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Re: Web Audio API sequencer capabilities

From: Srikumar Karaikudi Subramanian <srikumarks@gmail.com>
Date: Sat, 6 Oct 2012 09:33:33 +0530
Cc: Joe Berkovitz <joe@noteflight.com>, Jussi Kalliokoski <jussi.kalliokoski@gmail.com>, "public-audio@w3.org Group" <public-audio@w3.org>
Message-Id: <7843D4AA-EA6B-493A-9C70-B9AC091A14BE@gmail.com>
To: Chris Rogers <crogers@google.com>
On 6 Oct, 2012, at 4:27 AM, Joe Berkovitz <joe@noteflight.com> wrote:
> Actually, I didn't ever think a GainNode would generate its own signal. Rather, it did not occur to me to drive a set of AudioParams with an envelope via the audio rate modulation feature, using a gain controlled unity signal. It is this last idea that seems a bit tricky and unclear for API novices. If there were something like a UnitySourceNode, I would feel better.
> 

Chris R - I see that the AudioBufferSourceNode's 'gain' attribute was removed from the spec in Apr '11 (https://dvcs.w3.org/hg/audio/file/908b6b7b8702/webaudio/specification.html), but it is present in all webkit implementations even today, including Chrome Canary. In http://lists.w3.org/Archives/Public/public-audio/2012AprJun/0072.html, you wrote -- "We may need to re-visit the removal of these gain attributes from the API, since I've found several pages out in the wild using them.  They're not harmful attributes, just ones I felt could be cleaned up (removed) since AudioGainNode can be used instead.  We may need to choose a deprectation path, or simply keep them."

With the 'gain' parameter, the AudioBufferSourceNode would offer a single node solution to envelope generation. You can set a one sample buffer with sample value = 1, turn on looping and work with its gain parameter. This is simple enough that a special UnitySourceNode and an EnvelopeNode would be superfluous. (I only just realized I've been using the ABSN this way instead of the "GainNode with unity signal" approach I mentioned earlier .. but was surprised to find that the ABSN.gain parameter was removed from the spec.)

AudioBuffer.gain and AudioListener.gain are likely to be superfluous, but if AudioBufferSourceNode.gain is removed, a gain node seems likely to be necessary most of the time anyway. Given that the ability to connect a node to an AudioParam didn't exist when the ABSN.gain parameter was removed, it is worth reconsidering it in the context of envelopes as well.

Best,
-Kumar
Received on Saturday, 6 October 2012 04:03:52 UTC

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