[AUDIO_WORKLET] Add new emscripten_audio_node_connect API

[cwoffenden]

In all the examples and in the docs, connecting the context and worklet is done with the following type of code:

EM_ASM({
  emscriptenGetAudioObject($0).connect(emscriptenGetAudioObject($1).destination)
}, wasmAudioWorklet, audioContext);

Every example or usage needs this to play audio. Granted, more complex graphs will add more node types and emscriptenGetAudioObject() will have its uses, but for the general use case a simpler call without JS is preferred:

emscripten_audio_worklet_node_connect(audioContext, wasmAudioWorklet);

See here for how it's done in the examples:

emscripten/test/webaudio/audioworklet.c

Line 50 in 7df48f6

EM_JS(void, InitHtmlUi, (EMSCRIPTEN_WEBAUDIO_T audioContext, EMSCRIPTEN_AUDIO_WORKLET_NODE_T audioWorkletNode), {

I updated the examples and the documentation.

@juj Comments or ideas?

[sbc100]

Perhaps the title should something like "[AUDIO_WORKLET] Add new emscripten_audio_worklet_node_connect API"?

[cwoffenden]

Perhaps the title should something like "[AUDIO_WORKLET] Add new emscripten_audio_worklet_node_connect API"?

Good point. I’ll take a look tomorrow, plus I might roll it in with some other quality of life changes.

[sbc100]

Perhaps the title should something like "[AUDIO_WORKLET] Add new emscripten_audio_worklet_node_connect API"?

Good point. I’ll take a look tomorrow, plus I might roll it in with some other quality of life changes.

As always, I'd love to see separate smaller PR that kind of thing rather than trying combine stuff.

[juj]

This sounds fine.

Originally the connection was in JS since I did not want to start building a full Emscripten Web Audio API wrapper, but show developers in the examples how to do the JS side tasks on JS side.

However I can see that users who don't have a JS side web audio engine, might want to have a pure C API without needing to dip to JS side at all.

If we do this, I think it would be good to be forward-looking and generic, so instead of having a function

emscripten_audio_worklet_node_connect(EMSCRIPTEN_WEBAUDIO_T audioContext, EMSCRIPTEN_AUDIO_WORKLET_NODE_T audioWorkletNode);

let's instead have a function

emscripten_audio_node_connect(EMSCRIPTEN_WEBAUDIO_T sourceNode, int outputIndex, EMSCRIPTEN_WEBAUDIO_T destinationNode, int inputIndex);

and in the implementation of that function, do

sourceNode.connect(destinationNode.destination || destinationNode, outputIndex, inputIndex);

(https://developer.mozilla.org/en-US/docs/Web/API/AudioNode/connect)

This way the same function can be used to connect to AudioContext destination, but also to connect any arbitrary audio nodes together.

While we don't have capability to manipulate audio nodes in C side, maybe someone in the future might rationale to want to add that, so then the shape of the API would be generic to be compatible with that kind of expansion.

Would that make sense?

[cwoffenden]

If we do this, I think it would be good to be forward-looking and generic, so instead of having a function

I made something more generic that takes any two nodes, and added the indices as params as suggested.

I'll create a few smaller PRs with other proposed changes.

[sbc100]

lgtm, but I'll wait for @juj to chime in again before landing.

[cwoffenden]

I'll wait for @juj to chime in again before landing.

This PR also has the much smaller #22681 as a sibling for the public API parts I’d like to add to. Anything else will be internal.

[juj]

Perfect, this looks pretty clean!