Re: Web Audio API spec review

On Tue, May 15, 2012 at 4:45 AM, Philip Jägenstedt <>wrote:

> Marcus and I have begun spec review of the Web Audio API and MediaStream
> Processing with the expectation to start implementing something in the not
> too distant future.

Great, glad to hear it!

> We intend to create individual issues for the many different problems we
> have identified, this mail is a heads-up and a high-level commentary on the
> status of the Web Audio API.
> The executive summary is that the Web Audio API is largely underspecified
> and that we could not even begin to implement it based on the existing spec
> without reverse-engineering Chris Rogers' implementation. The spec consists
> mostly of interface documentation suitable for Web authors and is very
> sparse on normative requirements for user agents, which makes it impossible
> to write a test suite for.

Yes, in many places we need more detail and I really appreciate your
feedback to help improve the spec.  I'm sure that we can make many
improvements there.  Concerning test suites, we have a set of roughly
seventy layout tests specifically for the Web Audio API. We continue to
write additional tests and hope that these tests can be shared.

> There are a few aspects that make the Web Audio API fit poorly with the
> rest of the Web platform. For example, the integration with
> HTMLMediaElement is one-way; the audio stream of a <video> can be passed
> into AudioContext but the result cannot leave AudioContext or play in sync
> with the video channel. That an AudioContext cannot be paused means that
> certain filtering effects on any stallable input (<audio>, MediaStream)
> cannot be implemented, echo or reverb being the most obvious examples.

I don't believe there are any fundamental serious limitations here.  For
example, today it's possible to pause an <audio> element and have the
reverb tail continue to play, to fade-out slowly/quickly, or stop right
away.  We can discuss in more detail if you have some very specific use

> We will begin creating detailed issues shortly and will send out a summary
> when done. Our hope is that this email and the individual issues do not
> come across as needlessly negative, the shared purpose of the members of
> this WG is the same after all -- to produce a high-quality spec and
> interoperable implementations to match.

Thanks Philip, your feedback is much appreciated.


> --
> Philip Jägenstedt
> Core Developer
> Opera Software

Received on Tuesday, 15 May 2012 17:59:37 UTC