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{Audio,Video}Stream: use AsyncIterableIterator #272

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merged 4 commits into from
Sep 23, 2024
Merged

{Audio,Video}Stream: use AsyncIterableIterator #272

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453bd2b
make AudioStream use AsyncIterableIterator
nbsp Sep 19, 2024
8667110
Create real-toes-accept.md
nbsp Sep 20, 2024
32cf737
add mutex
nbsp Sep 23, 2024
aeb27e1
add same for videostream
nbsp Sep 23, 2024
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5 changes: 5 additions & 0 deletions .changeset/real-toes-accept.md
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@@ -0,0 +1,5 @@
---
"@livekit/rtc-node": minor
---

make AudioStream use AsyncIterableIterator instead of typed EventEmitter
44 changes: 27 additions & 17 deletions packages/livekit-rtc/src/audio_stream.ts
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@@ -1,39 +1,28 @@
// SPDX-FileCopyrightText: 2024 LiveKit, Inc.
//
// SPDX-License-Identifier: Apache-2.0
import type { TypedEventEmitter as TypedEmitter } from '@livekit/typed-emitter';
import EventEmitter from 'events';
import { AudioFrame } from './audio_frame.js';
import type { FfiEvent } from './ffi_client.js';
import { FfiClient, FfiClientEvent, FfiHandle } from './ffi_client.js';
import type { AudioStreamInfo, NewAudioStreamResponse } from './proto/audio_frame_pb.js';
import { AudioStreamType, NewAudioStreamRequest } from './proto/audio_frame_pb.js';
import type { Track } from './track.js';

export type AudioFrameEvent = {
frame: AudioFrame;
};

export type AudioStreamCallbacks = {
frameReceived: (frame: AudioFrameEvent) => void;
};

export enum AudioStreamEvent {
FrameReceived = 'frameReceived',
}

export class AudioStream extends (EventEmitter as new () => TypedEmitter<AudioStreamCallbacks>) {
export class AudioStream implements AsyncIterableIterator<AudioFrame> {
/** @internal */
info: AudioStreamInfo;
/** @internal */
ffiHandle: FfiHandle;
/** @internal */
eventQueue: (AudioFrame | null)[] = [];
/** @internal */
queueResolve: ((value: IteratorResult<AudioFrame>) => void) | null = null;

track: Track;
sampleRate: number;
numChannels: number;

constructor(track: Track, sampleRate: number = 48000, numChannels: number = 1) {
super();
this.track = track;
this.sampleRate = sampleRate;
this.numChannels = numChannels;
Expand Down Expand Up @@ -70,15 +59,36 @@ export class AudioStream extends (EventEmitter as new () => TypedEmitter<AudioSt
switch (streamEvent.case) {
case 'frameReceived':
const frame = AudioFrame.fromOwnedInfo(streamEvent.value.frame);
this.emit(AudioStreamEvent.FrameReceived, { frame });
if (this.queueResolve) {
this.queueResolve({ done: false, value: frame });
} else {
this.eventQueue.push(frame);
}
break;
case 'eos':
FfiClient.instance.off(FfiClientEvent.FfiEvent, this.onEvent);
break;
}
};

async next(): Promise<IteratorResult<AudioFrame>> {
if (this.eventQueue.length > 0) {
const value = this.eventQueue.shift();
if (value) {
return { done: false, value };
} else {
return { done: true, value: undefined };
}
}
return new Promise((resolve) => (this.queueResolve = resolve));
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@lukasIO lukasIO Sep 20, 2024 •
edited
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I think this.queueResolve might get overridden before being called?
so the async iterator could get stuck

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the Mutex helper that Théo has mentioned already might make sense here

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could it? i don't think that's the case, it only gets overridden if you call next() twice without awaiting the first one, which you shouldn't do anyway.

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which you shouldn't do anyway.

agreed that it shouldn't be done, but seems like a footgun regardless?

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would it make sense to return a copy of the same promise if next is called twice?

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I'm not sure, I think best case scenario is a promise chain, which is exactly what the Mutex class does.

}

close() {
this.eventQueue.push(null);
this.ffiHandle.dispose();
}

[Symbol.asyncIterator](): AudioStream {
return this;
}
}
2 changes: 1 addition & 1 deletion packages/livekit-rtc/src/index.ts
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Expand Up @@ -17,7 +17,7 @@ export {
} from './track.js';
export { VideoFrame } from './video_frame.js';
export { AudioFrame } from './audio_frame.js';
export { AudioStream, AudioStreamEvent, AudioFrameEvent } from './audio_stream.js';
export { AudioStream } from './audio_stream.js';
export { VideoStream, VideoStreamEvent, VideoFrameEvent } from './video_stream.js';
export { AudioSource } from './audio_source.js';
export { VideoSource } from './video_source.js';
Expand Down
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