Intent to Implement and Ship: WebAudio: Add IIRFilterNode

[Raymond Toy]

Contact emails rt...@chromium.org,hong...@chromium.org Spec https://webaudio.github.io/web-audio-api/ Summary Add a new node, IIRFilterNode, that implements a general IIR filter. The coefficients are fixed at creation and not changeable. No automation of the coefficients is allowed. Motivation

Currently, WebAudio supports a BiquadFilterNode that implements very specific 2nd order (biquad) IIR filters. These are quite useful, but the specification does not allow specifying 1st order filters and higher order filters must be created by cascading biquad filters together. It can be shown that the current biquad filters can be used to create any higher even-ordered filter, but decomposing such higher order filters into biquads is fairly difficult because it requires solving a large order polynomial for the roots.

To simplify this and to allow 1st order filters, an IIRFilterNode is proposed where the coefficients of the filter can be directly specified. Compatibility Risk Firefox: No public signals Internet Explorer: No public signals Safari: No public signals Web developers: Positive

Describe the degree of compatibility risk you believe this change poses This is a new node so there are no backwards compatibility issues. Any differences between browsers should be due only to numerical issues that depend on exactly how the IIR filter node is implemented. Ongoing technical constraints None Will this feature be supported on all six Blink platforms (Windows, Mac, Linux, Chrome OS, Android, and Android WebView)? Yes or no. Yes OWP launch tracking bug http://crbug.com/514782 Link to entry on the Chromium Dashboard https://www.chromestatus.com/features/6674104937611264 Requesting approval to ship? Yes

[TAMURA, Kent]

LGTM.

However can you show a URL of the specification discussion on IIRFilterNode?

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TAMURA Kent
Software Engineer, Google

[Hongchan Choi]

Here is the pull request for the spec change:

https://github.com/WebAudio/web-audio-api/pull/556

Although there might be some editorial changes in the PR above, the idea was discussed and accepted by WG at:

https://github.com/WebAudio/web-audio-api/issues/323#issuecomment-83653515

[Philip Jägenstedt]

Can you have that pull request merged so that we can read the spec at https://webaudio.github.io/web-audio-api/?

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[Raymond Toy]

Sorry about that.  You can find the merged version (unofficial) at http://rtoy.github.io/web-audio-api/#the-iirfilternode-interface.  This  is temporary, of course.  We don't expect any major changes since the general idea was accepted as Hongchan pointed out; the final design was basically waiting for me to design it.

[Philip Jägenstedt]

Thanks, LGTM2!

[Chris Harrelson]

LGTM3