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Use a MediaElementSourceAudioNode to process large audio files

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Fixes https://github.com/vector-im/element-web/issues/18149

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This commit is contained in:
Travis Ralston 2021-07-21 17:53:33 -06:00
parent b590b1d263
commit c53ed5be2e
1 changed files with 63 additions and 23 deletions
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86
src/voice/Playback.ts
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@ -59,9 +59,10 @@ export class Playback extends EventEmitter implements IDestroyable {
public readonly thumbnailWaveform: number[];
private readonly context: AudioContext;
private source: AudioBufferSourceNode;
private source: AudioBufferSourceNode | MediaElementAudioSourceNode;
private state = PlaybackState.Decoding;
private audioBuf: AudioBuffer;
private element: HTMLAudioElement;
private resampledWaveform: number[];
private waveformObservable = new SimpleObservable<number[]>();
private readonly clock: PlaybackClock;
@ -129,36 +130,59 @@ export class Playback extends EventEmitter implements IDestroyable {
this.removeAllListeners();
this.clock.destroy();
this.waveformObservable.close();
if (this.element) {
URL.revokeObjectURL(this.element.src);
this.element.remove();
}
}
public async prepare() {
// Safari compat: promise API not supported on this function
this.audioBuf = await new Promise((resolve, reject) => {
this.context.decodeAudioData(this.buf, b => resolve(b), async e => {
// This error handler is largely for Safari as well, which doesn't support Opus/Ogg
// very well.
console.error("Error decoding recording: ", e);
console.warn("Trying to re-encode to WAV instead...");
// The point where we use an audio element is fairly arbitrary, though we don't want
// it to be too low. As of writing, voice messages want to show a waveform but audio
// messages do not. Using an audio element means we can't show a waveform preview, so
// we try to target the difference between a voice message file and large audio file.
// Overall, the point of this is to avoid memory-related issues due to storing a massive
// audio buffer in memory, as that can balloon to far greater than the input buffer's
// byte length.
if (this.buf.byteLength > 5 * 1024 * 1024) { // 5mb
console.log("Audio file too large: processing through <audio /> element");
this.element = document.createElement("AUDIO") as HTMLAudioElement;
const prom = new Promise((resolve, reject) => {
this.element.onloadeddata = () => resolve(null);
this.element.onerror = (e) => reject(e);
});
this.element.src = URL.createObjectURL(new Blob([this.buf]));
await prom; // make sure the audio element is ready for us
} else {
// Safari compat: promise API not supported on this function
this.audioBuf = await new Promise((resolve, reject) => {
this.context.decodeAudioData(this.buf, b => resolve(b), async e => {
// This error handler is largely for Safari as well, which doesn't support Opus/Ogg
// very well.
console.error("Error decoding recording: ", e);
console.warn("Trying to re-encode to WAV instead...");
const wav = await decodeOgg(this.buf);
const wav = await decodeOgg(this.buf);
// noinspection ES6MissingAwait - not needed when using callbacks
this.context.decodeAudioData(wav, b => resolve(b), e => {
console.error("Still failed to decode recording: ", e);
reject(e);
// noinspection ES6MissingAwait - not needed when using callbacks
this.context.decodeAudioData(wav, b => resolve(b), e => {
console.error("Still failed to decode recording: ", e);
reject(e);
});
});
});
});
// Update the waveform to the real waveform once we have channel data to use. We don't
// exactly trust the user-provided waveform to be accurate...
const waveform = Array.from(this.audioBuf.getChannelData(0));
this.resampledWaveform = makePlaybackWaveform(waveform);
// Update the waveform to the real waveform once we have channel data to use. We don't
// exactly trust the user-provided waveform to be accurate...
const waveform = Array.from(this.audioBuf.getChannelData(0));
this.resampledWaveform = makePlaybackWaveform(waveform);
}
this.waveformObservable.update(this.resampledWaveform);
this.emit(PlaybackState.Stopped); // signal that we're not decoding anymore
this.clock.flagLoadTime(); // must happen first because setting the duration fires a clock update
this.clock.durationSeconds = this.audioBuf.duration;
this.clock.durationSeconds = this.element ? this.element.duration : this.audioBuf.duration;
}
private onPlaybackEnd = async () => {
@ -171,7 +195,11 @@ export class Playback extends EventEmitter implements IDestroyable {
if (this.state === PlaybackState.Stopped) {
this.disconnectSource();
this.makeNewSourceBuffer();
this.source.start();
if (this.element) {
await this.element.play();
} else {
(this.source as AudioBufferSourceNode).start();
}
}
// We use the context suspend/resume functions because it allows us to pause a source
@ -182,13 +210,21 @@ export class Playback extends EventEmitter implements IDestroyable {
}
private disconnectSource() {
if (this.element) return; // leave connected, we can (and must) re-use it
this.source?.disconnect();
this.source?.removeEventListener("ended", this.onPlaybackEnd);
}
private makeNewSourceBuffer() {
this.source = this.context.createBufferSource();
this.source.buffer = this.audioBuf;
if (this.element && this.source) return; // leave connected, we can (and must) re-use it
if (this.element) {
this.source = this.context.createMediaElementSource(this.element);
} else {
this.source = this.context.createBufferSource();
this.source.buffer = this.audioBuf;
}
this.source.addEventListener("ended", this.onPlaybackEnd);
this.source.connect(this.context.destination);
}
@ -241,7 +277,11 @@ export class Playback extends EventEmitter implements IDestroyable {
// when it comes time to the user hitting play. After a couple jumps, the user
// will have desynced the clock enough to be about 10-15 seconds off, while this
// keeps it as close to perfect as humans can perceive.
this.source.start(now, timeSeconds);
if (this.element) {
this.element.currentTime = timeSeconds;
} else {
(this.source as AudioBufferSourceNode).start(now, timeSeconds);
}
// Dev note: it's critical that the code gap between `this.source.start()` and
// `this.pause()` is as small as possible: we do not want to delay *anything*