer));
-        });
+            }).then(() => this.buffer);
     }
 
     public async upload(): Promise<string> {