WIP: Support for automated parameters

[martinholters]

This is a proof-of-concept implementation picking up the idea from https://github.com/GoogleChromeLabs/audioworklet-polyfill/issues/15#issuecomment-436105404. It works like a charm for my limited use case (exponentialRampToValueAtTime and cancelAndHoldAtTime only). I've tried to implement the whole spec (except for throwing on error conditions for now), and the complexity is somewhat alarming. I also haven't done much testing, so this is likely still rather buggy. Before investing more time to finish this, I'd appreciate some feedback:

• Does this approach look like a good idea? Does it have any drawbacks I'm not aware of (yet)?
• Is all this extra code worth it?

Fixes #15.

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[martinholters]

I signed it!

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[martinholters]

Any thoughts on this, @developit?

[developit]

Hey @martinholters! Sorry about the wait there - I read this but then forgot to come back to the tab. I like the approach and I think this is the right way to move forward. However, I have to wonder - do you think this would be worth pulling out into its own library as an AudioParam polyfill? I could certainly see other polyfills using it.

Cheers!

[martinholters]

However, I have to wonder - do you think this would be worth pulling out into its own library as an AudioParam polyfill?

I'm not sure I fully understand, so let me check we're on the same page. It might make sense to pull this into a library which provides a way to construct an AudioParam and then an API call to evaluate its value at a specific time/for a block of samples, basically putting the code now added toscriptProcessor.onaudioprocess into its own function. That might indeed be useful when implementing your own ScriptProcessor. (Although I wouldn't call it a polyfill; that might be part of the reason I'm not sure I understood you correctly.) Do you see other application scenarios?

[developit]

You described what I meant perfectly, and agreed regarding it not really needing to be a polyfill. Shouldn't block merging based on that goal though, I'll re-review (sorry for the delay!)

[chrisguttandin]

Hi @martinholters, I just came across this thread. I recently created a very similar abstraction for my standardized-audio-context package. The little library is called automation-events. It maintains a list of automation events and provides a method to get the value of the hypothetical AudioParam at a certain point in time. Maybe that comes in handy for what you're planning to do.