Web-audio-api: IFFT?

[rickygraham]

Is it possible to request an IFFT routine/support? Any more on that?
All the best.

[rtoy]

Presumably you also want an FFT routine. Can you describe what kind of interface you want and what you expect to be able to do with these routines?

[rickygraham]

Sure. Yes, FFT/IFFT for analysis and re-synthesis of an audio signal for time-stretching, phase-vocoding.

[rtoy]

But see also https://github.com/WebAudio/web-audio-api/issues/468#issuecomment-107584292

[rickygraham]

Sure. If narrowing the scope down to a few parameters is in-part the issue, then configurable analysis window size and overlap would suffice. Forgive me if that's oversimplified but it would be a solid start.

[rtoy]

Wait. Now you've conflated several things into one. This issue is about adding support for an FFT and IFFT routine. Presumably, this would mean just two routines taking arrays and returning the FFT or IFFT.

However, in https://github.com/WebAudio/web-audio-api/issues/1223#issuecomment-301305043, you're now talking about configurable analysis window size and overlap. This sounds as if you're now talking about modifying the AnalyserNode to do support some new feature.

What exactly is this issue about now? Are you proposing two things now? If so, file a separate issue for the AnalyserNode changes, if that's what you want.

[rickygraham]

This issue is about adding support for an FFT and IFFT routine. Presumably, this would mean just two routines taking arrays and returning the FFT or IFFT.

Correct. Can you provide this support?

you're now talking about configurable analysis window size and overlap. This sounds as if you're now talking about modifying the AnalyserNode to do support some new feature.

Well, no. That's not what I'm suggesting. Analysis window size and overlap are pretty common (configurable) parameters with FFT/IFFT.

[rtoy]

On Mon, May 22, 2017 at 1:58 PM, Ricky Graham [e-mail]
wrote:

This issue is about adding support for an FFT and IFFT routine.
Presumably, this would mean just two routines taking arrays and returning
the FFT or IFFT.

Correct. Can you provide this support?

​Since every implementation of WebAudio must have an DFT routine (to
implement the AnalyserNode) and therefore very likely has an FFT routine,
this can be easily provided. And since IFFT can easily be computed from
an FFT (at some small expense), this isn't hard either.

The question is whether WebAudio should or not.​

you're now talking about configurable analysis window size and overlap.
This sounds as if you're now talking about modifying the AnalyserNode to do
support some new feature.

Well, no. That's not what I'm suggesting. Analysis window size and overlap
are pretty common (configurable) parameters with FFT/IFFT.

​Well, now that's much more difficult to specify. If you have an FFT
routine you can do your own window size and overlap. Doing that within the
existing (or new) WebAudio infrastructure requires the actual use-case to
be specified better.

Specifying his seems unlikely to happen before version next.

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[rickygraham]

The question is whether WebAudio should or not.​

Given that many people would put this kind of feature to use and a good few have requested it, surely it makes sense to implement it, no?

[rtoy]

Just because we can, doesn't mean we should. :-)

As mentioned earlier, https://github.com/WebAudio/web-audio-api/issues/468#issuecomment-107584292 sums it very nicely. We should answer this before proceeding.

[joeberkovitz]

We're declining to put this into the Web Audio spec because an FFT library that is useful in a general sense is beyond the scope of the WG charter, and we don't want to just expose the internal FFT that Web Audio implementations use which is far more limited and wasn't designed for all purposes that developers might have in mind.