AudioWorkletStream VS streams

// Exits half way through reading response when --max-old-space-size=6 is set // Exits immediately when --jitless flag is set // // Usage: // // port.postMessage({ // url: 'https://github.com/guest271314/AudioWorkletStream/raw/master/house--64kbs-0-wav', // method: 'get', // body: null // })

Yes. Fetching a single or multiple files for an infinite stream of audio https://github.com/guest271314/AudioWorkletStream/blob/master/worker.js. Streaming (real-time) audio is non-trivial. Any gaps or glitches in playback will be audible to the user. We could test for expected Float32Arrays. I would suggest complentary manual test in, e.g., WPT to determine audio output does not have gaps or glitches; and renders the expected playback rate.

One way to do that is utilizing Native Messaging on Chromium or Firefox https://github.com/guest271314/native-messaging-espeak-ng, and https://github.com/guest271314/webtransport/blob/main/webTransportEspeakNg.js for some WebTransport experiments. Technically we don't need a local server. We can stream and parse the WAV directly and pipe to AudioWorklet or a MediaStreamTrackGenerator https://github.com/guest271314/AudioWorkletStream. The same is true for speech recognition, where audio is piped to the local application and text or JSON piped back. Note also espeak-ng has been compiled to WebAssembly. I created native-messaging-espeak-ng for the ability to pass SSML directly to espeak-ng.

You can stream audio and/or video over HTTP using fetch() https://github.com/guest271314/AudioWorkletStream as long as you know how to parse the codec, if the media is encoded.

Re using a dedicated Worker and AudioWorklet to stream, see, e.g., https://github.com/guest271314/AudioWorkletStream; https://plnkr.co/edit/nECtUZ.

Yup, this is what WHATWG's Streams spec[0] (linked in the article) says. It defines backpressure as a "process of normalizing flow from the original source according to how fast the chain can process chunks" where the reader "propagates a signal backwards through the pipe chain".

Mozilla's documentation[1] similarly defines backpressure as "the process by which a single stream or a pipe chain regulates the speed of reading/writing".

The article confuses backpressure (the signal used for regulation of the flow) with the reason backpressure is needed (producers and consumers working at different speeds). It should be fairly clear from the metaphor, I would have thought: With a pipe of unbounded size there is no pressure. The pressure builds up when consumer is slower than producer, which in turn slows down the producer. (Or the pipe explodes, or springs a leak and has to drop data on the ground.)

[0] https://streams.spec.whatwg.org/#pipe-chains

[1] https://developer.mozilla.org/en-US/docs/Web/API/Streams_API...

// https://streams.spec.whatwg.org/#example-transform-identity const { writable, readable } = new TransformStream(); fetch("...", { body: readable }).then(response => /* ... */); const writer = writable.getWriter(); writer.write(new Uint8Array([0x73, 0x74, 0x72, 0x65, 0x61, 0x6D, 0x73, 0x21])); // "streams!" writer.close();

Yeah, in your case I think most of the complexity is actually on the ReadableStream side, not the base64 side.

The thing that I'd actually want for your case is either a TransformStream for byte stream <-> base64 stream (which I expect will come eventually, once the simple case gets done), or something which would let you read the entire stream into Uint8Array or ArrayBuffer, which is a long-standing suggestion [1].

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> Why does de-chunking a byte array need to be complicated

Keep in mind the concat proposal is _very_ early. If you think it would be useful to be able to concat Uint8Arrays and have that implicitly concatenate the underlying buffers, [2] is the place to open an issue.

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> You have made me realize I don't even know what the right venue is to vote on stuff. How should I signal to TC39 that e.g. Array.fromAsync is a good idea?

Unfortunately, it's different places for different things. Streams are not TC39 at all; the right place for suggestions there is in the WHATWG streams repo [3]. Usually there's already an existing issue and you can add your use case as a comment in the relevant issue. TC39 proposals all have their own Github repositories, and you can open a new issue with your use case.

Concrete use cases are much more helpful than just "this is a good idea". Though `fromAsync` in particular everyone agrees is good, and it mostly just needs implementations, which are ongoing; see e.g. [4]. If you _really_ want to advance a stage 3 proposal, you can contribute a PR to Chrome or Firefox with an implementation - but for nontrivial proposals that's usually hard. For TC39 in particular, use cases are only really valuable pre-stage-3 proposals.

[1] https://github.com/whatwg/streams/issues/1019

[2] https://github.com/jasnell/proposal-zero-copy-arraybuffer-li...

[3] https://github.com/whatwg/streams

[4] https://bugs.chromium.org/p/v8/issues/detail?id=13321

// AudioWorkletStream // Stream audio from Worker to AudioWorklet // guest271314 2-24-2020 let port; onmessage = async e => { 'use strict'; if (!port) { [port] = e.ports; port.onmessage = event => postMessage(event.data); } const { urls } = e.data; // https://github.com/whatwg/streams/blob/master/transferable-streams-explainer.md const { readable, writable } = new TransformStream(); (async _ => { for await (const _ of (async function* stream() { while (urls.length) { yield (await fetch(urls.shift(), {cache: 'no-store'})).body.pipeTo(writable, { preventClose: !!urls.length, }); } })()); })(); port.postMessage( { readable, }, [readable] ); };